Novel evidence that beta adrenoceptors of the medial septal area regulate blood pressure and electrolyte balance.
We investigated the participation of the beta-adrenoceptors of the septa area (SA) in sodium and potassium excretion and urine flow. The alterations in arterial pressure and some renal functions were also investigated. The injection of 2.10(-9) to 16.10(-9) M of isoproterenol, through a cannula permanently implanted into the SA produced a significant dose-dependent decrease in urinary Na+ and K+ excretion and urinary flow. Pretreatment with 16.10(-9) M butoxamine antagonized the effect of 4.10(-9) M isoproterenol but pretreatment with 16.10(-9) M practolol did not abolish the effect of isoproterenol. The beta 2-agonist terbutaline and salbutamol (4.10(-9) M when injected intraseptally also caused a decrease in urine flow and in renal Na+ and K+ excretion. After injection of isoproterenol or salbutamol (4.10(-9) M) into the SA, the arterial pressure, glomerular, filtration rate (GFR) and filtered Na+ were reduced while Na+ fractional reabsorption was increased. The results indicate that the beta 2-adrenoceptors of the SA play a role in the decrease of Na+, K+ and urine flow and this effect may be due to a drop in GFR and filtered Na+ and to the rise in tubular Na+ reabsorption.
Saad
W A
WA
Department of Physiology, School of Dentistry, Paulista State University, Araraquara SP, Brazil.
Menani
J V
JV
Camargo
L A
LA
Antunes-Rodrigues
J A
JA
Saad
W A
WA
D000818:Animals; D001794:Blood Pressure / Q000502:physiology*; D004305:Dose-Response Relationship, Drug; D007545:Isoproterenol / Q000494:pharmacology; D008297:Male; D011188:Potassium / Q000652:urine; D051381:Rats; D011919:Rats, Inbred Strains; D011943:Receptors, Adrenergic, beta / Q000187:drug effects* / Q000502:physiology*; D012688:Septum Pellucidum / Q000502:physiology*; D012964:Sodium / Q000652:urine; D014882:Water-Electrolyte Balance / Q000502:physiology*
D011943:Receptors, Adrenergic, beta; D012964:Sodium; D007545:Isoproterenol; D011188:Potassium