Fig. 1.
Presynaptic CRF-1 receptors potentiate GABAA IPSCs in VTA DA neurons. a Traces of stimulus-evoked, picrotoxin-sensitive IPSCs showing potentiation by CRF (200 nM) and urocortin (UCN; 200 nM), but not the CRF-R2 agonist UCN-3 (300 nM). For the timeline, the amplitude of the evoked current was normalized for each cell using the mean amplitude recorded during the first 5 min and plotted as function of time (% of baseline, mean ± SEM). Although CRF (200 nM) and UCN (200 nM) potentiated IPSCs, UCN-3 did not. The smooth curves in the agonist concentration–response plot are the best fit to the data by the logistic equation. b CRF (300 nM) increased the amplitude of the first eIPSC (S1), with little measurable change in the second eIPSC (S2). Inset shows the first eIPSCs (S1) normalized to the second eIPSC (S2). CRF significantly decreased the paired pulse ratio (PPR; IPSC2/IPSC1, ***p < 0.001. c CRF (300 nM) enhances the frequency of spontaneous IPSCs (sIPSCs). Inset shows magnification of sIPSCs. Both UCN and CRF increased the frequency of sIPCS relative to their baseline (***p < 0.001). d, e The CRF (300 nM) potentiation is blocked by co-application of (e) CRF-R1 antagonists (CP154156 (CP154) or antalarmin (AA), but not (d) CRF-R2 antagonists (K41498 (K414) or astressin-2B (A2B) (*p < 0.05). f The CRF (300 nM) shift in the PPR is reduced by CRF-R1 blockers (CP154 or AA), but not CRF-R2 blockers (K414 or A2B). One-way ANOVA, *p < 0.05 vs CRF alone (Dunnett’s post test). g The CRF (200 nM) enhancement of sIPSC frequency is prevented by co-application of CRF-R1 blockers (CP154 or AA), but not CRF-R2 blockers (K414 or A2B). One-way ANOVA, ***p < 0.001 vs CRF alone (Dunnett’s post test). a–g Number of cells/mice per group: a CRF 13/7; UCN 11/6, UCN-3 9/4 for both timelines and concentration–response curves; b 7/4; c 7/5, d, e K414 9/5, A2B 9/5, CP154 8/4, AA 7/3; f 7/3-4 per group; g CRF+K414 7/4, and the following groups contained 8-9/4-5: UCN+A2B, CRF+A2B, CRF+CP154, and CRF+AA