Figure 2. Effects of ion substitution and drugs on membrane potential responses to TRH.

A, effect of 250 nm TRH on an orexin cell in ‘low Ca²⁺’ extracellular solution (see Methods). B, effect of 250 nm TRH on an orexin cell in ‘low Na⁺’ extracellular solution (see Methods). C, lack of effect of the Na⁺/Ca²⁺ exchange blocker KB−R7943 (70 μm) on depolarization induced by 250 nm TRH. D, summary of mean depolarization elicited by 250 nm TRH in the presence of different solutions and drugs. **P < 0.005, each bar corresponds to at least 4 cells. n.s. = no significant difference (P > 0.2).