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CART peptide immunoreactivity in the hypothalamus and pituitary in monkeys: Analysis of ultrastructural features and synaptic connections in the paraventricular nucleus
Author(s) -
Dall Vechia Stephanie,
Lambert Philip D.,
Couceyro Pastor C.,
Kuhar Michael J.,
Smith Yoland
Publication year - 2000
Publication title -
journal of comparative neurology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.855
H-Index - 209
eISSN - 1096-9861
pISSN - 0021-9967
DOI - 10.1002/(sici)1096-9861(20000117)416:3<291::aid-cne2>3.0.co;2-e
Subject(s) - hypothalamus , median eminence , biology , supraoptic nucleus , axon , nucleus , cocaine and amphetamine regulated transcript , pituitary stalk , arcuate nucleus , posterior pituitary , vasopressin , oxytocin , neuropeptide , neurosecretion , suprachiasmatic nucleus , anatomy , neurophysins , neuroscience , pituitary gland , endocrinology , hormone , biochemistry , receptor
Cocaine and amphetamine regulated transcript (CART) has been identified as one of the most abundant mRNAs in the rat hypothalamus. The objective of the present study was to elucidate the distribution of CART peptide immunoreactive (CARTir) neurons in the monkey hypothalamus and characterize their ultrastructural features and synaptic connections in the paraventricular nucleus (PVN). CARTir neurons were particularly abundant in the PVN, supraoptic nucleus (SON), infundibular nucleus, and premammillary nucleus, whereas the anterior, lateral, and posterior hypothalamic areas as well as the posterior nucleus displayed moderate immunoreactivity. Dense bundles of CARTir fibers exited the PVN and SON and followed a trajectory to the infundibulum similar to that previously shown for vasopressin and oxytocin fibers. The posterior pituitary was densely packed with large CARTir varicosities which, in some cases, were apposed to labeled pituicytes. The external/palisade zone of the median eminence contained rich plexuses of small CARTir varicose fibers, and the internal/fibrous zone was enriched in large axon‐like processes. Electron microscope analysis of the PVN revealed (1) that CART peptide immunoreactivity is found in neurosecretory and non‐neurosecretory neurons contacted predominantly by unlabelled terminals forming asymmetric synapses, (2) that CARTir terminals resemble glutamatergic and/or noradrenergic boutons and form asymmetric synapses with non‐neurosecretory dendrites, and (3) that neuropeptide Y (NPY)‐containing terminals are apposed to CARTir neurons in the medial part of the nucleus. In conclusion, our findings demonstrate that CART peptide is abundant in neuronal perikarya and axon terminals throughout the monkey hypothalamus and along the hypothalamopituitary axis. This strengthens the idea that CART peptides may act as putative neurotansmitters/neuromodulators that mediate various neuroendocrine and autonomic functions in primates. J. Comp. Neurol. 416:291–308, 2000. © 2000 Wiley‐Liss, Inc.