Figure 4.

Quantitation of nAChR subunit mRNA expression and radioligand binding in the thalamo-cortico-thalamic circuitry of the mouse. In-situ hybridization for β2, α4 and α5 nAChR subunit expression in comparable coronal sections taken from wild type (WT), heterozygous (HET) and β2 nAChR subunit knock out (KO) mice. HET and KO mice exhibit a marked reduction in β2 mRNA expression with no significant alteration in the α4 or α5 subunits. Analysis of subunit expression in the corticothalamic transgenic mice (TR) indicates that β2 mRNA expression is enhanced in deep cortical layers, at WT levels in superficial layers and at KO levels in all other areas analyzed. α4 and α5 expression is at approximately WT levels in the transgenic animals. A85380 and epibatidine binding on comparable coronal sections from these animals indicates a partial recovery of assembled nAChRs in the TR mice, relative to β2 knockout animals. Epibatidine binding is eliminated in the presence of cytisine (Epi+cytisine) and corresponds to the binding of A-85380 in these brain regions.