Endomorphin 1- and endomorphin 2-like immunoreactive neurons in the hypothalamus send axons to the parabrachial nucleus in the rat.
Endomorphin 1 (EM1) and endomorphin 2 (EM2) are the endogenous peptides with high affinity and selectivity for the mu-opioid receptor (MOR). We examined whether or not EM1- and EM2-expressing hypothalamic neurons might send their axons to the parabrachial nucleus (PBN), where many MOR-expressing neurons have been observed. Immunofluorescence histochemistry was combined with fluorescent retrograde tract-tracing method. In the rats injected with Fluoro-Gold (FG) into the PBN, some of EM1- and EM2-immunoreactive hypothalamic neurons were labeled retrogradely with FG. The majority of the EM1/FG and EM2/FG double-labeled neurons were distributed in the dorsomedial hypothalamus nucleus, centromedial hypothalamic region, and arcuate nucleus; a few of them were also seen in the periventricular hypothalamic nucleus and posterior hypothalamic nucleus. Endomorphins released from PBN-projecting hypothalamic neurons may modulate the gustatory, autonomic and nociceptive functions through MOR-expressing PBN neurons.
Chen
Tao
T
Department of Anatomy and K.K. Leung Brain Research Centre, The Fourth Military Medical University, Xi'an 710032, China.
Hui
Rui
R
Dong
Yuan-Xiang
YX
Li
Yun-Qing
YQ
Mizuno
Noboru
N
D000818:Animals; D001369:Axons / Q000737:chemistry / Q000378:metabolism*; D007031:Hypothalamus / Q000737:chemistry / Q000378:metabolism*; D008125:Locus Coeruleus / Q000737:chemistry* / Q000378:metabolism; D008297:Male; D009434:Neural Pathways / Q000737:chemistry / Q000378:metabolism; D009474:Neurons / Q000737:chemistry / Q000378:metabolism; D009842:Oligopeptides / Q000032:analysis / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D017450:Receptors, Opioid, mu / Q000096:biosynthesis*
D009842:Oligopeptides; D017450:Receptors, Opioid, mu; C105293:endomorphin 1; C105294:endomorphin 2