The effect of hot spring bathing (Misasa hot spring) and city water bathing on plasma catecholamines (CA) and other metabolites were studied in normal rats and hypercholesteremic rats. Following results were obtained.
1) Single bathing, in city water or hot spring, at 40°C for 10 minutes caused no significant long-standing changes in plasma noradrenaline (NA) and adrenaline (A) concentration in normal rats. The results suggest that single bathing has no significant long-standing influence on the sympathetic nerve and adrenal medulla axis.
2) Normal rats treated by 1- and 4-week hot spring bathing at 40°C or 34°C tended to show lower plasma NA and A concentrations than non-treated rats. This tendency was more obvious at 40°C. In contrast, the rats treated by 2-week hot spring bathing tended to show steady or rather higher plasma NA and A concentrations as compared with non-treated rats.
On the other hand, the rats treated by 2-week city water bathing at 40°C or 34°C tended to show lower plasma NA concentration and higher plasma A concentration than non-treated rats. The rats treated by 4-week city water bathing at 40°C tended to show lower plasma NA concentration and higher plasma A concentration than the rats treated by 34°C city water bathing or non-treated rats.
The results suggest that the function of the sympathetic nerve and adrenal medulla axis decreases with apparent fluctuations during the 4-week hot spring bathing at 40°C or 34°C. This tendency was more obvious at 40°C, unlike the result during the 4-week city weter bathing.
3) The rats fed on cholesterol diets for 2 months tended to show lower plasma CA concentration than control rats, suggesting that the function of sympathetic nerve and adrenal medulla axis was decreased in the hypercholesteremic rats. The hypercholesteremic rats treated by 3-week serial bathing, particularly by serial hot spring bathing, tended to show higher plasma CA concentration than non-treated ones, unlike the results in normal rats.
The results suggest normalizing effect of hot spring bathing on the sympathetic nerve and adrenal medulla axis.
4) The circadian variation of plasma CA in normal rats was significantly affected by 1-week hot spring bathing, but was hardly affected by 4-week hot spring bathing, suggesting that “Habitual Phenomenon” or “defense mechanism” was brought about after the 4-week bathing.
5) The circadian variation of plasma CA in old hypercholesteremic rats, in contrast, showed no significant change after 1- and 4-week serial bathing, suggesting that the effects of serial bathing on plasma CA values were suppressed with aging.
6) There was no relation between plasma CA values and glucose as well as lipid metabolism during the serial bathing. However, it was suggested that the 4-week serial hot spring bathing affected the FFA release by NA.

View full abstract

The effect of serial bathing in city water or Misasa hot spring on the circadian variation of plasma corticosteroid (11-OHCS) was studied in both young normal and old hypercholesteremic rats. Both groups of rats were divided into three subgroups: rats bathed in hot spring, 40°C, once daily for one and four weeks; rats bathed in city water, 40°C, once daily for one and four weeks; rats non-treated for one and four weeks. Plasma obtained by decapitation at 8:00, 12:00, 16:00, (18:00), 20:00 and 24:00 hours was analyzed for 11-OHCS. Following results were obtained.
1) In young normal rats, the range of the circadian variation tended to decrease after 1-week serial bathing, particularly after the serial hot spring bathing. However, it remained almost unaltered after 4-week serial bathing. The results suggest adaptation of the rats to the serial bathing. Average concentration of plasma 11-OHCS tended to increase after 1-week and 4-week serial bathing.
2) Old hypercholesteremic rats showed less circadian variation as compared with young normal rats and old normal rats.
The circadian variation in the old hypercholesteremic rats was almost unaffected after 1-week serial bathing, although the average concentration of plasma 11-OHCS was increased, particularly after the 1-week city water bathing.
After the 4-week serial bathing, on the other hand, the range of the circadian variation tended to be augmented, particularly in the 4-week hot spring bathing rats: the nadir value was decreased by about 30 percent and the peak value was increased by about 30 percent as compared with each value in non-treated rats.
The results suggest the normalizing effect of the 4-week serial hot spring bathing on the circadian rhythm. Average concentration of plasma 11-OHCS was scarcely affected after the 4-week serial bathing.

View full abstract