Overview Type 1 and II personality correlates of excessive alcohol consumption, such as differential social adjustment, risk taking, violence, as well as differential survival, are studied in free-ranging field settings, where subjects engage in species-typical behaviors with minimal human interference. This naturalistic population is large, with over 5000 rhesus monkeys, offering a unique opportunity to investigate numerous behavioral and physiological phenotypes. These research subjects are also studied developmentally using a longitudinal design. Real world outcomes can be studied in these subjects, placing the phenotypes in the natural environments from which the traits evolved. I. Staff and Contract Changes There was a significant change in this area of research this year. Our staff scientist who supervised the program purchased the company, resulting in the replacement of our research staff, including a new senior scientist, Dr. Sue Howell. While this has tempered our pace, several findings have emerged. II. Analyses of Genotype Effects on Type II Personality Traits in a Large Population with Unrestrained Breeding Over 200 male and female subjects have been observed and studied longitudinally since 1993 with the result being an impressive body of meticulously recorded behavioral data. Of particular relevance are measures of impulsivity and aggression, primary traits of Type II alcoholics. Most recently, Drs. Newman and Howell tested the hypothesis that MAOA, but not serotonin transporter genotype influences age of first migration and acquired dominance status in males. This was based on previous observations that younger male migrants tended to be impulsive and violent, consequently suffering increased mortality. Based on the behavioral data collected from our South Carolina adolescent male subjects, Drs. Newman and Howell showed that MAOA, but not serotonin transporter, genotype interacts with age of first migration to influence interindividual differences in later acquired dominance status. Males that emigrated later had more difficulty acquiring high rank, and consequently achieved lower acquired dominance status compared to earlier migrants, but having the low activity MAOA allele exaggerated the effect. That is, early migrants with the low activity allele attained the highest acquired dominance, and later migrants with the low activity allele attained the lowest acquired dominance. Males with the high activity allele were intermediate in acquired dominance. III. Studies of Alcohol Intake in monkeys from the free-ranging environment To date our naturalistic studies of subjects with low concentrations of CSF 5-HIAA have focused the behavioral phenotypes of Type II alcoholism-like behaviors without empirical demonstration that they would consume alcohol. This year for the first time we were able to test whether these subjects that are reared in natural settings would freely consume alcohol. While preliminary in scope, four free-ranging male rhesus macaques were trapped and held in single cages for 10 days. They were provided free-access to our standard aspartame sweetened 8.4% ethanol solution for one hour on all ten consecutive days. One subject drank well above laboratory averages seen in Poolesville, drinking as much of the alcohol solution as we could readily provide over the one hour test session. When his remaining alcohol was removed at the end of the test period, he became considerably aggressive. His inebriation was evident, swaying, holding onto the cage to maintain balance, showing stupor and a sleep state near the end of each test period. While the other subjects drank most of their alcohol during the first 15-minutes, this subject drank continuously during the entire hour period. This initial result suggests that at least one of our subjects had a general affinity for high alcohol intake and suggests that when an alcohol solution is palatable, about one in four subjects reared in natural settings readily consumes it in quantities that produce behaviors indicative of intoxication-related pharmacological effects. Among the other subjects, very little alcohol was consumed by any of the subjects during the first three days following capture. By the fourth day, all of the subjects consumed sufficient alcohol to experience a pharmacological effect, thereafter showing a stable or increased rate of consumption across the remaining days. This average rate was similar to that seen in the laboratories in our mother-reared subjects, which in the laboratory produces modest blood alcohol levels of about 0.05%. IV. Comparison of Alcohol Intake in 2 Different Species of Macaques Compared with other macaque species, cynomolgus macaques show high levels of anxiety and fear, suggesting that they might be more predisposed to consume high amounts of alcohol to mediate their anxious temperament. Consistent with this hypothesis, Dr. Grant and her colleagues at Wake Forest have reported consistent high alcohol intake in this species that is closely related to the rhesus, although her induction procedure differs relative to that employed in our laboratory. To test whether the cynomolgus subjects consume more alcohol than the rhesus, we initiated a study using our common paradigm to compare age and sex matched rhesus and cynomolgus macaques for alcohol intake. With about half of our subjects tested, results indicate that both cynomolgus and rhesus macaques consume modest amounts of alcohol, although cynomolgus macaques drank more than the rhesus macaques. We began a collaboration with this Dr. Grant and her group to test whether she gets similar results using her induction procedure. One other interesting result from this project is that rates of consumption were ascertained for 60 days, but average interindividual consumption over the last 50 days are highly stable and can be predicted using the first 10 days and there was no difference in average amounts consumed over the first 10 days when compared to the remaining 50 days. III. Impaired CNS Hemispheric Specialization A number of studies have shown that alcoholics and alcohol abusers are more likely to be left handed and to show abnormalities of brain lateralization. In adult rhesus there is a general bias to left-handedness, but with subjects showing interindividual differences in the strength of the preference. An infant monkeys nipple side bias has been shown to predict long-term right/left handedness. To test the developmental process of this bias, we examined right/left nipple preference in the free-ranging rhesus macaque infants. Each subject was observed for 30 minutes every two weeks for the first two months of life and for 30 minutes once a month thereafter until the infant reached one year of age. Overall, there was no difference in nipple side preference. However, the infants did show a strong and consistent individual preference for nipple side and this did not appear to correspond to infant sex. Across ages, there was a weak positive correlation (r = .260) between side preference in infants at 48 hours of age and 1 to 2 months of age. There were strong correlations between the repeated measurements thereafter, with interindividual differences showing stability in excess of r= .70 between the later months. These results suggest that nipple preference may not be formed in the initial hours after birth but is probably fixed in the first month of life and is consistent thereafter.
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