Aqueous aldehyde (Faglu) histofluorescence for catecholamines in 2 micron sections using polyethylene glycol embedding.

A technique is described which couples the aqueous aldehyde fluorescence (Faglu) method [5,6] with polyethylene glycol (PEG) embedding to obtain sections of brain as thin as 2 microns for light microscopic examination. Blocks from rat brains perfused with Faglu solution were embedded in PEG, sectioned on a rotary microtome and examined for amine fluorescence. Both catecholaminergic perikarya and their terminal arborizations were observed with high resolution in 2 micron sections. Single neurons could be traced in serial sections and varicosities as well as intervaricose segments were visible in terminal regions. This technique offers the further advantage of fixation compatible with electron microscopy, immunohistochemistry and other neuroanatomical methods. PEG-embedding of Faglu-fixed tissue thus provides a useful addition to existing fluorescence histochemical techniques for the visualization of catecholamines.

Immunocytochemical, Golgi and electron microscopic characterization of putative dendrites in the ventral glial lamina of the rat supraoptic nucleus.

Processes of magnocellular neurosecretory cells in the rat supraoptic nucleus which project along the pial surface in the ventral glial lamina were investigated using immunocytochemistry, Golgi stains and electron microscopy. Immunocytochemical studies revealed that although both oxytocin- and vasopressin-containing processes were evident in the ventral glial lamina, vasopressin-containing processes predominated. Ventral processes were thicker and of a different morphology than dorsal axon-like processes which joined the hypothalamo-neurohypophysial tract and exhibited large varicosities along their length or at their apparent termination. Golgi stains revealed that classically defined dendrites of supraoptic neurons projected primarily ventrally and often invaded the ventral glial lamina. No axons were traced to the lamina. Ultrastructurally, processes within the ventral glial lamina characterized as dendrites could be stained immunocytochemically for neurophysin and were post-synaptic to a variety of presynaptic elements. The results suggest that many dendrites from magnocellular neurosecretory cells in the supraoptic nucleus project to the ventral glial lamina and form a restricted, receptive plexus. The previously demonstrated coexistence of catecholamine-containing varicosities and other axon types with these processes in the lamina indicates an important role for supraoptic dendrites in integrating a wide variety of information relevant to neurohypophysial hormone release.

Immunocytochemical localization of CRF in the ovine hypothalamus.

A population of neuronal cell bodies and their fiber pathways have been elucidated within the ovine hypothalamus. The immunoreactive neurons were located in the anterior and dorsal hypothalamus interspersed throughout the paraventricular nucleus. These perikarya were only observed when an antiserum that was generated against the C-terminal of CRF was employed. A dense fiber projection traversed the medial-basal hypothalamus and ended within the palisade-contact zone of the median eminence and neural stem. Fibers were revealed by antisera generated against both the N-terminal and the C-terminal of CRF. Antisera pre-absorbed with synthetic CRF failed to yield immunoreactivity.

Supraoptic nucleus of the Brattleboro rat has an altered afferent noradrenergic input.

The distribution of fluorescent varicosities in the supraoptic nucleus of Brattleboro rats was compared to that in normal rats. The Brattleboro rat, which is characterized by a genetic absence of vasopressin, had fewer fluorescent varicosities in apposition to the vasopressin-deficient perikarya. The oxytocin-producing neurons in the same nucleus were hyperinnervated. These data suggest that the target neuron peptide (vasopressin) is necessary for the maintenance of normal noradrenergic innervation patterns.