In yet another possible gender difference, a Penn State graduate student has found that cocaine may affect a man's brain differently than a woman's.

Melloni Cook, a Ph.D. student in biobehavorial health, is currently conducting research on the effects of cocaine in the brain. Cook used two different inbred strains of mice for her research.

A strain of mice is a specially bred group of mice that is genetically similar. Using a DBA strain and a C strain of mice, Cook examined cocaine-induced changes in the activity of a neurotransmitter called dopamine.

Research has shown that cocaine causes dopamine to increase in the left synapse, which gives the user a desired pleasurable feeling. To look at the actual effects of cocaine on four separate regions of the brain, Cook injected it into the two strains of mice.

In the DBA strain, Cook said there was no difference in reaction. But in the C strain, male and female mice reacted differently to the cocaine.

"In the male C-strain mice, the dopamine utilization level dropped, and in the female mice the level rose," she said.

The dopamine utilization-level drop in the male C-strain mice may suggest a decrease in the amount of pleasure the drug gives for men. But Byron C. Jones, associate professor of biobehavioral health, said the results are still preliminary.

"An initial theory may be too simple," Jones said.

Cook's research is an offshoot of a larger study, "Chromosome Location of Genes Affecting Cocaine Action," funded by the National Institute on Drug Abuse.

Jones, Cook's adviser, is a co-researcher along with V. Gene Erwin, co-director of the Alcohol Research Center at the University of Colorado Health Sciences Center School of Pharmacy. The primary researcher of the study is Gerald E. McClearn, Evan Pugh professor of Health and Human Development.

Jones said the main goal of the study is to develop an animal model to help understand individual differences in cocaine sensitivity. The on-going research is difficult because it is hard to examine the genetic factors that influence drug seeking.

"You can't ask a mouse induced with cocaine how it feels," Jones said.

Meanwhile, Cook will be continuing her research on sex differences and the effects of cocaine. After receiving Cook's findings, the NIDA has agreed to fund Cook's dissertation research.