The action of Hoe 140 on the bradykinin-induced splenic pressor reflex of the anaesthetized cat.

1. Intrasplenic injection of bradykinin (BK) induced a dose-dependent pressor response in the anaesthetized cat, with an ED50 of 0.98 +/- 0.43 nmol. In contrast, intrasplenic administration of desArg9bradykinin (desArg9BK) was without significant effect at doses of up to 200 nmol. 2. Intravenously administered BK induced a dose-dependent depressor response in the anaesthetized cat, with an ED50 of 0.86 +/- 0.09 nmol kg-1. desArg9BK was again without significant effect in this system at doses of up to 200 nmol kg-1. 3. Both the pressor and depressor responses to BK were antagonized to a similar degree in a dose-dependent manner by Hoe 140 (10 and 100 nmol kg-1, i.v.). 4. At these doses, Hoe 140 appears to be a specific BK antagonist as it was ineffective against pressor responses to intrasplenic injection of capsaicin (5 nmol), while blocking those to an approximately equieffective dose of BK (1 nmol) in a dose-dependent fashion. 5. Both the pressor response to intrasplenic BK and the depressor response to intravenous BK in the anaesthetized cat appear to be mediated by B2-receptors. This model may be useful in the quantitative determination of the antinociceptive potency of BK antagonists.