Effects of co-administration of ketamine and ethanol on the dopamine system via the cortex-striatum circuitry

Ketamine and ethanol are increasingly being used together as recreational drugs in rave parties. Their effects on the dopamine (DA) system remain largely unknown. This study aimed to investigate the effects of consuming two different concentrations of ketamine with and without alcohol on the DA system. We employed the conditioned place preference (CPP) paradigm to evaluate the rewarding effects of the combined administration of two different doses of ketamine (30mg/kg and 60mg/kg) with ethanol (0.3156g/kg). We evaluated the effects of the combined drug treatment on the transcriptional output of tyrosine hydroxylase (TH), dopa decarboxylase (DDC), synaptosomal-associated protein 25 (SNAP25), and vesicular monoamine transporter 2 (VMAT2) as well as protein expression level of brain-derived neurotrophic factor (BDNF) in rat prefrontal cortex (PFC) and striatum. We found that rats exhibited a dose-dependent, drug-paired, place preference to ketamine and ethanol associated with an elevated DA level in the striatum but not in the PFC. Moreover, treatment involving low- or high-dose ketamine with or without ethanol caused a differential regulatory response in the mRNA levels of the four DA metabolism genes and the cellular protein abundance of BDNF via the cortex-striatum circuitry. This study investigated the molecular mechanisms that occur following the combined administration of ketamine and ethanol in the DA system, which could potentially lead to alterations in the mental status and behavior of ketamine/ethanol users. Our findings may aid the development of therapeutic strategies for substance abuse patients.