GABA B receptor gene expression is not altered in cocaine‐sensitized rats

Recent behavioral and neurobiological data indicate that GABA B receptor transmission is involved in cocaine‐induced hyperactivity and reinforcement. GABA B receptor gene expression in cocaine‐sensitized rats was examined in this study. Rats were injected with cocaine (15 mg/kg, daily, i.p.) or saline for 5 consecutive days, and challenged with the same dose of cocaine after a 1‐, or 20‐day hiatus. The locomotor activities of rats were recorded after challenge, and the rats were killed 24 hr later. GABA B R1a, 1b, and GABA B R2 mRNA in discrete brain regions was detected by RPA and In Situ Hybridization; GABA B R1a protein was measured by Western blotting. Rats pretreated with cocaine developed a hyperactivity to the cocaine challenge after a 1‐day or 20‐day hiatus, but GABA B R subunit mRNA and GABA B R1a protein densities in the targeted regions showed no significant difference compared to those in control rats. These data indicate that GABA B receptor gene expression is not necessarily relevant to the behavioral sensitization of cocaine. © 2002 Wiley‐Liss, Inc.