Figure 5: GLP-1 activates IPN neurons by stimulating habenular terminals.

(a) Example traces of mEPSCs in IPN neurons before and after bath application of Ex-4 (100 nM). (b,c) Cumulative probability (± s.e.m.) (b) and summarized results (c; mean ± s.e.m.) showing that the relative amplitude of mEPSCs in IPN neurons is not altered by Ex-4. (d,e) Cumulative probability (± s.e.m.) (d) and summarized results (e; mean ± s.e.m.) showing that the relative frequency of mEPSCs in IPN neurons is increased by Ex-4. *P =0.0165, paired t-test; n = 9 cells from 4 animals. (f) Top: the MHb–IPN circuit (green). Bottom: cholinergic MHb neurons (left) send axonal projections to the IPN (right) as evinced by fluorescence from ChAT-ChR2-eYFP mice. Nuclear DAPI staining is shown in blue. Scale bars, 50 μm. (g) Sample trace showing that the amplitude of light-evoked EPSCs in IPN neurons from ChAT-ChR2-eYFP mice is increased by Ex-4. (h) Summarized results (mean ± s.e.m.) showing that Ex-4 significantly increases the amplitude of light-evoked EPSC in IPN neurons. ***P = 0.0005, paired t-test; n = 13 cells from 9 cells animals. (i) Representative micrographs showing induction of Fos in IPN following nicotine challenge in GLP-1R knockout and wild-type mice. Scale bar, 100 μm. (j) Mean (± s.e.m.) number of Fos-positive neurons per IPN section in GLP-1R knockout (saline, n = 6; nicotine, n = 7) and wild-type (saline, n = 6; nicotine, n = 7) mice following nicotine challenge. Two-way ANOVA, genotype: F_(1,22) = 17.69, P = 0.0004; nicotine: F_(1,22) = 51.71, P < 0.0001; genotype × nicotine: F_(1,10) = 13.36, **P = 0.0014.