Opiate modulation of separation-induced distress in non-human primates.
Infant rhesus monkeys respond to separation from their mothers with a dramatic increase in vocalizations and activation of autonomic and pituitary-adrenal systems. Using the mother-infant separation paradigm in rhesus monkeys, we focused on the role of opiate systems in modulating the behavioral and neuroendocrine consequences of a brief, naturally occurring stressor. In the first experiment, morphine 0.1 mg/kg significantly decreased separation-induced vocalizations without affecting activity levels. In the second experiment, naloxone 1.0 mg/kg increased distress vocalizations but lower doses had no effect. In the third experiment we blocked the effect of morphine 0.1 mg/kg with naloxone 0.1 mg/kg, a dose of naloxone that had no intrinsic effects of its own. This suggests that the reduction of separation-induced vocalizations by morphine is mediated by opiate receptors. The last experiment demonstrated that separation-induced increases in pituitary-adrenal hormones can also be modulated by opiate agonists and antagonists. These findings are consistent with work in non-primate species and support the hypothesis that opiate receptors are specifically involved in mediating separation-induced vocalizations and pituitary-adrenal activation in primates.
Kalin
N H
NH
Department of Psychiatry, University of Wisconsin-Madison.
Shelton
S E
SE
Barksdale
C M
CM
D000818:Animals; D001010:Anxiety, Separation; D004723:Endorphins / Q000502:physiology*; D005260:Female; D008253:Macaca mulatta; D008297:Male; D009020:Morphine / Q000494:pharmacology*; D009270:Naloxone / Q000494:pharmacology*; D014828:Vocalization, Animal / Q000187:drug effects
D004723:Endorphins; D009270:Naloxone; D009020:Morphine