In memoriam: Robert W. Bell, November 22, 1931- September 16, 2000.
Explore the source record for details and available documents.
Behavior↗
Biomedical subjects
M B Hennessy
Publications and source records attributed to M B Hennessy.
Stress-induced sickness behaviors: an alternative hypothesis for responses during maternal separation.
During maternal separation, some primate and nonprimate species show a biphasic (active/passive) response. The second stage is characterized by reduced activity, a hunched body posture, and other behaviors. Traditionally, the second stage has been referred to as "despair" and is considered an animal model for human depression. Recent research in psychoneuroimmunology suggests an alternative hypothesis--that behaviors occurring during the second passive phase represent stress-induced "sickness behaviors." This perspective more readily accounts for findings in widely divergent species, does not require assumptions regarding the ability to express complex emotional states, is empirically testable, and aligns the separation model with recent hypotheses regarding the nature and ontogeny of depressive illness.
Animals↗
Consequences of the presence of the mother or unfamiliar adult female on cortisol, ACTH, testosterone and behavioral responses of periadolescent guinea pigs during exposure to novelty.
Periadolescent guinea pigs were exposed to a novel environment for 10, 30, 60, or 90 min while either alone or with either their biological mother or an unfamiliar adult female. Both classes of females reduced plasma cortisol, ACTH and vocalization responses to the novel environment, and did so to an equivalent degree. However, behavioral interactions with the mother and unfamiliar female differed considerably. The offspring exhibited more defensive behavior and were the targets of more agonistic acts when with the unfamiliar female, though one agonistic behavior, kicking, was observed more often in tests with the mother. Males displayed more social/courtship behavior and tumescence with the unfamiliar female. Further, males exhibited higher plasma testosterone levels when with the unfamiliar female than when either with the mother or alone. These data in conjunction with earlier findings suggest that the ability of unfamiliar adult females to moderate hypothalamic-pituitary-adrenal activity fully emerges during the periadolescent period, is not dependent on nurturant behavior by the adult female, and may facilitate the redirection of social behavior from the mother to unrelated adults. Further, mothers appear to inhibit maternally directed sexual behavior and plasma testosterone elevations in their periadolescent sons, effects which likely serve to inhibit inbreeding.
Adrenocorticotropic Hormone↗
Comparison of the effects of the mother and an unfamiliar adult female on cortisol and behavioral responses of pre- and postweaning guinea pigs.
In the guinea pig, the presence of the mother, but not littermates, has been found to inhibit hypothalamic-pituitary-adrenal (HPA) responses during brief (30-60 min) exposure to novel surroundings both prior to and several weeks following the completion of weaning. In the present study, we found that an unfamiliar adult female inhibited plasma cortisol and vocalization responses of pre- and postweaning guinea pigs during a 60-min exposure to a novel environment. However, the presence of the mother still had a greater effect on the cortisol levels of the young, at least during the preweaning period. The moderating influence of the unfamiliar adult female on vocalizations and cortisol levels occurred despite behavioral interactions, such as heightened aggression and sexual behavior, not seen during tests with the mother. It is suggested that the unfamiliar adult female's effectiveness in reducing HPA activity during exposure to novelty may facilitate the change in patterns of social interaction occurring in recently weaned animals.
Age Factors↗
Social influences on endocrine activity in guinea pigs, with comparisons to findings in nonhuman primates.
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.
Animals↗
Rehousing periadolescent male guinea pigs (Cavia porcellus) apart from their mothers for 24 hours increases maternally directed sexual behavior and plasma testosterone.
Periadolescent male guinea pigs (Cavia porcellus) housed continuously with their mother displayed little or no sexual behavior when they were tested with her in a novel environment. However, if males were rehoused without their mother for 24 hr before testing, they frequently directed courtship and sexual behavior toward her. This effect occurred whether the mother was isolated or not during the rehousing period. In addition, rehousing without the mother produced a significant rise in the plasma testosterone levels of the males. It appears that continuous housing with the mother inhibits sexual and courtship behavior directed toward her, as well as gonadal activity, in periadolescent male guinea pigs. These effects may serve to prevent inbreeding.
