Effects of formalin as a peripheral noxious stimulus on the nucleus reticularis paragigantocellularis neurons of ansethetized rats

ABSTRACT

In the present study, the effects of formalin as a peripheral noxious stimulus on spontaneously active units of the nucleus reticularis paragigantocellularis [PGi], a narrow region of the ventral pontine reticular formation, was examined in urethane anesthetized rats. Spontaneous discharge of the PGi neurons was variable, ranging from I to 37 spikes per second. Formalin as a chemical irritant and prolonged noxious stimulus induced changes in the firing of spontaneously active PGi neurons. There were three neuronal subpopulations in the PGi that responded to formalin excited [19.35%], inhibited [45.16%] and unchanged [35.48%]. Thus we suggest that PGi neurons may be involved in the processing of information related to formalin as a chemical irritant