Fig. 1

Elevation of tyrosine hydroxylase and dopamine by tibial loading. TH tyrosine hydroxylase, load tibial loading, ES electrostimulation, NB nerve block. The single and double asterisks indicate P < 0.05 and 0.01, respectively. a Setup for tibial loading with a BALB/c mouse. The ventral tegmental area (VTA) is shown in the sagittal section of a mouse brain. b Elevation of TH immunostaining in the VTA in the sagittal section of the loaded sample. c, d Load-driven elevation of TH in the VTA of C57BL/6 mice. e, f Elevation of TH induced by electrostimulation, and TH level suppression by local administration of lidocaine, a nerve block agent. g TH-immunostained area (in %) in the VTA induced by electrostimulation (ES) and tibial loading (load) showing that the application of a nerve block (NB) reduced the stained area. h Elevation of TH, p-Erk, and p-p38 in the brain induced by electrostimulation and tibial loading. The elevation of these factors was suppressed by the nerve block agent. i Elevation of dopamine in the serum by tibial loading. The serum was harvested 1 h after tibial loading