PEPTIDERGIC AND ADRENERGIC-INNERVATION OF THE LACRIMAL GLAND IN THE EURYHALINE TURTLE, MALACLEMYS TERRAPIN

The controlling factors of lachrymal gland secretions were examined in the euryhaline turtle, Malaclemys terrapin. Histochemical and immunoc ytochemical methods were used to localize some of the possible neurotr ansmitters involved. There was no immunoreactivity to choline acetyltr ansferase, the enzyme synthesizing acetylcholine, nor did the histoche mical technique for acetylcholinesterase produce positive results. Imm unofluorescence and immunoperoxidase labels revealed vasoactive intest inal peptide (VIP)- and neuropeptide Y (NPY)-like immunoreactivity in high concentrations surrounding the secretory tubules and ducts. Subst ance P produced a weak immunoreactivity in the interstitial space surr ounding the ducts. Dopamine beta-hydroxylase, the enzyme synthesizing norepinephrine and epinephrine, was localized around the blood vessels . Immunogold labeling confirmed the presence of VIP- and NPY-like reac tivity in nerve varicosities close to the basement membrane of the sec retory epithelium, and double-labeling showed VIP and NPY are co-local ized within the same nerve terminals. The results suggest that the sec retory epithelium may be primarily under peptidergic control while the vascular system is under adrenergic control. This is possibly a new p attern of innervation for exocrine glands and may be related to the pa rticular function of this salt gland in an euryhaline turtle. (C) 1995 Wiley-Liss, Inc.