Elevations in plasma angiotensin II with prolonged ethanol treatment in rats

Cardiovascular effects of ethanol in anaesthetized, conscious and pithed rats

The influence of ethanol (2.0 g/kg p.o.) on heart rate and blood pressure in anaesthetized, conscious and pithed rats was studied. In anaesthetized rats we observed an increase in heart rate and a marked and very sudden decrease in blood pressure. In pithed rats blood pressure decreased more slowly than in anaesthetized and conscious animals and there were no changes in heart rate. These results show that the central nervous system may be responsible for the increase in heart rate and early phase of hypotension caused by acute ethanol administration. The slower decrease (up to 1 h) in blood pressure may be caused by central and different indirect peripheral mechanisms.

Ethanol as a reinforcer for rats: factors of facilitation and constraint

This review examines some particular approaches that have been used to investigate factors that facilitate or constrain the self-administration of ethanol by rats. A technique for increasing ethanol self-administration in rats, the prandial drinking method, was examined and the effect of body-weight reduction on drug intake was discussed. Emphasis was placed on how ethanol intake may be controlled by processes in addition to the direct pharmacological actions of the drug in the CNS. These processes may be physiological. Evidence was presented for a relationship between activity in the renin-angiotensin system and the self-administration of ethanol. These processes may also be environmental. Using the place-conditioning technique, demonstrations were presented of how the context or situation in which ethanol is experienced may determine whether preference or aversion for the drug develops. Such a diversity in the factors that can potentially control ethanol intake may complicate the identification of the causes of alcohol abuse, but this same diversity also holds out greater hope that manipulations may be found to reduce excessive drinking in humans.

Voluntary alcohol intake is attenuated in two-kidney, one-clip, but not in one-kidney, one-clip Goldblatt hypertensive rats

Voluntary alcohol intake was examined in two models of renovascular hypertension known to differ in their effects on the renin-angiotensin system. In experiment 1, Two-Kidney, One-Clip (renin-dependent) hypertensive rats (T-K,O-C) or their sham operated controls were offered limited access to alcohol for 1 hr each day. Over a four week period the T-K,O-C rats drank significantly less 3% and 6% (w/v) alcohol solution than the sham operated controls. In experiment 2, One-Kidney, One-Clip (renin-independent) hypertensive rats or their sham operated controls were offered alcohol on a similar limited access basis. Over a four week period, the O-K,O-C rats did not show a reduction in the intake of either a 3% or 6% alcohol solution compared to the sham operated controls. These results provide further documentation for the role of the renin-angiotensin system in modulating alcohol intake. The process by which this system might influence alcohol intake is outlined.

Angiotensin II reduces voluntary alcohol intake in the rat

The voluntary intake of alcohol has been shown to be attenuated by a variety of manipulations which increase activity in the renin-angiotensin system. In the present study we examined the effects of peripheral injections of the peptide angiotensin II on alcohol drinking. The peptide produced a dose-dependent decrease in alcohol intake with 20 micrograms/kg having little effect, 200 micrograms/kg reducing intake by approximately 50% and 1 mg/kg virtually abolishing all alcohol drinking. This decrease was not due to a peptide induced motor deficit, or state of sickness, and could also not be accounted for by the increased water intake, or by a change in pharmacokinetics and taste function. These data provide direct evidence that angiotensin II can modulate voluntary alcohol drinking. The possibility that the level of angiotensin II serves as a satiety signal in alcohol drinking is discussed.

Ca2+-mobilizing hormones elicit phosphatidylethanol accumulation via phospholipase D activation

Vasopressin, angiotensin II and epinephrine elicited the accumulation of phosphatidylethanol in rat hepatocytes exposed to ethanol and of phosphatidate in the absence of ethanol. When isolated liver plasma membranes were exposed to ethanol, GTP gamma S stimulated the production of phosphatidylethanol whereas phosphatidate was formed in the absence of ethanol. With increasing ethanol concentrations, phosphatidate formation declined whereas phosphatidylethanol production increased. These findings suggest that rat hepatocytes possess a hormone-dependent phospholipase D activity that can also catalyze the formation of phosphatidylethanol.

Alcohol satiety, hypertension and the renin-angiotensin system

Evidence is presented which supports the hypothesis that the renin-angiotensin (r-a) system regulates alcohol intake. Documented findings suggest that an elevated level of r-a activity represents a satiety signal which stops alcohol intake. The fact that alcohol itself is known to stimulate r-a activity suggests that its intake may in some sense be self-regulating and that levels of r-a activity below those which signal satiety may even be rewarding. The role of the r-a system in hypertension is also considered. The ability of alcohol to elevate r-a activity may be seen as a contributing factor to alcohol-induced hypertension because angiotensin is a potent pressor agent. Furthermore, the notion that lower levels of angiotensin may be rewarding permits the hypothesis that essential hypertension may, in part, be the result of a self-induced increase in endogenous angiotensin. This would explain the otherwise puzzling utility of the angiotensin converting enzyme inhibitors in the treatment of essential hypertension.