Hot Water Bathing and Neurotransmitters

Abstract

The purpose of the present study was to determine the involvement of central neurotransmitters in hot water bathing. In the first experiment, the alterations of the neurotransmitters, and in the second the effects of intracereb-roventricular (ICV) administration of the neurotransmitters, or their related substances on changes of gastric mucosal blood flow (GMBF) or foot BF were examined in the rats subjected to hot water bathing. The results were as follows.
1) Increases of dopamine (DA) metabolism and decreases of neurotensin (NT) -like immunoreactivity were observed in the nucleus accumbens and the amygdala of the rats subjected to 40°C hot water bathing.
2) 40°C hot water bathing normalized the GMBF decreased by the restraint stress with its duration of 60min almost to the level prior to the stress. The ICV administration of antiserum against NT inhibited the normalization of the GMBF.
3) The pretreatment with reserpine and with naloxone (β-endorphin (β EP) antagonist) inhibited the effects of NT and EP, respectively, on normalization of GMBF.
4) An inhibitory effect of ICV administration of saralasin (angiotensin II (A II) antagonist) was recognized on the FBF elevated by 34°C hot water bathing.
These results suggest central mechanisms of cerebral DA, NT and β EP during 40°C hot water bathing in which DA neuron systems activated by the bathing, together with NT and β EP, protect the gastric mucosa via the actions of increased GMBF through the sympathetic nervous system. Cerebral A II was assumed to be involved in the hydrostatic actions of hot water bathing on peripheral circulation.