Expression of nitric oxide-containing structures in the rat carotid body.
The carotid body (CB) is a major peripheral arterial chemoreceptor organ that evokes compensatory reflex responses so as to maintain gas homeostasis. It is dually innervated by sensory fibers from petrosal ganglion (PG) neurons, and autonomic fibers from postganglionic sympathetic neurons of the superior cervical ganglion (SCG) and parasympathetic vasomotor fibers of intrinsic ganglion cells in the CB. The presence of nitric oxide (NO), a putative gaseous neurotransmitter substance in a number of neuronal and non-neuronal structures, was examined in the CB, PG and SCG of the rat using nicotinamide adenine dinucleotide phosphate diaphorase (NADPH-d) histochemistry, nitric oxide synthase (NOS) immunohistochemistry and retrograde tracing. One week after injecting the retrograde tracer Fast Blue (FB) in the CB, we found that a subset of perikarya in the caudal portions of the PG and SCG were FB-labeled. Histochemistry and immunohistochemistry revealed that the majority of large- and medium-sized PG and SCG cells were NADPH-d positive and displayed a strong NOS immunostaining. We also observed that many varicose nerve fibers penetrating the CB and enveloping the glomus cells and blood vessels were NADPH-d reactive and expressed the constitutive isoforms of NOS, nNOS and eNOS. In addition, some autonomic microganglion cells embedded within, or located at the periphery of the CB, and not glomus or sustentacular cells were nNOS-immunopositive while CB microvasculature expressed eNOS. The present results suggest that NO is a transmitter in the autonomic nerve endings supplying the CB and is involved in efferent chemoreceptor inhibition by a dual mechanism.
Institute of Neurobiology, Bulgarian Academy of Sciences, Sofia 1113, Bulgaria; Department of Anatomy, Faculty of Medicine, Trakia University, Stara Zagora 6003, Bulgaria. Electronic address: didiatan@bio.bas.bg.
Dimitrinka Y
DY
Atanasova
Department of Anatomy, Faculty of Medicine, Trakia University, Stara Zagora 6003, Bulgaria. Electronic address: nikolaydd@abv.bg.
Nikolay D
ND
Dimitrov
Institute of Neurobiology, Bulgarian Academy of Sciences, Sofia 1113, Bulgaria; Department of Anatomy and Histology, Medical University of Sofia, Sofia 1431, Bulgaria. Electronic address: nlazarov@medfac.acad.bg.
Nikolai E
NE
Lazarov
D000818:Animals; D002344:Carotid Body / Q000378:metabolism*; D005260:Female; D005724:Ganglia / Q000378:metabolism; D007150:Immunohistochemistry / Q000379:methods; D008297:Male; D009252:NADPH Dehydrogenase / Q000378:metabolism; D009412:Nerve Fibers / Q000378:metabolism*; D009474:Neurons / Q000378:metabolism*; D018377:Neurotransmitter Agents / Q000378:metabolism*; D009569:Nitric Oxide / Q000378:metabolism*; D019001:Nitric Oxide Synthase / Q000378:metabolism; D017208:Rats, Wistar
D018377:Neurotransmitter Agents; D009569:Nitric Oxide; D019001:Nitric Oxide Synthase; D009252:NADPH Dehydrogenase
Glomus cells; Histochemistry; Immunohistochemistry; NADPH diaphorase; Nitric oxide; Nitric oxide synthase