DIFFERENTIAL EFFECT OF BUSPIRONE AND DIAZEPAM ON NEGATIVE CONTRAST INONE-WAY AVOIDANCE-LEARNING

The main aim of the present work was to investigate the effect of busp irone, a 5-HT1A receptor agonist, on successive negative contrast in o ne-way avoidance learning. Successive negative contrast was induced by shifting rats from a large reward (30 s spent in the safe compartment ) to a small reward (1 s). Acute administration of buspirone (0.25, 0. 5, 0.75 and 1.0 mg/kg i.p.) did not attenuate the contrast effect, as opposed to that observed for diazepam (1 mg/kg i.p.). The highest dose of buspirone used, however, did interfere with the learning of the av oidance response itself. Chronic buspirone (20 days, 0.5 and 0.75 mg/k g i.p.) did not have any effect on successive negative contrast either . Overall, these results could suggest that the 5-HT1A receptor is not involved in the negative contrast effect studied, quite different to that observed for the gamma-aminobutyric acid (GABA) system. The findi ngs are compared to results obtained with animal models selectively se nsitive to some anxiolytic drugs, as are the so-called 'conflict model s'.