The cerebellum is involved in the control of not only motor but also autonomic functions (Moruzzi, 1950; Ito, 1984). Blood pressure, heart rate and respiration have been shown to be affected by electrical stimulation of the anterior vermis and the fastigial nucleus (Moruzzi, 1950; Ban, Hilliard & Sawyer, 1960; Achari & Downman, 1970; Nisimaru & Kawaguchi, 1984). Previously, we reported that electrical stimulation of localized regions in the posterior lobe (lobules VII, VIII and X) produced inhibition of renal sympathetic nerve activity and a fall in blood pressure in anaesthetized rabbits (Nisimaru, Yamamoto & Shimoyama, 1984b; Nisimaru & Watanabe, 1985). More recently, Bradley et al., (1987a, b) also reported that electrical stimulation of the medial uvula (lobule IXb) induced cardiovascular responses in rabbits and cats. Interestingly, they showed that the effect of stimulation of the medial uvula was reversed when the anaesthesia wore off in decerebrate rabbits. However, little attention has been paid to the involvement of the lateral portion of the nodulus–uvula in cardiovascular function, on which I shall focus in this chapter. As an index of cardiovascular effects of cerebellar stimulation, we recorded, integrated and averaged efferent discharges from renal sympathetic nerves, which were affected by cerebellar stimulations with trains of only a few pulses. For stimulus mapping, a platinum–iridium needle electrode (diameter 200 μm, excluding the layer of insulation) was inserted into the cerebellum.

Stimulation of the lateral nodulus–uvula in anaesthetized rabbits.

In rabbits anaesthetized with α-chloralose plus urethane (30 and 600 mg/kg), lateral parts of the dorsal nodulus and the most ventral uvula were stimulated with a train of ten brief current pulses no stronger than 100 μA (200 Hz).