Extinction blunts paraventricular thalamic contributions to heroin relapse

Figure 1.. Validation of the combinatorial virus approach and optogenetic parameters (A) Schematic illustration of combinatorial virus approach and optogenetic approach used to target the PVT→NAc pathway. (B) Representative images (left) of ChR2-eYFP (green) and Flp-mCherry (red) expression in the PVT neurons. Placement map (right) shows ChR2-YFP spread in the PVT (each animal represented at 10% opacity). (C) Optogenetic stimulation (stim, 20 Hz, 20 ms) of ChR2-expressing neuron in the PVT induced Fos (top) compared to the non-stimulation condition (no stim, bottom). (D) Quantification of Fos-positive cells in PVT neurons (no stim, n = 6; stim, n = 9; **p < 0.01 versus no stim condition). (E) Schematic illustration of the slice electrophysiology approach employed to investigate ChR2 functionality in the PVT neurons (left) and functional connectivity of the PVT→NAc pathway (right). (F) Example traces of photo-evoked (20 Hz) action potentials (top) and photocurrent (bottom) in ChR2-expressing PVT neurons. (G) Quantification of light-evoked action potential firing at different frequencies of light stimulation (5, 10, 20, and 40 Hz) in ChR2-expressing PVT neurons (n = 11 cells/3 rats). (H and…

Figure 2.. Optogenetic activation of the PVT→NAc pathway induces real-time CPA and drives heroin relapse after abstinence from heroin self-administration (A) Timeline employed for the behavioral experiments. (B and C) Example trace (left) and heatmap (middle) of real-time CPA test after 14 d of abstinence from heroin self-administration (B). Optogenetic activation of the PVT→NAc pathway induces aversion in real-time CPA (B, right; n = 6) and drives heroin relapse (C; n = 6) after 14 days of abstinence. *p < 0.05, **p < 0.01 versus no stim condition. Data are shown as mean ± SEM.

Figure 3.. Extinction training blunts the ability of the PVT→NAc pathway to drive aversion and heroin relapse (A) Timeline employed for the behavioral experiments. (B and C) Example trace (left) and heatmap (middle) of real-time CPA test after extinction training from heroin self-administration (B). Optogenetic activation of the PVT→NAc pathway did not induce aversion (B, right; n = 9) and did not potentiate heroin relapse (C; n = 15) after extinction. Data are shown as mean ± SEM.

Figure 4.. Extinction training induces a loss of synaptic plasticity in NAc D1-MSNs (A and B) Schematic illustration of the viral approach used in the D2-eGFP transgenic mice (A) and slide electrophysiology setup (B) employed in our study. (C) Representative image of ChrimsonR-tdT expression in the PVT (left, red), ChrimsonR-expressing terminals in the NAc (middle, red), eGFP expression in D2-NAc MSNs (middle, green), and overlap (green + red, right). (D) Example traces of EPSCs recorded in NAc D1-MSNs before (pre-, left) and after (post-, right) LTD protocol application following extinction (top) or abstinence (bottom). (E) Time course (left) of optically evoked EPSCs in D1-MSNs before and after LTD protocol application (***p < 0.001, group by time interaction). Extinction, but not abstinence, produces a loss of LTD in D1-MSNs (right) (extinction, n = 6 cells/4 rats; abstinence, n = 7 cells/4 rats; ***p < 0.001, baseline versus the average of the last 10 min post-LTD; ###p < 0.001, abstinence versus extinction). (F) Example traces of EPSCs recorded in NAc D2-MSNs before (pre-, left) and after (post-, right) LTD protocol application following extinction training (top) or abstinence…

Figure 5.. Chemogenetic inhibition of the PVT→NAc pathway reduces heroin relapse (A) Schematic illustration of the combinatorial virus approach employed in our study. (B) Placement map showing hM4Di-mCherry expression in the PVT (each animal represented at 8% opacity). (C and D) Chemogenetic inhibition of the PVT→NAc pathway with the DREADD agonist J60 reduced cocaine-induced Fos expression in hM4Di-mCherry-expressing neurons (vehicle [Veh], n = 10; J60, n = 12). (E) Timeline employed for the behavioral experiment. (F and G) Chemogenetic inhibition of the PVT→NAc pathway reduces heroin relapse after abstinence (F; n = 11) but not extinction training (G; n = 12) from heroin self-administration. *p < 0.05, **p < 0.01 versus vehicle. Scale bars, 50 μm. Data are shown as mean ± SEM.