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Close microtopographical relationships between sympathetic nerve terminals and bulbous process endings of pinealocytes in the pineal gland of the Mongolian gerbil
Author(s) -
Redecker Peter
Publication year - 1993
Publication title -
journal of pineal research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.881
H-Index - 131
eISSN - 1600-079X
pISSN - 0742-3098
DOI - 10.1111/j.1600-079x.1993.tb00905.x
Subject(s) - pinealocyte , gerbil , free nerve ending , pineal gland , synaptophysin , biology , anatomy , synaptic vesicle , pathology , vesicle , neuroscience , immunohistochemistry , medicine , melatonin , genetics , ischemia , membrane , immunology
Previous studies have shown that pinealocytes of the gerbil pineal gland exhibit processes that form terminal swellings filled with abundant electron‐lucent microvesicles. The membrane of these presumptive secretory microvesicles is known to contain synaptophysin, a major integral glycoprotein of neuronal synaptic vesicles. The present study was conducted to evaluate the microtopographical relationships between the vesicle‐rich process swellings and intra‐pineal nerve terminals. For this purpose, both nerve terminals and pinealocyte process endings were visualized immunohistochemically in the same semi‐thin sections of plastic‐embedded gerbil pineals, using antibodies directed against synaptophysin. This approach consistently revealed close spatial associations of punctate immunopositive nerve endings with intensely stained bulbous process terminals of pinealocytes in or near the perivascular spaces. The light‐microscopic observations of intimate neuronal‐pinealocytic relationships were corroborated at the electron‐microscopic level. Perivascular varicosities with ultrastructural features characteristic of sympathetic nerve terminals were frequently juxtaposed to vesicle‐filled process endings of pinealocytes. Analysis of serial thin sections showed that multiple point‐to‐point contacts are encountered between noradrenergic nerve terminals and pinealocytic process swellings. Our morphological findings imply that bulbous process terminals, at least in the gerbil pineal gland, are major targets for the neuronal control of the secretory activity of pinealocytes.