C‐Fos expression in the piriform cortex and periaqueductal gray after hecogenin acetate administration on carrageenan‐induced hypernociception test

Abstract

We evaluate the c‐Fos expression in the mice central nervous system areas (CNS), piriform cortex and periaqueductal gray (PAG), after acute administration of hecogenin acetate (HC) on carrageenan‐induced nociception test. So, carrageenan‐induced hypernociception model was performed in mice as reported by Guimarães et al. (2012); c‐Fos analysis was held according to Brito et al. (2013) and grip strength test according to Meyer et al. (1979. Protocols were approved by the Animal Care and Use Committee at the UFS (CEPA/UFS # 04/12). Ninety minutes after the HC intraperitoneal injections (5, 10, or 20 mg/kg), the mice submitted to hypernociception induced by carrageenan (300 μg/paw), the average number of neurons showing Fos protein was increased in PAG area and only in higher dose produced increase in olfatory bulb area. HC not produced significant alterations in piriform cortex area. Interestingly, systemic administration of HC, in all tested doses, produced an anti‐hypernociceptive effect in this model. So, such results were unlikely to be provoked by motor abnormality when evaluated in grip strength test. Our results provide evidence to propose that HC produced a lack activation of olfatory bulb, but induced a strong PAG‐activation, at the all tested doses, indicates a possible involvement in descending pathways that modulate pain.