3.3 Short-term DREADD specifically activate BLA astrocytes induces mechanical pain but not anxiety-like behavior in naive rats.
To further investigate whether the activation of BLA astrocytes was sufficient to cause mechanical allodynia, we activated BLA astrocytes in naive rats with the gfaABC1D-M3-EGFP virus (Fig. 3A). We observed that in the gfaABC1D-M3-EGFP group, mechanical allodynia was gradually induced, peaked at 2 hours after CNO administration, and then returned to normal 6 hours after CNO treatment. However, no significant changes in MWT were found in the gfaABC1D-M3-EGFP group treated with normal saline (Fig. 3B). CNO caused the MWT to significantly decrease in the gfaABC1D-M3-EGFP group compared with the gfaABC1D-EGFP group (Fig. 3C).
Next, we observed the effects of chemical genetic activation of BLA astrocytes on the behavioral performance of rats in open field and elevated cross maze. The results of open field test showed that after intraperitoneal administration of CNO (0.5 mg/kg), rats transfected with gfaABC1D-EGFP or gfaABC1D-M3-EGFP virus had similar trajectories in the open field (Fig. 3D), showing no significant difference in the total distance (Fig. 3E) and the central motor distance (Fig. 3F). Results from the elevated plus maze also showed that after CNO administration, the activity trajectories of the rats transfected with gfaABC1D-EGFP or gfaABC1D-M3-EGFP in the elevated cross maze were similar (Fig. 3G), which showed that there was no significant difference in the activity time in the open arm (Fig. 3H) and the number of explorations into the open arm (Fig. 3I).
Then, we assessed the expression of astrocytes in the BLA to prove that CNO specifically activated gfaABC1D-M3-EGFP-infected cells. We found that CNO significantly enhanced astrocyte expression in the gfaABC1D-M3-EGFP group compared with the gfaABC1D-EGFP group (Fig. 3J-3L). Based on these findings, BLA astrocytes may be an integral part of DNP pathogenesis.