Dopamine modulates a voltage-gated calcium channel in rat olfactory receptor neurons

Dopamine D2 receptors exist in the soma of rat olfactory receptor neurons. Actions of dopamine on the voltage-gated Ca2+ channels in the neurons were investigated using the perforated whole-cell voltage-clamp. In 10 mM Ba2+ solution, rat olfactory receptor neurons displayed the inward currents elicited by the voltage ramp (167 mV/s) and depolarizing step pulses from a holding potential of -91 mV The inward Ba2+ currents were greatly reduced by 10 muM nifedipine (L-type Ca2+ channel blocker). The Ba2+ currents were inhibited by the external application of dopamine. The IC50 for the inhibition was about 1 muM. Quinpirole (10 muM, a D2 dopamine agonist) also inhibited the Ba2+ currents. Quinpirole did not affect the activation and inactivation kinetics of the Ba2+ currents. The results suggest that dopamine modulates the L-type Ca2+ channels in rat olfactory receptor neurons via the mechanism independent of voltage. (C) 2003 Elsevier Science B.V. All rights reserved.