The influence of endogenous opioids an the diuretic-natriuretic action of head-out water immersion in healthy volunteers

Author(s): Jungmann, E., Schmidt, P., Scheuermann, E. -H., Usadel, K.

Journal/Book: Physikalische Medizin Rehabilitationsmedizin Kurortmedizin. 1992; 2/4: 113-117.

Abstract: Elevated endogenous dopaminergie activity plays an important role in the responses of natriuresis and diuresis following water immersion to the neck. To examine whether endogenous opioids are involved in the stimulation of endogenous dopaminergic activity and the physiological mechanisms of head-out water immersion, 8 healthy male volunteers were studied. According to a randomized, doubleblind, placebo controlled study design the volunteers received 10 mg i.v. of the dopaminergic antagonist metoclopramide and 10mg/2 h i.v. of the opioid antagonist naloxone during a 2-hour immersion to the neck at 36 °C.Immersion resulted in an increase in natriuresis and a decrease in plasma renin activity, aldosterone and cortisol levels. Natriuresis but not diuresis was blocked by metoclopramide given in combination with naloxone. The combination of both agents reversed the suppression of plasma renin activity, aldosterone and cortisol levels while naloxone given alone reduced the decrease in cortisol following head-out water immersion.Thus, endogenous opioids may act as central mediators of the activation of endogenous dopaminergic pathways which mediate predominantly the natriuretic response to head-out water immersion.

Keyword(s): Vollbad

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