CARDIOVASCULAR ADJUSTMENTS IN LIMB RETRACTION PROVOKED BY NOXIOUS-STIMULATION IN DECEREBRATE AND SPINAL CATS - EVIDENCE FOR A SOMATOTOPIC ORGANIZATION

Arterial blood pressure, heart rate and iliac blood flow were continuo usly recorded in 61 adult cats and their alteration induced by noxious stimulation of the interdigital spaces of the four limbs was studied in intact (anesthetized) and in decerebrate and spinal preparations. N oxious stimulation of any limb in the decerebrate animals provoked ret raction 61% of the times and an increase of blood pressure and heart r ate in approximately 80% of the stimulations. Stimulation of a hindlim b provoked an increase of blood flow in the same limb in about 80% of the stimulations, due to active vasodilation. Contralateral stimulatio n provoked a smaller increase of blood flow but with an increase in va scular resistance, indicating some degree of vasoconstriction. Stimula tion of the forelimbs induced small increases of blood flow in the hin dlimbs but the calculated vascular resistance was higher than the basa l values, also indicating vasoconstriction. Neuromuscular blockade wit h gallamine did not affect the increase of hindlimb blood flow, sugges ting a central regulation of the intricate distribution of blood to th e limbs. The vasodilation was not due to activation of sympathetic cho linergic vasodilator neurons inasmuch as the blood flow responses were not affected by cholinergic blockade with atropine. In spinal animals , stimulation of any limb provoked small increases of blood pressure, extremely low degrees of tachycardia and an increase of hindlimb blood flow, with active vasodilation. Neuromuscular paralysis, however, abo lished the adjustments of blood flow in the hindlimbs, indicating that metabolites and/or sensory information caused by muscle contraction i nduced them. In intact cats anesthetized with sodium pentobarbiturate, blood pressure and heart rate increased under noxious stimulation, al though less than in the decerebrate animals. Nearly 40% of the stimula tions provoked hypotension rather than hypertension. Blood flow increa sed due to stimulation of any limb but, as in the decerebrate preparat ion, there was active vasodilation in the ipsilateral hindlimb and vas oconstriction in the contralateral one.