Journal of Dental Research, Vol 68, 59-63, Copyright © 1989 by International & American Associations for Dental Research Online Journals
5-Hydroxytryptamine modulation of rat parotid salivary gland secretion
W. Chernick, E. Bobyock and P. Bradford
Hahnemann University School of Medicine, Department of Pharmacology, Philadelphia, Pennsylvania 19102.
5-Hydroxytryptamine (5-HT) has been reported to produce significant
responses in blowfly salivary glands, but little information is available
concerning its action on mammalian salivary glands. When 5-HT (0.1 mumol/L
to 10 mumol/L) is infused i.a. into anesthetized rats, no salivary
secretion is obtained from either parotid or submandibular glands. However,
when 5-HT is infused along with a threshold concentration of acetylcholine
(0.1 mmol/L), potentiation of parotid secretory response is seen with 5-HT
(1 mumol/L, 260% increase; 10 mumol/L, 146% increase). Substance P (0.3
mumol/L) combined with 5-HT (1 mumol/L) also resulted in a potentiation of
parotid secretion (160% increase). Protein and calcium concentrations were
not altered during such treatments. No potentiation of submandibular
secretion was noted. Experiments in vitro with parotid cell aggregates
exhibited no potentiation associated with the combined use of 5-HT and
carbachol, as measured by amylase secretion and inositol trisphosphate
accumulation. The experiments indicate that 5-HT substantially modulates
parotid salivary secretion in vivo; however, the in vitro findings suggest
that 5-HT does not act directly on surface glandular receptors. The
magnitude of the in vivo potentiation could very well implicate circulating
or released 5-HT as a physiological modulator of endogenous
neurotransmitter action.
