Effects of cocaine on y-aminobutyrate, glutamate and aspartate levels in rat nucleus accumbens and hippocampus

Abstract

The acute and chronic effects of cocaine on y-aminobutyrate (GABA), aspartate and glutamate levels both in nucleus accumbens and hippocampus were investigated. Doses of cocaine were administered intraperitoneally to groups of rats at levels to produce acute and chronic physiological responses. The acute treatment consisted of a dose of 30 mg/kg. The chronic treatment was initiated with a dose of 30 mg/kg and then increased 5 mg/kg at Cday iniervals up to 20 days. The control groups were treated with the corresponding volume of saline solution with the same route of administration and at the same times. Thirty minutes after the acute dose and 24 hours after the last dose in the chronic group, the animals were decapitated and the brain quickly removed and placed in saline solution at O OG for 10 minutes. Control groups were treated identically. GABA, aspartate and glutamate levels were measured by enzymatic assays with the aid of a spedtrophotometer. A significant increase of aspartate and glutamate was recorded in the nucleus accumbens and hippocampus after acute or chronic administration of cocaine. The chronic treatment induced significant decrease of GABA levels in both areas. These data support the hypothesis that cocaine produces its excitatory effects possibly through an increase of glutaaspartatergic activity andlor a decrease of GABAergic activity in the nucleus accumbens and hippocampus.