Rats received a concomitant treatment with the selective << beta(1)-adrenoceptor >> antagonist, [[ bisoprolol ]] (50 mg/kg/day p.o.) or were chronically pretreated with the selective beta(2)-adrenoceptor agonist salbutamol (40 microg/kg/h) for 1 week to induce beta(2)-adrenoceptor desensitization.