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Differential localization of Ca 2+ channel α 1 subunits in the enteric nervous system: Presence of α 1B channel‐like immunoreactivity in intrinsic primary afferent neurons
Author(s) -
Kirchgessner A.L.,
Liu M.T.
Publication year - 1999
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(19990621)409:1<85::aid-cne7>3.0.co;2-x
Subject(s) - enteric nervous system , biology , voltage dependent calcium channel , immunocytochemistry , calbindin , neuroscience , neurotransmission , interstitial cell of cajal , channel blocker , cholinergic , microbiology and biotechnology , soma , myenteric plexus , endocrinology , medicine , calcium , immunohistochemistry , receptor , immunology , biochemistry
Abstract Immunocytochemistry was employed to locate calcium (Ca 2+ ) channel proteins in the enteric nervous system (ENS) of the rat and guinea pig. Anti‐peptide antibodies that specifically recognize the α 1 subunits of class A (P/Q‐type), B (N‐type), C and D (L‐type) Ca 2+ channels were utilized. α 1B channel‐like immunoreactivity was abundant in both enteric plexuses, the mucosa, and circular and longitudinal muscle layers. Immunoreactivity was predominantly found in cholinergic varicosities, supporting a role for Ca 2+ channels, which contain the α 1B subunit, in acetylcholine release. Immunoreactivity was also associated with the cell soma of calbindin‐immunoreactive submucosal and myenteric neurons, cells that have been proposed to be intrinsic primary afferent neurons. α 1C channel‐like immunoreactivity was distributed diffusely in the cell membrane of a large subset of neuronal cell bodies and processes, whereas α 1D was found mainly in the cell soma and proximal dendrites of vasoactive intestinal polypeptide‐immunoreactive neurons in the guinea pig gut. α 1A channel‐like immunoreactivity was found in a small subset of cell bodies and processes in the rat ENS. The differential localization of the α 1 subunits of Ca 2+ channels in the ENS implies that they serve distinct roles in neuronal excitation and signaling within the bowel. The presence of α 1B channel‐like immunoreactivity in putative intrinsic primary afferent neurons suggested that class B Ca 2+ channels play a role in enteric sensory neurotransmission; therefore, we determined the effects of the N‐type Ca 2+ channel blocker, ω‐conotoxin GVIA (ω‐CTx GVIA), on the reflex‐evoked activity of enteric neurons. Demonstrating the phosphorylation of cyclic AMP (cAMP)‐responsive element‐binding protein (pCREB) identified neurons that became active in response to distension. Distension elicited hexamethonium‐resistant pCREB immunoreactivity in calbindin‐immunoreactive neurons in each plexus; however, in preparations stimulated in the presence of ω‐CTx GVIA, pCREB immunoreactivity was found only in calbindin‐immunoreactive neurons in the submucosal plexus and not in myenteric ganglia. These data confirm that intrinsic primary afferent neurons are located in the submucosal plexus and that N‐type Ca 2+ channels play a role in sensory neurotransmission. J. Comp. Neurol. 409:85–104, 1999. © 1999 Wiley‐Liss, Inc.