Influence of morphine and haloperidol on the bioelectrical activity of n. raphe, n. caudatus, s. nigra and the visual cortex of cats.

The changes in the bioelectrical activity of n. raphe dorsalis (RD), s. nigra (SN), n. caudatus (NC) and the visual cortex (VC), induced by administration of morphinee, haloperidol, and morphine after pretreatment with haloperidol, were studied in acute experiments on 18 cats. Morphine caused changes in RD and NC, characteristic of increased excitability (increase in the amplitude and frequency of the spontaneous EEG-activity, improved assimilation upon light stimulation, higher amplitudes of the evoked potential). These phenomena were most marked until the 30th min, then they gradually decreased. In SN the bioelectrical activity was inhibited. After the initial changes suggesting inhibition, excitation phenomena occurred in the visual cortex after the 30th min. Haloperidol in SN caused changes characteristic of excitation, while in NC and VC--of inhibition. After pretreatment with haloperidol, morphine prevented its effects in all structures studied. The authors assume that the EEG-effects of morphin are conditioned both by its direct action on the serotoninergic neurones in RD and by the changes in the relationships between serotoninergic and dopaminergic neurones in RD, SN and NC.