Observations on the nature and mechanism of secretory inhibition.

Abstract

Little consideration appears to have been given to the nature and complexity of the conditioned secretory response. An analysis of investigations and observations made with subjects where it was possible to observe quantitative changes in the secretion of 2 or more of the digestive glands at the same time, seems to warrant the assumption that the positive or negative conditioned salivary response represents but a component of an extensive and complex reaction involving all the major nutritive glands. The nature of these reactions suggests a close relationship with the antagonistic divisions of the autonomic nervous system. The increase in saliva when food is seen may be the result of innervation of the cranial nerve supply, while inhibition of conditioned secretion may be due to sympathetic innervation. In the light of these facts the theories of secretory inhibition advanced by Cannon and Pavlov are compared. Recent investigations made in the Cornell Laboratory, showing the inhibitory influence of mild affective states on parotid secretion, seem to support Cannon''s theory that inhibition is of sympathetic origin and is controlled in the optic thalamus, as against Pavlov''s theory that the inhibitory process is cortical in origin and is the result of cellular activity rather than the functioning of a system of nerves. Many of the difficulties encountered by investigators of conditioned salivary responses could be explained if this close relationship of mild affective states and inhibition were assumed.