Mechanisms involved in the water intake-related pressor response in the rat.
OBJECTIVE
In this study we aimed to characterize and clarify the mechanisms involved in the acute blood pressure increase observed concomitantly with water intake in moderately dehydrated rats.


METHODS
Short-term water deprivation was employed as a model to induce controlled water intake to study concomitant cardiovascular responses in the rat.


METHODS
Male Wistar rats were deprived of water for 18-24 h before the experiments and were allowed to drink for 20 s periods during the experimental session. During these periods water intake was accompanied by steady arterial pressure increases. This pressor response was unaffected by topical anesthesia of the oral cavity. Direct administration of water into the stomach did not cause pressor responses. The pressor response was not affected by bilateral adrenal demedullation or by pretreatment with diazepam, homatropine methyl bromide, d(CH2)5 Tyr(Me)AVP, losartan or RX821002. The pressor response was significantly reduced by ganglionic blockade with mecamylamine or pretreatment with the alpha1-adrenoceptor antagonist, prazosin.


CONCLUSIONS
Our results show that: (1) short-term dehydration can be used as a model to study cardiovascular responses associated with water intake in rats; and (2) the sympathetic nervous system and vascular smooth muscle alpha1-adrenoceptors are involved in the pressor response to water intake by dehydrated rats.
Tavares
Rodrigo F
RF
Department of Pharmacology, School of Medicine of Ribeirão Preto, University of São Paulo, Brazil.
Peres-Polon
Vera L
VL
Corrêa
Fernando M A
FM
D000818:Animals; D000959:Antihypertensive Agents / Q000008:administration & dosage; D001158:Arteries / Q000737:chemistry / Q000187:drug effects; D001794:Blood Pressure / Q000187:drug effects*; D001938:Brazil; D003975:Diazepam / Q000008:administration & dosage; D004305:Dose-Response Relationship, Drug; D004326:Drinking; D006339:Heart Rate / Q000187:drug effects; D019329:Idazoxan / Q000008:administration & dosage / Q000031:analogs & derivatives; D008012:Lidocaine / Q000008:administration & dosage; D019808:Losartan / Q000008:administration & dosage; D008297:Male; D008464:Mecamylamine / Q000008:administration & dosage; D023421:Models, Animal; D009125:Muscle Relaxants, Central / Q000008:administration & dosage; D011224:Prazosin / Q000008:administration & dosage; D011803:Quinine / Q000008:administration & dosage; D051381:Rats; D017208:Rats, Wistar; D012965:Sodium Chloride / Q000008:administration & dosage; D014326:Tropanes / Q000008:administration & dosage; D014867:Water / Q000008:administration & dosage*
D000959:Antihypertensive Agents; D009125:Muscle Relaxants, Central; D014326:Tropanes; D014867:Water; D012965:Sodium Chloride; C056244:homatropine methylbromide; D008464:Mecamylamine; D008012:Lidocaine; D011803:Quinine; C058525:2-methoxyidazoxan; D019808:Losartan; D003975:Diazepam; D011224:Prazosin; D019329:Idazoxan