Abstract # 124:

Scheduled for Friday, June 22, 2007 05:00 PM-07:00 PM: Session 14 (South Main Hall) Poster Presentation

Effects of Light Intensity on Fecal Cortisol Concentrations in Macaca mulatta

A. M. Dupuy, M. N. Wilkes and M. B. Fontenot
University of Louisiana - New Iberia Research Center, Lafayette, Louisiana, USA
     Previous research suggests that, in rhesus monkeys, self-injurious behavior (SIB) is associated with reduced adrenocortical (AC) secretion. We examined whether exposure to dim versus bright intensity ambient light further alters AC activity. Seventeen adult male rhesus macaques (aged 6-13 yrs) with a history of SIB were divided into two groups, balanced for age and stereotypies, and exposed to either dim (176 – 201 lux) or bright light (1391 - 1475 lux) on a 12:12 h cycle for one month. Following a two-week return to baseline light (563 - 769 lux), each group was exposed to the reverse light condition for an additional month. Morning (1030 – 1200 h) and afternoon (1430 - 1600 h) fecal samples were collected from each animal five times per week and frozen (-30°C) until assayed for cortisol concentration. Results of ANOVA indicated a Light X Order interaction effect on cortisol concentrations [F(1,13)8.44; p<0.01]. Fecal cortisol concentrations decreased only in animals exposed to bright light after initial exposure to dim light [F(1,13)7.57; p<0.05]. Pearson’s r correlation revealed that cortisol concentration was positively correlated with self-biting [r(83)0.30; p<0.01] and neutral behavior [r(83)=0.23; p<0.05] and negatively correlated with pacing [r(83)-0.26; p<0.05]. Contrary to previous findings, our results suggest that rates of self-biting are associated with increased AC activity. No clear relationship between AC activity and light intensity was found.