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Immunocytochemical studies of the 5‐HT 1A receptor in ventral medullary neurons that project to the intermediolateral cell column and contain serotonin or tyrosine hydroxylase immunoreactivity
Author(s) -
Helke C.J.,
Capuano S.,
Tran N.,
Zhuo H.
Publication year - 1997
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(19970310)379:2<261::aid-cne7>3.0.co;2-1
Subject(s) - rostral ventrolateral medulla , medulla oblongata , biology , tyrosine hydroxylase , serotonergic , raphe nuclei , catecholaminergic , raphe , serotonin , medicine , catecholaminergic cell groups , medulla , endocrinology , dorsal raphe nucleus , receptor , central nervous system , catecholamine , dopamine , biochemistry
Activation of serotonin‐1A receptors (5‐HT 1A R) in the medulla oblongata lowers sympathetic nerve discharge and blood pressure. Binding sites for 5‐HT 1A R ligands are present in ventral medullary nuclei [e.g., rostral ventrolateral medulla (RVLM), raphe pallidus (RPa), and parapyramidal region (PPR)] that project to sympathetic preganglionic neurons in the intermediolateral cell column (IML). However, the projections and the neurochemical contents of the ventral medullary neurons that are likely to be involved in the hypotensive actions of 5‐HT 1A agonists are unclear. Using a sheep antibody to a fragment of the third intracellular loop of the 5‐HT 1A R, we localized 5‐HT 1A R immunoreactivity (ir) to IML‐projecting neurons that were retrogradely labeled with rhodamine beads injected into the IML of adult male rats. The percentages of IML‐projecting neurons containing 5‐HT 1A R‐ir were 49% in RPa, 34% in PPR, and 44% in RVLM. Using multiple‐immunofluorescence labeling, we also demonstrated 5‐HT 1A R‐ir in serotonergic (5‐HT) and in catecholaminergic (tyrosine hydroxylase; TH‐ir) neurons of the ventral medulla. The percentages of 5‐HT‐ir neurons containing 5‐HT 1A R‐ir were 28% in RPa, 18% in PPR, and 31% in raphe obscurus. In addition, 5‐HT 1A R‐ir was present in 14% of TH‐ir neurons of the RVLM. Moreover, some IML‐projecting neurons in the PPR and RPa were doubly immunolabeled for 5‐HT 1A R‐ir and 5‐HT, and some IML‐projecting neurons in the RVLM were doubly immunolabeled for 5‐HT 1A R‐ir and TH‐ir. These data provide anatomical evidence for the presence of 5‐HT 1A R on serotonergic and catecholaminergic bulbospinal neurons and for their potential role in directly modifying the activity of these ventral medullary neurons. J. Comp. Neurol. 379:261–270, 1997. © 1997 Wiley‐Liss, Inc. This article is a US government work and, as such, is in the public domain in the United States of America.