DISTRIBUTION OF SUBSTANCE P-LIKE IMMUNOREACTIVE NEURONS AND TERMINALSTHROUGHOUT THE NUCLEUS OF THE SOLITARY TRACT IN THE HUMAN BRAIN-STEM

The anatomical distribution of substance P-like immunoreactivity acros s the subnuclear divisions of the nucleus of the solitary tract has be en examined in the human medulla oblongata. A differential distributio n of neurons, fibres, and terminals was observed throughout the ten su bnuclear divisions of this nucleus. Substance P-like immunoreactive ne urons were observed most frequently in the nucleus gelatinosus, with m oderate numbers in the medial, intermediate subnuclei and very few in the commissural, ventral, dorsal, and dorsolateral subnuclei. The para commissural, ventrolateral, and interstitial subnuclei did not contain substance P-like-immunoreactive neurons. These neurons were typically bipolar and moderate-sized to large, except for the neurons in the nu cleus gelatinosus, which were substantially smaller. The highest densi ties of fibres and terminals were observed in the gelatinosus, medial, and intermediate nuclei, with moderate densities in the paracommissur al and dorsal subnuclei. Sparse substance P-like-immunoreactive fibres and terminals were seen in the ventral and interstitial nuclei as wel l as within the solitary tract. The dorsolateral nucleus was character ized by a light distribution of fibres and terminals, except for a den se aggregation along its lateralmost border. A prominent innervation o f pigmented neurons by substance P-like-immunoreactive terminals and f ibres was also observed in the dorsolateral nucleus. The results revea l that the subnuclear complexity of the nucleus of the solitary tract is richly reflected by its differential pattern of substance P-like-im munoreactive structures. (C) 1994 Wiley-Liss, Inc.