Electron microscopic autoradiography for demonstration of pineal serotonin in rat

Monoamine synaptic structure and localization in the central nervous system

The monoamines dopamine, noradrenaline, adrenaline, and serotonin as well as the diamine histamine have a widespread distribution in the central nervous system within synaptic terminals and nonsynaptic varicosities. In certain regions of the central nervous system the monoamines are contained in varicosities that have no synaptic specialization associated with them, suggesting a possible neuromodulatory role for some of the monoamines. The majority of monoamine labelled structures are synaptic terminals which are characterized by the presence of small, clear vesicles (40-60 nm) and large, granular vesicles (70-120 nm) within the terminal. A third population of vesicles--small, granular vesicles--which are visible only after histochemical staining, are probably the equivalent of the small, clear vesicles present after either autoradiographic or immunohistochemical labelling. Most monoamine containing terminals contact dendrites and dendritic spines and, less frequently, neuronal somata and other axons. Both asymmetrical and symmetrical membrane specializations are associated with monoaminergic terminals; however, asymmetrical contacts are the most frequent type found. These ultrastructural results indicate that monoamine containing terminals and varicosities in general share many common morphological features, but still have diverse functions.

A light and electron microscopic study of the pineal gland of the viscacha (Lagostomus maximus maximus)

The pineal of viscacha (Lagostomus maximus maximus) is formed by two main cellular populations of pinealocytes and interstitial cells. A connective capsule surrounds the gland sending numerous septa containing blood vessels and nerves. In the specimens collected during summer the pinealocyte displays a defined contour and a clear cytoplasm with abundant ribosomes and numerous cisternae of endoplasmic reticulum. The pinealocytes observed during winter have cytological characteristics of active cells with dense and elongated mitochondria, dense bodies, and a developed Golgi complex. These seasonal glandular changes could be related to the environmental condition and mainly to the summer photoperiod. The presence of abundant nerve terminals in the perivascular spaces suggests a neural control on the blood vessels.

Morphology of the pineal gland in pregnant and nursing sows

The pineal glands of pregnant and nursing sows were studied by light and electron microscopy. Similar structural changes in the pineal gland during pregnancy and lactation were noted as follows: a proliferation of glial cells concurrent with a decrease in the number of pinealocytes, a relative increase in the number of pinealocytes with cytoplasmic accumulation of dense bodies, and an increase in number of presumptive microglia. It appears that pregnancy and lactation exert a complex influence on pineal function, with a predominantly stimulating effect.

Radioautographic investigation of monoaminergic neurons: an evaluation

This review outlines the most relevant contributions currently available on the detection and ultrastructural characterization of monoaminergic neurons by radioautography after administration of radiolabeled monoamines. It includes methodological considerations and then a critical analysis of the diagnostic value of the radioautographic method for catecholaminergic and serotoninergic neurons, emphasizing in particular its recent applications to the visualization of dopaminergic axon terminals. An attempt is then made to evaluate the method in terms of specificity, sensitivity and resolution and its possibilities with regard to quantitative analysis. Lastly, its value for approaching the dynamic and metabolic properties of monoaminergic neurons is stressed.