Influences on the defecation and micturition reflexes by the cerebellar fastigial nucleus.

The influence of the cerebellar fastigial nucleus on the defecation and micturition reflexes was investigated in chloralosed cats with recordings of colonic blood flow and motility, intravesical and intraabdominal pressures. Whenever effective, topical fastigial stimulation regularly suppressed both somatomotor and autonomic components of the defecation reflex, to the extent that the straining movements as well as the colnic vasodilatator and motor responses associated with defecation could be completely inhibited. Bladder motility could either be suppressed or enhanced, depending both on prevailing bladder tone and on the fastigial site stimulated. The autonomically conveyed inhibitory responses were in both cases independent of the adrenergic sympathetic pathways, since they were unaffected both by sympathetic nerve sectioning and by adrenergic blocking drugs but eliminated by pelvic nerve section. It is suggested that the mentioned fastigial inhibitory influences are exerted on the spinal parasympathetic reflexes controlling the bladder and colon. Parallels between fastigial control of autonomic somatomotor mechanisms are discussed.