Journal of Neuroscience, Vol 9, 160-166, Copyright © 1989 by Society for Neuroscience
Secretin and vasoactive intestinal peptide activate tyrosine hydroxylase in sympathetic nerve endings
MA Schwarzschild and RE Zigmond
Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts 02115.
Secretin and vasoactive intestinal peptide (VIP) are known to stimulate
tyrosine hydroxylase (TH) activity acutely in the rat superior cervical
ganglion (SCG). Because TH-containing neurons in the SCG innervate the
iris, submaxillary gland, and pineal gland, we examined the effects of
secretin and VIP in these 3 autonomic end organs in vitro. Both peptides
stimulated TH activity in each tissue. These stimulations resembled those
in the SCG in that (1) secretin displayed a higher potency than VIP in all
3 end organs, (2) the peptide effects were unchanged when calcium was
excluded from the incubation medium, and (3) they were mimicked by
activators of the cyclic adenosine monophosphate (cAMP) pathway. These
findings indicate that secretin and VIP can regulate transmitter metabolism
in both the cell bodies and axon terminals of neurons originating in the
SCG. Furthermore, the data raise the possibility that catecholamine
synthesis in sympathetic nerve terminals is modulated by peptides released
by other, nearby nerve endings.