Fig. 4.

Lack of effect of naloxone on the OFQ modulation of high-voltage-gated Ca²⁺ channel currents. Orphanin FQ (OFQ; 300 nm) was applied alone or in the presence of the broad spectrum opioid receptor antagonist naloxone (10 μm) for the time indicated by the bars. The currents were elicited by 50 msec voltage steps to 0 mV from a holding potential of −80 mV at 3 sec intervals. In addition to the rapid coapplication with OFQ, naloxone was present in the bath 1 min before and during the test.