Abstract
NK3 receptor (neurokinin B receptor)-expressing neurons in the basal forebrain region of rats were characterized histochemically by combining immunocytochemistry, in situ hybridization and retrograde labeling, and electrophysiologically by whole-cell clamp recording. NK3 receptor-immunoreactive neurons were found in the basal forebrain region including the substantia innominata where axon terminals immunoreactive for preprotachykinin B, the precursor peptide of neurokinin B, were densely distributed. More than 90% of NK3 receptor-expressing neurons in the basal forebrain region showed signals for GAD mRNA, GABAergic neuron marker. In retrograde labeling study, NK3 receptor immunoreactivity was detected in about 25% of cortically projecting basal forebrain neurons. In the whole-cell clamp recording study, a selective NK3 receptor agonist evoked membrane depolarization or inward currents with decrease of input impedance in 10 of 100 cortically projecting basal forebrain neurons. Since neurokinin B-producing striatal neurons send axons selectively to the basal forebrain region (Furuta et al., 2000), the present results suggest that the release of neurokinin B by those striatal neurons induces inhibitory effect on cortical neurons via facilitation of GABAergic basal forebrain neurons expressing NK3 receptor. [Jpn J Physiol 54 Suppl:S190 (2004)]
