Rsb Liem

Projections from the rostral parvocellular reticular formation to pontine and medullary nuclei in the rat: Involvement in autonomic regulation and orofacial motor control

The efferent connections of the rostral parvocellular reticular formation to pontine and medullary nuclei in the rat were studied with anterogradely transported Phaseolus vulgaris leucoagglutinin. Dense innervations from the rostral parvocellular reticular formation were found in the mesencephalic trigeminal nucleus, the supratrigeminal area, the motor trigeminal nucleus, the motor trigeminal nucleus, the facial, hypoglossal and parabrachial nuclei and specific parts of the caudal parvocellular reticular formation, including nucleus linearis and the dorsal reticular nucleus of the medulla. The raphe nuclei, nucleus of the solitary tract, inferior olive, dorsal principal sensory, spinal trigeminal nuclei and gigantocellular reticular nucleus and the ventral reticular nucleus of the medulla received moderate projections. In general, the projections from the rostral parvocellular reticular formation were bilateral with an ipsilateral dominance. The dorsal motor vagus and the ambiguus nuclei were not labeled. It is concluded that the rostral parvocellular reticular formation participates in regulation of orofacial motor control and in neural networks for limbic control of metabolic homeostasis.

Neurotransmitters and neuropeptides within the mesencephalic trigeminal nucleus of the rat: An immunohistochemical analysis

In order to determine which neurotransmitters and neuropeptides are utilized by the neurons of the mesencephalic trigeminal nucleus and by the fibres making synaptic contact with these primary sensory cells, we have set up an immunohistochemical study using antibodies against 17 major neurotransmitters and neuropeptides in the rat. Apart from some intracellular immunostaining for glutamate, no immunoreactivity to any of the tested neurotransmitters and neuropeptides could be detected inside mesencephalic nucleus of the trigeminal nerve neurons. Our immunohistochemical observations indicate that mesencephalic nucleus of the trigeminal nerve neurons receive input from various nerve fibres that appear to utilize serotonin, GABA, dopamine, noradrenaline (and likely glutamate) as transmitters. The innervation appeared randomly distributed over all mesencephalic nucleus of the trigeminal nerve neurons. The presence of substance P, cholecystokinin, vasoactive intestinal polypeptide, bombesin/gastrin releasing peptide, [Leu]enkephalin and neuropeptide Y observed in some fibres that contact with mesencephalic nucleus of the trigeminal nerve neurons, presumably reflect the co-existence of these peptides with one of the neurotransmitters.

Ultrastructure of the Rat Mesencephalic Trigeminal Nucleus

The subcellular morphology of the mesencephalic trigeminal (Me5) nucleus in the rat was studied by transmission electron microscopy. Most neurons in the thin rostral as well as in the major caudal part of Me5 appeared as large (40-50 microns), round- to ovoid-shaped unipolar cells. A few neurons (estimated 5%) appeared to be multipolar, usually bipolar. The Me5 neurons had a large, round, centrally located nucleus, and their cytoplasm was characterized by a dense network of lamellar granular endoplasmic reticulum, an abundant Golgi apparatus, many mitochondria and neurofilaments suggesting very active cells with a high rate of synthesis and axoplasmatic transport. Numerous small spinous processes covered the surface of the Me5 neurons. Clustering of 2 or 3 cells was accomplished by maculae, i.e. zones of gap junctions and close cell appositions. Boutons contacting the soma of Me5 neurons and boutons contacting large and small dendrites were defined as axosomatic and axodendritic synapses, respectively. Four types of synaptic boutons were distinguished: (1) S boutons, with round vesicles and asymmetrical as well as symmetrical synapses, (2) F boutons, with pleomorphic admixture of flattened and spherical vesicles and asymmetrical synapses, (3) P boutons, which resembled the F-type boutons but contained predominantly spherical vesicles and symmetrical synapses, and (4) G boutons, characterized by a heterogeneous population of vesicles. This description of the Me5 nucleus is particularly useful for future studies that attempt to correlate the structure of a particular synapse with its function.

ORIGIN, DISTRIBUTION AND MORPHOLOGY OF SEROTONERGIC AFFERENTS TO THE MESENCEPHALIC TRIGEMINAL NUCLEUS OF THE RAT

We have studied the localization, the morphology and sources of serotonergic input on the primary afferent neurons in the mesencephalic trigeminal nucleus (Me5) of the rat with light and electronmicroscopy immunocytochemistry and with anterograde and retrograde neuroanatomical tract tracing methods. Me5 neurons were found to receive a serotonergic input that is part of a serotonergic fibre plexus extending over the neighbouring parabrachial nucleus and locus coeruleus. These serotonergic afferents originate predominantly from serotonergic cells in the dorsal raphe nucleus.

DOPAMINERGIC AFFERENTS TO THE MESENCEPHALIC TRIGEMINAL NUCLEUS OF THE RAT - A LIGHT AND ELECTRON-MICROSCOPE IMMUNOCYTOCHEMISTRY STUDY

The localization and sources of dopaminergic projections on the primary afferent neurons in the mesencephalic trigeminal nucleus (Me5) of the rat were studied using light and electron microscopic immunocytochemical staining techniques combined with anterograde and retrograde neuroanatomical tract tracing methods. Me5 neurons were found to receive a dopaminergic input that is part of a dopaminergic fibre plexus extending over the neighbouring nucleus parabrachialis and locus coeruleus. These dopaminergic afferents originate from the substantia nigra, the ventral tegmental area and the medial hypothalamus.

