DOPAMINE-INDUCED IONIC CURRENTS IN ACUTELY DISSOCIATED RAT NEURONS OFCNS

AIM: To determine whether or not the dopamine (DA) can induce ionic cu rrent in single neuron acutely dissociated from different central area s including striatum, ventral tegmental area (VTA), substantia nigra p ars compacta (SNC) and hippocampal CA(1) area. METHODS: Using a new pa tch-clamp whole-cell recording technic, namely nystatin-perforated who le-cell configuration under voltage-clamp mode. RESULTS: In 36 single neurons isolated-from the striatum and VTA, DA 10-1000 mu mol . L(-1) was quite diverse to elicit ionic current response. In 19 SNC neurons, 5 neurons (26%) response to 1 mmol . L(-1) DA represented as a small outward current (11.3 +/- 2.4 pA) at a holding potential (V-H) of - 20 mV. In. 25 of 69 (36%) examined hippocampal CA(1) pyramidal neurons, however, application of DA induced 3 types of current responses: outwa rd current (8 neurons) accompanied with an increase of membrane conduc tance, slow inward current (5 neurons) with an decrease of membrane co nductance and outward-following inward current (12 neurons) at a V-H o f - 20 mV. The concentration-response relationship of DA-induced curre nts showed the typical sigmoid shape with the threshold dose, being th e maxium response dose are 3 mu mol . L(-1) and 1 mmol . L(-1) respect ively. The current-voltage (I-V) relationship of DA-induced responses did not show any voltage-dependent manner and the reversal potential ( EDA) was close to the equilibrium potential of potassium (E(K)) calcul ated with the Nernst equation. TEA 5 mol . L(-1) effectively inhibited the DA-induced response. CONCLUSION: These results suggest that DA-in duced outward current is carried by K+ in single hippocampel CA(1) pyr amidal neuron.