title: Heterogeneity of nicotinic acetylcholine receptor expression in the caudal nucleus of the solitary tract.
abstract: The nucleus of the solitary tract (NTS) is the principal integrating relay in the processing of visceral sensory and gustatory information. In the present study, patch-clamp electrophysiological experiments were conducted using rat horizontal brainstem sections. Pre-synaptic and somatic/dendritic nicotinic acetylcholine receptors (nAChRs) expressed in neurons of the caudal NTS (cNTS) were found to be randomly distributed between pre-synaptic and somatic/dendritic sites (chi(2)=0.72, df=3, p>0.87, n=200). Pre-synaptic nAChRs were detected by their facilitating effects on glutamatergic neurotransmission of a sub-population of cNTS neurons (categorized as "effect-positive") upon brief picospritzer applications of 0.1-0.5mM nicotine. These effects were resistant to inhibition by 20nM methyllycaconitine (MLA) and 4muM dihydro-beta-erythroidine (DHbetaE), and were replicated by brief picospritzer applications of 0.2-1mM cytisine. Picospritzer applications of 0.2mM RJR-2403, a potent agonist of alpha4beta2 nAChRs, did not facilitate synaptic release of glutamate in effect-positive cNTS neurons. The population of somatic/dendritic nAChRs has been found to be heterogeneous and included nAChRs that were activated by RJR-2403 and/or cytisine, or insensitive to cytisine, or inhibited by MLA. The presented results are consistent with the expression of beta4-containing (i.e., beta4*) nAChRs, likely alpha3beta4*, in pre-synaptic terminals of effect-positive cNTS neurons. Somatic/dendritic nAChRs appear to involve both alpha7 and non-alpha7 subunits. Heterogeneity in the subunit composition of pre-synaptic and somatic/dendritic nAChRs may underlie diverse roles that these receptors play in regulation of behavioral and visceral reflexes, and may reflect specific targeting by endogenous nicotinic agents and nicotine.
authors: Department of Anatomy and Neurobiology, University of Tennessee Health Science Center, Memphis, TN, USA.
authors: David V
authors: DV
authors: Smith
authors: Victor V
authors: VV
authors: Uteshev
mesh_terms: D000465:Algorithms; D000818:Animals; D003627:Data Interpretation, Statistical; D004594:Electrophysiology; D019706:Excitatory Postsynaptic Potentials / Q000187:drug effects; D005260:Female; D007478:Iontophoresis; D008239:Lysine / Q000031:analogs & derivatives; D008297:Male; D009538:Nicotine / Q000008:administration & dosage / Q000494:pharmacology; D018722:Nicotinic Agonists / Q000008:administration & dosage / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D051381:Rats; D017207:Rats, Sprague-Dawley; D011978:Receptors, Nicotinic / Q000096:biosynthesis* / Q000187:drug effects / Q000235:genetics; D017552:Solitary Nucleus / Q000187:drug effects / Q000378:metabolism*; D064569:alpha7 Nicotinic Acetylcholine Receptor
chemical_list: C579165:Chrna7 protein, rat; D018722:Nicotinic Agonists; D011978:Receptors, Nicotinic; D064569:alpha7 Nicotinic Acetylcholine Receptor; D009538:Nicotine; C013411:biocytin; D008239:Lysine