The present study explored psychological predictors of response to a series of three 25 second inhalations of 20% carbon dioxide-enriched air in 60 nonclinical participants. Multiple regression analyses indicated that only anxiety sensitivity physical concerns predicted self-reported fear, whereas both physical anxiety sensitivity concerns and behavioural inhibition sensitivity independently predicted affective ratings of emotional arousal. In contrast, the psychological concerns anxiety sensitivity dimension predicted ratings of emotional displeasure (valence), and both psychological anxiety sensitivity concerns and behavioural inhibition sensitivity (...) independently predicted emotional dyscontrol. No variables significantly predicted heart rate. These data are in accord with current models of emotional reactivity that highlight the role of cognitive variables in the production of anxious and fearful responding to somatic perturbation, and help further clarify the particular predictors of anxiety-related responding to biological challenge. (shrink)

BackgroundMethamphetamine addicts can experience severe emotional processing disorders, with abnormal responses to emotional and drug-related stimuli. These aberrant behaviors are one of the key factors leading to relapse. Nevertheless, the characteristics of addicts’ responses to drug-related stimuli and their responses to emotional stimuli remain controversial.Methods52 methamphetamine addicts from China passively viewed three different categories of images: Drug-related; positive emotional; and negative emotional. In the first task, participants completed a 9-point Self-Assessment Manikin (SAM) scale, rating the valence of each image. In (...) the second, they performed a cued-action task while electroencephalography (EEG) data were recorded.ResultDrug-related images were rated negatively, with an average rating of 3.57. However, reaction times to drug-related stimuli were significantly faster than for negative stimuli (p = 0.030), and were indistinguishable from positive stimuli (p > 0.99). Similarly, EPN amplitudes evoked by drug-related images were significantly larger than those evoked by negative stimuli (p 0.99). LPP amplitudes evoked by drug-related stimuli were significantly smaller than those evoked by negative (p < 0.001) and positive stimuli (p = 0.004).ConclusionDespite negative self-assessments of drug-related imagery, MA-addicts reaction times were no slower than positive reactions. Similarly, drug-related and positive imagery EPN amplitudes were indistinguishable. Together, these results suggest increased attentional resources were allocated to the processing of drug-related stimuli and the pathways responsible partially overlap with the those recruited in processing positive emotional imagery in addicts. Moreover, in the late stage of visual processing, MA-addicts showed reduced brain activity in response to drug-related stimuli, suggesting reverse inhibition in response preparation and emotional appraisal. These findings may provide a reference for clinicians treating drug-taking behavior and for the development of new models of rehabilitation therapy. (shrink)

This study analyzed the effects of aging on post-error behavioral adjustments from the perspective of cognitive control. A modified error awareness task was administered to young and older adults. In this task, two buttons were placed on the left and right sides in front of the participants, who were instructed to use the right button to perform a go/no-go task, and were notified if they made an error. There were three experimental conditions : participants had to push the right button (...) once in Condition A and twice in Condition B and C when a go-stimulus was presented. Conversely, participants were asked to withhold their response when a no-go stimulus was presented. Response inhibition differed depending on the experimental condition. The participants were asked to push the left button as quickly as possible when an error occurred. The results showed relatively longer reaction times to sudden errors among older adults compared with young adults. Furthermore, the difference in the error responses strongly influenced older adults’ response time after an error. These results suggest that the shift from proactive to reactive control may significantly influence post-error behavioral adjustments in older adults. (shrink)

