Effects of α‐pyrrolidino‐phenone cathinone stimulants on brain reward function in female rats

Abstract

Synthetic cathinones, commonly known as “bath salts”, are potent reinforcers and produce stimulant-like effects. In these studies, the intracranial self-stimulation (ICSS) procedure was used to investigate the facilitation of brain reward functioning, as indexed by reduction in reward thresholds, in female rats following exposure to α-PPP, α-PVP or α-PHP. Female Wistar rats were prepared with unilateral electrodes aimed at the medial forebrain bundle (coordinates: AP -0.5mm, ML ±1.7mm, DV skull -9.5mm). Rats were trained in a procedure adapted from the discrete-trial current-threshold procedure, with thresholds being defined as the mean of four alternating descending-ascending series. Prior to ICSS testing, rats were administered saline vehicle, α-PPP (0-2.0 mg/kg, i.p.), α-PVP (0-2.0 mg/kg, i.p.), α-PHP (0-2.0 mg/kg, i.p.) or methamphetamine (0.56 mg/kg, s.c) with a 15 minute pretreatment interval. Active drug days were conducted a maximum of twice per week, separated by at least one nondrug session. Brain reward thresholds were significantly decreased (p<0.05) in rats exposed to α-PPP or α-PHP, with similar efficacy and lesser potency compared with methamphetamine. Exposure to α-PVP resulted in modest decrease in ICSS threshold. These data are the first to confirm the effects of cathinone stimulants on ICSS reward function in female rats. Reduced reward thresholds in the ICSS procedure were consistent with pro-reward effects shown for other psychomotor stimulants such as methamphetamine.