تأثیرات اجتماعی بر فعالیت غدد درون ریز در خوکچه هندی، با مقایسه یافته ها در پستانداران غیرانسان

Guinea pigs exhibit a rich and varied social organization. Studies in recent years have demonstrated that social stimuli have widespread neuroendocrine effects in guinea pigs. Here, effects on the hypothalamic–pituitary–adrenal, adrenal medullary/sympathetic, and hypothalamic–pituitary–gonadal systems of both adult and developing guinea pigs are reviewed. These systems respond to various social variables, or factors that affect social variables, including: separation from attachment objects, housing conditions, changes in housing, the familiarity of the environment in which social interactions occur, foraging conditions, surrogate-rearing, agonistic interactions, and the establishment of dominance rank. Similarities and differences between these findings and those in nonhuman primates are discussed. It is argued that the guinea pig is well suited for the study of socioendocrine effects throughout the life span, and can provide a valuable complement to nonhuman primate research in this area.

Social behavior is intimately tied to neuroendocrine function. Not only does hormonal activity underlie or promote sexual and other forms of social behavior, but social behavior and social cues have powerful effects on neuroendocrine processes. These interactive effects serve, among other purposes, to regulate or enforce species-typical social grouping patterns and ensure successful reproduction. Much of the early work in behavioral endocrinology was driven by recognition of the profound influences that hormones could have on behavior, particularly the sexual behavior of rodents [6] and [61]. Although effects running in the opposite direction—influences of social behavior on endocrine activity (i.e. socioendocrine effects)—have long been known to exist (e.g. [17]), an appreciation of their pervasiveness, subtlety, and impact has grown slowly. The study of socioendocrine effects in guinea pigs is a case in point. Although much of what we know today about hormonal influences on mammalian reproduction stems from Young and colleagues’ classic studies with guinea pigs in the 1950s and 1960s [102], research concerning social influences on endocrine activity in this animal is of much more recent vintage, having been published largely within the last 10–15 years. The research shows that the neuroendocrine activity of guinea pigs is exquisitely sensitive to social variables. The first purpose of the present article is to provide a comprehensive review of these findings.

The domestic guinea pig possesses a rich and varied social system. The young appear to exhibit a strong attachment for the mother. Although the mother's caretaking behavior is relatively passive, she recognizes her young and may even display an attachment to them during the early postpartum days. The period after weaning is characterized by a lingering, preferential capacity of the mother to reduce the plasma cortisol response to novel surroundings. Yet under certain circumstances, this apparent calming effect of the mother can be observed at the same time that her male offspring are approaching her sexually. In adulthood, dominance hierarchies are pronounced in males and evident in females. The nature of the social structure among adults is dynamic, changing predictably with shifts in population density. Long-lasting attachment-like associations between males and females are observed under high-density conditions. The response of males to the formation of new social groups can be intensely antagonistic and stressful. This reaction varies greatly with the past social experience of the males and appears to depend on the opportunity to obtain social skills some time after weaning. For the purpose of the present article, it is clear that the guinea pig affords an opportunity to investigate the neuroendocrine consequences, as well as underpinnings, of a diversity of social phenomena. On the other hand, it is unfortunate that so little is yet known about the social organization and interactions of wild cavies. If this information were available, contrasts with the guinea pig might tell us much about the adaptive significance of various socioendocrine relations, as well as how they have been modified with domestication.