Theories of affective influences on cognition posit that negative mood may increase cognitive load, causing a decrement in task performance (Seibert & Ellis, [1991]. Irrelevant thoughts, emotional mood states, and cognitive task performance. Memory & Cognition, 19(5), 507–513), or cause a shift to more analytic thinking, which benefits tasks requiring attention to detail (Schwarz & Clore, [1983]. Mood, misattribution, and judgments of well-being: Informative and directive functions of affective states. Journal of Personality and Social Psychology, 45(3), 513–523). We previously reported (...) that individuals who are higher in the trait of emotional reactivity performed better on an inhibitory task with increasing negative mood whereas low-reactive individuals showed the converse pattern (Gabel & McAuley, [2018]. Does mood help or hinder executive functions? Reactivity may be the key. Personality and Individual Differences, 128, 94–99; [2020]. React to act: Negative mood, response inhibition, and the moderating role of emotional reactivity. Motivation and Emotion, 44(6), 862–869). Because high-reactive individuals are more accustomed to negative affect (Nock et al., [2008]. The emotion reactivity scale: Development, evaluation, and relation to self-injurious thoughts and behaviors. Behavior Therapy, 39(2), 107–116), we speculated that negative mood engendered analytic thinking but without a task-incongruent increase in cognitive load – thereby facilitating performance. Here, we induced a heuristic or analytic approach to information processing prior to performance of an inhibitory task and expected different results pending the thinking style induced. In the heuristic condition, increasing negative mood was associated with better performance for high-reactive participants but not their low-reactive counterparts. In the analytic condition, increasing negative mood was associated with better performance irrespective of emotional reactivity. Our results are consistent with the notion that negative mood engenders analytic thinking which may benefit response inhibition provided it does not increase task-incongruent cognitive load. (shrink)

Mitochondrial respiration is the predominant source of ATP. Excessive rates of electron transport cause a higher production of harmful reactive oxygen species (ROS). There are two regulatory mechanisms known. The first, according to Mitchel, is dependent on the mitochondrial membrane potential that drives ATP synthase for ATP production, and the second, the Kadenbach mechanism, is focussed on the binding of ATP to Cytochrome c Oxidase (CytOx) at high ATP/ADP ratios, which results in an allosteric conformational change to CytOx, causing (...) inhibition. In times of stress, ATP‐dependent inhibition is switched off and the activity of CytOx is exclusively determined by the membrane potential, leading to an increase in ROS production. The second mechanism for respiratory control depends on the quantity of electron transfer to the Heme aa3 of CytOx. When ATP is bound to CytOx the enzyme is inhibited, and ROS formation is decreased, although the mitochondrial membrane potential is increased. (shrink)

A model positing that perception of another's affective state automatically generates matching emotional and instrumental responses predicts more than has ever been observed. Reflexive empathicness would produce emotional exhaustion, inhibitory strain, and debilitate everyday functioning. Self-regulation of empathic responses involves, not only reactive inhibition, but agentic proactive control. Pervasive inhumanities involve selective disengagement of empathic restraints through dissociative psychosocial mechanisms.

How do social media affect interpersonal relationships? Adopting a Strawsonian framework, I argue that social media make us more likely to adopt the objective attitude towards persons. Technologically mediated communication tends to inhibit interpersonal emotions and other reactive attitudes. This is due to a relative lack of the social cues that typically enable us to read minds and react to them. Adopting the objective attitude can be harmful for two reasons. First, it tends to undermine the basis of interpersonal (...) relationships. In particular, I argue that friendship is a relationship between persons that requires the participant stance. Second, it is a morally risky attitude that makes us more likely to treat persons in problematic, thing-like ways. Some philosophers have rightly urged that social media are compatible with virtuous, Aristotelian friendship. Notwithstanding, I argue that the harms associated with the objective attitude are more pressing than they might appear if we restrict our focus to relatively virtuous people with the social competence to flourish in morally risky online environments. (shrink)

