Inhibition of water intake by the central administration of IL-1beta in rats: role of the central opioid system.
In the present study we investigated, the effect of third ventricle injections of IL-1beta on water intake, in rats, induced by three different physiological stimuli: dehydration induced by water deprivation, hypernatremia associated with hyperosmolarity induced by intragastric salt load, and hypovolemia produced by subcutaneous polytethyleneglycol administration. Central administration of IL-1beta at the doses of 4 and 8 ng reduced water intake in all three conditions studied. Third ventricle injections of IL-1beta (8 ng) were unable to diminish water intake in the groups of rats pretreated with central injections of the non-selective opioid antagonist naloxone (10 microg) in the three different conditions studied. Furthermore, the central administration of IL-1beta was neither able to modify the intake of a 0.1% saccharin solution when the animals were submitted to a "dessert test" nor to induce any significant locomotor deficit in the open-field test. These results suggest that the central activation of interleukin-1 receptors by IL-1beta is able to impair the thirst-inducing mechanisms triggered by the physiological stimuli represented by dehydration, hyperosmolarity and hypovolemia. These results lead us to conclude that the antidipsogenic effects observed following central administration of IL-1beta require the functional integrity of the brain opiatergic system.
Luz
P A
PA
Department of Physiology, Health Sciences Institute, Federal University of Bahia, Vale do Canela s/n, 40110-100 Salvador, Bahia, Brazil.
Andrade
L
L
Miranda
N
N
Pereira
V
V
Fregoneze
J
J
De Castro e Silva
E
E
D000818:Animals; D001831:Body Temperature; D003681:Dehydration; D004305:Dose-Response Relationship, Drug; D004326:Drinking / Q000187:drug effects*; D006801:Humans; D006955:Hypernatremia; D020896:Hypovolemia; D007276:Injections, Intraventricular; D007375:Interleukin-1 / Q000008:administration & dosage / Q000494:pharmacology*; D008297:Male; D009043:Motor Activity / Q000502:physiology; D009270:Naloxone / Q000378:metabolism*; D009292:Narcotic Antagonists / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D012439:Saccharin / Q000008:administration & dosage; D014868:Water Deprivation
D007375:Interleukin-1; D009292:Narcotic Antagonists; D009270:Naloxone; D012439:Saccharin