Innervation of the pineal gland in the Mongolian gerbil (Meriones unguiculatus)

Summary Parasympathetic stimulation of parotid glands has been studied in vivo, a) in normal resting glands, b) 72 h after post-ganglionic sympathectomy and c) after adrenergic degranulation of the acinar cells.Morphological results in each gland were compared with a similarly pretreated, but not parasympathetically stimulated, contralateral gland from the same animal.On parasympathetic stimulation of glands with densely granulated acinar cells (groups a- and b-) a variable, but usually relatively small, tendency for vacuole formation occurred in some cells. After prior degranulation of the cells (group c-) the tendency for vacuole formation was greatly accentuated. This indicates that the pre-existing metabolic state of the cells can influence the responses to stimulation of a single nerve. Dilatation of rough endoplasmic reticulum and nuclear changes were also more prominent after parasympathetic stimulation of previously degranulated acinar cells, and this suggests that parasympathetic impulses may have strong activating effects on resynthesis under these conditions. It is also likely that parasympathetic stimulation induced some, albeit small, degree of degranulation and, since this occurred in the absence of sympathetic nerves (group b-) it was probably the consequence of a direct cholinergic effect. The present results therefore indicate that the concept of an absolute dichotomy between parasympathetic and sympathetic responses is not tenable in this tissue.Analyses of saliva for amylase and peroxidase gave complex results but indicate that the two enzymes are not necessarily secreted in parallel. The morphological results support the idea that some enzyme molecules may have entered the saliva without being prepackaged into secretory granules, but could have passed directly from dilated cisterns of rough endoplasmic reticulum into intra-cellular vacuoles, and this tendency was most apparent after para-sympathetic stimulation of previously degranulated cells.Travel grants from the Wellcome Trust to J.R. Garrett are gratefully acknowledged. This work has been helped by the technical assistance of Mr. P.S.A. RowleyM.R.C. Research Assistant