Researchers rely on psychometric principles when trying to gain understanding of unobservable psychological phenomena disconfounded from the methods used. Psychometric models provide us with tools to support this endeavour, but they are agnostic to the meaning researchers intend to attribute to the data. We define method effects as resulting from actions which weaken the psychometric structure of measurement, and argue that solution to this confounding will ultimately rest on testing whether data collected fit a psychometric model based on a substantive (...) theory, rather than a search for a model that best fits the data. We highlight the importance of taking the notions of fundamental measurement seriously by reviewing distinctions between the Rasch measurement model and more generalised 2PL and 3PL IRT models. We then present two lines of research that highlight considerations of making method effects explicit in experimental designs. First, we contrast the use of experimental manipulations to study measurement reactivity during the assessment of metacognitive processes with factor-analytic research of the same. The former suggests differential performance-facilitating and -inhibiting reactivity as a function of other individual differences, whereas factor-analytic research suggests a ubiquitous monotonically predictive confidence factor. Second, we evaluate differential effects of context and source on within-individual variability indices of personality derived from multiple observations, highlighting again the importance of a structured and theoretically grounded observational framework. We conclude by arguing that substantive variables can act as method effects and should be considered at the time of design rather than after the fact, and without compromising measurement ideals. (shrink)

Serpins are members of a family of structurally related protein inhibitors of serine proteinases, with molecular masses between 40 and 100kDa. In contrast to other, simpler, proteinase inhibitors, they may interact with proteinases as inhibitors, as substrates, or as both. They undergo conformational interconversions upon complex formation with proteinase, upon binding of some members to heparin, upon proteolytic cleavage at the reactive center, and under mild denaturing conditions. These conformational changes appear to be critical in determining the properties of (...) the serpin. The structures and stabilities of these various forms may differ significantly. Although the detailed structural changes required for inhibition of proteinase have yet to be worked out, it is clear that the serpin does undergo a major conformational change. This is in contrast to other, simpler, families of protein inhibitors of serine proteinases, which bind in a substrate‐like or product‐like manner. Proteolytic cleavage of the serpin can result in a much more stable protein with new biological properties such as chemo‐attractant behaviour. These structural transformations in serpins provide opportunities for regulation of the activity and properties of the inhibitor and are likely be important in vivo, where serpins are involved in blood coagulation, fibrinolysis, complement activation and inflammation. (shrink)

Anxious temperament (AT) in human and non-human primates is a trait-like phenotype evident early in life that is characterized by increased behavioural and physiological reactivity to mildly threatening stimuli1–4. Studies in children demonstrate that AT is an important risk factor for the later development of anxiety disorders, depression and comorbid substance abuse5. Despite its importance as an early predictor of psychopathology, little is known about the factors that predispose vulnerable children to develop AT and the brain systems that underlie its (...) expression. To characterize the neural circuitry associated with AT and the extent to which the function of this circuit is heritable, we studied a large sample of rhesus monkeys phenotyped for AT. Using 238 young monkeys from a multigenerational single-family pedigree, we simultaneously assessed brain metabolic activity and AT while monkeys were exposed to the relevant ethological condition that elicits the phenotype. High-resolution 18F-labelled deoxyglucose positron-emission tomography (FDG–PET) was selected as the imaging modality because it provides semi-quantitative indices of absolute glucose metabolic rate, allows for simultaneous measurement of behaviour and brain activity, and has a time course suited for assessing temperament-associated sustained brain responses. Here we demonstrate that the central nucleus region of the amygdala and the anterior hippocampus are key components of the neural circuit predictive of AT. We also show significant heritability of the AT phenotype by using quantitative genetic analysis. Additionally, using voxelwise analyses, we reveal significant heritability of metabolic activity in AT-associated hippocampal regions. However, activity in the amygdala region predictive of AT is not significantly heritable. Furthermore, the heritabilities of the hippocampal and amygdala regions significantly differ from each other. Even though these structures are closely linked, the results suggest differential influences of genes and environment on how these brain regions mediate AT and the ongoing risk of developing anxiety and depression. Anxiety disorders are among the most common forms of psychopathology6, and frequently begin during childhood and adolescence. Although all children experience acute anxiety, children with AT display extreme behavioural and physiological reactivity to novel stimuli, and in the presence of strangers inhibit their locomotor activity and vocalizations3.. (shrink)

