Effects of chronic lesions of the anteroventral region of the third ventricle on cardiac beta-adrenoceptor function in conscious rats

This study examined whether cardiac beta -adrenoceptor (beta -AR) function was altered in conscious rats with lesions surrounding the anteroventral th ird ventricle (AV3V). The findings were: (1) beta (1,2)-AR-mediated tachyca rdia was similar in sham and AV3V-Iesion rats, (2) beta (3)- and/or atypica l beta -AR-mediated tachycardia elicited by isoproterenol (10 mug/kg, i.v.; ISO) was diminished in AV3V-lesion rats treated with beta (1,2)-AR antagon ists, but was not in similarly-treated sham-lesion rats, and (3) the tachyc ardia elicited by the membrane permeable cAMP-analogue, 8-(4-chlorophenylth iol)-cAMP (10 mu mol/kg, i.v.), was similar in AV3V- and sham-lesion rats. The possibility that increased plasma sodium/osmolality in AV3V-lesion rats down-regulated cardiac beta (3)- and/or atypical beta -ARs, but not beta ( 1,2)-ARs or intracellular cAMP signaling is discussed. (C) 2001 Elsevier Sc ience B.V. All rights reserved.