IMMUNOHISTOCHEMICAL STUDIES ON SYMPATHETIC AND NON-SYMPATHETIC NERVE-FIBERS AND NEURONAL CELL-BODIES IN THE PINEAL-GLAND OF COTTON RATS, SIGMODON HISPIDUS

Immunohistochemistry revealed the presence of tyrosine hydroxylase (TH )-, neuropeptide Y (NPY)-, calcitonin gene-related peptide (CGRP)- and substance P (SP)-immunoreactive nerve fibers and SP-immunoreactive ne uronal cell bodies in the pineal gland of the cotton rat (Sigmodon his pidus). Abundant TH- and NPY-immunoreactive fibers were distributed ev enly throughout the gland; less numerous CGRP- and SP-immunoreactive f ibers were distributed in the superficial pineal and the stalk, but we re scarce in the deep pineal. All the immunoreactive fibers were usual ly found around blood vessels. Since TH- and NPY-immunoreactive fibers in various pineal regions disappeared completely with superior cervic al ganglionectomy, these fibers are all considered postganglionic symp athetic fibers. Intrapineal CGRP- or SP-immunoreactive fibers decrease d considerably in number following superior cervical ganglionectomy, s uggesting that some sympathetic fibers contain CGRP or SP. Bilateral b undles of nerve fibers under the transverse sinuses, corresponding to the nervi conarii, contained TH-, NPY-, CGRP- and SP-immunoreactive fi bers, which continued into those distributed in the pineal capsule. In the nervi conarii, fibers immunoreactive for TH and NPY disappeared a fter superior cervical ganglionectomy, but those immunoreactive for CG RP and SP persisted. Thus, non-sympathetic, CGRP- and SP-immunoreactiv e fibers, together with sympathetic fibers, are presumed to enter the gland by way of the nervi conarii. Neuronal cell bodies, containing SP -like immunoreactivity and being possibly parasympathetic in nature, o ccurred occasionally in the superficial pineal.