Modifications of acoustic habituation by interruption of visual input in quipazine treated cats

The influence of interruption of the visual input on acoustic habituation was studied in cats before and following the administration of quipazine, 3 mg/kg iv. The characteristics of acoustic habituation were analyzed through the magnitude and temporal course of multiunit activity (MUA) responses elicited in the mesencephalic reticular formation (MRF) by repetitive acoustic stimuli (70 db, 50 Hz trains of 2 sec duration) in 6 freely moving cats with cortical electrodes over the parietal cortex and bipolar electrodes chronically implanted in MRF and basolateral amygdala (AMN). The cats were submitted to repetitive acoustic stimulation during one 30 min period before, and three 30 min periods after drug administration in the following conditions: a) with unmasked eyes; b) with masked eyes by means of dark contact lenses. Persistent attentive behavior, catatonic attitudes, hypersynchronous (6 Hz, 100-150 microV) EEG activity and significant increase of spontaneous MUA in FRM and AMN were induced by quipazine both in the cats tested with unmasked and with masked eyes. This increase of MUA was higher immediately following drug administration and progressively decreased, although MUA values remained significantly higher than controls 110 min after quipazine administration. Acoustic habituation, evidenced through the progressive decrease of MUA responses of MRF to acoustic stimuli, was observed before quipazine administration when the cats were tested with unmasked and with masked eyes; as well as in cats tested with unmasked eyes following drug administration. However, the MUA responses to acoustic stimuli did not decrease in cats with masked eyes during acoustic stimulation periods 0-30 min and 40-70 min after quipazine administration.(ABSTRACT TRUNCATED AT 250 WORDS)