Wu J, Jin G Z
Department of Neurology, University of New Mexico, School of Medicine, Albuquerque 87131, USA.
Neurosci Lett. 1996 Apr 5;207(3):155-8. doi: 10.1016/0304-3940(96)12522-2.
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.
