The localization of adrenoceptors and opiate receptors in regions of the cat central nervous system involved in cardiovascular control

Abstract

The distribution of adrenoceptors and opiate receptors in the nucleus of the tractus solitarius and the intermediolateral cell column of the thoracic spinal cord of the cat have been investigated using an in vitro autoradiographic technique. Specific binding of [3H]yohimbine and [3H]rauwolscine (alpha 2-adrenoceptor ligands) was seen within the intermediolateral cell column but no obvious binding of [3H]prazosin, an alpha 1-ligand, was observed. No evidence of a significant population of opiate receptors was obtained in the intermediolateral cell column. Within the nucleus of the tractus solitarius a marked binding of [3H]yohimbine and [3H]rauwolscine was accompanied, however, by a more restricted binding of [3H]naloxone and [3H]dihydromorphine indicating the presence of both alpha 2-adrenoceptors and opiate receptors. As with the intermediolateral cell column no evidence of [3H]prazosin binding was seen. These observations may have particular relevance for the physiology and pharmacology of cardiovascular control. In the case of the intermediolateral cell column it is consistent with evidence of a catecholamine innervation originating from the brainstem. With regard to the nucleus of the tractus solitarius the location of the receptor groups is discussed in the light of the anatomy and physiology of its afferent innervation.