Approach–avoidance theories describe the major systems that motivate behaviours in reaction to classes of appetitive (rewarding) and aversive (punishing) stimuli. The literature points to two major “avoidance” systems, one related to pure avoidance and escape of aversive stimuli, and a second, to behavioural inhibition induced by the detection of goal conflict (in addition, there is evidence for nonaffective behavioural constraint). A third major system, responsible for approach behaviour, is reactive to appetitive stimuli, and has several subcomponents. A number (...) of combined effects of these systems are outlined. Finally, the hierarchical nature of behavioural control is delineated, including the role played by conscious awareness in behavioural inhibition. (shrink)

Early theorists speculated that extremely shy children, or those with anxious temperament, were likely to have anxiety problems as adults. More recent studies demonstrate that these children have heightened responses to potentially threatening situations reacting with intense defensive responses that are characterized by behavioral inhibition and physiological arousal. Confirming the earlier impressions, data now demonstrate that children with this disposition are at increased risk to develop anxiety, depression, and comorbid substance abuse. Additional key features of anxious temperament are that (...) it appears at a young age, it is a stable characteristic of individuals, and even in non-threatening environments it is associated with increased psychic anxiety and somatic tension. To understand the neural underpinnings of anxious temperament, we performed imaging studies with 18- fluoro-deoxyglucose high-resolution Positron Emission Tomography in young rhesus monkeys. Rhesus monkeys were used because they provide a well validated model of anxious temperament for studies that cannot be performed in human children. Imaging the same animal in stressful and secure contexts, we examined the relation between regional metabolic brain activity and a trait-like measure of anxious temperament that encompasses measures of BI and pituitaryadrenal reactivity. Regardless of context, results demonstrated a trait-like pattern of brain activity that is predictive of individual phenotypic differences. Importantly, individuals with extreme anxious temperament also displayed increased activity of this circuit when assessed in the security of their home environment. These findings suggest that increased activity of this circuit early in life mediates the childhood temperamental risk to develop anxiety and depression. (shrink)

Society has historically not taken a benign view of genetic disease. The laws permitting sterilization of the mentally re tarded~ and those proscribing consanguineous marriages are but two examples. Indeed as far back as the 5th-10th centuries, B.C.E., consanguineous unions were outlawed (Leviticus XVIII, 6). Case law has traditionally tended toward the conservative. It is reactive rather than directive, exerting its influence only after an individual or group has sustained injury and brought suit. In contrast, state legislatures have not (...) been inhibited in enacting statutes. Many of their products can be characterized as hasty, unnecessary, ill-conceived, and based on the heart rather than the head. Moreover the lack of expert consultation sought has also been remarkable. One state legislature, for example, has advocated immunization for sickle cell anemia! Many others have enacted laws for the screening of inborn errors of metabolism, e.g., phenylketon uria, but have poorly defined the lines of responsibility to secure compliance. A spate of specific disease-related bills has emerged in the u.S. Congress, each seeking recognition and appropriations. Sickle cell anemia, hemophilia, Cooley's anemia and Tay-Sachs disease have been among the front-runners for support. Finally, in 1975, Congress has begun to examine an omnibus bill concerning all forms of genetic disease. The bill, termed the National Genetic Diseases Act is, however, still far from being enacted. (shrink)

Akt, a protein kinase hyperactivated in many tumors, plays a major role in both cell survival and resistance to tumor therapy. A recent study,1 along with other evidences, shows interestingly, that Akt is not a single‐function kinase, but may facilitate rather than inhibit cell death under certain conditions. This hitherto undetected function of Akt is accomplished by its ability to increase reactive oxygen species and to suppress antioxidant enzymes. The ability of Akt to down‐regulate antioxidant defenses uncovers a novel (...) Achilles' heel, which could be exploited by oxidant therapies in order to selectively eradicate tumor cells that express high levels of Akt activity. (shrink)

