PrRP inhibits the MCH neurons. A, Left, Immunohistochemical detection of MCH neurons in 30-d-old rats. Right, Schematics (Paxinos and Watson, 2007) of the brain slice preparation for patch-clamp recording. Acute coronal slices containing the hypothalamus were used with the thalamus, and the cortex removed. Neurons in the PFA were patched using a biocytin (bi) filled electrode. B, Electrophysiological identification of the MCH neurons was performed by their response to current steps (van den Pol et al., 2004). C, Identity of the measured cells was confirmed by post hoc IHC. D, PrRP (3.5 µm) elicits a transient outward current in MCH neurons in the absence of TTX. Student's t test (paired), t = 14.745, df = 5, *p = 0.000. E, Membrane potential changes (ΔV_rest) of MCH neurons in response to PrRP in the absence of TTX. Student's t test (paired), t = 9.785, df = 5, *p = 0.000. F, There is no response to PrRP in the presence of TTX. G, ΔV_rest in response to repeated administration of NA (10 µm, dashed arrows), and after pretreatment with PrRP (solid arrow) in the absence (left) and presence of TTX (right). H, Graphs summarize the effects of PrRP on the NA-induced responses. One-way repeated-measures ANOVA. ΔV_rest no TTX: F_(2,10) = 32.6, p < 0.001, Holm–Sidak multiple comparison tests, PrRP+NA versus first and second NA, *p < 0.0001. I, ΔV_rest in response to NA in the absence (–) and presence (+) of the α2-adrenergic receptor antagonist yohimbine (2 µm, horizontal line above the recording). Student's t test, t = 8.900, df = 5, *p = 0.000. J, ΔV_rest in response to repeated administration of NA (dashed arrows), and after pretreatment with PrRP (solid arrow) in the presence of the GABA(A) receptor antagonist picrotoxin (100 µm) and absence of TTX. K, Graphs summarize the effects shown in J. Error bars indicate mean ± SEM. n_cells = 6 for all except n_cells = 4 in F. One or two cells/animal were measured in independent experiments.