CAPSAICIN BLOCKS CA2-NEURONS( CHANNELS IN ISOLATED RAT TRIGEMINAL ANDHIPPOCAMPAL)

EFFECTS Of capsaicin, an essential ingredient of hot peppers, on high voltage-activated (HVA) calcium channels were investigated in voltage- clamped and internally perfused acutely dissociated rat trigeminal and hippocampal neurones. In micromolar concentrations capsaicin inhibite d the whole HVA Ca2+ current without affecting resting membrane conduc tance in both types of neurones. IC50 values of 14.5 mu M and 21.2 mu M (n = 5) were obtained in sensory and hippocampal neurones, respectiv ely. Capsaicin-induced inhibition became irreversible after prolonged incubation (30 s) with the drug. It is concluded that capsaicin is a n onspecific blocker of HVA Ca2+ channels in different types of nerve ce lls.