Modulation of voltage-dependent potassium currents by opiates in facial motoneurons of neonatal rats.
We examined the modulation of rat facial motoneurons (FMNs) by opiates in a slice preparation (7-15 days old) using whole-cell patch clamp techniques. Although application of methionine enkephalin (ME) did not change the peak value of the transient outward current (A-current, IA), it reduced the persistent voltage-dependent K(+) currents (IKs) in a dose-dependent manner. The reduction was antagonized by naloxone (40 microM). IKs were reduced only by mu-selective agonist [D-Ala(2),N-Me-Phe(4),Gly(5)-ol]enkephalin (DAMGO, 2-121.6 microM). This reduction was antagonized by naloxone (40 microM) or the mu-selective antagonist, D-Phe-Cys-Tyr-D-Trp-Orn-Thr-Phe-Thr-NH(2) (CTOP, 1 microM). Agonists for other opiate receptors (delta- and kappa-opiate receptor) showed no effect on IKs. In accord with the effects on IKs, DAMGO (100 microM) prolonged the duration of the action potential evoked in Ca(2+)-free external solution containing 4-aminopiridine (1mM). These results suggest that the activation of mu-opiate receptors contributes to signal transduction in FMNs primarily by modulating action potential duration.
Department of Physiology, Faculty of Medicine, Mie University, Tsu, Mie 143-8540, Japan.
Yuichi
Y
Kumazawa
Yoshihiro
Y
Nishimura
Takanobu
T
Akamine
Min
M
Lin
Toshihiro
T
Asahara
Hiroshi
H
Shibuya
Tetsuro
T
Yamamoto
D000818:Animals; D000831:Animals, Newborn; D004305:Dose-Response Relationship, Drug; D005154:Facial Nerve / Q000187:drug effects* / Q000502:physiology; D005260:Female; D066298:In Vitro Techniques; D008297:Male; D009046:Motor Neurons / Q000187:drug effects* / Q000502:physiology; D009294:Narcotics / Q000494:pharmacology*; D024642:Potassium Channels, Voltage-Gated / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley
D009294:Narcotics; D024642:Potassium Channels, Voltage-Gated