Effect of acute cocaine administration on the cholinergic enzyme levels of specific brain regions in the rat.

Adult male Sprague-Dawley rats weighing between 170 and 204 g and maintained under controlled lighting and temperature conditions were used in this experiment. One group of animals was treated with 30 mg/kg of cocaine hydrochloride and the other group with saline. Rats were decapitated 20 min after cocaine injection and their brains were removed and the different regions including the medulla, pons, midbrain, cerebellum, hypothalamus, thalamus, hippocampus, and the cortex were dissected. All brain regions were assayed for choline acetyltransferase (ChAT) and acetylcholinesterase (AChE) activities. The results obtained indicated that the administration of cocaine was associated with significant increases (p less than 0.01) in AChE activity in the medulla, pons, midbrain, hypothalamus, thalamus, and also in the hippocampus (p less than 0.05). A significant decrease in ChAT activity was found in the pons (p less than 0.01), hypothalamus, and thalamus (p less than 0.05), while a significant increase in ChAT activity was found in the cortex (p less than 0.05). The results suggest that the changes in general activity followed by stereotypic behavior may be related to the changes in the levels of cholinergic enzymes in specific brain regions.