Dorsal root ganglion neurons of embryonic chicks contain nitric oxide synthase and respond to nitric oxide.
We investigated the function of nitric oxide (NO) in dorsal root ganglion (DRG) neurons from 10 day embryonic chicks and adult birds. NADPH-diaphorase activity, a histochemical marker for nitric oxide synthase (NOS) in paraformaldehyde-fixed neurons, and NOS-like immunoreactivity were localized in all neurons in thoracic and lumbar ganglia from embryos. However, only a subset of neurons from adults contained NOS-like immunoreactivity and NADPH-diaphorase activity. Thus, embryonic chick DRG neurons have the potential to synthesize NO in response to elevated cytoplasmic Ca2+. We also investigated the ability of dissociated embryonic chick DRG neurons to respond to NO by examining the effects of NO donors and 8-bromoguanosine 3',5'-cyclic monophosphate (8-Br-cGMP) on Ca2+ current (ICa) using the amphotericin-permeabilized patch-clamp technique: sodium nitroprusside (5 microM) reduced ICa to 0.68 +/- 0.06 (mean +/- S.D., n = 5) of control, S-nitroso-N-acetylpenicillamine (1 microM) reduced ICa to 0.44 +/- 0.06 (n = 4) of control, while 8-Br-cGMP (1 mM) reduced ICa to 0.58 +/- 0.22 (n = 5) of control. ICa was reduced in every neuron tested and this effect was partially reversed after approximately 10 min of washing. Thus, ICa of embryonic chick DRG neurons is inhibited by NO, possibly by a cGMP-dependent mechanism. These results indicate that all DRG neurons in embryonic chicks contain NOS-like immunoreactivity and respond to NO. Further, the percentage of NADPH-diaphorase positive neurons is reduced during development.
Ward
S M
SM
Department of Physiology, University of Nevada School of Medicine, Reno 89557.
Shuttleworth
C W
CW
Kenyon
J L
JL
D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology; D000594:Amino Acid Oxidoreductases / Q000378:metabolism*; D000818:Animals; D002118:Calcium / Q000378:metabolism; D015220:Calcium Channels / Q000187:drug effects; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D002478:Cells, Cultured; D002642:Chick Embryo; D004594:Electrophysiology; D005727:Ganglia, Spinal / Q000166:cytology / Q000187:drug effects* / Q000201:enzymology*; D007150:Immunohistochemistry; D009252:NADPH Dehydrogenase / Q000378:metabolism; D009474:Neurons / Q000187:drug effects* / Q000201:enzymology*; D009569:Nitric Oxide / Q000494:pharmacology*; D019001:Nitric Oxide Synthase; D018408:Patch-Clamp Techniques
D015220:Calcium Channels; D015124:8-Bromo Cyclic Adenosine Monophosphate; D009569:Nitric Oxide; D019001:Nitric Oxide Synthase; D000594:Amino Acid Oxidoreductases; D009252:NADPH Dehydrogenase; D002118:Calcium