Cholinergic modulation of basal and amphetamine-induced dopamine release in rat medial prefrontal cortex and nucleus accumbens

Abstract

Behavioral evidence suggests that muscarinic/cholinergic inhibition of brain dopaminergic activity may be a useful principle for developing novel antipsychotic drugs (APDs). Thus, oxotremorine, a muscarinic agonist, attenuates amphetamine-induced locomotor activity in rodents, an effect also produced by a wide variety of proven APDs, whereas scopolamine, a muscarinic antagonist, has the opposite effect. Since atypical APDs such as clozapine, olanzapine, risperidone, ziprasidone and quetiapine, increase brain acetylcholine as well as dopamine (DA) release in a region-specific manner, their effects on cholinergic and dopaminergic neurotransmission may also contribute to various actions of these drugs. Oxotremorine (0.5–1.5 mg/kg) dose-dependently and preferentially increased DA release in rat medial prefrontal cortex (mPFC), compared to the nucleus accumbens (NAC). However, S-(−)-scopolamine (0.5–1.5 mg/kg) produced similar increases in DA release in the mPFC, but the effect was much less than that of oxotremorine. Whereas a dose of S-(−)-scopolamine of 0.5 mg/kg comparably increased DA release in the mPFC and NAC, 1.5 mg/kg had no effect on DA release in the NAC. Oxotremorine-M (0.5 mg/kg), a M 1/4-preferring agonist, also increased DA release in the mPFC, but not the NAC, an effect completely abolished by telenzepine (3 mg/kg), a M 1/4-preferring antagonist, which by itself had no effect on DA release in either region. Oxotremorine (0.5, but not 1.5, mg/kg) attenuated amphetamine (1 mg/kg)-induced DA release in the NAC, whereas S-(−)-scopolamine did not. Oxotremorine (1.5 mg/kg) and S-(−)-scopolamine (0.5 mg/kg) modestly but significantly potentiated amphetamine (1 mg/kg)-induced DA release in the mPFC. These results suggest that stimulation of muscarinic receptors, in particular M 1/4, as indicated by the effect of oxotremorine-M and telenzepine, may preferentially increase cortical DA release and inhibit amphetamine-induced DA release in the NAC.