INHIBITION BY THE PUTATIVE POTASSIUM CHANNEL OPENER PINACIDIL OF THE ELECTRICALLY-EVOKED RELEASE OF ENDOGENOUS DOPAMINE AND NORADRENALINE IN THE RAT VAS-DEFERENS

• Type: Article in International Scientific Journal
• Date: 1990

Authors

soares-da-silva, p (Author) FMUP; Fernandes MH (Author) FMDUP

Journal

Title: Naunyn-Schmiedeberg's Archives of Pharmacology

Vol. 342

Pages: 415-421

ISSN: 0028-1298

Publisher: Springer Nature

Indexing

ISI Web of Knowledge - 18 Citations

Scopus - 18 Citations

Other information

Authenticus ID: P-001-RGM

Abstract (EN): The effect of pinacidil on the release of endogenous noradrenaline and dopamine from the sympathetic innervation of the rat vas deferens was examined. Amine release was evoked by electrical stimulation (1, 2, 5 and 10 Hz) or by depolarization with high potassium (75 mmol/l) in the medium. Dopamine and noradrenaline were measured by means of high pressure liquid chromatography with electrochemical detection. Pinacidil (1, 5, 10 and 50 ¿mol/l) produced a concentration-dependent inhibition of the electrically stimulated (2 Hz) overflow of noradrenaline and dopamine. Only pinacidil 50 ¿mol/l increased the spontaneous loss of dopamine and noradrenaline. The inhibitory effects of pinacidil (5 ¿mol/l) on amine overflow were also observed at other frequencies of stimulation (1, 5 and 10 Hz). The magnitude of the inhibitory effect or noradrenaline release was approximately the same at all frequencies (63% to 56% reduction); for dopamine, the higher the frequency of stimulation, the greater the inhibitory effect of pinacidil (up to 73% reduction). When the preparations were continuously stimulated for 70 min at 2 Hz, pinacidil (5 ¿mol/l) reduced the overflow of dopamine and noradrenaline during the first 40 or 30 min of stimulation only. The addition of phentolamine (1 ¿mol/l) to the perifusion medium slightly reduced the inhibitory effect of pinacidil on amino overflow, but the inhibition by pinacidil remained statistically significant. Tetraethylammonium (10 mmol/l) completely abolished the inhibitory effect of pinacidil (10 ¿mol/l). Pinacidil (5 ¿mol/l) did not reduce the potassium-evoked release of the amines. The results demonstrate that pinacidil impairs transmitter release from the sympathetic innervation of the rat vas deferens, probably as a consequence of the opening of potassium channels.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 7