In the United States, information about a person’s criminal history is accessible with a name and date of birth. Ruth Crampton has studied nurses’ care for prisoner-patients in hospital settings and found care to be perfunctory and reactive. This article examines whether it is morally permissible for nurses in hospital settings to access information about prisoner-patients’ criminal histories. Nurses may argue for a right to such information based on the right to personal safety at work or the obligation to (...) provide prisoner-patients with the care that they deserve. These two arguments are considered and rejected. It is further argued that accessing information about a prisoner-patient’s criminal history violates nurses’ duty to care. Care, understood through Sarah Ruddick’s account as work and relationship, requires nurses to be open and unbiased in order to do their part in forming a caring relationship with patients. Knowledge of a prisoner-patient’s criminal history inhibits the formation of this relationship and thus violates nurses’ duty to care. (shrink)

It is hypothesized that iron from biological tissues, liberated during decay, may have played a role in inhibiting loss of anatomical information during fossilization of extinct organisms. Most tissues in the animal kingdom contain iron in different forms. A widely distributed iron‐bearing molecule is ferritin, a globular protein that contains iron crystallites in the form of ferrihydrite minerals. Iron concentrations in ferritin are high and ferrihydrites are extremely reactive. When ancient animals are decaying on the sea floor under anoxic (...) environmental conditions, ferrihydrites may initialize the selective replication of some tissues in pyrite FeS2. This model explains why some labile tissues are preserved, while other more resistant structures decay and are absent in many fossils. A major implication of this hypothesis is that structures described as brains in Cambrian arthropods are not fossilization artifacts, but are instead a source of information on anatomical evolution at the dawn of complex animal life. (shrink)

Approach–avoidance generally describes appetitive motivation and fear of punishment. In a social context approach motivation is, however, also expressed as social aggression and dominance. We therefore link approach–avoidance to dominance–submissiveness, and provide a neural framework that describes how the steroid hormone testosterone shifts reflexive as well as deliberate behaviors towards dominance and promotion of social status. Testosterone inhibits acute fear at the level of the basolateral amygdala and hypothalamus and promotes reactive dominance through upregulation of vasopressin gene expression in (...) the central-medial amygdala. Finally, the hormone can, depending on social context and prenatal hormone exposure, promote both pro- and antisocial behaviors and decisions through its effects on prefrontal–amygdala interactions. All these effects of testosterone, however, serve to increase and maintain social status. (shrink)

This study investigates the role of sensory processing sensitivity as a predictor of employees’ proactive work behavior. SPS is a multidimensional concept that depicts differences in people’s sensory awareness, processing, and reactivity to internal and external influences. Based on research on SPS as grounded in a heightened sensitivity of the behavioral inhibition and activation systems, it was argued that the relationships with task proactivity and personal initiative as indicators of proactive work behavior differ for the three SPS dimensions. Furthermore, (...) based on the person–environment fit perspective, SPS was assumed to moderate the relationship between employees’ job complexity and proactivity. The hypotheses were tested in two two-wave studies. Across both studies, ease of excitation was unrelated to proactivity. Low sensory threshold was negatively related to personal initiative, only in Study 2, but it did not predict task proactivity. Meanwhile, aesthetic sensitivity was positively related to proactivity, but in Study 2, this relationship could only be established for personal initiative. Moreover, job complexity was positively related to proactivity for those employees high but not for those low in AES. EOE and LST did not act as moderators. This study offers evidence of positive behavioral implications among highly sensitive persons when dealing with job complexity. Overall, the study presents an interesting point of departure for the role of SPS in employee proactivity that calls for more research. (shrink)

