SALIVATION IS UNNECESSARY FOR THE ESTABLISHMENT OF THE SALIVARY CONDITIONED REFLEX INDUCED BY MORPHINE

Abstract

In 5 dogs given 2 mgm. daily subcutaneous doses of atropine for 30 days a salivary conditioned reflex failed to appear. No saliva secretion, conditioned or unconditioned, occurred in dogs given atropine previous to injection of morphine; but on discontinuance of the atropine injection after a time long enough to produce a fully conditioned reflex (7-9 days), the animals secreted as much saliva as at any subsequent time. Hence the effector response is not indispensable for the establishment of a typical salivary conditioned reflex, showing that less than the entire efferent limb is necessary for the conditioning process. In another group of experiments, a conditioned reflex was established and continued until the daily secretion rate was practically constant. Pilocarpine hydrochloride was then substituted for the morphine; in spite of the continuation of the effector response, the conditioned salivary reflex disappeared within the normal time. Whether or not this extinction process is retarded by pilocarpine can not be determined from the data presented, because, as Kleitman and Crisler have shown, the curves of extinction are by no means as constant as the curves for the establishment of the conditioned reflex owing to great individual variation in different animals.