The effects of Cassia abbreviata on rat blood pressure

The effects of a crude extract of the stem bark of Cassia abbreviata on mean arterial pressure in anaesthetized rats were investigated. Bolus injections of the stem bark elicited a transitory fall in blood pressure which was dose-dependent. The depressor response was not blocked by atropine nor propranolol thus indicating that muscarinic and beta 2 receptors are not involved. However it was partially blocked by diphenhydramine, and H1 antagonist. The latter also partially blocked the depressor response to histamine which is mediated partially through both H1 and H2 receptors. It is concluded that the stem bark of C. abbreviata contains histamine or a chemically related substance and that it is this component which is responsible for lowering the blood pressure.