Autonomic and EEG responses to cerebellar stimulation in rabbits

The vermis of the cerebellum in 27 rabbits anesthetized topically with procaine and immobilized with Flaxedil was explored stereotaxically and stimulated (0.5-msec. square waves, 300 cps., 5-sec. bursts) at various voltages. Autonomic effects were recorded as were also EEG changes in frontal and limbic cortex, thalamus, hypothalamus and amygdala. Stimulation of the anterior lobe characteristically induced an arterial pressor effect associated with mydriasis-exophthalmos and an aroused EEG. Responses from stimulating the posterior lobe were more variable. Sympathetic effects and an aroused EEG were often accompanied by a depressor response during stimulation followed by a pressor ‘rebound’ at the end of stimulation. In several rabbits, stimulation of the pyramis or uvula evoked a sleeplike EEG with spindles in the frontal cortical record, accompanied by parasympathetic miosis-enophthalmos during stimulation, with a reversal to arousal and sympathetic phenomena immediately afterward. These effects were eliminated by coagulation of the diencephalon at a time when pressor responses, reflexly to pain or directly to stimulation of the lower brainstem, were unimpaired.