Fig. 6: Morphine impairs inhibitory synaptic transmission in GRP⁺ interneurons in the SDH.

A Recording traces of spontaneous inhibitory postsynaptic currents (sIPSCs) after vehicle and morphine (10 μM) treatments in GRP⁺ interneurons of the spinal slices from Grp^Cre;Ai9 mice. B Cumulative histograms of the inter-event interval and amplitude of sIPSCs after the vehicle and morphine treatments, P < 0.0001, respectively. two-tailed Kolmogorov-Smirnov test. C The sIPSC frequency before and after morphine treatment, 12 neurons from 5 mice were analyzed, paired two-tailed t-test. D The sIPSC amplitude before and after morphine treatment, 12 neurons from 5 mice were analyzed, P = 0.0340, paired two-tailed t-test. E The sIPSC frequency before and after vehicle treatment, 8 neurons from 4 mice were analyzed, paired two-tailed t-test. F The sIPSC amplitude before and after vehicle treatment, 12 neurons from 5 mice were analyzed, paired two-tailed t-test. Data are shown as means with dots. P values are indicated in the figures. G Recording traces of miniature IPSCs after morphine (10 μM) treatments in GRP⁺ interneurons of the spinal slices from Grp^Cre;Ai9 mice in the presence of 0.5 μM TTX. H The miniature IPSC frequency before and after morphine treatment, 14 neurons from 4 mice were analyzed, paired two-tailed t-test. I The miniature IPSC amplitude before and after morphine treatment, 14 neurons from 4 mice were analyzed, paired two-tailed t-test. J Schematic representation of the Grp^Cre;GCamp6f mice and spinal dorsal horn fiber photometry recording in vivo. K Heatmaps shows the calcium signals within the 10-25 min after drugs injection (i.t., 0.3 nmol morphine, 10 nmol naloxone + 0.3 nmol morphine, and 10 μg NPY + 0.3 nmol morphine), n = 5 mice per group. Source data are provided as a Source Data file. Created in BioRender. Wang, Z. (2025) https://BioRender.com/waectjd.