Cyclodextrin‐complexed Lippia grata essential oil reduce c‐fos expression in the periaqueductal gray area following the antinociceptive effect in mice

Abstract

Lippia grata Schauer (Verbenaceae) leaves essential oil/β‐cyclodextrin (EO/β‐CD) complex was used to evaluated if the complex formulation is able in reduces orofacial behavior in mice. Male Swiss mice were pretreated with EO/β‐CD (50, 100 and 200 mg/kg, p.o., per os, orally), morphine (5 mg/kg, i.p.) or vehicle (distilled water). Ninety minutes after the treatment, we injected formalin (20 μL, 2%), capsaicin (20 μL, 2.5 μg) or glutamate (40μL, 25 μM) into the right upper lip (perinasal area). For the action in the CNS, 90 minutes after the treatment, the animals were perfused, the brains collected, and submitted in an immunofluorescence protocol for Fos protein. Experimental protocols were approved by the Animal Care and Use Committee at the UFS (# 57/11). EO/β‐CD produced significant (p< 0,05; p<0.01) antinociceptive effect, in the formalin‐, capsaicin‐and glutamate‐induced orofacial nociception. The immunofluorescence showed that the EO/β‐CD activated significantly (p<0.05) the olfactory bulb, the piriform cortex, and the periaqueductal grey of the CNS. Together, our results provide first‐time evidence that EO/β‐CD attenuates orofacial nociception at least, in part, through an activation of CNS areas, such as periaqueductal grey.