Figure 4.
Estradiol-treated OVX females have an increased probability of glutamate release onto NPY/AgRP neurons. A, Representative traces from E2-treated and oil-treated OVX female POMCCre::ChR2:mCherry mice. Paired pulse protocol uses 5-ms 470-nm optogenetic stimulation with an interstimulus interval of 50 ms to measure release probability. The PPR is equal to the amplitude of peak 2 over peak 1. Lower numbers indicate a higher release probability. B, PPR is significantly lower with E2 treatment compared to oil-treated OVX mice. Traces are the average of 50 sweeps (t test, ** p < 0.01). C, Schematic illustrating how the PPR provides a measure of neurotransmitter release probability. In terminal 1, when the two peaks are of a similar amplitude, the first stimulus did not deplete the readily releasable pool of vesicles. In terminal 2, the first stimulus caused nearly all of the vesicles to fuse and release neurotransmitter, leaving little for the next stimulus.