Expression Of FOS-like Immunoreactive Neurons In Descrete Loci Of The Rat Central Nervous System After Subcutaneous Injection Of Formalin In The Trigeminal Region

FOS protein is the translation product of the protooncogene c-fos. After specific stimulation applied in the periphery, the expression and distribution of FOS protein in the central nervous system is specific and the detection of FOS could be used as an metabolic marker for the neural pathways in the central nervous system. Based on this, we took the formalin test as the noxious stimulation model, by using an immunocytochemical methods, we demonstrated that there was expression of FOS-like immunoreactive neurons in descrete loci of the rat central nervous system after subcutaneous injection of formalin in the perioral region.Under methoxyflurane anesthesia, subcutaneous injection of 150 μl 10% formalin in the left perioral region lateral to the nose was conducted on S-D rats, and then the animals were sacrificed to perform immunocytochemical staining. It is found that the expression of FOS-like immunoreactive neurons were time dependent: at 0.5 hour postinjection the FOS-like neurons began to appear; at 1.0 hour postinjection the expression of FOS-like neurons reached its peak at different loci which inculde the ipsilateral trigeminal spinal caudal subnucleus, the nucleus of solitary tract, bilateral nuclei of lateral...