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

This study examined whether cardiac β-adrenoceptor (β-AR) function was altered in conscious rats with lesions surrounding the anteroventral third ventricle (AV3V). The findings were: (1) β_1,2-AR-mediated tachycardia was similar in sham and AV3V-lesion rats, (2) β₃- and/or atypical β-AR-mediated tachycardia elicited by isoproterenol (10 μg/kg, i.v.; ISO) was diminished in AV3V-lesion rats treated with β_1,2-AR antagonists, but was not in similarly-treated sham-lesion rats, and (3) the tachycardia elicited by the membrane permeable cAMP-analogue, 8-(4-chlorophenylthiol)-cAMP (10 μmol/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 β₃- and/or atypical β-ARs, but not β_1,2-ARs or intracellular cAMP signaling is discussed.