LOCALIZATION AND POSSIBLE INTERACTIONS OF CATECHOLAMINE AND NADPH-DIAPHORASE NEURONS IN HUMAN MEDULLARY AUTONOMIC REGIONS

The human medulla contains catecholamine-and NADPH-diaphorase (NADPH-d ) neurons in both the ventrolateral medulla (VLM) and nucleus of the s olitary tract (NTS). There is abundant experimental evidence for the c ritical role of these areas in control of arterial pressure. We sought to determine the pattern of distribution and topographic relationship between tyrosine hydroxylase (TH)-immunoreactive and NADPH-d-reactive cell groups in normal human VLM and NTS, in view of their potential i mplications in human autonomic control and involvement in central auto nomic disorders. Medullae from three patients with no neurologic disea se were obtained at autopsy within 24 h of death. Individual sections, obtained from the rostral and caudal medulla, were stained for TH, NA DPH-d or both. We found that: (1) TH-and NADPH-d positive neurons are topographically segregated in the VLM; (2) in the VLM, TH and NADPH-d neurons may coexist within a given area but both markers do not appear to coexist in single neuron; (3) NADPH-d-reactive fibers and processe s overlap the distribution of TH neurons within the VLM; and (4) both TH-and NADPH-d-reactive processes appear to innervate intrinsic blood vessels in the VLM and NTS. Thus, there are important topographic rela tionships between catecholamine-and NO-synthesizing neurons in human V LM and perhaps NTS, including innervation of intrinsic blood vessels. This may have important implications in regulation of autonomic reflex es, sympathetic excitatory drive and intrinsic control of cerebral blo od flow in humans.