Nitric oxide in the extinction memory formation of lithium-induced conditioned taste aversion learning

This study was conducted to examine the tentative implications of nicotinic receptor activation and nitric oxide release in the acquisition and extinction of lithium-induced conditioned taste aversion learning. Rats were pretreated with nitric oxide synthase inhibitor N“-nitro-L- arginine methyl ester or nicotinic acetylcholine receptor antagonist mecamylamine either at the conditioning (sucrose-lithium pairing) or at each drinking test. The N“-nitro-L-arginine methyl ester prior to lithium chloride (unconditioned stimulus) did not affect the lithium-induced formation of conditioned taste aversion; however, N“-nitro-L-arginine methyl ester at a dose of 30 mg kg-1 prior to each sucrose (conditioned stimulus) drinking test significantly suppressed sucrose intake. Mecamylamine prior to lithium did not affect the acquisition of lithium-induced conditioned taste aversion, but at high dose (2 mg kg-1) it facilitated the extinction. Mecamylamine (2 mg kg-1) prior to each sucrose test delayed the extinction of lithium-induced conditioned taste aversion memory. Results suggest that nitric oxide may be implicated in the extinction memory formation of lithium-induced conditioned taste aversion, possibly in relation with the activation of nicotinic acetylcholine receptor.