Norepinephrine-induced diuresis in chronically ethanol-treated rats.

Area of Science:

• Pharmacology
• Neuroscience
• Toxicology

Background:

• Noradrenergic mechanisms are known to mediate ethanol-induced diuresis.
• Previous studies from this lab indicated a role for noradrenergic systems in ethanol diuresis.

Purpose of the Study:

• To investigate changes in the sensitivity of noradrenergic mechanisms during chronic ethanol treatment.
• To determine the role of norepinephrine in the development of tolerance to ethanol's diuretic effects.

Main Methods:

• Rats were treated with ethanol (8-11 g/kg/day) or a control (dextrin maltose) for 20 days.
• Intraventricular administration of norepinephrine hydrochloride (0-12 micrograms) was used to assess diuretic responses.
• Diuretic effects were measured on days 1, 10, and 20 of treatment.

Main Results:

• Ethanol produced a dose-dependent diuresis on the first day of treatment in both control and ethanol-treated rats.
• Tolerance to ethanol's diuretic effect was observed after 10 days of ethanol administration.
• A lack of responsiveness to norepinephrine-induced diuresis was noted on day 20 in both ethanol and control groups.

Conclusions:

• Norepinephrine does not appear to be the primary mediator in the development of tolerance to the diuretic action of ethanol.
• The study suggests other mechanisms may be responsible for ethanol diuretic tolerance.