An endogenous brain substance, CDS (clonidine-displacing-substance), inhibits the twitch response of rat vas deferens

The effect of CDS, an endogenous brain substance that specifically displaces bound [³H]clonidine and [³H]rauwolscine in rat brain membranes and human platelets, has been tested in isolated, field-stimulated rat vas deferens. CDS, obtained after an extensive purification procedure as a single peak from an HPLC sizing column, inhibited the electrically stimulated rat vas deferens similarly to the inhibitory action of clonidine, an α₂-agonist. The effective dose of CDS as an inhibitor of the vas deferens is equivalent to its effective dose in displacing specifically bound [³H]clonidine in rat brain membranes. Furthermore, the CDS inhibition of the twitch response is reversed by two α₂-adrenergic antagonists, yohimbine and phentolamine. From these results, it is suggested that CDS extracted from brain, with affinity for clonidine sites, may be involved in the non-adrenergic fast response of the sympathetic transmission of the vas deferens.