Office: 210-567-8205
Email: mcginnism@uthscsa.edu

My current research focus is to investigate the effects of anabolic-androgenic steroids (AAS) on brain and behavior. Anabolic steroid use is on the rise, especially in adolescent males. Since increases in androgen levels are known to prodoundly influence the nervous system during adolescence, chronic exposure to high levels of androgens during pubertal development may produce enduring changes in brain maturation and subsequent behavioral expression. Using pubertal rats as the animal model, our laboratory has shown that exposure to AAS increases agression, and that this effect can be permanent. We demonstrated that AAS-induced aggression is not indiscriminate (i.e. 'roid rage). Current projects are aimed at determining the specific factors and conditions that predict whether or not aggression will be displayed in pubertal male rats exposed to AAS. For example, reports from the human literature suggested that males taking AAS were violent toward women. Using our animal model, we identified factors that contribute to aggression toward females by AAS-exposed males. We have also shown that males exposed to AAS are more likely to respond aggressively to provocation. Our laboratory has devised novel behavioral test procedures to identify the mechanisms underlying the increased aggression in response to provocation in male rats exposed to AAS. These data will be correlated with hormonal and neurochemical measures in brain.

Another area of active investigation is the role of serotonin in mediating increased aggression in AAS-treated males. Low serotonin has been associated with enhanced aggression and there is some evidence that testosterone lowers serotonin. Thus we are measuring brain serotonin in areas known to contain serotonin and/or androgen receptors. Specifically, we are using PCPA to lower serotonin and HPLC to measure 5HT and its major metabolites in frontal cortex, striatum, hippocampus, hypothalamus and brainstem. One intriguing finding thus far, is that males with low serotonin are very aggressive when exposed to AAS during puberty. This suggests that low serotonin may be a predictive factor in determining whether AAS use will potentiate aggression.

We are also interested in the effects of adolescent AAS exposure on brain development. Using DiI to label neurons and confocal microscopy combined with image analysis to quantify dendritic spines, we recently demonstrated that pubertal AAS exposure increases dendritic spine density in the amygdala and the hippocampus. Moreover, the increased spine density in the hippocampus remained even after AAS withdrawal. This is the first demonstration of a neuroanatomical change in the brain due to AAS exposure and supports the hypothesis that pubertal AAS exposure can affect brain maturation. We are currently investigating the effects of AAS on spine density in other brain regions.

Selected Publications

Cunningham RL, Claiborne BJ, McGinnis MY. Pubertal exposure to anabolic androgenic steroids increases spine densities on neurons in the limbic system of male rats. Neuroscience, 2007 (in press).

McGinnis MY, Lumia AR, Tetel MJ, Molenda-Figueira HA, Possidente B. Effects of anabolic androgenic steroids on the development and expression of running wheel activity and circadian rhythms in male rats. Physiol Behav., 2007 (in press)

Keleta YB, Lumia AR, Anderson GM, McGinnis MY. Behavioral effects of pubertal anabolic androgenic steroid exposure in male rats with low serotonin. Brain Res, 1132:129-138, 2007.

Cunningham RL, McGinnis MY. Factors influencing aggression toward females by male rats exposed to anabolic androgenic steroids during puberty. Horm Behav, 51:135-141, 2006.

Wesson DW, McGinnis MY. Stacking anabolic androgenic steroids (AAS) during puberty in rats: A neuroendocrine and behavioral assessment. Pharmacol Biochem Behav, 83:410-419, 2006.

Cunningham RL, McGinnis MY. Physical provocation of pubertal anabolic androgenic steroid exposed male rats elicits aggression towards females. Horm Behav, 50:410-416, 2006.

Farrell SF, McGinnis MY. Long-term effects of pubertal anabolic-androgenic steroid exposure on reproductive and aggressive behaviors in male rats. Horm Behav, 46:193-203, 2004.

McGinnis MY. Anabolic androgenic steroids and aggression: Studies using animal models. In: Scientific Approaches to Youth Violence Prevention. New York Academy of Sciences, pg. 399-415, 2004.

Farrell SF, McGinnis MY. Effects of pubertal anabolic-androgenic steroid (AAS) administration on reproductive and aggressive behaviors in male rats. Behav Neurosci, 117(5):904-911, 2003.

McGinnis MY, Vakulenko M. Characterization of 50-kHz ultrasonic vocalizations in male and female rats. Physiol Behav, 80:81-88, 2003.