Mapping of different neuropeptides in the lower brainstem of the rat: with special reference to the ventral surface.

A neuropeptide map of beta-endorphin-, vasoactive intestinal peptide-, substance P-, and somatostatin-like reactive neurons and nerve fibers was made by means of immunohistochemistry. Indirect immunofluorescence was carried out in parallel to peroxidase-antiperoxidase reaction using a modified fixation technique. Special interest was directed to the superficial ventral regions of the medulla oblongata where regulative centers for respiration and circulation have been localized. The atlas presented offers a reliable tool for a precise neuromorphological localization of these neuropeptides in pharmacophysiological experiments.

Mapping of cholinoceptive(nicotinoceptive)neurons in the lower brainstem: with special reference to the ventral surface of the medulla.

The distribution of cholinoceptive neurons in the lower brainstem of the rat was investigated by means of a histochemical method for specific acetylcholinesterase. Nicotinoceptive neurons were characterized using an alpha-bungarotoxin-horseradish peroxidase conjugate for the detection of nicotinic acetylcholine receptors. For the first time a nearly complete mapping of the location of cholinoceptive (nicotinoceptive) neurons of the lower brainstem was achieved. Special attention was focused on the organization of the cholinoceptive neuronal matrix of the ventral surface of the medulla, where regulative centers for vasomotor and respiratory control are located.

Morphology of the medullary chemosensitive fields. 1. Mapping of the neuronal matrix by a horseradish peroxidase technique.

A modified horseradish peroxidase labelling technique was used to study the distribution pattern of neurons in the central chemosensitive fields of the medulla oblongata of cats. In several cryosectioned medullae a mapping of superficially located HRP-labelled neurons was achieved. The distribution and configuration of the labelled neurons indicate that most of them belong to the nucleus paragigantocellularis lateralis. However, by varying the time of incubation it was possible to identify different types of neurons. On the basis of certain aspects of the HRP incorporation mode and neuronal topography a specific type of small-sized neurons has been identified. Some functional implications of these small neurons with respect to their possible chemosensitive activity are discussed.

Interlamellar tight junctions of central myelin. II. A freeze fracture and cytochemical study on their arrangement and composition.

The interlamellar tight junctions (ITJ) of central myelin (white matter from the parietal lobe and the medulla oblongata of the rat) were analyzed electron microscopically, making use of a wide range of different preparatory techniques. Freeze-fracture observations indicate that the ITJ are composed of rows of particulate subunits in glutaraldehyde-fixed or formaldehyde-fixed material, and in the unfixed state. The particulate subunits of the ITJ are preferentially associated with the protoplasmic (P) face in the aldehyde-fixed state, and no shift in the binding characteristics of the particles was observed after omission of aldehyde fixation. Tracer studies in conjunction with the dissociated appearance of the junctional globules suggest that the ITJ represent a leaky type of zonula occludens. It is assumed that the ITJ particles represent an "integral-type protein" that preferentially serves as a mechanical device maintaining the structural integrity of the central myelin sheath. By means of cytochemical experiments, the proteinaceous character of the ITJ subunits is established. An attempt is made, based on results from lipid extraction and protein digestion, to define certain cytochemical parameters of the ITJ proteins and to compare them with the current collection of chemically identified proteins of central myelin.

The microvascular pattern and perivascular linings of the area postrema. A combined freeze-etching and ultrathin section study.

The microvasculature and perivascular linings of the area postrema (A.P.) were studied electron microscopically with the ultrathin section and freeze-etching techniques. Special attention was given to the intercellular contacts of the different cellular entities. Two types of microvascular segments were identified. The endothelium of these vascular segments reveals fenestrations and a high pinocytotic activity. There are no significant differences in the frequency and distribution of the endothelial "openings" between both types of capillaries. The endothelium of the blood vessels, however, is joined by different types of tight junctions. Focal tight junctions occur between pericytes and the endothelium, and between leptomeningeal cellular elements in the perivascular space. The cell membrane of the perivascular glia shows intramembrane particles which are either distributed at random or organized in the form of membrane-associated orthogonal particle complexes (MOPC, Dermietzel, 1974). The significance of these findings is discussed with respect to the modified blood-brain barrier mechanism in the A.P.