Time course of plasticity-related alterations following the first exposure to amphetamine in juvenile rats

Abstract

In vulnerable consumers, the first drug exposure induces various neurobehavioral adaptations that may represent the starting point toward addiction. Elucidating the neuroplastic mechanisms underlying that first rewarding experience would contribute to understanding the transition from recreational to compulsive drug use. In a preclinical model with juvenile rats, we analyzed the time-dependent fluctuations in the expression of neuroplasticity-related genes like the brain-derived neurotrophic factor (BDNF), its tropomyosin receptor kinase B (TrkB), the cAMP response element-binding protein (CREB), the microRNA-132, the Rho GTPase-activating protein 32 (p250GAP), the corticotropin-releasing factor (CRF), and the neurotransmitters contents in the nucleus accumbens (NAc) and the dorsal striatum (DS) 45, 90, and 180 min after an amphetamine (AMPH) injection. As expected, AMPH altered the concentration of norepinephrine, dopamine, DOPAC, and serotonin in a region- and time-dependent manner. Regarding gene expression, AMPH at 45 min upregulated BDNF and primiR-132 expression in NAc and downregulated TrkB expression in DS. At 90 min, AMPH upregulated TrkB, CREB, p250GAP, and primiR-132 expression in NAc and BDNF, primiR-132, and CRF in DS. At 180 min, only BNDF in NAc continued to be upregulated by AMPH. Based on the levels of AMPH-induced hyperactivity, we classified the rats as low and high AMPH responders. High AMPH responders characterized by overexpressing BDNF, CREB, p250GAP, and CRF in NAc and by showing lower levels of dopamine and serotonin metabolites and turnovers in both regions. Our findings demonstrated that a single AMPH administration is enough to induce neuroplastic adaptations, especially in the NAc of prone rats.

Keywords: Dopamine; Drug dependence; Locomotion; Plasticity; Psychostimulant drugs; Reward.