Acidosis-Induced Pain Sensitivity in Females

Considering the gender differences in pain caused by acidosis in our previous reports, only female rats were used to study in the current experiment (57 (link)). Rats were first habituated for 30 min in a Plexiglas chamber during the nociceptive behavioral experiment. The rats received two intraplantar injections, each with a volume of 50 μl. For the first time, rats in five different groups (n = 10/group) injected with either 50 μl of 10 μM AMG 9810 + vehicle, a 50 μl of cocktail containing10 μM AMG 9810 + different doses (0.1, 1, and 10 ng) of LY354740, or 50 μl of cocktail containing AMG 9810 + 50 ng LY341495 + 10 ng LY354740. After 10 min, another experimenter injected 50 μl of acetic acid solution (1% v/v, pH value was adjusted to 6.0 with NaOH and external solution containing 10 mM MES) into the ipsilateral hind paws and tested the nociceptive behavior. The assessor of the behavioral measures was blinded to the prior treatment conditions. Nociceptive behavior (i.e., number of flinching, shaking, and licking) was counted within 5 min after injection. In one group, acetic acid was injected into one hind paw and 10 ng LY354740 was injected into the contralateral hind paw. Nociceptive behaviors were expressed as the number of flinches and counted immediately within 5 min after injection (29 (link), 35 (link)).