Survival and neurite formation of mesencephalic trigeminal neurones of the rat in vitro

In order to study the development and functional properties of single, isolated, rat mesencephalic trigeminal neurones, a cell-culture procedure was developed for these specific primary sensory neurones. Mesencephalic trigeminal neurones were isolated from the brainstem of 16-day-old rat embryos. Various factors thought to promote the survival and growth of these neurones in vitro were examined. Outgrowth and maintenance of mesencephalic trigeminal neurones in vitro appeared to be stimulated by a muscle-derived factor, present in muscle-conditioned medium or in muscle extract. Of the neurotrophic factors examined, brain-derived neurotrophic factor and neurotrophin-3, but not nerve-growth factor, promoted the survival of rat mesencephalic trigeminal neurones. Optimal survival of these neurones was found to occur on a monolayer of astrocytes, an effect mediated through direct cell-to-cell interactions

Immunogold localization of serotonin within synaptic terminals in the rat mesencephalic trigeminal nucleus

With the use of postembedding electron-microscopic immunogold cytochemistry, the vesicular distribution of serotonin within serotonergic synaptic terminals in the mesencephalic trigeminal nucleus was determined in order to obtain further insight into the mechanisms and function, significance of serotonin release to these jaw muscle spindle afferent neurons, Immunogold labelling was restricted to the previously described type I and type Il terminals. The distribution of immunogold particles over the synaptic terminals indicated that serotonin was stored in small round or pleomorphic (RSV) vesicles and in large granular dense-cored (DSV) vesicles. The amount of serotonin present in the DSV vesicles, which are generally considered to contain colocalized neuropeptides, showed a high degree of variation. These DSV vesicles were usually located at some distance from the synaptic area of the terminals suggesting that they represent a nondirectly releasable vesicle pool. The serotonergic RSV vesicles were,in general, irregularly distributed over the terminals, However, in about 19% of the analyzed labelled synaptic terminals serotonergic RSV vesicles were clustered together near their release site at the synaptic cleft. These synaptic terminals may represent highly active serotonergic synapses with a high release frequency and a high reuptake level, resulting in a dense concentration of vesicles containing a high amount of serotonin neat the synaptic cleft

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

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

MERKEL CELL NEURITE COMPLEXES IN THE HARD PALATE OF THE WISTAR RAT (RATTUS-NORVEGICUS)

The complexes were found in the basal layer of the epithelium of the rugae of the ante- and intermolar area of the palate. Asymmetric membrane densities were observed between the Merkel cell and its neurite or the adjacent keratinocytes. The cytoplasm of the Merkel cell was characterized by an accumulation of membrane-bound dense granules at the neurite side of the cell and by a well developed Golgi apparatus at its keratinocyte side