Extracellular recordings of membrane potential from guinea-pig isolated trigeminal ganglion: lack of effect of sumatriptan.
The aim of this study was to investigate the effect of the anti-migraine drug and selective 5-HT1 receptor agonist, sumatriptan, on membrane potential of guinea-pig isolated trigeminal ganglion. Ganglia were divided into three longitudinally, placed in two-compartment baths and the d.c. potential between compartments was recorded extracellularly. Drugs were applied to the Krebs superfusion fluid of one compartment. KCl (3 mmol/l) and GABA (0.1 mmol/l) caused depolarization (0.30 +/- 0.05 and 0.55 +/- 0.08 mV respectively, n = 11-19). 5-HT (1-10 mumol/l) caused small depolarizations (0.06 +/- 0.02 mV, n = 8) but sumatriptan (0.1-10 mumol/l) had no effect on trigeminal ganglion membrane potential. Collagenase pretreatment, to enhance desheathing, or modification of the composition of the Krebs solution failed to reveal any effect of sumatriptan. These data provide no evidence to suggest that sumatriptan inhibits neurotransmission in trigeminal ganglion. However, 5-HT1 receptors may be present in insufficient numbers in the trigeminal ganglion to elicit a change in membrane potential. Further studies are required to investigate the effect of sumatriptan at the level of the sensory nerve terminals within the intracranial vasculature, where 5-HT1 receptors may be concentrated.
Department of Neuropharmacology, Glaxo Group Research Ltd, Ware, UK.
C T
CT
O'Shaughnessy
H E
HE
Connor
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W
Feniuk
D000818:Animals; D015740:Calcitonin Gene-Related Peptide / Q000494:pharmacology; D002211:Capsaicin / Q000494:pharmacology; D006168:Guinea Pigs; D066298:In Vitro Techniques; D007211:Indoles / Q000494:pharmacology*; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology*; D011189:Potassium Chloride / Q000494:pharmacology; D011985:Receptors, Serotonin / Q000187:drug effects / Q000502:physiology; D012701:Serotonin / Q000494:pharmacology; D017366:Serotonin Receptor Agonists / Q000494:pharmacology*; D013449:Sulfonamides / Q000494:pharmacology*; D018170:Sumatriptan; D012668:Trigeminal Ganglion / Q000187:drug effects / Q000502:physiology*; D005680:gamma-Aminobutyric Acid / Q000494:pharmacology
D007211:Indoles; D011985:Receptors, Serotonin; D017366:Serotonin Receptor Agonists; D013449:Sulfonamides; D012701:Serotonin; D005680:gamma-Aminobutyric Acid; D011189:Potassium Chloride; D018170:Sumatriptan; D015740:Calcitonin Gene-Related Peptide; D002211:Capsaicin