Premium
A population of nicotinic receptors is associated with thalamocortical afferents in the adult rat: Laminal and areal analysis
Author(s) -
Lavine Natalie,
Reuben Melanie,
Clarke Paul B.S.
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(19970407)380:2<175::aid-cne3>3.0.co;2-0
Subject(s) - neuroscience , thalamus , nicotinic agonist , biology , neocortex , population , cerebral cortex , cortex (anatomy) , nicotine , lesion , anatomy , receptor , pathology , medicine , biochemistry , environmental health
In the adult rat brain, a prominent population of nicotinic cholinoceptors binds 3 H‐nicotine with nanomolar affinity. These receptors are abundant in most thalamic nuclei and in neocortical layers 3/4, which receive a major thalamic input. To test whether cortical nicotinic receptors are associated with thalamocortical afferents, unilateral excitotoxic (N‐methyl‐D‐aspartate) lesions were made in one of four thalamic nuclear groups (anterior, ventral, medial geniculate, or dorsal lateral geniculate) or in temporal cortex. After 1 or 4 weeks of survival, cortical 3 H‐nicotine binding was quantified via autoradiography. Thalamic lesions resulted in a partial loss of 3 H‐nicotine binding in ipsilateral cerebral cortex. In each thalamic lesion group, the greatest decrease (35–45%) occurred within the cortical layers and area (i.e., cingulate, parietal, temporal, or occipital cortex) receiving the densest thalamocortical innervation. Binding of 3 H‐nicotine was also reduced within the thalamus local to the lesion, particularly at the longer survival time. Saturation analysis, performed in frontoparietal cortical tissue homogenates following ventral thalamic lesions, revealed a significant (34%) reduction in receptor density but not affinity. Direct excitotoxic lesions of the neocortex (temporal cortex) tended to preserve 3 H‐nicotine binding in layers 3/4, despite local neuronal loss. These results, taken with other published findings, suggest that some nicotinic cholinoceptors in adult rat cerebral cortex are located on thalamocortical terminals. This organizing principle appears to apply not only to sensory and motor relay projections but also to association nuclei that project to allocortical areas. These receptors may provide a local mechanism for nicotinic cholinergic modulation of thalamocortical input. J. Comp. Neurol. 380:175–190, 1997. © 1997 Wiley‐Liss, Inc.