Enhancement of pharmacologically induced bronchoconstriction by Ro 5-4864

Pretreatment with Ro 5-4864 enhanced the bronchoconstrictor responses to histamine or carbachol in the anaesthetized artificially ventilated guinea pig. This suggests the involvement of a peripheral-type benzodiazepine receptor as also indicated by the lack of effect of clonazepam. PK 11195 did not antagonize the Ro 5-4864-induced enhancement, but itself enhanced the bronchoconstrictor responses to histamine or carbachol. The data indicate that Ro 5-4864 and PK 11195 behave as metactoid sensitizers of histamine or carbachol.