Physiology & Behavior, Vol. 49, pp. 201-206. ©Pergamon Press plc, 1991. Printed in the U.S.A.
0031-9384/91 $3.00 + .00
Effects of Catecholamines on Water Intake in Rats 1 M . R U S S E K , 2 L. M . S O T O - M O R A ,
T. U R I O S T E G U I A N D R. R A C O T I ' A 3'4
Departamento de Fisiologfa, Escuela Nacional de Ciencias Bioltgicas Instituto Polit~cnico Nacional M(xico, D. F. M(xico R e c e i v e d 5 July 1990
RUSSEK, M., L. M. SOTO-MORA, T. URIOSTEGUI AND R. RACOTTA. Effects of catecholamines on water intake in rats. PHYSIOL BEHAV 49(1) 201-206, 1991 .--It is known that intraperitoneally (IP) injected adrenaline (A) inhibits food intake in otherwise hungry animals. In a recent work, Hinton et al. (6) showed that IP A also inhibits water intake in thirsty rats, concluding that A's effect is unspecific. We administered A IP or intramuscularly (IM) in different doses in rats made thirsty either by 18-h water deprivation or by subcutaneous injection of hypertonic saline or polyethylene glycol. 1P A reduced water intake in all experimental conditions. A dose-related inhibition was observed in water-deprived animals. On the other hand, IM A showed a small effect only at the highest dose (50 I~g/100 g body weight). When some of these experiments were repeated using noradrenaline (NA) and isoproterenol (IS), IM administration of either substance showed no effect. IP administration reduced water intake significantly only at the highest dose of NA (50 Ixg/100 g). It is concluded that water intake inhibition by catecholamines in rats made thirsty either by osmotic or by volumetric challenges is of porto-hepatic origin and, in contrast with food intake inhibition, has no betaadrenergic component. Water intake
Catecholamines
Alpha-adrenergic inhibition
INTRAPERITONEAL (IP) injection of adrenaline (A) has been shown to produce a strong inhibition of food intake in dogs and rats (10, 19-22, 25, 28, 33). This inhibition of feeding seems to have several characteristics similar to normal satiety: it depends on palatability (26) and on the amount of work necessary to obtain the food (13,24); it produces sedation and sleep (21); and it inhibits self-stimulation only in those cerebral loci that elicit stimulus-bound feeding (13,20). Intramuscular (IM) A has no effect on feeding, even though it produces a greater hyperglycemia (14,27) and stronger cardio-vascular reactions (19,23). All the above indicate that the effect of IP A is exerted via porto-hepatic receptors and that it seems to be rather specific for feeding. In a recent work (18) we have shown that in 6-h waterdeprived rats, IP A had no effect on water intake but that the same dose injected in 6-h food-deprived animals produced a dose-related inhibition of milk intake. However, Hinton et al. (6) found that IP A inhibits water intake of rats on a 6-h water access/18-h water deprivation schedule. In order to clarify these contradictory results, it was decided to perform a more thorough study on the effects of A and other catecholamines (norepinephrine and isoproterenol) on water intake by rats in different thirst-induced conditions: water deprived,
Porto-hepatic receptors
food deprived, hypertonic saline, or polyethylene glycol injection. GENERAL METHOD All experiments were performed on groups of ten male and ten female Wistar rats (250-350 g), housed in individual cages at a regulated temperature of 23 -- 1°C and light from 0700 to 1900 h, with food (powdered chow) and water ad lib. Tests were performed twice a week with at least two days between them, always at 0900 h. Water and food intakes (when food was offered) were measured at 30, 60 and 120 minutes by weighing the tubes containing water and the food containers. Only the results for the first 30 min will be reported in the figures since the data obtained during the other intervals do not add any useful information. All rats in each experiment received all treatments in a random order. Catecholamines were administered in different concentrations in order to maintain constant the injected volume at 1 ml/ kg. The results were treated with random block ANOVA (2-way treatment x subject) and then with post hoc Newman-Keuls comparisons when more than two groups were compared, or with Student t-test when only two groups have to be compared.
~This article was presented at the Xth International Congress on the Physiology of Food and Fluid Intake held in Pads, France, July 4--8, 1989. Other selected articles from this meeting have been published in Physiology & Behavior, Volume 48, Number 6, 1990 and Brain Research Bulletin, Volume 25, Number 6, 1990 and Volume 26, Number I, 1991. 2Deceased January 6, 1990. 3Fellow of DEDICT-COFAA-IPN. 4Requests for reprints should be addressed to Dr. Radu Racotta, Departamento de Fisiologfa, ENCB-IPN Prolongaci6n de Carpio y Plan de Ayala, Mtxico, D. F. 11340 Mtxieo.
201
202
RUSSEK ET AL INTAKE
IB
HR.