Distribution of Synaptic Boutons in the Mesencephalic Trigeminal Nucleus of the Rat – A Quantitative Electron-Microscopical Study

The distribution of synapses and synaptic bouton types in the mesencephalic trigeminal (Me5) nucleus was examined in a quantitative electron-microscopical study. Of 588 terminal boutons that were counted in the compact caudal part of the Me5 nucleus, less than 8% formed synapses on the somata of the predominantly unipolar Me5 neurons. About 79% formed synapses on fibres located between the Me5 somata, while about 13% of the vesicle-containing terminals had no clear synaptic specialization. All of these non-synaptic terminals were G type boutons, with pleomorphic and large characteristic dense-core vesicles. Approximately 60% of the axosomatic synapses were of the S type, containing spherical vesicles and an asymmetrical or symmetrical synaptic specialization. About 20, respectively 15% of the axosomatic synapses, were of the F, respectively P type; both are symmetrical synapse types containing either a majority of flat or pleomorphic vesicles. Less than 10% of the axosomatic synapses were of the G type. Although some proportional differences were noted, an almost similar bouton type distribution pattern was found for the axodendritic synapses suggesting that the axosomatic and axodendritic synapses in the Me5 nucleus are part of the same afferent fibre plexus covering the Me5 nucleus.

IN-TOTO STAINING AND PRESERVATION OF PERIPHERAL NERVOUS-TISSUE

A simple quantitative modification of the in toto staining technique for nervous networks of Sihler is described. The results are demonstrated on the innervation pattern of the hard palate of the rat. Formalin fixed hard palates of rat were macerated and bleached in an aqueous solution of 3% potassium hydroxide with a few drops of 3% hydrogen peroxide added. Thereafter, the specimens were decalcified in Sihlers solution I (1 part glacial acetic acid, 1 part pure glycerin and 6 parts 1% chloral hydrate), the process being controlled by radiography. The specimens were next stained in Sihlers solution II (1 part Ehrlichs hematoxylin, 1 part pure glycerin and 6 parts 1% chloral hydrate). After staining, the non-nervous tissues were destained in Sihlers solution I. Destaining was checked microscopically and was stopped before the finest branches of the nerves began to fade. The specimens were then washed in a weak aqueous solution of lithium carbonate and cleared in increasing concentrations of glycerin. Good visualization of nervous structures and a deep field of observation resulted; orientation of the peripheral nerves with respect to surrounding structures was readily seen and a three-dimensional image of the nervous networks was obtained.

Ultrastructural localisation of intramuscular expression of BDNF mRNA by silver-gold intensified non-radioactive in situ hybridisation.

Abstract. A non-radioactive in situ hybridisation method is described for the detection of low intramuscular levels of brain-derived neurotrophic factor (BDNF) mRNA at the electron microscope level. Application of high-grade silver-gold intensification of the diaminobenzidine end product of in situ hybridisation revealed that in adult rat muscle the constitutive expression of muscular BDNF is confined to the myofibres; satellite cells, Schwann cells, endothelial cells, fibroblasts or axons do not appear to contribute to BDNF production in normal muscle. Although muscular BDNF is a neurotrophic factor for innervating motoneurons and supposedly released only at the motor endplates, the production of BDNF mRNA appears to occur along the entire length of the myofibres and is not confined to nuclei in the postsynaptic regions.

Collagenous Network in Cartilage of Human Femoral Condyles. A Light Microscopic and Scanning Electron Microscopic Study

To determine the spatial arrangement of collagen fibrils in articular cartilage of the human femoral head, three healthy femoral heads, obtained at necropsy, were examined by light microscopy and scanning electron microscopy. Light microscopic observations revealed no collagen fibril organization. Scanning electron microscopic observations showed a fine fibrillar texture throughout the articular cartilage. At the articular surface, smooth and fibrillated areas were detectable. Underneath the articular surface, the collagen network in the superficial zone showed a tighter appearance when compared with the homogeneous collagen network of the matrix in the deeper zones. The calcified cartilage zone was well demarcated from the uncalcified cartilage. The arcade model of Benninghoff [Z. Zellforsch. Mikrosk. Anat. 2: 783-862 (1925)] could not be confirmed. It was concluded that the organization of collagen fibrils in hyaline cartilage shows a three-dimensional network of randomly oriented fibrils.

CONTRALATERAL PROJECTIONS OF CELLS IN THE MOTOR TRIGEMINAL NUCLEUS OF THE RAT

With horseradish peroxidase and Phaseolus vulgaris lectin as tracers, a direct connection between the jaw closing parts of the ipsi- and contralateral motor trigeminal (Mo5) nuclei of the rat is shown. The contralateral projecting cells in Mo5 were small (18 X 11 microns) ovoid and bipolar. It is speculated that these contralateral projecting cells in Mo5 are interneurons that are involved in the coordination of the bilateral activity of jaw closing motoneurons during orofacial motor behavior.