Increased plasma ACTH responses to stress in nonhandled compared with handled rats require basal levels of corticosterone and are associated with increased levels of ACTH secretagogues in the median eminence

Abstract

Postnatal handling of rat pups is known to alter permanently hypothalamic-pituitary-adrenal (HPA) responses to a wide variety of stressors. As adults, handled (H) and nonhandled (NH) animals also differ in sensitivity to the delayed negative-feedback effects of glucocorticoids on stress-induced HPA activity. However, it is not understood how handling alters neuroendocrine responses to stressful stimuli, and how differences in feedback sensitivity might account for changes in HPA activity both during and following stress. In the present studies, plasma ACTH responses to both restraint and ether stress were significantly greater in NH compared with H animals. Administration of 100 micrograms/kg corticosterone (B) immediately prior to restraint stress significantly decreased subsequent plasma ACTH responses to restraint to the same extent in H and NH animals, suggesting that H and NH animals do not differ in glucocorticoid fast feedback. H and NH animals adrenalectomized (ADX) 5 d prior to testing did not differ in plasma ACTH responses to restraint stress, demonstrating that the differences between the groups are dependent upon the presence of circulating B. However, the handling effect was apparent in ADX animals provided with a low level of B replacement (approximately 5-6 micrograms/dl). B replacement significantly decreased plasma ACTH levels under both basal conditions and in response to restraint stress in H/ADX rats. In contrast, although B replacement also decreased basal ACTH levels in ADX/NH rats, there were no differences in plasma ACTH responses to restraint between NH/ADX and NH/ADX+B animals.(ABSTRACT TRUNCATED AT 250 WORDS)

Manipulations During the Second, but not the First, Week of Life Increase Susceptibility to Cocaine Self-Administration in Female Rats

“…Specifically, handling-induced increases in licking and grooming on the first 10 days of life have been found to be 'protective', resulting in decreased LHPA responsivity and behavioral reactivity to stress in adulthood (Ader, 1969;Hess et al, 1969;Levine, 1967;Meaney and Aitken, 1985;Meaney et al, 1989;Viau et al, 1993). We speculate that in the present study, increased maternal care during the first week of life protected those animals manipulated during this period, regardless of treatment.…”

An Initial, Three-Day-Long Treatment with Alcohol Induces a Long-Lasting Phenomenon of Selective Tolerance in the Activity of the Rat Hypothalamic–Pituitary–Adrenal Axis

“…In this model, increased median eminence levels of V P have been held responsible for the changes in HPA axis activity (Dijken et al, 1993). Finally, there is the well known example of the permanent increase in HPA axis function in rats exposed to maternal deprivation during neonatal development (Stanton et al, 1988;Rosenfeld et al, 1991;Suchecki et al, 1993;Viau et al, 1993), a response in part caused by an upregulation of CRF in nerve terminals (Ladd et al, 1996). It therefore seems that, in the present model, alcohol exerts an influence that is unique in its ability to dampen f urther responses of the HPA axis.…”

Neonatal maternal separation alters stress-induced responses to viscerosomatic nociceptive stimuli in rat

“…Female pups were culled, and standardized litters of either 8 or 10 male pups were randomly assembled for fostering. Rearing conditions have been previously described (11,42,59,73). Briefly, the dams and their litters were then randomly assigned to one of two rearing conditions: 1) handling/maternal separation group, exposed to a 180-min period of daily maternal separation on PND 2-14 inclusive (MS180) or 2) nonhandled comparison group, not exposed to handling or maternal separation (NH).…”