Persistent expression of methamphetamine-induced CTA in periadolescent rats

It is well documented that the transition from periadolescence to adulthood produces profound changes in motivated behavior, and furthermore, attenuates the aversive experience of abused drugs. Little is known, however, about adolescent memory for the conditioned aversive effects of abused drugs following retention intervals that span this developmental transition. The present experiment investigated methamphetamine-induced conditioned taste aversion (CTA) in periadolescent rats to determine if the magnitude of conditioning was altered following retention intervals that extend to adulthood. Rats consumed saccharin (0.1%, w/v) and were immediately injected with saline or methamphetamine (3.0 mg/kg) either once (PND 40) or three times (PND 38–40), and memory was assessed one or 50 days later on post natal days 41 or 90, respectively. Rats exhibited robust methamphetamine-induced CTA one and 50 days after conditioning, and the strength of responding did not change as a function of retention interval, regardless if animals were trained with one or three saccharin–methamphetamine pairings. These findings indicate that the expression of memory for the aversive effects of methamphetamine was resistant to degradation throughout the developmental period of periadolescence to adulthood.

Research Highlights►Periadolescent rats acquired methamphetamine-induced CTA following one or three saccharin (0.1%, w/v)–methamphetamine (3.0 mg/kg; sc) pairings. ►Retention for methamphetamine-induced CTA was observed one and 50 days after conditioning, and the expression of aversive conditioning was not altered following the 50-day retention interval. ►The maturational changes that occur between periadolescence and adulthood did not alter the expression for methamphetamine conditioned avoidance behavior.