Figure 5.

Effects of endomorphin 1 on SON cells in vitro. (A) The firing rate (in 10 s bins) of a SON oxytocin cell (measured with whole cell current-clamp recording in vitro in hypothalamic slices; oxytocin and vasopressin cells were distinguished by their different responses to hyperpolarizing pulses as described in Methods). This cell shows a dose-dependent inhibition of the firing rate by endomorphin 1 (EM1) (typical of three experiments). (B) The mean firing rate (+s.e.mean in 10 s bins) of five oxytocin cells recorded as in (A). For each cell, the firing rate was inhibited by over 50% by 100 nM endomorphin 1. (C) The mean firing rate of 11 vasopressin cells recorded as in (A); there was no significant effect of 10 μM endomorphin 1 on the firing rate of this group of cells (10 cells were unaffected by endomorphin 1, while the firing rate of just one cell was reduced, by 25%).