Comparison of the effects of the benzodiazepine midazolam and three serotonin antagonists on a consummatory conflict paradigm

A consummatory conflict procedure that involves an abrupt reduction in magnitude of an expected reward (negative contrast) has been shown to be particularly sensitive to the effects of anxiolytic agents. As previously reported with chlordiazepoxide, another benzodiazepine (BDZ), midazolam released suppressed consummatory performance in a dose-dependent manner. This effect was not due to a general appetite stimulatory effect of the drug. The effects of three 5-HT antagonists on negative contrast were examined to evaluate the role serotonin may play in the anxiolytic action of BDZ. Methysergide was found to be ineffective, cinanserin tended to reduce contrast at two intermediate doses, and cyproheptadine eliminated the contrast effect in a similar fashion as midazolam. The effectiveness of cyproheptadine may not be attributed to its anticholinergic or antihistaminergic actions since scopolamine and pyrilamine did not produce similar effects. The results are discussed in terms of the role serotonin may play in the anti-conflict action of BDZ, as well as possible interactional effects of GABA.