FIG. 1.

GnRH neurons from OVX+E mice but not from OVX mice exhibited a diurnal change in voltage-gated potassium currents. A) A voltage clamp protocol was used to identify voltage-gated potassium currents in GnRH neurons; for clarity, only three prepulse potentials (−110, −40, and −20 mV) are shown. Most of the 500 msec step to −100 mV for removal of inactivation from the A-type channel was omitted. Prepulses and test pulses shown were both 500 msec in duration. B) Representative traces of total potassium current illustrate two components: a fast transient current (I_A) and a sustained current (I_K) from GnRH neurons from OVX mice, recorded during negative feedback, morning hours (left), and during positive feedback, evening hours (right). The short duration current peak at the beginning of the −40 mV prepulse is the activation of I_A, followed by its inactivation during the remainder of the prepulse, allowing measurement of isolated I_K during the test pulse. C) Representative traces are shown from GnRH neurons from OVX+E mice recorded during morning hours (left) and evening hours (right).