Importance of beta 2-adrenoceptor stimulation in the suppression of intradermal antigen challenge by adrenaline.

1. Seven atopic subjects received two injections of antigen and one of saline intradermally in the back on each of 4 separate days. They were pretreated with four different drug combinations: (a) adrenaline 0.3 mg subcutaneously over the deltoid muscle (b) subcutaneous adrenaline preceded by 5 mg of the specific beta 2-adrenoceptor antagonist ICI 118,551 orally (c) 8 mg of salbutamol orally (d) placebo. Tablets were given 2 h before and subcutaneous injections 15 min before the intradermal injections of saline and antigen. 2. The median flare response to intradermal low dose antigen and high dose antigen after pretreatment with adrenaline was 4% and 49% of the response seen following pretreatment with placebo (P less than 0.001). When adrenaline was preceded by ICI-118,551, the corresponding median flare responses were 2% and 44% (P less than 0.001) of the placebo response. The flare response after pretreatment with salbutamol was not significantly different from placebo. 3. Adrenaline suppressed the median weal response to the higher dose of antigen to 52% of the response after pretreatment with placebo (P less than 0.05). This suppression by adrenaline was blocked by pretreatment with ICI 118,551. The median weal response after the highest dose of antigen was suppressed by salbutamol to 66% of the response seen after placebo, although this was not significant even when a further three subjects were studied with either salbutamol or placebo.(ABSTRACT TRUNCATED AT 250 WORDS)