naloxone and Water-Electrolyte-Imbalance

Topics: Adult; Anaphylaxis; Cardiac Tamponade; Cardiopulmonary Resuscitation; Emergency Medical Services; Fat Emulsions, Intravenous; Female; Heart Arrest; Humans; Hypothermia; Naloxone; Near Drowning; Percutaneous Coronary Intervention; Pregnancy; Pregnancy Complications, Cardiovascular; Pulmonary Embolism; Water-Electrolyte Imbalance; Wounds and Injuries

Normonatremic and chronically hyponatremic rats were pretreated with naloxone (5 mg/kg) or isotonic (150 mM) NaCl, then were given i.v. injections of 2 M NaCl (2 ml) or were hemorrhaged (20 ml/kg). Baseline and post-stimulus blood samples were withdrawn through indwelling jugular venous catheters. Baseline levels of plasma vasopressin (AVP) and oxytocin (OT) were similar in both normonatremic and hyponatremic rats and did not change after naloxone pretreatment. Increases in plasma AVP and OT levels in response to both hypertonic saline and hemorrhage were markedly blunted in the hyponatremic rats compared to the normonatremic rats. Naloxone pretreatment caused augmented AVP and OT secretion in response to hypertonic saline stimulation and hemorrhage in both the normonatremic and hyponatremic rats; the magnitude of the naloxone augmentations in the hyponatremic rats were sufficient to normalize the OT response to hypertonic saline and both the OT and AVP responses to hemorrhage. Our results therefore suggest that endogenous opioids are likely involved in the inhibition of stimulus-induced AVP and OT release that accompanies chronic hypoosmolality.

Topics: Animals; Arginine Vasopressin; Cerebral Hemorrhage; Hypothalamus; Isotonic Solutions; Male; Naloxone; Osmolar Concentration; Oxytocin; Rats; Rats, Sprague-Dawley; Sodium; Sodium Chloride; Water-Electrolyte Imbalance

Shapiro's syndrome comprises agenesis of the corpus callosum in association with episodic hyperhidrosis and hypothermia. We describe a 25-year-old man who is the twentieth case to be reported. There was no evidence of epilepsy, sympathetic nervous system dysfunction or inappropriate vasopressin release. However, investigation demonstrated a central defect in temperature regulation with an abnormally low hypothalamic set-point and normal homeothermic reflexes. Therapy with clonidine, an alpha 2-adrenoceptor agonist, was associated with remission of symptoms: these recurred on four occasions when clonidine was withdrawn. Clonidine therapy was also associated with a return to normal central temperature regulation. We suggest that the efficacy of clonidine reflects an action on hypothalamic thermoregulation rather than on peripheral catecholamine release. These findings have implications for the use of clonidine in other patients with Shapiro's syndrome and in more common disorders of temperature control, including perimenopausal flushing.

Topics: Adult; Agenesis of Corpus Callosum; Body Temperature Regulation; Clonidine; Humans; Hyperhidrosis; Hypothermia; Magnetic Resonance Imaging; Male; Naloxone; Syndrome; Water-Electrolyte Imbalance

The influence of naloxone (10 mg/kg i.p.) on water and electrolyte excretion was assessed in water-loaded rats subjected to fasting or fasting and refeeding. In fed animals, naloxone had no effect on water or electrolyte excretion compared to saline injected controls. However, during fasting, which has been shown to activate endogenous opioid systems, naloxone had a marked natriuretic effect (43 +/- 10 vs. 11 +/- 4 muEq/100 g X 2 h, p less than 0.05). Naloxone increased the sodium excretion to a level not significantly different from fed animals. Potassium and water excretion were not significantly changed compared to saline injected rats. The results suggest that fasting activates a naloxone-sensitive mechanism for sodium retention, perhaps by increasing the release of endogenous opioid peptides, and that refeeding inhibits this mechanism.

Topics: Animals; Circadian Rhythm; Endorphins; Fasting; Female; Food Deprivation; Glomerular Filtration Rate; Naloxone; Natriuresis; Potassium; Rats; Sodium; Water-Electrolyte Imbalance