THE PRESENCE OF NERVE-FIBERS IMMUNOREACTIVE FOR VASOACTIVE-INTESTINAL-PEPTIDE (VIP), PEPTIDE HISTIDINE ISOLEUCINE (PHI), AND PREPROVIP(111-122) IN THE MOUSE PINEAL-GLAND

A low to moderate number of vasoactive intestinal peptide (VIP) and pe ptide histidine isoleucine (PHI)-immunoreactive nerve fibers with prom inent boutons-en-passage were demonstrated in the pineal gland of the mouse. The two peptides, which are parts of the same precursor molecul e, were distributed identically in the gland. Positive fibers were pre sent in the connective tissue septae in the gland, in the pineal capsu le, and in the pineal parenchyma. No VIP-PHI-immunoreactive elements w ere found in the deep pineal gland, in the pineal stalk, or in habenul ar and posterior commissures. This morphological distribution of immun oreactive nerve fibers, which is similar to the distribution in other mammals, indicates that the VIP/PHI fibers of the mouse pineal gland o riginate exclusively from perikarya in a peripheral ganglion, presumab ly one of the cholinergic ganglia of the head. No evidence for a VIPer gic central innervation was found. VIP and PHI are connected via a bri dging peptide equivalent to amino acids 111-122 of the precursor (prep roVIP(111-122)). In order to demonstrate the possible existence of thi s peptide in intra-pineal nerve fibers, antisera directed against a sy nthetic sequence identical to preproVIP(111-122) and immunohistochemis try were applied. PreproVIP(111-122)-immunoreactive nerve fibers were observed in the mouse pineal gland, with the same distribution pattern and morphology as those immunoreactive for VIP and PHI. To quantify t he peptide-immunoreactivities, 50 mice pineals were pooled, extracted, and the concentrations were measured radioimmunologically. The concen trations of the VIP and preproVIP(111-122) immunoreactivities were 1.7 and 2.0 pmol/g, respectively, whereas the concentration of PHI was 0. 9 pmol/g. This indicates that not only VIP and PHI, but also other fra gments of preproVIP are present in the mammalian pineal gland. Whereas the stimulatory role of VIP is well documented, the effect of other f ragments processed from preproVIP on pinealocytes remains to be establ ished.