Nitrergic neurons in the medial amygdala project to the hypothalamic paraventricular nucleus of the rat.
We investigated nitric oxide (NO)-producing neurons in the amygdala which project to the hypothalamic paraventricular nucleus (PVN) of the rat using retrograde tracing and NADPH-diaphorase histochemistry. Numerous NADPH-diaphorase positive neurons with moderate staining were observed mainly in the medial amygdaloid nucleus. We confirmed that these NADPH-diaphorase positive neurons are identical to NO synthase (NOS)-immunoreactive neurons by double staining with NADPH-diaphorase histochemistry and NOS immunocytochemistry. Most neurons containing cholera toxin B subunit (CTb) - which was retrogradely transported from the PVN - were observed in the medial amygdaloid nucleus. In other amygdaloid nuclei, they were observed much less in the central nucleus, basomedial and anterior cortical nucleus. Double labeled neurons by NADPH-diaphorase and CTb were also identified mostly in the medial nucleus. Approximately 40% of the neurons projecting to the PVN were nitrergic neurons and 16% of NADPH-diaphorase positive neurons in the medial nucleus were revealed to project to the PVN. These results suggest that NO-producing neurons in the medial amygdala directly innervate PVN neurons and regulate neuroendocrine systems such as vasopressin and corticotropin releasing factor release.
Tanaka
M
M
Department of Anatomy and Neurobiology, Kyoto Prefectural University of Medicine, Japan.
Ikeda
T
T
Hayashi
S
S
Iijima
N
N
Amaya
F
F
Hisa
Y
Y
Ibata
Y
Y
D000679:Amygdala / Q000166:cytology*; D000818:Animals; D002772:Cholera Toxin; D007150:Immunohistochemistry; D008297:Male; D016253:Microscopy, Immunoelectron; D009252:NADPH Dehydrogenase / Q000032:analysis; D009434:Neural Pathways; D009474:Neurons / Q000737:chemistry / Q000201:enzymology* / Q000648:ultrastructure; D009569:Nitric Oxide / Q000502:physiology*; D010286:Paraventricular Hypothalamic Nucleus / Q000166:cytology*; D051381:Rats; D017208:Rats, Wistar
D009569:Nitric Oxide; D002772:Cholera Toxin; D009252:NADPH Dehydrogenase