Audio description remains the cornerstone of accessibility for visually impaired audiences to all sorts of audiovisual content, including porn. Existing work points to the efficacy of audio description to guarantee immersion and emotional engagement, but evidence on its role in sexual arousal and engagement in porn is still scant. The present study takes on this challenge by comparing sighted and visually impaired participants’ experiences with porn in terms of their physiological response [i.e., cortisol and heart rate ] and self-report measures (...) of affect [Positive and Negative Affect Schedule ; Watson et al., 1988], anxiety [State-Trait Anxiety Inventory ; Spielberger et al., 1970], sexual reactivity and arousal [Sexual Inhibition/Sexual Excitation Scale ; Moyano and Sierra ; and the Ratings of Sexual Arousal ; Mosher ], and narrative engagement or transportation [The Transport Narrative Questionnaire, Green and Brock ]. 69 Spanish participants were allocated into three different groups: 25 sighted participants who watched and heard the porn scenes in their audio-visual version ; 22 sighted participants who listened to the audio described version without images ; and 22 visually impaired participants who also listened to the audio described version without images. Overall, results on physiological and self-report measures revealed no significant differences between groups or different versions of the clips. The analysis of cortisol reactivity to porn as the maximum increase or decrease in cortisol with respect to baseline values revealed no significant differences between the groups, but pointed to a higher percentage of non-responders than responders in the three groups, the highest being found in the ONCE group. As for participants’ cardiac response to the clips, no significant differences were found across the groups, with the highest HR levels being registered in the baseline phase. Self-report measures revealed significant between-group differences in negative affect. The ONCE group displayed the highest pre-task levels of negative affect and was the only group that showed a decrease in negative affect after exposure to the clips. Sighted and visually impaired participants reported to be moderately aroused and immersed in the films, regardless of exposure to AV or AD porn. In addition, correlations found between participants’ levels of self-report sexual arousal and transportation and post-task affect pointed to a positive relationship between exposure to porn and perceived levels of sexual arousal and affect. Results from the study reflected the efficacy of audio description in providing sighted and visually impaired audiences with a similar experience to that offered by original AV porn scenes. This study is exploratory but provides valid, initial groundwork for further research on the impact of audio description on porn reception. (shrink)

This article addresses the physical chemical processes underlying biological self-organisation by which a homogenous solution of reacting chemicals spontaneously self-organises. Theoreticians have predicted that self-organisation can arise from a coupling of reactive processes with molecular diffusion. In addition, the presence of an external field, such as gravity, at a critical moment early in the process may determine the morphology that subsequently develops. The formation, in-vitro, of microtubules, a constituent of the cellular skeleton, shows this type of behaviour. The preparations (...) spontaneously self-organise by reaction-diffusion and the morphology that develops depends upon the presence of gravity at a critical bifurcation time early in the process. Here, we present numerical simulations of a population of microtubules that reproduce this behaviour. Microtubules can grow from one end whilst shrinking from the other. The shrinking end leaves behind a chemical trail of high tubulin concentration. Neighbouring microtubules preferentially grow into these regions, whilst avoiding regions of low tubulin concentration. The chemical trails produced by individual microtubules thus activate and inhibit the formation of neighbouring microtubules and this progressively leads to self-organisation. Gravity acts by way of its directional interaction with the macroscopic density fluctuations present in the solution arising from microtubule disassembly. (shrink)

Research has begun to suggest that cognitive ability contributes to emotional processes and responses. The present study sought novel evidence for this hypothesis by examining the relationship between individual differences in the capacity for inhibitory control and responses to a common emotion-induction procedure involving autobiographical memories. Participants first completed a stop-signal task to measure inhibitory control and then underwent an anger, anxiety, or neutral emotion induction. Performance on the stop-signal task predicted emotional responses such that participants with poorer inhibitory control (...) reported larger increases in anger following the anger induction and larger increases in anxiety across emotion induction conditions, relative to better inhibitors. These results suggest that individual differences in cognitive ability may influence the intensity of emotional states induced by common laboratory methods of emotion induction. (shrink)

According to I3 Theory, individuals enact aggressive behaviors when (a) instigating triggers are severe, (b) impelling forces are strong, and/or (c) inhibiting forces are weak. Archer's analysis of human sex differences in aggression could be bolstered by a careful analysis of male-female discrepancies in reactivity (or exposure) to instigating triggers, proneness toward impelling forces, and/or proneness toward inhibiting forces.