WATER
DEPRIVATION
MEASURED
GROUP
I,
+
W
-
F
P
0031-9384/91 $3.00 + .00
Effects of Catecholamines on Water Intake in Rats 1 M . R U S S E K , 2 L. M . S O T O - M O R A ,
T. U R I O S T E G U I A N D R. R A C O T I ' A 3'4
Departamento de Fisiologfa, Escuela Nacional de Ciencias Bioltgicas Instituto Polit~cnico Nacional M(xico, D. F. M(xico R e c e i v e d 5 July 1990
RUSSEK, M., L. M. SOTO-MORA, T. URIOSTEGUI AND R. RACOTTA. Effects of catecholamines on water intake in rats. PHYSIOL BEHAV 49(1) 201-206, 1991 .--It is known that intraperitoneally (IP) injected adrenaline (A) inhibits food intake in otherwise hungry animals. In a recent work, Hinton et al. (6) showed that IP A also inhibits water intake in thirsty rats, concluding that A's effect is unspecific. We administered A IP or intramuscularly (IM) in different doses in rats made thirsty either by 18-h water deprivation or by subcutaneous injection of hypertonic saline or polyethylene glycol. 1P A reduced water intake in all experimental conditions. A dose-related inhibition was observed in water-deprived animals. On the other hand, IM A showed a small effect only at the highest dose (50 I~g/100 g body weight). When some of these experiments were repeated using noradrenaline (NA) and isoproterenol (IS), IM administration of either substance showed no effect. IP administration reduced water intake significantly only at the highest dose of NA (50 Ixg/100 g). It is concluded that water intake inhibition by catecholamines in rats made thirsty either by osmotic or by volumetric challenges is of porto-hepatic origin and, in contrast with food intake inhibition, has no betaadrenergic component. Water intake
Catecholamines
Alpha-adrenergic inhibition
INTRAPERITONEAL (IP) injection of adrenaline (A) has been shown to produce a strong inhibition of food intake in dogs and rats (10, 19-22, 25, 28, 33). This inhibition of feeding seems to have several characteristics similar to normal satiety: it depends on palatability (26) and on the amount of work necessary to obtain the food (13,24); it produces sedation and sleep (21); and it inhibits self-stimulation only in those cerebral loci that elicit stimulus-bound feeding (13,20). Intramuscular (IM) A has no effect on feeding, even though it produces a greater hyperglycemia (14,27) and stronger cardio-vascular reactions (19,23). All the above indicate that the effect of IP A is exerted via porto-hepatic receptors and that it seems to be rather specific for feeding. In a recent work (18) we have shown that in 6-h waterdeprived rats, IP A had no effect on water intake but that the same dose injected in 6-h food-deprived animals produced a dose-related inhibition of milk intake. However, Hinton et al. (6) found that IP A inhibits water intake of rats on a 6-h water access/18-h water deprivation schedule. In order to clarify these contradictory results, it was decided to perform a more thorough study on the effects of A and other catecholamines (norepinephrine and isoproterenol) on water intake by rats in different thirst-induced conditions: water deprived,
Porto-hepatic receptors
food deprived, hypertonic saline, or polyethylene glycol injection. GENERAL METHOD All experiments were performed on groups of ten male and ten female Wistar rats (250-350 g), housed in individual cages at a regulated temperature of 23 -- 1°C and light from 0700 to 1900 h, with food (powdered chow) and water ad lib. Tests were performed twice a week with at least two days between them, always at 0900 h. Water and food intakes (when food was offered) were measured at 30, 60 and 120 minutes by weighing the tubes containing water and the food containers. Only the results for the first 30 min will be reported in the figures since the data obtained during the other intervals do not add any useful information. All rats in each experiment received all treatments in a random order. Catecholamines were administered in different concentrations in order to maintain constant the injected volume at 1 ml/ kg. The results were treated with random block ANOVA (2-way treatment x subject) and then with post hoc Newman-Keuls comparisons when more than two groups were compared, or with Student t-test when only two groups have to be compared.
~This article was presented at the Xth International Congress on the Physiology of Food and Fluid Intake held in Pads, France, July 4--8, 1989. Other selected articles from this meeting have been published in Physiology & Behavior, Volume 48, Number 6, 1990 and Brain Research Bulletin, Volume 25, Number 6, 1990 and Volume 26, Number I, 1991. 2Deceased January 6, 1990. 3Fellow of DEDICT-COFAA-IPN. 4Requests for reprints should be addressed to Dr. Radu Racotta, Departamento de Fisiologfa, ENCB-IPN Prolongaci6n de Carpio y Plan de Ayala, Mtxico, D. F. 11340 Mtxieo.
201
202
RUSSEK ET AL INTAKE
IB
HR.
WATER
DEPRIVATION
MEASURED
GROUP
I,
+
W
-
F
P