Animals↗
Short- and long-term consequences of corticotropin-releasing factor in early development.
Corticotropin-releasing factor (CRF) mediates various stress-related responses in adult animals. Little is known about the effects of CRF during early development. Young mammals often vocalize when isolated in novel surroundings. Heightened levels of CRF inhibit vocalizing in isolated rat and guinea pig pups. Still lower levels of CRF may facilitate or permit vocalizing in rat pups. In guinea pigs, CRF appears to move pups from an initial active, to a subsequent passive, stage of behavioral responsiveness. CRF activity prior to birth can also affect the young. Exposing pregnant female rats to stressors during the last trimester of pregnancy alters the morphological and behavioral development of the offspring. Effects of gestational stress can be mimicked by injecting pregnant females with CRF during the last trimester. CRF appears to mediate both short- and long-term responses to stressors during developmental in rodents.
Animals↗
Stress during pregnancy alters rat offspring morphology and ultrasonic vocalizations.
Stress during pregnancy, or prenatal stress, is known to alter offspring behavior, morphology and physiology. We found that a heat, light and restraint stressor applied during the third trimester of pregnancy: 1) decreased the weight gain of adult female rats during pregnancy; 2) reduced the weight of pups, as well as the anogenital distance of male offspring, at birth; and 3) increased the number of ultrasonic vocalizations emitted by pups during isolation in a novel environment on Postnatal Day 14. These results closely approximate those we previously observed after peripheral administration of corticotropin-releasing factor to pregnant females during the third trimester. Together, the studies strongly suggest a role for corticotropin-releasing factor and/or other hormones of the hypothalamic-pituitary-adrenal system in mediating some of the effects of gestational stress.
Animals↗
Evidence that endogenous corticotropin-releasing factor suppresses behavioral responses of guinea pig pups to brief isolation in novel surroundings.
Guinea pig pups were injected subcutaneously with a corticotropin-releasing factor antagonist (CRF12-41) or saline vehicle and then placed into a novel cage for 30 or 60 min. Isolated 20- to 26-day-old pups vocalized more and exhibited more locomotor activity when given 15 to 150 micrograms of CRF12-41 than when given saline. The presence of the mother in the test cage prevented the antagonist from affecting behavior. The influence of the antagonist during isolation was not limited to guinea pigs near weaning age: CRF12-41 increased levels of vocalizing in isolated, 4- to 6-day-old pups, though no changes were seen in locomotor activity. Results support the hypothesis that endogenous corticotropin-releasing factor, perhaps acting at a peripheral binding site, suppresses the active behavioral response characteristic of pups during the early phase of isolation in novel surroundings.
Age Factors↗
Plasma cortisol levels of dogs at a county animal shelter.
Plasmacortisol levels were examined to assess the stress of dogs in a county animal shelter. Groups of dogs confined in the shelter for their 1st, 2nd, or 3rd day had higher cortisol levels than did a group maintained in the shelter for more than 9 days. Dogs in the shelter for an intermediate period (Day 4-9) had intermediate levels of cortisol. The cortisol concentrations of dogs during their first day in the shelter were greater than either those of the same dogs on Day 4/5 in the shelter or those of a group of pet dogs sampled in their own homes. There was no overall effect of 20 min of social interaction with a human (e.g., petting) on the plasma cortisol levels of dogs in the shelter on Day 1-3. However, the gender of the petter did affect cortisol levels. Those dogs interacting with a female had lower cortisol concentrations at the end of the session than did dogs interacting with a male. The results suggest that confinement in a public animal shelter produces a prolonged activation of the hypothalamic-pituitary-adrenal axis. Further, it appears that some subtle aspect of interaction with a human may be capable of moderating this response. Possible implications for the welfare of confined dogs, and for the development of behavior problems in dogs obtained from shelters, are discussed.
