Role of Potassium Channels in the GABA Inhibitory Action on the Purinergic Response to Electrical Field Stimulation in Rat Isolated Vas Deferens

Abstract

The involvement of potassium channels in the GABAB receptor‐mediated modulatory effects of γ‐aminobutyric acid (GABA) on the purinergic response of rat isolated vas deferens exposed to electrical field stimulation (EFS) was investigated. Non‐selective Ca2+‐dependent K+ (KCa) channel antagonists, tetraethylammonium chloride (TEA) and 4‐aminopyridine (4‐AP), and a selective large conductance Ca2+‐activated K+ (BK) channel antagonist, iberiotoxin, reduced the inhibitory effects of GABA on the purigenic response to EFS. The GABA induced‐inhibition of the EFS contractions was not affected by the small conductance Ca2+‐activated K+ (SK) channel blocker, apamin, or by the ATP‐sensitive K+ channel (KATP) channel blocker, glibenclamide. These observations seem to indicate a coupling between GABAB receptors and BK channels in rat vas deferens.

Role of Potassium Channels in the GABA Inhibitory Action on the Cholinergic Response to Electrical Field Stimulation in Guinea-pig Ileum

“…In a functional study on the rabbit urinary bladder, Ferguson & Marchant (1995) demonstrated that the GABA B receptor action was mediated by a class of K channels. In a previous investigation we have suggested a possible involvement of large conductance Ca 2 -dependent K channels in the inhibitory action of GABA on the purinergic response in rat vas deferens exposed to EFS (Calderone et al 1999). The aim of this study was to investigate the role of potassium channels in the GABA-induced inhibition of the cholinergic response in guinea-pig ileum exposed to EFS.…”

“…The inhibitory effects of baclofen, a GABA B agonist, on carbacholinduced contractions of rabbit urinary bladder muscle strips are mediated by a class of K channels blocked by tetraethylammonium chloride, 4-aminopyridine, Cs and Ba 2 (Ferguson & Marchant 1995). We have previously suggested that the GABA B -induced modulatory action on the purinergic response in rat vas deferens exposed to EFS is mediated by activation of large conductance Ca 2dependent K channels (Calderone et al 1999).…”