AUTORADIOGRAPHIC LOCALIZATION OF NMDA BINDING-SITES IN BRAIN-STEM CARDIORESPIRATORY AREAS OF ADULT AND NEWBORN CATS

Quantitative autoradiography was used to determine the distribution of [H-3]1-[1-(2-thienyl)cyclohexyl] piperidine ([H-3]TCP) binding sites in the brainstem in order to localize the possible targets activated b y excitatory amino acids in adult and newborn cats during autonomic rh ythmic functions. Medium to high densities of binding sites were found in the nucleus tractus solitarius complex and the laterodorsal part o f the pontine tegmentum. In the kitten, there was an apparent higher d ensity in cranial motor nuclei proximal to these structures. It is con cluded that there is an overlapping between the high density of NMDA r eceptors and the localization of cardiorespiratory neurons in cat as w ell as in kitten.