Animal Welfare↗
Hypothalamic-pituitary-adrenal responses to brief social separation.
Involuntary separation from close social companions is widely held to lead to pathophysiological outcomes. Presumably, the relationship with, or category of, the separated individual determines the nature of the physiological response. Here, experiments examining the consequences of brief involuntary separation on the activity of the stress-responsive hypothalamic-pituitary-adrenal (HPA) system are reviewed. Only those studies designed specifically to assess the effect of the absence of the social partner are considered. Evidence for HPA activation in response to social separation has been obtained in a number of species; yet, many studies find no effect of separation of affiliative partners on HPA activity. The occurrence of an HPA response to separation does not appear to be related to the phylogenetic position or cognitive capacity of the species studied, nor is it a universal response to mother-infant separation. Rather, it is suggested that the pattern of results can be largely understood in the context of attachment. Separation of partners exhibiting signs of emotional attachment leads to an immediate and persistent HPA response, whereas separation of partners that are affiliative, but do not exhibit attachment, has little or no effect on HPA activity.
Animals↗
The fate of filial attachment in juvenile guinea pigs housed apart from the mother.
Thirty-five-day-old juvenile guinea pigs exhibited higher levels of plasma cortisol following 60 min of exposure to a novel environment when tested alone than when in the presence of the mother. This effect occurred regardless of whether the offspring had been housed continuously with mother and littermates from birth until testing or had been rehoused with just littermates 1 or 2 days prior to testing. Offspring vocalized more when alone then when in the presence of the mother only if they had been housed continuously with her until testing. In addition, juvenile males reunited with the mother after 1 or 2 days directed sexual behavior toward her. The sexual behavior was not accompanied by a significant change in plasma testosterone levels, though there was an overall suppression of levels following isolation in the novel test environment. The results show that guinea pig mothers maintain the capacity to prevent their offspring from exhibiting a plasma cortisol stress response even when the offspring are well beyond weaning and have been housed apart from her for up to 2 days. This suggests the existence of filial attachment in juveniles under these conditions. Further, juvenile males appear capable of simultaneously directing filial attachment and sexual behavior toward the same female.
Animals↗
Peripheral administration of a corticotropin-releasing factor antagonist increases the vocalizing and locomotor activity of isolated guinea pig pups.
Guinea pig pups vocalized more and were more active during a 60-min period of isolation in a novel environment when injected SC with 50 micrograms of the corticotropin-releasing factor (CRF) antagonist, [D-Phe]CRF12-41, than when injected with saline vehicle only. More pups exhibited eye closing and extensive piloerection when injected with saline than when injected with the antagonist. Plasma levels of cortisol following testing were not affected by the injections. These results support the hypothesis that endogenous CRF contributes to the normal decline in vocalizing and locomotor activity that guinea pig pups show with continued isolation. The results also suggest that endogenous CRF plays a role in the eye closing and piloerection of isolated pups. The finding that the dose of the antagonist used altered behavior, yet was not sufficient to lower plasma cortisol levels, supports earlier evidence that the observed effects of CRF are not due to the actions of ACTH or glucocorticoids.
Animals↗
Behavioral and glucocorticoid responses of adult domestic dogs (Canis familiaris) to companionship and social separation.
Removal of 1 member of a long-standing pair of adult domestic dog (Canis familiaris) kennel mates from the home run for 4 hr had no effect on the behavior or plasma glucocorticoid levels of the remaining dog. When tested in a novel environment, dogs showed increased activity and elevated glucocorticoid levels at the end of the session, but these responses were as large when the dogs were with their kennel mates as when they were alone. However, activity and glucocorticoid levels were not elevated if the dogs were exposed to the novel environment in the presence of their human caretaker. Dogs more often were observed in proximity with, and soliciting social behavior from, the human than the kennel mate. These results highlight the importance of human companionship for the domestic dog and point to a difference in the nature of the social relationships of dogs with humans and with conspecifics.
