Abstract: Objective To investigate whether cold or heat stress affected signal transduction of p38 mitogen-activated protein kinase (MAPK) in the spinal cords and ganglia.Methods The rat models of acute cold and heat stresses were established, and the immunohistochemistry and Western blotting analysis were used.Results The phospho-p38 (p-p38) immuno-positive cells were observed in the Rexed Ⅱ layer of normal thoracic spinal cord, with low cell density and brown nucleus staining, and without staining in Rexed Ⅲ～Ⅹ layers. In the spinal ganglia, the p-p38 immunoreaction was mainly located in the nuclei of a few small-sized neurons. Acute heat stress (10 min & 20 min) reduced the number of positive cells in Rexed Ⅱ layer, with body-temperature (38℃) stress (20 min) having no effect. No immunostaining was changed in the spinal ganglia. Acute cold stress (10 min & 20 min) slightly reduced the positive cells in the Rexed Ⅱ layer, with unchanged immunostaining in spinal ganglia. Western immunoblot analysis showed that activation level of p-p38 was differently downregulated by heat and cold stresses compared to the normal groups and body temperature (38℃)-bathed groups.Conclusion Constitutive activation of p38 can be observed in the normal spinal cord and ganglia; heat stress and cold stress significantly and gentlely inhibite the phosphorylation level of p38, respectively.

Key words: cold stress, heat stress, p38, mitogen-activated protein kinase (MAPK), rat