Contribution of nucleus medianus to the drinking and pressor responses to angiotensin II acting at subfornical organ.
The contribution of neurons in the nucleus medianus (NM) in mediating the drinking and pressor responses elicited by administration of angiotensin II (AII) either directly into the subfornical organ (SFO) or intravenously was investigated in conscious, unrestrained rats. Microinjection of AII into the SFO elicited a robust drinking (7.9 +/- 0.8 ml in 15 min; n = 24) and pressor (peak rise in mean arterial pressure (MAP), 15 +/- 1 mm Hg; n = 20) response. On the other hand, intravenous infusion of AII elicited an increase in MAP (36 +/- 3 mm Hg; n = 14) accompanied by a marked reflex bradycardia (134 +/- 18 beats/min), but not a significant drinking response. Lesions of NM cells, dorsal to the anterior commissure and between the fornical columns, with the neurotoxin kainic acid significantly (P less than 0.05) attenuated the drinking response (prelesion volume, 8.3 +/- 0.8 ml in 15 min; postlesion volume, 1.9 +/- 1.4 ml in 15 min; n = 7), but did not alter the pressor response to AII injected directly into the SFO. Similarly, kainic acid lesions of NM cells did not significantly effect the pressor response or the associated reflex bradycardia to intravenous administration of AII. Sham lesions of NM cells or control kainic acid lesions of adjacent structures did not alter the AII-induced drinking or pressor responses. These data suggest that neurons in the dorsal NM are part of a forebrain neuronal circuit that is involved in the drinking, but not the pressor responses to AII acting at the SFO in the conscious rat.
Gutman
M B
MB
Department of Physiology, University of Western Ontario, London, Canada.
Jones
D L
DL
Ciriello
J
J
D000804:Angiotensin II / Q000494:pharmacology*; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects*; D004327:Drinking Behavior / Q000187:drug effects*; D008297:Male; D009490:Neurosecretory Systems / Q000502:physiology*; D011301:Preoptic Area / Q000502:physiology*; D051381:Rats; D011919:Rats, Inbred Strains; D013356:Subfornical Organ / Q000502:physiology*
D000804:Angiotensin II