Hormones and behavior
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Hormones and behavior · Apr 2005
Comparative StudyNew evidence that the MHC influences odor perception in humans: a study with 58 Southern Brazilian students.
Increasing evidence suggests a correlation between mate choice, odor preference, and genetic similarity at the Major Histocompatibility Complex (MHC) in a variety of animals, including our species. The MHC is a highly polymorphic group of genes that play an important role in the immunological self/nonself recognition. Its products have been reported to take part on the variety of compounds and reactions that together build an individual's body odor. ⋯ Body odors were collected via sweat and urine from all participants. Women smelled and scored all male odor samples and men did the same with all female samples. We found a significant correlation only when female smellers evaluated male sweat odors.
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Hormones and behavior · Dec 2004
Comparative Study Clinical TrialDigit length ratios predict reactive aggression in women, but not in men.
Considerable evidence suggests that digit length and dermatoglyphic asymmetry patterns in the hand are affected by early exposure to androgens. Because androgens play an important role in sexual differentiation of morphological and behavioral traits, digit length patterns often display sex differences. When present, sex differences in digit lengths are more pronounced on the right side as compared to the left side. ⋯ High aggression scores were associated with high directional asymmetry of 2D:4D and masculinized (low) right hand 2D:4D, only in females and under high provocation. Directional asymmetry of 2D:4D was positively correlated with T in males (pooled data, n = 97). Taken together, these data confirm the predominantly right-sided influence of androgens on digit length and suggest that digit length ratios may be associated with female reactive aggression when sufficient provocation is present.
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Hormones and behavior · Sep 2004
ReviewEmerging views on the distinct but related roles of the main and accessory olfactory systems in responsiveness to chemosensory signals in mice.
In rodents, the nasal cavity contains two separate chemosensory epithelia, the main olfactory epithelium, located in the posterior dorsal aspect of the nasal cavity, and the vomeronasal/accessory olfactory epithelium, located in a capsule in the anterior aspect of the ventral floor of the nasal cavity. Both the main and accessory olfactory systems play a role in detection of biologically relevant odors. The accessory olfactory system has been implicated in response to pheromones, while the main olfactory system is thought to be a general molecular analyzer capable of detecting subtle differences in molecular structure of volatile odorants. ⋯ The most salient feature of our review of the literature is that there are no general rules that allow classification of the accessory olfactory system as a pheromone detector and the main olfactory system as a detector of general odorants. Instead, each behavior must be considered within a specific behavioral context to determine the role of these two chemosensory systems. In each case, one system or the other (or both) participates in a specific behavioral or hormonal response.
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Hormones and behavior · Nov 2003
Comparative StudyPrior exposure to a single stress session facilitates subsequent contextual fear conditioning in rats. Evidence for a role of corticosterone.
Previous studies showed that exposure of rats to chronic restraint stress for 21 days enhances subsequent contextual fear conditioning. Since recent evidence suggest that this effect is not dependent on stress-induced neurodegenerative processes, but to elevated training-elicited glucocorticoid release in chronically stressed animals, we aimed to explore here whether a single exposure to restraint stress, which is not expected to induce neuronal damage, would also affect contextual fear conditioning. We also questioned whether post-training corticosterone levels might be associated with any potential effect of stress on fear conditioning. ⋯ Furthermore, the facilitating effect of prior stress was not evident when animals were trained in the hippocampal-independent auditory-cued conditioning task. Therefore, these findings support the idea that stress experiences preceding exposure to new types of stressors facilitate the development of contextual fear conditioning. They also indicate that not only repeated, but also a single exposure to aversive stimulation is sufficient to facilitate context-dependent fear conditioning, and suggest that increased glucocorticoid release at training might be implicated in the mechanisms mediating the memory facilitating effects induced by prior stress experiences.
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A brief exposure to social defeat in male Syrian hamsters (Mesocricetus auratus) leads to profound changes in the subsequent agonistic behavior exhibited by the defeated animals. Following defeat in the home cage of an aggressive conspecific, male hamsters will subsequently fail to defend their home territory even if the intruder is a smaller, nonaggressive male. This phenomenon has been called conditioned defeat. ⋯ These results suggest that in male hamsters conditioned defeat is a profound, persistent behavioral change characterized by a total absence of territorial aggression and by the frequent display of submissive and defensive behaviors. Conversely, social defeat in female hamsters does not appear to induce long-term behavioral changes. Finally, in Experiment 3, we determined that plasma adrenocorticotropin-like immunoreactivity increases in females following social defeat in a manner similar to that seen in males, suggesting that the disparate behavioral reactions of males and females are not due to sex differences in the release of, or response to, plasma adrenocorticotropin.