Effects of hippocampal injections of a novel ligand selective for the α5β2γ2 Subunits of the GABA/benzodiazepine receptor on Pavlovian conditioning

Benzodiazepine pharmacology has led to greater insight into the neural mechanisms underlying learning and anxiety. The synthesis of new compounds capable of modulating responses produced by these receptors has been made possible by the development of an isoform model of the GABA(A)/benzodiazepine receptor complex. In the current experiment, rats were pretreated with several concentrations of the novel ligand RY024 (an alpha5beta2gamma2-selective benzodiazepine receptor inverse agonist) in the hippocampus and were trained in a Pavlovian fear conditioning paradigm. RY024 independently produced fear-related behavior prior to training and, at the highest concentration, decreased the strength of conditioning observed 24 h after training. These data provide further evidence for the involvement of hippocampal GABAA/benzodiazepine receptors in learning and anxiety. (C) 2002 Elsevier Science (USA).