Effects of anisodamine and scopolamine on pulmonary circulation in rabbits

In experiments with anesthetized rabbits anisodamine 5 mg/kg iv resulted in a brief decrease in the pulmonary vascular resistance as calculated from the mean arterial pressure and the cardiac output, with a concomitant fall of the femoral arterial pressure, especially the diastolic, to a considerable extent. In contrast, scopolamine 0.5 mg/kg iv led to an abrupt increase in the pulmonary vascular resistance, but only a midl drop in the femoral arterial pressure which was kept at a less fluctuating level. Besides, scopolamine 0.5 mg/kg iv given during hypoxic pulmonary hypertension prevented the post-hypoxia pulmonary hypotension observed in the control animals under the same conditions of hypoxia but without scopolamine.
Neither anisodamine nor scopolamine at their respective doses produced and significant effect with regard to PaO2 and pHa.
The above results suggest that anisodamine dilates both pulmonary and systemic vessels although its action on the pulmonary circulation is relatively weak, while scopolamine mainly increases pulmonary vascular resistance and tends to counteract systemic arterial hypotension.