Noradrenergic neurons expressing substance P receptor (NK1) in the locus coeruleus complex: a double immunofluorescence study in the rat

By using a double immunofluorescence method we examined the distribution of noradrenergic neurons expressing substance P receptor (NK1) or neuromedin K receptor (NK3) in the rat brainstem. The distribution of SPR-like immunor eactive (-LI) neurons completely overlapped that of tyrosine hydroxylase (T H)-LI neurons in the locus coeruleus (A6), ventrolateral and lateral reticu lar formation of pens (A5 and A7). Partially overlapping distribution of SP R- and TH-LI neurons were found in certain regions of the medulla oblongata (A1-A4). Neurons showing both SPR- and TH-like immunoreactivities, however , were only found in the locus coeruleus complex (A5-A7): 100% of these TH- LI neurons displayed SPR-like immunoreactivity. Neurons showing both NKR- a nd TH-like immunoreactivities were not detected in the aforementioned areas of brainstem. The present study has provided morphological evidence for di rect physiological modulation of noradrenergic neurons by tachykinins throu gh SPR in locus coeruleus complex (A5-A7). (C) 2000 Elsevier Science B.V. A ll rights reserved.