ABSTRACT
ObjectiveTo investigate the role of NRM in the antinociceptive effect of muscle spindle afferents, the influence of NRM lesion on the inhibitory effect of muscle spindle afferents on the nociceptive responses of wide dynamic range (WDR) neurons and the effects of the muscle spindle afferents on the NRM neuronal activities were observed. MethodsThe single units of WDR neurons in the spinal dorsal horn were recorded extracellularly, and the inhibitory effects of activating muscle spindle afferents by intravenous administration of succinyicholine (SCH) on the C-fibers evoked responses (C-responses) of WDR neurons were tested before and after lesion of NRM. The ef- fects of the muscle spindle afferents activated by administrating SCH on the single NRM neurons were also examined. Results①lt was found that the C-responses of WDR neurons were significantly inhibited by intravenously adminis- tration of SCH, and the inhibitory effect was reduced after lesion of NRM ;②The activities of most of the NRM neu- rons could be changed significantly by administrating SCH. According to their responses, NRM neurons could be classified into three types:excitatory, inhibitory and non-responsive neurons, and the responses were dose-depen- dent. ConclusionThese results suggest that the muscle spindle afferents evoked by SCH may activate the NRM neu- rons, which plays an important role in the antinociception of muscle spindle afferents.
ABSTRACT
Neurons in the nucleus raphe magnus are involved in descending modulation of nociceptive transmission. In this study, we attempted to investigate electrophysiological properties of the NRM neurons dissociated from the postnatal rat medulla. The NRM neurons in the coronal slices of and the dissociated neurons from the postnatal rat medullae were immunohistochemically identified using antibody against serotonin. Relatively small number of neurons were positively stained in both preparations. The positively stained neurons displayed large cell body with double or multiple neurites. Using whole-cell patch clamp configuration ionic currents were recorded from the dissociated NRM-like neurons selected by criteria such as size and shape of cell body and cell population. Two types, high- and low-threshold, of voltage-dependent calcium currents were recorded from the dissociated NRM-like neurons. Some neurons displayed both types of calcium currents, whereas others displayed only high-threshold calcium current. Voltage-dependent potassium currents were also recorded from the dissociated NRM neurons. Some neurons displayed both transient outward and delayed rectifier currents but others showed only delayed rectifier current. These results suggest that there are at least two types of calcium currents and two types of potassium currents in the dissociated NRM neurons.
Subject(s)
Animals , Rats , Calcium , Neurites , Neurons , Potassium , SerotoninABSTRACT
A series of the positive cord dorsum potentials (CDP)were recorded in the dorsal surface of the spinal cord when the region of the nucleus raphy magnus (NRM)was stimulated by electricity. This CDP (NRM—CDP) consisted of three potentials. They were a Compound potential with a short time course and two slow potentials with a long time course which followed the compound one. The characteristics of the slowly potentials—NRM—CDP—1 and NRM—CDP—2 waves were analysed the parameters concerned were recorded. Therefore, a good experiment animal model and new information are provided for the further a study of the NRM action.
ABSTRACT
Immunoelectron microscopic technique was used in the present study to observe the serotonin (5-HT)-, substance P (SP)-, and leucine-enkephalin (L-Enk)-like immunoreactive ultrastructures in the nucleus raphe magnus (NRM) of the rat. 5HT-like immunoreactive (5-HT-LI) axonal terminals were found to form axosomatic, axo-dendritic, and axo-axonic synapses with non-5-HT-LI neuronal cell bodies, 5-HT-LI and non-5-HT-LI dendrites, and non-5-HT-LI axonal terminals respectively. Non-5-HT-LI axonal terminals formed axo-somatic and axo-dendritic synapses with 5-HT-LI neuronal cell bodies and dendrites. SP-LI (or L-Enk-LI) axonal terminals formed axo-somatic, axo-dendritic synapses with SP-LI (or L-Enk-LI) and non-SP-LI (or non-L-Enk-LI) neuronal cell bodies and dendrites, respectively. L-Enk-LI axonal terminals constituting axo-axonic synapses with L-Enk-LI axonal boutons were observed less frequently. The most common synaptic type made by 3 kinds immunoreactive profiles mentioned above was axo-dendritic synapses made by non-immunoreactive axonal terminals with immunoreactive dendrites. The majority of the immunoreactive axonal boutons were mainly filled by clear spherical vesicles, but sometimes were mixed with small number of flat and granular vesicles. The immunoreactive products were irregular electron-dense substances, and were located on both inner and outer surfaces of the vesicles, or on the surface of the membranous cell organelles in the cytoplasm, etc.
ABSTRACT
Using immunoelectron microscopic technique the SPergic autoregulatory synapses in the nucleus raphe magnus were studied. The results showed that there were SPlike perikarya and nerve fibers. The positive perikarya mainly were large polypolar cells. The positive fibers appeared as beaded-like and formed axodendritic synapses with SP-positive dendrites besides synapses formed with SP-negative structures. In the autoregulatory synapses the pre- and postsynaptic element were both labeled with immunoreactive products which precipitated at the periphery of small clear synaptic vesicles and the dendritic tubes, on the outer membrane of mitochondria, and in the cytoplasmic matrix. The pre- and postsynaptic membrane were symmetrical, and the synaptic vesicles aggregated near the presynaptic membrane. The synaptic cleft was about 20 nm in width and contained electron dense materials. The generality, structural characteristics and functional significance of the autoregulatory sysnapses were discussed.
