Supersensitivity of the submaxillary gland following exclusion of the postganglionic parasympathetic neurone.

The repeated subcutaneous injection of four different parasympatholytic agents into cats has been found to cause a supersensitivity of the submaxillary glands to adrenaline. The fact that the level of sensitivity reached is the same with all four drugs is taken as evidence that the supersensitivity is due to the absence of an action of acetylcholine on the gland cells. This acetylcholine can only in part be that released by the secretory impulse, for the supersensitivity produced is more marked than that caused by preganglionic parasympathetic denervation. It is assumed that the postganglionic cholinergic neurone exerts some action of its own on the gland cell. Sensitization above the level reached after decentralization ensues when such an action is abolished by parasympatholytic agents. Degenerative section of the postganglionic fibres would also exclude this action, but for anatomical reasons this cannot be made complete. The supersensitivity which follows this operation is greater than after decentralization but less than that produced by treatment with atropine-like drugs.