Chemogenetic activation of the perirhinal cortex reverses methamphetamine-induced memory deficits and reduces relapse

Prolonged use of methamphetamine (meth) has been associated with episodic memory deficits in humans, and preclinical rat models of meth self-administration indicate the memory deficits are a consequence of meth use. Others have suggested that the meth-induced memory deficits may promote a cyclical pattern of drug use, abstinence, and relapse, although preclinical evidence for this relationship is somewhat lacking. The memory deficits in preclinical models manifest as a loss of novel object recognition (NOR) memory. These deficits occur one to two weeks after cessation of meth use and involve the perirhinal cortex, a parahippocampal region essential to NOR memory. We hypothesized that a loss of perirhinal cortex function contributes to both the NOR memory deficits and increased vulnerability to relapse in a novel-cue reinstatement model. To test this, we attempted to restore NOR memory in meth rats using an excitatory Gq-DREADD in perirhinal neurons. Activation of these neurons not only reversed the meth-induced deficit in NOR memory, but also restored novelty salience in a novel-cue reinstatement model. Thus, perirhinal cortex functionality contributes to both memory deficits in relapse in a long-access model of meth self-administration in rats, and chemogenetic restoration of perirhinal function restores memory and reduces relapse.