Fig. 1: Anatomical prefrontal substrates and functional interrogation of the interplay between long-term memory and tonic pain.
From: Prefrontal engrams of long-term fear memory perpetuate pain perception
a, Viral-mediated, Dox-controlled expression of protein tags under the Fos promoter, leading to activity-dependent tagging of prelimbic neurons with mCherry following painful foot shock or capsaicin or during recall of fear memory 28 d after cued fear conditioning. b, Experimental scheme (top left), typical examples (bottom left) showing successive labeling of neuronal populations over discrete behavioral states with mCherry and Fos immunohistochemistry (arrowheads: double-labeled neurons; scale bar, 50 µm) and quantitative summary (top right) of overlapping activated neuronal populations; total numbers of positive/tagged cells are shown underneath. Data were analyzed by one-way ANOVA with Tukey’s multiple comparisons test; *P < 0.05; foot shock followed by foot shock and fear recall followed by fear recall, n = 4 mice per group; fear recall followed by capsaicin, n = 5 mice per group; capsaicin followed by fear recall, n = 6 mice per group; IHC, immunohistochemistry. c, Characterization of labeled prefrontal neurons in fear recall engrams or by tonic pain using markers of excitatory and GABAergic neurons. Typical examples (left) and a quantitative summary (right) are shown; scale bar, 50 µm. Data were analyzed by two-way ANOVA with a Šidák correction for multiple comparisons test; *P < 0.05; n = 3 mice per group; PV, parvalbumin. d–f, Experimental scheme (d) for activity-dependent tagging of long-term fear engrams with optogenetic actuators ArchT or ChR2 and testing effects of light-induced silencing (e) or activation (f) of fear engrams on prelimbic Fos immunohistochemistry, fear recall behavior and capsaicin-evoked tonic pain-related behavior are shown. In e and f, an average of 4,280 neurons per mm3 were labeled with ArchT and 3,894 neurons per mm3 were labeled with ChR2, respectively; light-induced silencing and activation: unpaired t-test, n = 7 mice per group (e) and laser off n = 7 mice per group and laser on n = 8 mice per group (f); fear recall behavior: paired t-test, n = 17 mice (e) and n = 17 mice (f); tonic pain-related behavior: paired t-test, n = 18 mice (e) and n = 15 mice (f). All P and F values are shown in Supplementary Table 1.
