N-type Ca2+ channels in cultured rat sphenopalatine ganglion neurons: an immunohistochemical and electrophysiological study.
Results from pharmacological studies have suggested that presynaptic N-type Ca2+ channels play an important role in regulating neuronal Ca2+ influx and transmitter nitric oxide (NO) release in isolated cerebral arteries. However, the presence of N-type Ca2+ channels in cerebral perivascular nerves has not been directly demonstrated. As a major source of cerebral perivascular NOergic innervation is the sphenopalatine ganglion (SPG), adult rat SPGs were cultured and examined by whole-cell patch-clamp technique. One week after growing in the culture medium, significant neurite outgrowth from the SPG neuronal cells was observed. Both soma and neurites of these cells were immunoreactive for N-type Ca2+ channels, transmitter-synthesizing enzymes (choline acetyltransferase and NO synthase), and several neuropeptides (vasoactive intestinal peptide, neuropeptide Y, calcitonin gene-related peptide, substance P, and pituitary adenylate cyclase-activating peptide-38) that had been found in cerebral perivascular nerves in whole-mount vascular preparations. In current-clamp recordings, injection of a small depolarizing current caused action potential firing. In voltage-clamp recordings, the fast inward currents were blocked by tetrodotoxin and outward currents by tetraethylammonium, which is typical for neurons. Most Ca2+ currents isolated by blockade of sodium and potassium currents were blocked by omega-conotoxin, indicating that N-type Ca2+ channels are the dominant voltage-dependent Ca2+ channels regulating Ca2+ influx during membrane depolarization of SPG neurons. The ability to culture postganglionic SPG neurons provides an opportunity to directly study the electrophysiological and pharmacological properties of these neurons.
Liu
J
J
Department of Pharmacology, Southern Illinois University School of Medicine, Springfield, USA.
Evans
M S
MS
Brewer
G J
GJ
Lee
T J
TJ
D000200:Action Potentials / Q000502:physiology; D000818:Animals; D020864:Calcium Channels, N-Type / Q000378:metabolism* / Q000502:physiology; D002455:Cell Division; D002478:Cells, Cultured; D004553:Electric Conductivity; D004594:Electrophysiology; D005726:Ganglia, Parasympathetic / Q000166:cytology / Q000378:metabolism* / Q000502:physiology; D007150:Immunohistochemistry; D009474:Neurons / Q000166:cytology / Q000378:metabolism* / Q000502:physiology; D018408:Patch-Clamp Techniques; D051381:Rats; D017207:Rats, Sprague-Dawley
D020864:Calcium Channels, N-Type