Cholinergic neurons expressing neuromedin K receptor (NK3) in the basal forebrain of the rat: A double immunofluorescence study

By using a double immunofluorescence method we have examined the distributi on of cholinergic neurons expressing neuromedin K receptor (NK3) in the rat brain and spinal cord. The distribution of neuromedin K receptor-like immu noreactive neurons completely overlapped with that of choline acetyltransfe rase-positive neurons in certain regions of the basal forebrain, e.g. the m edial septal nucleus, nucleus of the diagonal band of Broca, magnocellular preoptic nucleus and substantia innominata. Partially overlapping distribut ions of neuromedin K receptor-like immunoreactive and choline acetyltransfe rase-positive neurons were found in the basal nucleus of Meynert, globus pa llidus, ventral pallidum of the forebrain, tegmental nuclei of the pens and dorsal motor nucleus of the vagus. Neurons showing both neuromedin K recep tor-like and choline acetyltransferase immunoreactivities, however, were fo und predominantly in the medial septal nucleus, nucleus of the diagonal ban d of Broca and magnocellular preoptic nucleus of the basal forebrain: 66-80 % of these choline acetyltransferase-positive neurons displayed neuromedin K receptor-like immunoreactivity. Neurons showing both neuromedin K recepto r-like and choline acetyltransferase immunoreactivities were hardly detecte d in other aforementioned regions of the forebrain, brainstem and spinal co rd. The present study has provided morphological evidence for direct physiologi cal modulation or regulation of cholinergic neurons by tachykinins through the neuromedin K receptor in the basal forebrain of rats. (C) 2001 IBRO. Pu blished by Elsevier Science Ltd. All rights reserved.