ABSTRACT
The ultrastructure of the rat nucleus raphe magnus (NRM) was observed under transmission electron microscope in the present study. Most of the neurons of the NRM were medium and small sized fusiform and triangular in shape, they had spherical or ellipsoid nuclei and rather high nucleo-cytoplasmic ratio. Nuclear rodlets which composed of parallel filaments could be seen in some fusiform NRM neurons. There were numerous organelles in the cytoplasm. Axonal terminals apposed to most neuronal bodies and formed axo-somatic synapses. The predominant type of these synapses was symmetric. Sometimes, rod-like or spine-like cytoplasmic protrusions could be seen on the neuronal bodies, they often made axo-somatic synapses with axonal terminals. The neuropil of the NRM was quite complex. It was formed by transverse sections of myelinated fibers, unmyelinated fibers, synapses, and neuroglia. The axo-dendritic synapses were the major synaptic type in the neuropil. The predominant type of these axo-dendritic synapses was also symmetric and asymmetric axo-dendritic synapses. Some axonal terminals were arranged parallel with dendrites and formed symmetric synapses. Beneath subsynaptic membrane of some postsynaptic bags, there were some electrical dense spherules or bands which formed subsynaptic dense bodies. There were. no typical axo-axonic synapses in the NRM, but the parallelly arranged axonal terminals were often seen. Most of the presynaptic bags contained clear spherical vesicles or mixed with flattened and granular vesicles. Some postsynaptic bags were filled with flattened vesicles, they were also often mixed with spherical and granular vesicles.
ABSTRACT
Substance P-like immunoreactive (SP-li) cell bodies and processes and their synaptic relations with other neural elements in the nucleus raphe magnus (NRM) of rats were studied by electron microscope. The results showed that SP-li neurons are fusiform, oval and multipolar cells which distribute evenly over the nucleus. Immunostaining was present in the cytoplasmic matrix and membranes of mitochondria, endoplasmic reticulum and vesicles. Both unmyelinated and myelinated SP-li axons are found in the NRM. SP-li dendrites are numerous in the NRM. SP-li dendrites and somata are contacted by a variety of round, flat and granular vesicle-containing terminals. A central SP-li dendrite receivie convergent inputs from unlabelled axonal boutons is frequently seen in the NRM. SP-li terminals are presynaptic to the unlabelled dendrites, also some SP-li terminals are apposed or presynaptic to SP-li dendrites. Axo-axonic (SP-li) synapses were found in the NRM. The unlabelled presynaptic boutons contain clear round vesicles or mixed with granular vesicles. A central SP-li terminalis contacted by several unlabelled terminals is also found in the NRM.
ABSTRACT
Serotonin (5-HT) neurons in the nucleus raphe magnus (NRM) of the rat were identified by light and electron microscope immunocytochemistry methods. Serotoninlike immunoreactive (5-HT-li) neurous were large multipolar and fusiform cells which mainly located in the ventrocaudal part of the NRM. With electron microscopic immunocytochemistry the following findings were revealed: 1. Immunostaining was present in the cytoplasmic matrix, outer membrane of mitochondria, rough endoplasmic reticulum, multivesicular bodies and vesicles. Some nuclei of the cells were stained. 2.5-HT-li somata, dendrites and axons were postsynaptic to numerous unlabeled terminals which contained clear round vesicles (20-30 nm) or mixed with small granular vesicles (40-70 nm), large granular vesicles (90-110 nm) and flat clear vesicles. 3. The 5-HT-li axons were unmyelinated fibers, and the 5-HT-li axon terminals were scarce in the NRM. 4.5-HT-li axon terminals and dendrites abutting on capillaries and 5-HT-li dendrite-glial direct appositions were found in the NRM.These results revealed the ultrastructural characteristics of 5-HT-li neuron in the NRM. The variety of unlabeled terminals making contact with 5-HT-li somata and dendrites suggests that several neuronal system with possibly different transmitters may regulate 5-HT raphe-spinal neurons which may play integrative role in the NRM. Tae relationship between 5-HT neuron and the significance of the local microcirculation and the relationship between 5-HT neurons and glia cells were also discussed in the present paper.
ABSTRACT
In order to study the bifurcate projections of midbrain periaqueductal gray and nucleus raphe dorsalis to nucleus accumbens and nucleus raphe magnus, the fluorescence double-labeled method was used in the present study. Bisbenzimide (Bb) and propidium iodide (PI) were injected into nucleus raphe magnus and unilateral nucleus accumbens stereotaxically according to the time period necessary for their axonal transport. The percentages of double-labeled neurons were 21％; PI single labeled neurons were 32％; Bb single labeled neurons were 47％. Most of the labeled neurons were located in the middle and caudal parts of periaqueductal gray and the nucleus raphe dorsalis, and most were medium sized and fusiform and triangular in shape.
ABSTRACT
Different fluorescent tracers, Fast Blue (FB), Nuclear Yellow(NY), Propidium iodide (PI), Bisbenzimide (Bb), Evans Blue(EB), DAPI-Primuline (Pr), were injected into the frontal cortex, hippocampus, thalamus, cerebellum and cervical cord respectively in 31 rats to observe the fluorescent retrograde double labeling cells in the nucleus raphe magnus. The results showed that the axon collaterals of the nucleus raphe magnus projected to the :thalamus-cerebellum, thalamus-hippocampus, frontal cortex-thalamus, frontal cortex-cerebellum, hippocampus-cerebellum, hippocampus-cervical cord, cerebellum-cervical cord, thalamus-cervical cord and bilateral hippocampus and thalamus. The topographical organizations of divergent projection neurons of the nucleus raphe magnus were also found.