BENZODIAZEPINE AGONISTS REVERSE THE EFFECTS OF NOISE EXPOSURE ON CENTRAL BENZODIAZEPINE RECEPTORS AND CARDIAC RESPONSIVENESS

Rats were submitted to 110 dB white noise exposure for 1, and 6 hours and brain alpha(1), beta(1) and benzodiazepine receptor binding was evaluated with selective ligands. An increase in cerebral benzodiazepine receptor (CBR) concentration, without any significant change in affinity constant, occurred after the 6 h treatment; no change was observed in adrenergic receptor binding at any period of exposure. Both diazepam and clonazepam pre-treatment reversed the effects of noise on CBR binding, confirming a role of these receptors in the response to noise stress. Furthermore, these benzodiazepine agonists influenced the response of cardiac and aortic tissues, which are known to be changed by stress exposure. Diazepam and clonazepam pre-treatment protected cardiac tissue from the effects of 6h noise stress, and a potentiation of aortic responses was detected, although at different times of exposure. The differences between the responses of these peripheral tissues to benzodiazepine treatment suggest that the expression depends on the tissue examined and the period of exposure.