THE PHARMACOLOGICAL ACTIONS OF CONESSINE AND ISO-CONESSINE

¹ From the Pharmacology Laboratory, Oxford University

The approximate m.l.d. per kilogram of conessine by subcutaneous injection is, for the frog, 0.10 gram and for the guinea pig, 0.115 gram. The M.L.D. per kilogram by intraperitonial injection for the mouse is about 0.126 gram.

Toxic doses of conessine produce paralysis of the central nervous system in frogs but this effect is not appreciable in mammals. With intravenous injections death is mainly due to cardiac failure.

Small doses of conessine produce a slight rise of blood pressure without any effect on the respiration.

Large doses cause a fall due mainly to slowing and weakening of the heart. Conessine has no effect on the coronary vessels in the isolated rabbit’s heart but it constricts the renal vessels and dilates those of the intestine.

Conessine has no appreciable action on the voluntary muscle of the frog. The smooth muscle of the intestine and uterus is stimulated by conessine.

Conessine kills Paramoecium caudatum and Amoebae proteus in concentrations of 1:40,000 and 1: 8000 respectively in three hours.

Iso-conessine is approximately half as toxic as conessine towards laboratory animals but it is eight times more toxic towards Paramoecium caudatum and two and a half times more toxic towards Amoeba proteus.

Iso-conessine resembles conessine in its action on the central nervous system of the frog. With intravenous injections death is mainly due to respiratory paralysis.

Small doses of iso-conessine produce a slight rise of blood pressure without any effect on the respiration.

Large doses cause a fall due mainly to irregularity and weakening of the heart. Iso-conessine dilates the coronary vessels in the perfused heart of the rabbit.

The stimulating action of iso-conessine on the plain muscle of the intestine and uterus is much more marked than that of conessine.