Animals↗
Corticotropin-releasing factor modulation of the ultrasonic vocalization rate of isolated rat pups.
The effect of corticotropin-releasing factor (CRF) on ultrasonic vocalizations (USVs) and other behaviors of isolated rat pups was examined at 5/6-, 9/10-, and 13/14-days. The hypothesis tested was that central CRF affects USV rate biphasically: as endogenous CRF increases from low basal levels it initiates USV production, but at higher levels CRF diminishes USV production. As predicted, the largest doses of CRF (0.1 and 1 microgram) and of its antagonist alpha-helical CRF9-41 (aH-CRF; 20 micrograms) administered intracerebroventricularly (ICV) reduced USV rate compared to saline treatment during a 2-min isolation at ambient temperature in pups of all ages. Other behaviors were either unaffected or increased by drug treatment. Effects were not attributable to sedation or to a change in core temperature. Peripheral administration of 1 microgram CRF or 20 micrograms aH-CRF had no effect. When isolation occurred in a heated chamber containing soiled bedding from the home cage to minimize baseline USV rate, ICV-CRF (0.001, 0.01, 0.1, or 1 microgram) did not enhance the rate. The quieting ability of aH-CRF is evidence that central endogenous CRF enhances the rate of ongoing USVs during brief isolation; the quieting ability of CRF suggests that this peptide may also be responsible for the reduction in USV rate that normally occurs during more protracted isolation. However, CRF alone is not sufficient to induce vocalizing in quiet pups.
Animals↗
Plasma cortisol and vocalization responses of postweaning age guinea pigs to maternal and sibling separation: evidence for filial attachment after weaning.
Postweaning guinea pigs housed with their mother and littermates since birth vocalized more and exhibited greater increases in plasma cortisol levels when placed for 1 hr into a novel test cage alone than they did when tested in the identical fashion with the mother present. These responses were apparent beyond 50 days of age, but had waned by 90 days of age. When tested with a familiar sibling cagemate, postweaning guinea pigs emitted fewer vocalizations than when tested alone but exhibited no less of an elevation of plasma cortisol levels. These results were obtained regardless of whether the subjects had been housed with mother and littermates from birth until the time of testing or with mother and littermates until weaning and then just the single sibling cagemate until the time of testing. The present findings closely approximate those seen in preweaning guinea pigs during tests of maternal and sibling separation, and indicate that guinea pigs can continue to exhibit a specific attachment to the mother beyond the time of weaning.
Animals↗
Responses of infant titi monkeys, Callicebus moloch, to removal of one or both parents: evidence for paternal attachment.
The response to parental separation in infant titi monkeys was evaluated. Separation from the mother for 1 hr did not elicit an adrenocortical response from the infant unless the father was also removed. Separation from the father elicited a significant elevation in adrenocortical activity even when the mother remained with the infant during the separation period. Infants showed the highest cortisol levels and vocalization rates when both parents were removed and the infant remained alone in the living cage for 1 hr. As in previous research, infants maintained higher levels of contact with the father than with the mother. The results indicate that in this monogamous New World primate, the father is the primary attachment figure for the developing infant.
Animals↗
Endocrine sensitivity to novelty in squirrel monkeys and titi monkeys: species differences in characteristic modes of responding to the environment.
The present study examined plasma cortisol and behavioral responses to environmental novelty in squirrel monkey and titi monkey male-female pairs. Overall, seemingly trivial increments in novelty evoked sustained plasma cortisol elevations. In individually tested animals, the minimal level of novelty sufficient to evoke a cortisol response was smaller, and the ability of the response to discriminate among levels of novelty was greater, in titis than in squirrel monkeys. When tested with the pairmate, the sensitivity of the response was reduced in titis but not in squirrel monkeys. Behavioral measures were not as sensitive to novelty as was the cortisol response. The results suggest that differential endocrine responsiveness to novelty is an important physiological concomitant to previously described differences between squirrel monkeys and titi monkeys in their characteristic modes of relating to the environment.
Animals↗