Effect of chronic constant light on sensitivity of rat submandibular gland.

A consistent difference in the secretory response between submandibular (SM) glands of rats maintained under constant light (CL) during 50 days and those of rats under a photoperiod (14 h light: 10 h dark) was found. We have used alpha 1-adrenergic, muscarinic, peptidergic and beta-adrenergic secretagogue agents to study the secretory response of rat SM glands "in vivo". The response to phenylephrine, methacholine and substance P, was increased by exposure CL, while that to isoproterenol was diminished. The changes in the sensitivity of the secretory response from SM gland of rats under CL might be related to changes in the normal interplay of various receptors as well as to possible alteration in the intracellular signal transduction. It may represent and adaptive process of the nervous control of saliva secretion by environmental light and be of physiological and clinical interest.