Abstract
Protein kinase B (also known as Akt) signaling regulates dopamine-mediated locomotor behaviors. Here the ability of cocaine to regulate Akt and glycogen synthase kinase 3 (GSK3) was studied. Rats were injected with cocaine or saline in a binge-pattern, which consisted of three daily injections of 15 mg/kg cocaine or 1 mL/kg saline spaced 1 h apart for 1, 3, or 14 days. Amygdala, nucleus accumbens, caudate putamen, and hippocampus tissues were dissected 30 min following the last injection and analyzed for phosphorylated and total Akt and GSK3(alpha and beta) protein levels using western blot analysis. Phosphorylation of Akt on the threonine-308 (Thr308) residue was significantly reduced in the nucleus accumbens and increased in the amygdala after 1 day of cocaine treatment; however, these effects were not accompanied by a significant decrease in GSK3 phosphorylation. Phosphorylation of Akt and GSK3 was significantly reduced after 14 days of cocaine administration, an effect that was only observed in the amygdala. Cocaine did not alter Akt or GSK3 phosphorylation in the caudate putamen or hippocampus. The findings in nucleus accumbens may reflect dopaminergic motor-stimulant activity caused by acute cocaine, whereas the effects in amygdala may be associated with changes in emotional state that occur after acute and chronic cocaine exposure.