Research on cognitive processes has primarily focused on cognitive control and inhibitory processes to the detriment of other psychological processes, such as defense mechanisms, which can be used to modify aggressive impulses as well as self/other images during interpersonal conflicts. First, we conducted an in-depth theoretical analysis of three socio-cognitive models and three psychodynamic models and compared main propositions regarding the source of aggression and processes that influence its enactment. Second, 32 participants completed the Hostile Expectancy Violation Paradigm in which (...) scenarios describe a hostile vs. non-hostile social context followed by a character's ambiguous aversive behavior. The N400 effect to critical words that violate expected hostile vs. non-hostile intent of the behavior was analyzed. Prepotent response inhibition was measured using a Stop Signal task and DMs were assessed with the Defense Style Questionnaire. Results showed that reactive aggression and HIA were not significantly correlated with response inhibition but were significantly positively and negatively correlated with image distorting defense style and adaptive defense style, respectively. The present article has highlighted the importance of integrating socio-cognitive and psychodynamic models to account for the full complexity underlying psychological processes that influence reactive aggressive behavior. (shrink)

This essay will address the question for what good or purpose is evil. First, an examination of the use-mention distinction between evil and “evil” produces two distinct questions: what good is the presence of evil in the world, and what good is the concept of evil as part of our ethical vocabulary describing human interaction. By severing all logically necessary connections between evil and greater goods, we discover that the answer to the first question—what good is evil in the world—is (...) none whatsoever. Evil deeds leave an enduring and destructive impact on people’s lives. Attempts to justify this ruination belittle the torment that sufferers of evil sustain. Because there is no normative vindication of evil’s existence, recognizing it as an indelible fact of human interaction proves to be crucial to understanding elemental features of the moral community and one’s role within it. Hence, the answer to the second question—what good is the concept of evil—is that it is of the utmost importance. Insofar as evil is a perpetual element of human interaction, being aware of this very fact—that is, understanding the concept of evil—is central to comprehending one’s moral agency, to appropriately reacting to others in the moral community, and to possibly inhibiting future incidents of evil. (shrink)

Plants belonging to the genus Salsola (Family: Chenopodiaceae) are common in the arid and semiarid regions of our planet with no less than 69 different Salsola species found in Namibia and the Republic of South Africa. This genus is used as a traditional medicine and aqueous extracts of Salsola have been used by Bushmen women as an oral contraceptive. Ingestion of the Namibian shrub Salsola tuberculatiformis Botsch. by pregnant Karakul sheep leads to prolonged gestation and fetal post‐maturity and, as a (...) result, the pelts of the new‐born karakul lambs are worthless. This initiated an investigation into the active agents in the plant, using the terminal enzyme in adrenal corticosteroidogenesis, cytochrome P450‐dependent 11β‐hydroxylase (P450c11), as a bioassay. Although the active fraction, S2, was extremely labile, partial structure determination suggested the presence of synephrine and a highly reactive aziridine. Therefore a more stable analogue, 2‐(4‐acetoxyphenyl)2‐chloro‐N‐methylethylammonium‐chloride (compound A), was synthesised, which, like the active plant extracts, inhibited adrenal steroidogenesis and acted as a contraceptive. In addition, compound A was stabilised by interaction with steroid‐binding globulins in plasma thus enhancing biological activity in vivo. These findings provided explanations for the complex biological effects of the shrub as well as a new insight into the mode of action of chemically labile plant products in vivo. BioEssays 25:612–619, 2003. © 2003 Wiley Periodicals, Inc. (shrink)