Central depressants and evoked click responses with special reference to the reticular formation in the cat.

高折 修二 ・中井 義尚 ・笹 征史 ・島本 暉朗 The present authors (1-3) have reported that the evoked potentials and ensuing rhythmic after-discharges in the auditory cortex of the unanesthetized cat caused by click stimuli are easily affected by change of environmental conditions. Furthermore, they have found that pentobarbital sodium, chloralose and chlorpromazine in small doses increase the magnitude of the cortical click responses without facilitating the evoked click responses in the inferior colliculus. Urethane and ethyl alcohol are quite unique in their actions, producing only a progressive decrease in the cortical responses. Since the demonstration of central role of the reticular formation (RF) in the brain mechanisms by Moruzzi and Magoun (4), the ascending inhibitory and facili tatory functions have been discussed by many investigators. Domino (5) and Killam (6) have emphasized that the potentiation of the recruiting response by barbiturates is due to a release phenomenon of the recovery cycle in the thalamic relay through the ascending influence of the brain stem RE In the previous papers (1, 3), small doses of pento barbital sodium, chloralose and chlorpromazine are likely to facilitate the transmission of the auditory ascending impulses to the auditory cortex by inhibiting the activity of RE The essential role of the RF in modification of the evoked auditory responses has been described by Hernandez-Peon et al. (7, 8), Desmedt et al. (9) and Chin et al. (10). However, the complex nature of interaction between the auditory responses and the RF still remains to be settled in detail. In the present experiments the effects of electrical stimulation of the RF on the click responses in the auditory cortex and the relay nuclei were studied before and after the administration of central depressants in the cat.