aversive actions [47]–[50]. Animal research suggests possible mechanisms for this effect related to persistent changes in brain structure and function. For instance, significantly greater high affinity nicotinic receptor binding is observed in the midbrain and striatum of adolescent versus adult onset nicotine-self-administering rats [51], indicating receptor up-regulation. Also, nicotine exerts greater differential mRNA expression effects on α5, α6 and β2 nAChR transcripts and on genes that influence neuroplasticity (e.g., arc) when it is administered to adolescent, as opposed to adult rats [25],[52].
