Abstract # 3228 Poster # 86:

Scheduled for Saturday, September 17, 2011 07:00 PM-09:00 PM: Session 14 (Salon G (Sixth Floor)) Poster Presentation


HORMONAL RESPONSE TO A FENTANYL CHALLENGE DIFFERS DEPENDING ON BITING FREQUENCY IN RHESUS MONKEYS (MACACA MULATTA) WITH SELF-INJURIOUS BEHAVIOR

B. J. Kelly1, M. A. Novak1,2, K. M. Stonemetz1, C. A. Major1 and J. S. Meyer2
1Harvard Medical School, One Pine Hill Drive, NEPRC, Southborough, MA 01772, USA, 2Psychology Department, University of Massachusetts, Amherst, MA 01003
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We previously reported that monkeys displaying SIB preferentially bit acupressure points and had reduced levels of plasma beta-endorphin as compared to non-SIB controls. These data support an endogenous opioid self-administration hypothesis in which SIB leads to an increase in beta-endorphin. In the present study we examined mu-opioid receptor (MOR) sensitivity in male rhesus monkeys [nSIB=14; ncontrol=7] by measuring the prolactin and cortisol responses to intra-muscular injections of the selective MOR agonist fentanyl in a crossover design (vehicle, 0.01 mg/kg, 0.03 mg/kg). Additionally, behavior was recorded following each treatment. Behaviorally, all monkeys showed a dose-dependent increase in scratching [ANOVA: F(2,38)=21.91, p<0.001] and there was a cessation of biting when the monkeys received the drug as compared to the saline treatment [ANOVA: F(2,38)=4.07, p<0.05]. Hormonally, monkeys classified as high-frequency biters showed a blunted prolactin response as compared to low-frequency biters [t(12)=-2.48, p<0.05] at the highest dose. With regards to cortisol, there was a dose by biting-frequency interaction manifested in a marginally blunted response at the highest dose of fentanyl in low-frequency biters as compared to control monkeys [t(11)=1.93, p<0.08]. Interestingly, prolactin and cortisol response did not follow the same patterns for high- and low-frequency biters; however, different populations of MOR are involved in each system indicating the possibility of differential effects of endogenous opioids in relation to biting status. Supported by NCRR grants #RR011122 and #RR00168.