Related Experiment Videos
Immunohistochemical evidence of indolamine neurons in monkey spinal cord
Abstract:
In this study, we have identified over 150 cells in the adult macaque spinal cord that are immunoreactive when stained with an antibody to 5-HT by means of the PAP method. The staining was blocked by preabsorption of the primary antibody by the 5-HT-BSA conjugate (used to generate the antibody) and by 5-HT, while BSA, dopamine, norepinephrine, 5-methoxytryptamine and tryptamine preabsorption did not block staining. In addition, the Falck-Hillarp histofluorescence technique was applied to the lumbosacral cord from one of the three monkeys studied; results confirm the presence of cells with yellow fluorescence and rapid fading to brown characteristic for serotoninergic cells. The neuronal identity of these immunoreactive cells is based on light and electron microscopic morphology and the presence of synaptic terminals in contact with labeled somata and dendrites. Most of these neurons were small (10-25 micrometers) and located ventral to the central canal in lamina X. Some processes of the cells extended into the intermediate gray and the ventromedial area of the ventral horn; other processes wrapped around large blood vessels in lamina X or around the wall of the central canal. Cells were most frequent in the cervical cord (approximately 6-7/mm length of cord) and less frequent in the thoracic (1.5/mm), lumbar (3/mm), and sacral (2/mm) cord. A few cells were also found in the marginal and gelatinosa regions of the dorsal horn of the sacral cord. Examination of sections from the medulla-spinal cord junction (obex level) indicates that the spinal cells may be an extension of cell groups located near the raphe obscurus in the gray region around the IVth ventricle. The indolamine spinal cells may act as interneurons in spinal circuits, control spinal blood flow through vessel innervation, or play a role in CSF composition through central canal innervation.
Insights
Researchers identified over 150 serotonin (5-HT) immunoreactive neurons in the adult macaque spinal cord using PAP and Falck-Hillarp methods. These neurons, primarily in lamina X, may function as interneurons or regulate spinal blood flow and cerebrospinal fluid.
Area of Science:
- Neuroscience
- Spinal Cord Research
- Serotonergic System
Background:
- The distribution and function of serotonergic neurons in the primate spinal cord remain incompletely understood.
- Serotonin (5-HT) plays crucial roles in various physiological processes, including motor control, pain modulation, and autonomic functions.
Purpose of the Study:
- To identify and characterize 5-HT immunoreactive neurons in the adult macaque spinal cord.
- To investigate the precise location, morphology, and potential functions of these spinal serotonergic cells.
Main Methods:
- Immunohistochemistry using a specific antibody against 5-HT and the Peroxidase-Antiperoxidase (PAP) method.
- Histofluorescence using the Falck-Hillarp technique to detect catecholamines and indolamines.
- Light and electron microscopy for detailed morphological analysis and synaptic connections.
Main Results:
- Over 150 5-HT immunoreactive cells were identified in the macaque spinal cord, primarily located in lamina X ventral to the central canal.
- Staining specificity was confirmed through antibody preabsorption experiments and corroborated by histofluorescence findings characteristic of serotonergic cells.
- Morphological analysis revealed small neurons (10-25 µm) with processes extending into adjacent gray matter, surrounding blood vessels, and the central canal.
Conclusions:
- The identified spinal 5-HT neurons are likely serotonergic and possess neuronal characteristics, including synaptic contacts.
- These neurons exhibit a distinct distribution pattern across different spinal cord levels, with a potential origin from brainstem raphe nuclei.
- Potential roles include acting as interneurons in spinal circuits, regulating spinal blood flow, and influencing cerebrospinal fluid composition.