Inhibition of the LH Surge by Restraint Stress in Cyclic Rats: Studies on the Role of GABAA and GABAB Receptors

There is evidence that stress can alter the activity in the brain of gamma-aminobutyricacid (GABA), a neurotransmitter that has been implicated in the regulation of LH secretion. In the present study the role of GABA in the restraint stress-induced inhibition of the LH surge was investigated in the intact cyclic rat. Intracerebroventricular (icv) administration of the GABAA receptor agonist muscimol (0.1, 0.5 or 1 μg) 5 min before the presumed onset of the pro-oestrous LH surge (at 0900 h) caused a dose dependent suppression of the surge. A single dose of the GABAB receptor agonist baclofen (1 μg; icv) injected at 0855 h postponed the onset of the LH surge, and repeated injections at 0855 and 1130 h suppressed the surge. These data indicate that GABA-ergic activity in the brain can inhibit the LH surge in the cyclic rat via GABAA and GABAB receptors. Pro-oestrous rats were subjected to 5 hrs of restraint starting at 0855 h. Pretreatment with the GABAA receptor antagonist bicuculine (1 μg; icv) at 0840, 0940 and 1040 h or pretreatment with the GABAB receptor antagonist phaclofen (10 μg; icv) at 0840 h were ineffective in preventing the restraint-induced inhibition of the LH surge. The results suggest that GABAA and GABAB receptors are not involved in the inhibitory effect of restraint stress on the LH surge.     

Social competence is reduced in socially deprived rhesus monkeys (Macaca mulatta)

Rhesus monkeys deprived for some period from their mother have often served as a model for the effect of adverse rearing conditions on social competence in humans. Social competence is the capacity to react in a species-specific way to social interactions. The current study assesses whether early deprivation from peers also affects the rates of behavior and social competence in rhesus monkeys. This was studied in groups of rhesus monkeys with different rearing conditions: subadult females that were mother-only reared during their first year of life and subsequently housed with peers were compared with subadult females from five naturalistic social groups. Socially deprived monkeys showed higher rates of submission and stereotypic behaviors than socially reared individuals. In addition, they show socially incompetent behavior, since they react with agonistic behavior to nonthreatening social situations. The results suggest that this socially incompetent behavior is rooted in a general feeling of anxiety toward group companions. The authors hypothesize that anxiety negatively affects social information processing, which results in socially incompetent behavior.