Treadmill exercise improves memory by up-regulating dopamine and down-regulating D2 dopamine receptor in traumatic brain injury rats

Il-Gyu Ko, Chang-Ju Kim, Hong Kim, Il-Gyu Ko, Chang-Ju Kim, Hong Kim

Abstract

Traumatic brain injury (TBI) causes a variety of neuropathological manifestations including cognitive, emotional, physiological and psychological deficits. Physical exercise is known to ameliorate neurological impairments induced by various brain injuries. We investigated the effects of treadmill exercise on memory impairments due to TBI in relation to dopamine and D2 dopamine receptor. TBI was induced with an electromagnetic-controlled cortical impact device. The rats in the exercise groups were scheduled to run on a treadmill for 30 min once a day for 28 days after TBI induction. Then, step-down avoidance task, radial 8-arm maze test, immunohistochemistry for tyrosine hydroxylase (TH), and western blot for D2 dopamine receptor were performed. TBI impaired short-term and spatial learning memories. TBI decreased TH expressions in the prefrontal cortex (PFC), striatum, hippocampus dentate gyrus, and substantia nigra (SN). By contrast, the expressions of D2 dopamine receptor in the PFC, striatum, hippocampus, and SN were increased by TBI. Treadmill exercise alleviated the impairments of short-term and spatial learning memories observed in TBI rats. TH expression was decreased and D2 dopamine receptor expression was increased in TBI rats. Treadmill exercise enhanced TH expression and suppressed D2 dopamine receptor expression in TBI rats. TBI deteriorated short-term and spatial learning memories, in contrast, treadmill exercise alleviated the TBI-induced memory impairments by up-regulating dopamine level and down-regulating D2 dopamine receptor expression.

Keywords: Brain injuries; Dopamine; Dopamine D2 receptor; Exercise; Memory.

Conflict of interest statement

CONFLICT OF INTEREST No potential conflict of interest relevant to this article was reported.

Figures

Fig. 1
Fig. 1
Effects of treadmill exercise on latency in the step-down avoidance task. A, sham-operation group; B, sham-operation and treadmill exercise group; C, traumatic brain injury (TBI)-induced group; D, TBI-induced and treadmill exercise group. *P<0.05 compared to the sham-operation group. #P<0.05 compared to the TBI-induced group.
Fig. 2
Fig. 2
Effects of treadmill exercise on performance time, correct number, and error score in the radial 8-arm maze test. A, sham-operation group; B, sham-operation and treadmill exercise group; C, traumatic brain injury (TBI)-induced group; D, TBI-induced and treadmill exercise group. *P<0.05 compared to the sham-operation group. #P<0.05 compared to the TBI-induced group.
Fig. 3
Fig. 3
Effects of treadmill exercise on tyrosine hydroxylase (TH) expressions in the prefrontal cortex, striatum, hippocampal dentate gyrus, and substantia nigra. A, sham-operation group; B, sham-operation and treadmill exercise group; C, traumatic brain injury (TBI)-induced group; D, TBI-induced and treadmill exercise group. The scale bar represents 150 μm. *P<0.05 compared to the sham-operation group. #P<0.05 compared to the TBI-induced group.
Fig. 4
Fig. 4
Effects of treadmill exercise on D2 dopamine receptor (D2DR) expressions in the prefrontal cortex, striatum, hippocampus, and substantia nigra. A, sham-operation group; B, sham-operation and treadmill exercise group; C, traumatic brain injury (TBI)-induced group; D, TBI-induced and treadmill exercise group. *P<0.05 compared to the sham-operation group. #P<0.05 compared to the TBI-induced group.

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Source: PubMed

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