The benzodiazepine receptor partial agonist bretazenil and the partial inverse agonist Ro 15-4513: effects on salt preference and aversion in the rat.

The general aim of the present series of experiments was to contrast the effects of the benzodiazepine receptor (BZR) partial agonist bretazenil and those of the partial inverse agonist Ro 15-4513 in two-choice tests between saline (0.9% or 1.8%) and water, using water-deprived rats. Since BZR agonists appear to enhance positive hedonic reactions to taste stimuli selectively, it was hypothesized that bretazenil (and a second BZR partial agonist Ro 17-1812) would selectively enhance intake of a preferred 0.9% salt solution, but not necessarily reduce the relative aversion to a more concentrated 1.8% salt solution, in these choice tests. The results were in general agreement with these hypotheses. Despite an earlier finding that Ro 15-4513 abolished sweet taste preference, there was no evidence here that it reduced the relative preference expressed for 0.9% NaCl solution. Moreover, Ro 15-4513 did not enhance the relative avoidance of the 1.8% NaCl solution. The BZR antagonist, flumazenil, had no effect on either salt preference or aversion. These results indicate that the type of taste stimulus (sweet or salt), the type of behavioural response (preference or aversion) and the type of BZR ligand (agonist, antagonist or inverse agonist) interact to determine the observed behavioural consequences in choice tests.