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Student Prize Award Abstract
2002 Oral Paper Honorable Mention

DIFFERENCES IN PERSONALITY AND NEUROENDOCRINE RESPONSES TO PHARMALOGICAL TREATMENT IN ADULT MALE RHESUS MACAQUES (MACACA MULATTA)

J. D. Ruys; J. P. Capitanio and S. P. Mendoza
University of California, Davis, Psychology Department, One Shields Avenue, University of California, Davis, CA, 95616, USA

Research has suggested that personality is related to central monoamine function. A multidimensional model of personality was used to relate personality to the neuroendocrine response to drugs that alter central monoaminergic activity. Adjective ratings of 88 rhesus macaques were factor analyzed and a 4-factor solution was found. A subset of animals (N=36) was selected to represent the extremes on the dimension of Sociability and to exclude animals showing extreme scores for the dimensions Confidence, Irritability, and Equability. On each of 4 test days subjects were injected with fenfluramine (4 mg/kg), haloperidol (0.1 mg/kg), clonidine (0.02 mg/kg), or saline. Blood samples were collected before and 30, 60, 90 and 120 minutes following injection for assay of plasma prolactin. ANOVA revealed that fenfluramine, a serotonergic agonist, and haloperidol, a dopaminergic antagonist, significantly increased prolactin. Also, clonidine, a noradrenergic agonist, significantly decreased prolactin and saline produced no change in prolactin. To obtain a single measure of the prolactin response to each drug, the area under the curve was estimated for each subject. A moderate positive correlation was found between Confidence and the prolactin responses to haloperidol and fenfluramine. ANOVA indicated that high Sociable subjects showed higher prolactin levels following clonidine treatment than low Sociable subjects. The results show that low Sociable animals are more sensitive to noradrenergic inhibition of prolactin and that monoamine activity is related to personality.


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