Fig. 1.

KOR agonist, U50,488, bidirectionally altered LHb neuronal excitability in distinct subpopulations of LHb neurons identified by Ih currents. A-B, inset: Example traces of AP generation in response to +50 pA current injection at baseline (black) and post-U50,488 (red). A. U50,488 significantly decreased the number of AP generated across depolarizing current steps of Ih- neurons B. U50,488 significantly increased the number of AP generated across depolarizing current steps in Ih+ neurons C. Scatter plot of Ih values across Ih- (n = 20/15) and Ih+ (n = 16/13) groupings; Mean ± SEM displayed as bar/whisker; traces: Ih current traces (mean [line] ± SEM [shaded region]) in response to a hyperpolarizing voltage step from −50mV to −100mV in Ih- (≤-10 pA, n = 20/15) and Ih+ (>−10 pA, n = 16/13) groups. D. At baseline, Ih- neurons had larger input resistance (Rin) compared to Ih+ neurons and U50,488 treatment significantly increased Rin only in Ih+ neurons. E. At baseline, Ih- neurons had significantly lower (less negative) AP thresholds compared to Ih+ neurons. U50,488 significantly increased AP thresholds of both Ih- neurons and Ih+ neurons F. U50,488 induced a significant increase in fAHPs of Ih+ neurons, inset: sample traces for fAHPs before (black) and after the addition of U50,488 recorded from an Ih+ neuron in a non-MD control rat G. At baseline, Ih- neurons had significantly larger mAHP compared to Ih+ neurons. U50,488 significantly decreased mAHPs of Ih- neurons and Ih+ neurons. inset: sample traces for mAHPs before (black) and after the addition of U50,488 recorded from an Ih+ neuron in a non-MD control rat. *p < 0.05, **p < 0.01. In this and subsequent figures n represents the number of recorded cells/rats. (For interpretation of the references to colour in this figure legend, the reader is referred to the Web version of this article.)