SECRETION AND SEROTONIN RELEASE IN THE ISOLATED RAT LACRIMAL GLAND - THE EFFECTS OF SUBSTANCE-P AND CALCITONIN-GENE-RELATED PEPTIDE

A close anatomical relationship between nerves containing substance P and calcitonin gene-related peptide (CGRP) and mast cells containing s erotonin has been demonstrated in the rat lacrimal gland. This study i nvestigates the potential for peptidergic regulation of lacrimal mast cells by examining the actions of substance P, CGRP and serotonin on p rotein and peroxidase secretion from isolated lacrimal segments and on substance P and CGRP to release serotonin from the lacrimal mast cell s. Substance P, CGRP and serotonin evoked marked increases in total pr otein and peroxidase from the lacrimal. Sodium cromoglycate, a mast ce ll stabilizer, significantly reduced or blocked the secretory response s elicited by these agonists. Chromatographic analysis using electroch emical detection revealed that substance P, but not CGRP, augmented th e release of serotonin from the gland. The substance P evoked peroxida se secretion and serotonin release was blocked by CGRP and by sodium c romoglycate. These results support a role for mast cells in the regula tion of lacrimal secretion and suggest a novel regulatory interaction between substance P and CGRP in the control of lacrimal function throu gh a neuro-immune interaction.