Sheng li xue bao : [Acta physiologica Sinica]
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Oxygen is an active stimulus of cerebral blood vessels. Hyperoxia can induce decrease in cerebral blood flow and intracranial pressure, but hypoxia increases cerebral blood flow and intracranial pressure. Both hyperoxia and hypoxia play an opposite role in cerebral circulation and intracranial pressure. Recent studies of cerebral circulation and intracranial pressure under hyperoxia and hypoxia were reviewed in the present paper with special reference to the correlation between cerebral circulation and intracranial pressure.
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Experiments were performed on 32 rabbits anaesthetized with alpha-chloralose and urethane, paralyzed with flaxidil and artificially ventilated. The pressor response was elicited by stimulation of dorsal part of midbrain periaqueductal gray (dPAG). Intravenous injection of diazepam (2 mg/kg) or intracerebroventricular application of flurazepam (2 mg/50 microliters) resulted in attenuation of the pressor response induced by the stimulation of midbrain. ⋯ Microinjection of flurazepam of the same dosage into caudal ventrolateral medulla (cVLM), however, had no depressant effect. Pretreatment with bicuculline in rVLM prevented the inhibitory effect of flurazepam on the pressor response. These results mentioned above suggest that diazepam or flurazepam inhibits the pressor response evoked by midbrain stimulation, and the effect may be mediated by the activation of the GABAA receptor in rVLM.