Sensory stimulation (massage) reduces blood pressure in unanaesthetized rats

The objective of this study was to investigate how sensory stimulation by massage-like stroking influences blood pressure and heart rate in conscious rats. Also, the influence of different locations and durations of the stimulation were assessed. For this purpose, the ventral side of the abdomen or the dorsal side of the back was manually stroked at a speed of approximately 20 cm/s, with a frequency of 0.67 Hz and at an estimated pressure of 100 mm H2O. During the treatment, the rats were held across the scapula and the neck region. Blood pressure and heart rate were measured with the cuff technique before treatment and repeatedly during the post-stimulatory period. Massage-like stroking for 5 min of the abdominal area produced a maximum decrease of approximately 20 mm Hg in blood pressure and 60 beats/min in heart rate. This reduction remained significant at 3 and 4 h after stimulation, respectively. Stimulation of the abdominal area for 2 min produced a less pronounced decrease in blood pressure as compared to the 5-min stroking. Stroking of the back resulted in a short-lasting blood pressure increase that gradually returned to the baseline level within the post-stimulatory observation time. Control animals that were handled in the same way as the experimental animals except for the stroking showed an increase of approximately 20 mm Hg in blood pressure and 60 beats/min for about 1 h after the cessation of the handling. The responses of the blood pressure and heart rate to both abdominal and back massage were significantly inhibited as compared to the control animals. These results suggest that massage-like stroking of the skin produces an inhibitory effect on the cardiovascular excitatory responses in rats. Especially, the results of the present study demonstrate that massage-like stroking of the abdomen reduces both blood pressure and heart rate below the pre-stimulus baseline levels.