HUMORAL INTERMEDIATION OF NERVE CELL ACTIVATION IN THE CENTRAL NERVOUS SYSTEM

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Abstract
Central neuro-humoral nerve cell activation was studied on the respiratory act of the dog. Acetylcholine produced hyperactivity of the respiratory center whether injected intra-arterially or applied to the floor of the 4th ventricle. This effect was in relation to the conc. of acetylcholine at the center as revealed by the graded response to graded inj. and by the greater effect of intra-vertebral than intra-carotid injs. after denervation of the carotid and aortic chemoceptors. The activity produced was essentially a normal hyperpnea showing the characteristic series of changing and coordinated events (about 10 in all) during a respiratory cycle. The response to acetylcholine was modified by the concurrent balance of incoming impulses as shown by the. difference with intact and blocked vagi. Acetylcholine injs. (extrinsic acetylcholine) had an additive effect to that liberated by incoming impulses (intrinsic acetylcholine) as shown by combining either Hering''s nerve stimulation or the lung inflation reflex with acetylcholine injs. Eserine potentiated the action of acetylcholine (extrinsic and intrinsic) as shown by the increased stimulation of acetylcholine deposited on the floor of the 4th ventricle and the greater and more prolonged reflexogenic response to faradic stimulation of the superior laryngeal and Hering''s nerve. Potentiation of activity was demonstrated in both half-centers. Because the crude and shapeless chemical stimulation produced by central inj. of acetylcholine evoked a highly co-ordinated activity, neuro-architectural patterns rather than sensory patterns of impinging impulses evidently exercise the dominant role in nervous integration. It was proposed that the basic conclusions reached in these studies on the respiratory act are applicable to the C. N. S. in general.

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