tokens: Using the conflict drinking test as a model , we studied in rats the effect of the nonselective beta - adrenoceptor blockers pindolol and cyanopindolol which bind to 5 - HT1A and 5 - HT1B receptors , and of the selective beta 1 - and beta 2 - adrenoceptor antagonists betaxolol and ICI 118 , 551 , respectively , which have a negligible affinity for 5 - HT receptors .