Tetrahydroberberine suppresses dopamine-induced potassium current in acutely dissociated CA1 pyramidal neurons from rat hippocampus.
Effects of tetrahydroberberine (THB) on dopamine (DA)-induced response have been investigated in single pyramidal neurons freshly dissociated from CA1 area of the hippocampus using the nystatin perforated patch-clamp, whole-cell recording technique under voltage-clamp configuration. At a holding potential (VH) of -20mV, DA-induced responses included a transient outward current, a slow inward current and a combination of the two. The outward current had a reversal potential of -83.5 +/- 8.0 mV which was close to K+ equilibrium potential and was sensitive to TEA, suggesting that this outward current was carried by K+. Application of THB reversibly suppressed three type responses induced by DA with different degrees of inhibitory ratio. THB inhibited the DA-induced outward current in a concentration-dependent manner with an IC50 of 13 microM. The maximal value of the concentration-response curve for DA-induced outward current was suppressed by THB, suggesting a non-competitive inhibition. The results support the hypothesis that THB acts as a novel dopaminergic system antagonist. Furthermore, THB inhibits the DA-induced K+ current non-competitively in single dissociated cells, implying that THB may exhibit other pharmacological action on the central nervous system.
Wu
J
J
Department of Neurology, University of New Mexico, School of Medicine, Albuquerque 87131, USA.
Jin
G Z
GZ
D000818:Animals; D001599:Berberine / Q000031:analogs & derivatives* / Q000494:pharmacology; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D004298:Dopamine / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D006624:Hippocampus / Q000187:drug effects*; D015221:Potassium Channels / Q000187:drug effects*; D017966:Pyramidal Cells / Q000187:drug effects*; D051381:Rats; D017208:Rats, Wistar
D002121:Calcium Channel Blockers; D015221:Potassium Channels; D001599:Berberine; C004645:canadine; D004298:Dopamine