α-Pinene Attenuates Methamphetamine-Induced Conditioned Place Preference in C57BL/6 Mice

Methamphetamine (METH) is a powerful neurotoxic psychostimulant affecting dopamine transporter (DAT) activity and leading to continuous excess extracellular dopamine levels. Despite recent advances in the knowledge on neurobiological mechanisms underlying METH abuse, there are few effective pharmacotherapies to prevent METH abuse leading to brain damage and neuropsychiatric deficits. α-Pinene (APN) is one of the major monoterpenes derived from pine essential oils and has diverse biological properties including anti-nociceptive, anti-anxiolytic, antioxidant, and anti-inflammatory actions. In the present study, we investigated the therapeutic potential of APN in a METH abuse mice model. METH (1 mg/kg/day, i.p.) was injected into C57BL/6 mice for four alternative days, and a conditioned place preference (CPP) test was performed. The METH-administered group exhibited increased sensitivity to place preference and significantly decreased levels of dopamine-related markers such as dopamine 2 receptor (D2R) and tyrosine hydroxylase in the striatum of the mice. Moreover, METH caused apoptotic cell death by induction of inflammation and oxidative stress. Conversely, APN treatment (3 and 10 mg/kg, i.p.) significantly reduced METH-mediated place preference and restored the levels of D2R and tyrosine hydroxylase in the striatum. APN increased the anti-apoptotic Bcl-2 to pro-apoptotic Bax ratio and decreased the expression of inflammatory protein Iba-1. METH-induced lipid peroxidation was effectively mitigated by APN by up-regulation of antioxidant enzymes such as manganese-superoxide dismutase and glutamylcysteine synthase via activation of nuclear factor-erythroid 2-related factor 2. These results suggest that APN may have protective potential and be considered as a promising therapeutic agent for METH-induced drug addiction and neuronal damage.