Drugs such as benzodiazepines which enhance the effects of inhibitory neuro
transmitter gamma-amino butyric acid (GABA), are known to modulate the meso
corticolimbic dopaminergic system, which is considered to mediate the rewar
ding effects of psychostimulants. The effects of diazepam, a benzodiazepine
that binds unspecifically to omega 1- (omega 1-) and omega 2-receptors, an
d zolpidem, a nonbenzodiazepine drug that binds preferentially to omega 1-r
eceptors, on cocaine- and amphetamine-induced place preference were evaluat
ed in Wistar rats. In tests using the counterbalanced method, neither diaze
pam (0.2, 1, and 5 mg/kg) nor zolpidem (2.5, 5, and 10 mg/kg) alone induced
place preference or place aversion. Diazepam pretreatment prevented both c
ocaine- and amphetamine-induced (15 and 9 mg/kg, respectively) place prefer
ence; however, at doses that were earlier shown to cause sedation and amnes
ia, zolpidem failed to prevent either cocaine- or amphetamine-induced place
preference. These results suggest that diazepam interferes with the reward
ing properties of the psychostimulants, whereas zolpidem is less effective
in this respect, possibly due to differential distribution of omega 1- and
omega 2-receptors in the brain. (C) 1998 Elsevier Science Inc.