Cardiac arrhythmic response evoked by stimulation of fastigial nuclei in the anesthetized cat.

Using the Horsley-Clarke sterotaxic technique for positioning electrodes in the cerebellum of the cat, the present study has shown that electrical stimulation of the nucleus fastigius produces cardiac arrhythmia in addition to the already known pressor response. These arrhythmias ranged from sinus tachycardia to various kinds of ectopic beats, and the effects of the arrhythmias on cardiovascular haemodynamics are discussed. Administration of the beta-adrenergic-blocking drug (propranolol) and the adrenergic neuron-blocking drug (bretylium tosylate) showed that the cardiac arrhythmic responses were predominantly due to sympathetic activation.

Autonomic effector responses to stimulation of nucleus fastigius.

1. In anaesthetized cats electrical stimulation of the nucleus fastigius caused cardiovascular responses, electrodermal responses of the paws and pupil dilation with retraction of the nictitating membranes.2.

Supraspinal control of reflex activity in renal nerves.

1. In anaesthetized cats distension of carotid sinus inhibited renal nerve activity and intercostal-renal nerve reflexes. The degree of inhibition was dependent on the amount of rise in sinus pressure.

Reflex discharges into thoracic white rami elicited by somatic and visceral afferent excitation.

1. Reflex discharges in white rami (WR) were elicited by single-shock stimulation of dorsal roots (DR), splanchnic (SPL) and intercostal nerves (IC).2.

Central pathways of some autonomic reflex discharges.

1. Electrical stimulation of spinal sensory nerves evoked discharges in inferior cardiac and renal nerves. In the anaesthetized cat both an early and a late response could be recorded in each nerve.