Immediate increase in benzodiazepine binding in rat brain after a single brief experience in the plus maze: a paradoxical effect

A single drug-free experience in the elevated plus-maze is well documented to reduce the behavioral effects of benzodiazepines (BZs) in subsequent tes ts. To ascertain the possible role of altered BZ receptor binding to in thi s phenomenon, rats received a 5-min exposure to the elevated plus maze and were immediately sacrificed. Receptor autoradiography revealed that [H-3]fl unitrazepam binding was significantly elevated in several amygdaloid and hi ppocampal nuclei (range: 13-23%); [3H]muscimol binding in adjacent sections was not significantly altered. These results suggest that BZ receptors can change very rapidly in response to anxiogenic conditions. However, the une xpected finding that [3H]flunitrazepam binding is increased by maze exposur e suggests that the subsequent loss of BZ anxiolytic effects in the plus-ma ze is probably unrelated to alterations in BZ binding in brain. (C) 1999 El sevier Science Ireland Ltd. All rights reserved.