Distribution of muscarinic cholinergic receptors in the dorsal vagal complex and other selected nuclei in the human medulla.

Muscarinic cholinergic receptors were localized in human brainstem by quantitative autoradiography, using the radioligand [3H]quinuclidinyl benzilate. Receptor densities were highest in the hypoglossal nucleus. The second highest density was found in the medial region of the nucleus of the solitary tract (NTS). Moderately high numbers of receptors were present in the dorsal motor nucleus of the vagus, the dorsal NTS, subpostremal NTS, lateral NTS and ventral NTS. Intermediate densities were present in the dorsal and medial accessory nuclei of the inferior olive and the spinal trigeminal nucleus pars interpolaris. Low densities were found in the area postrema, principle nucleus of the inferior olive, gracile nucleus, cuneate nucleus and the tractus of the NTS. Muscarinic cholinergic receptors in the dorsal vagal complex are an important component of the neural substrate governing visceral function. These receptors may be the central site of action of anticholinergic medications in suppressing emesis.