Availability of saliva for the assessment of alterations in the autonomic nervous system caused by physical exercise training

Abstract 

Objective

The purpose of the study was to assess the alterations of the autonomic nervous system activities caused by physical exercise training under food restriction using a running wheel in mice based on an analysis of saliva.

Methods

Male ICR mice, weighing 39–50g, at 32 weeks of age were divided into three groups; an exercise with food restriction (EXP), an exercise without food restriction (EXA) and a control (CTL). The EXP group was fed the same amount of diet as the CTL group (pair-feeding). The EXP and EXA groups used a “voluntary running wheel” for exercise. The pilocarpine stimulated whole saliva was collected from the oral cavity by micropipette over 15min 4, 8 and 12 weeks after the beginning of the experiment. The salivary flow rate, protein concentration and amylase and kallikrein activities were determined, since amylase and kallikrein release have been shown to be evoked by β- and α-adrenergic receptor stimulation, respectively.

Results

There was no significant difference in the sera corticosterone levels among the three experimental groups. The flow rate of saliva per total salivary gland weight in the EXP was significantly lower than that in the CTL and the EXA groups. The total protein secretion and kallikrein activity decreased by 20–30% in the EXP mice between 4 and 12 weeks after the starting of experiments in comparison to the CTL mice, thus suggesting that signal transduction in the α-sympathetic nervous system was downregulated. There was no significant difference in the amylase activity between the EXP and the CTL groups.

Conclusion

Physical exercise under diet control induced alterations in saliva secretion, while exercise training alone did not affect the content of saliva. The results demonstrate the availability of saliva and suggest that the present experimental situation is a suitable experimental model for sports activity performed under diet control.

Keywords: Exercise training, Diet restriction, Salivary flow, Salivary protein, Kallikrein, Autonomic nerve