Trigger activation of the paradoxical salivatory response to atropine in the parasympathetically denervated human parotid gland.

The author describes a specific intermediate condition of the response to atropine during the 2nd stage of denervation of the human parotid gland. Of the entire cohort of 110 subjects, some 20 subjects have been observed systematically. They demonstrated an extremely intense atropine salivation that followed an additional trigger activation, namely food or acid irritation of the mouth mucosa. The initial phase of such a stimulation was characterized by a sharp, explosive increase in secretion. The following conclusions have been inferred: (1) in the 2nd stage of parasympathetic denervation of the human parotid gland, there emerges a specific intermediate condition of 'readiness' for an extremely intense paradoxical salivatory response to atropine and other cholinolytics; (2) the pre-start 'readiness' state may be activated by means of adding a trigger signal followed by an explosive occurrence of abundant secretion; (3) only food or acid irritation, even to a minimal extent, of the mouth cavity may serve a specific trigger signal; (4) a stable state of this trigger readiness has been observed in 20 subjects for years, while in other subjects it has been observed as a transitory event between the 1st and the 3rd stages of denervation and during the regression of symptoms in the rehabilitation period; (5) suggestions have been made concerning the trigger activation mechanism of the atropine salivatory paradox and the evolutionary, model and clinical significance of the events described.