Fig. 4: VTADA-NAc pathway activates inhibitory feedback targeting VTA-BLA neurons and inducing inhibition in the VTA.
a Retrobeads were injected into the basolateral amygdala (BLA), and ChR2 was expressed in the nucleus accumbens (NAc), specifically in the lateral shell (NAcLSh), medial shell (NAcMSh), or core (NAcCore). b Representative light-evoked IPSCs recorded from BLA-projecting VTA dopamine (DA) neurons. Neurons were identified post hoc via co-labeling of tyrosine hydroxylase (TH), neurobiotin (NB), and retrobeads (RB). Scale bar: 20 µm. c Proportion of BLA-projecting VTA DA neurons exhibiting light-evoked IPSCs (oIPSCs) following optogenetic stimulation from NAcMSh, NAcLSh, or NAcCore inputs. Mean oIPSC amplitudes are shown for responsive neurons (n = 7/17, 8/13, and 11/12, respectively). d Left: A Cre-dependent, retrogradely transported AAV encoding ChR2 was injected into the NAc (NAcLSh + NAcMSh + NAcCore) of DAT-Cre mice. Patch-clamp or multi-unit extracellular recordings were then performed. Middle: YFP-positive cells recorded ex vivo responded to 10 Hz and 20 Hz photostimulation. Scale bar: 20 µm. Right: Representative viral expression in the VTA and schematic of fiber (Op.st) and tetrode (T.rec) placement during in vivo recordings. Scale bars: 200 µm. e Distribution of changes in firing frequency (%) evoked by 10 Hz light stimulation (blue) compared to baseline spontaneous change of activity (gray) in VTA pDA neurons (n = 43; Kolmogorov-Smirnov test: D = 0.4, **p = 0.002). f Left: Mean time course of normalized firing frequency in light-activated pDA neurons during 10 Hz regular and 20 Hz burst photostimulation. Right: Firing rate change from baseline for regular and burst patterns (n = 15 and 6; paired Wilcoxon test: 10 Hz, V = 0, ***p = 6.1e-05; 20 Hz, V = 0, *p = 0.03). g same as (f) for light-inhibited pDA neurons (n = 13 and 8, respectively; paired t-test: 10 Hz, t12 = 6.1, ***p = 5.3e-05; 20 Hz, t7 = 3.87, **p = 0.006). Data are presented as mean ± SEM. All statistical tests are two-sided.
