CHEMOSENSITIVITY, PLASTICITY, AND FUNCTIONAL-HETEROGENEITY OF PARAGANGLIONIC CELLS IN THE RAT CELIAC SUPERIOR MESENTERIC COMPLEX

Chemosensitivity and plasticity of paraganglionic cells in the rat coe liac-superior mesenteric complex (CSMC) were investigated at a basal s tate of normoxia (21% O-2) and after long-term moderate hypoxia (10% O -2, 14 days). Chemical sympathectomy previous to hypoxia was performed to destroy principal ganglionic neurons and thus to allow measurement of the norepinephrine and dopamine content of paraganglionic cells. A t the basal state, the CSMC contained dopaminergic (TH+/DBH-) and nora drenergic (TH+/ DBH+) paraganglionic cells, the majority being of the noradrenergic type. After 14 days of hypoxia, this ratio was reversed and dopaminergic cells predominated, as indicated by a twofold increas e of TH+ cells and a twofold decrease of DBH+ cells. Biochemically, hy poxia produced an increase in the content (1.6-fold) and utilization ( 1.4-fold) of dopamine as well as a smaller increase in the content of norepinephrine, with no change in its utilization rate. The dopaminerg ic activation induced by hypoxia persisted after sympathectomy with gu anethidine. It is concluded that paraganglionic cells in the CSMC disp lay a chemosensitive function. Furthermore, our findings indicate that paraganglionic cells are differentially affected by hypoxia, dependin g on their distribution and the nature of their neuromodulators. The a lterations induced by hypoxia point out the phenotypic plasticity deve loped by paraganglionic cells in adaptation to hypoxia and further dem onstrate the functional heterogeneity of this autonomic cell populatio n in the rat CSMC. (C) 1994 Wiley-Liss, Inc.