Behavioral effects of oral yohimbine in differentially reared nonhuman primates

Eight unrestrained macaques were observed for 2 hours following either two oral doses of yohimbine (0.2 mg/kg and 2.0 mg/kg) or placebo administration. Four of the subjects were normally reared and four subjects had early maternal and social deprivation. In the normal subjects, yohimbine, at both doses, produced increased tension and enervation and decreased species-typical "normal" behaviors. In deprivation-reared subjects, low-dose yohimbine produced reductions in tension and enervation, and increases in "normal" behaviors. High doses of yohimbine diminished behavioral score differences between groups. The prominent increases in enervation observed in normally reared subjects suggests that yohimbine is not unequivocally anxiogenic. Moreover, early social deprivation may alter the pattern of response to yohimbine, perhaps as a result of aberrant neurodevelopment. This study reflects the role of experiential factors in determining patterns of affective response to putative anxiogenic agents.