Facilitation of conditioned taste aversion learning by systemic amphetamine:: role of nucleus accumbens shell dopamine D1 receptors

The role of dopamine (DA) in associative learning was studied in a conditioned taste aversion (CTA) paradigm with sucrose as the conditioned stimulus (CS) and intraperitoneal lithium chloride as the unconditioned stimulus (US). Drinking on trial of a 15% sucrose solution followed 1 h later by lithium chloride (20 or 40 mg/kg i.p.) resulted in mild CTA, as shown by reduction of drinking of the sucrose solution 24 h later. Amphetamine sulphate (0.125, 0.25, 0.50 and 1.0 mg/kg s.c.), administered on trial 5 min after sucrose drinking, facilitated CTA with maximal effects at 0.25 mg/kg s.c. Amphetamine given in the absence of lithium or 45 min after sucrose did not affect sucrose intake. The DA D-1 receptor antagonist SCH 39166, administered before amphetamine either systemically (0.0125 mg/kg s.c.) or in the nucleus accumbens shell (NAc; 0.025 mug/muL on each side) prevented the facilitation of CTA induced by amphetamine. It is concluded that amphetamine facilitates CTA learning by strengthening the consolidation of gustatory short-term memory via D-1 receptors of the NAc shell.