Depressive-like behavioral response of adult male rhesus monkeys during routine animal husbandry procedure

Abstract

Social isolation is a major risk factor for the development of depressive illness; yet, no practical nonhuman primate model is available for studying processes involved in this effect. In a first study, we noted that adult male rhesus monkeys housed individually indoors occasionally exhibited a hunched, depressive-like posture. Therefore, Study 2 investigated the occurrence of a hunched posture by adult males brought from outdoor social groups to indoor individual housing. We also scored two other behaviors—lying on the substrate and day time sleeping—that convey an impression of depression. During the first week of observation following individual housing, 18 of 26 adult males exhibited the hunched posture and 21 of 26 displayed at least one depressive-like behavior. Over 2 weeks, 23 of 26 males showed depressive-like behavior during a total of only 20 min observation. Further, the behavior during the first week was positively related to the level of initial response to a maternal separation procedure experienced in infancy. In Study 3, more than half of 23 adult males of a new sample displayed depressive-like behavior during 10 min of observation each of Weeks 7–14 of individual housing. The surprisingly high frequency of depressive-like behavior in Studies 2 and 3 may have been due to recording behavior via camera with no human in the room to elicit competing responses. These results suggest that a common animal husbandry procedure might provide a practical means for examining effects of social isolation on depression-related endpoints in a nonhuman primate. The findings also suggest that trait-like differences in emotional responsiveness during separation in infancy may predict differences in responsiveness during social isolation in adulthood.

Depressive-like behavior, its sensitization, social buffering, and altered cytokine responses in rhesus macaques moved from outdoor social groups to indoor housing

“…The results of this prospective study confirm our earlier observation from retrospective data that adult male rhesus monkeys brought from large outdoor social groups to socially restricted, indoor housing frequently exhibit a depressive-like hunched posture that is very rarely observed in the outdoor social groups (Hennessy et al, 2014). All monkeys of both conditions brought indoors displayed the hunched posture in each round.…”

“…Males were selected for the current experiment because retrospective observations from our previous study suggested that males may be more-sensitive than females to rehousing indoors (Hennessy et al, 2014). Nonetheless, how males and females would differ under the conditions tested here remains unknown and certainly warrants future investigation.…”

“…Behaviors (definitions in Table 1) included the duration in s that the animals exhibited the hunched posture, lying down, sleeping, and activity, as well as the frequency of environmental exploration. As in our earlier paper (Hennessy et al, 2014), we also calculated an index of “total depressive-like responding” by summing the durations of the hunched posture, lying down, and sleeping. However, since analysis of this index yielded a pattern of results identical to that for the hunched posture, the index will not be considered further.…”

“…We recently noted that adult male rhesus monkeys brought from large outdoor social groups to indoor housing exhibited a hunched, depressive-like posture (Hennessy, McCowan, Jiang, & Capitanio, 2014). Records of routine observations by Behavioral Management Staff at the California National Primate Research Center (CNPRC) suggested a prevalence of roughly 7% for all animals housed indoors, with adult males apparently most affected.…”

Sertraline inhibits increases in body fat and carbohydrate dysregulation in adult female cynomolgus monkeys

“…Laboratory-housed nonhuman primates may exhibit behavioral depression (Camus et al, 2014; Hennessy et al, 2014; Shively et al, 1997; Shively et al, 2009; Shively et al, 2008; Shively and Willard, 2012) which resembles human depression in physiological, neurobiological, and behavioral characteristics including reduced body mass, hypothalamic-pituitary-adrenal axis perturbations, autonomic dysfunction, increased cardiovascular disease risk, reduced hippocampal volume, altered serotonergic function, decreased activity levels, and increased mortality (Shively and Willard, 2012; Willard and Shively, 2012). Physiological and neurobiological characteristics of monkeys that exhibit behavioral depression have been well characterized (Shively and Willard, 2012) and include dyslipidemia and exacerbated coronary atherosclerosis (Shively et al, 2009; Shively et al, 2008; Shively et al, 2005).…”