Cardiovascular responses to chemical stimulation of the inferior olive in the cat

Previous studies have suggested that electrical stimulation of the inferior olivary nucleus of anesthetized cats does not alter arterial pressure but does inhibit the depressor response to baroreceptor stimulation. However, it was not determined if the observed alteration of the baroreceptor reflex was due to an effect on cell bodies or on fibers of passage. The purpose of the present study was to determine the responses to selective activation of cell bodies in the inferior olive in anesthetized cats. Unilateral microinjections of kainic acid, D,L-homocysteic acid and glutamate were made into the inferior olive at the level of or just rostral to the obex. In addition, the baroreceptor reflex was examined before and after microinjection of kainic acid. The microinjections produced an increase in arterial pressure accompanied by variable effects on heart rate. However, the cardiovascular responses to activation of arterial baroreceptors were not altered by kainic acid microinjections. These results indicate that neurons in the inferior olivary nucleus can exert effects which increase arterial pressure but the inferior olive at this level does not modulate the baroreceptor reflex in anesthetized cats.