Spinal Trigeminal Nucleus Caudalis Research Articles

Three bulbospinal pathways from the rostral medulla of the cat: an autoradiographic study of pain modulating systems.

AbstractSmall amounts of 3H‐leucine were injected into discrete regions in the rostral medulla of the cat. Descending projections from these sites were studied with autoradiographic methods. On the basis of differential projections to the medulla and spinal cord, three distinct regions were delineated. Nucleus reticularis gigantocellularis (Rgc), located dorsally in the medullary reticular formation, projects primarily to “motor” related sites, including cranial motor nuclei VI, VII, XII, nucleus intercalatus, and a part of the ipsilateral medial accessory olive. The projection to the spinal cord is primarily via the ipsilateral ventrolateral and contralateral ventral funiculi. The Rgc terminal field is in lamina VII and VIII ipsilateral and lamina VIII contralateral to the injection site. In contrast, nucleus raphe magnus, (NRM) located ventrally, in the midline of the rostral medulla projects primarily to structures with known nociceptive and/or visceral afferent input. These sites include the solitary nucleus, the dorsal motor nucleus (X) and the marginal and gelatinous layers of the spinal trigeminal nucleus caudalis. The projection to the spinal cord is bilateral, via the dorsolateral funiculus. Terminal fields are found in the marginal zone and the substantia gelatinosa of the dorsal horn, and more deeply in lamina V, medial VI and VII. Nucleus reticularis magnocellularis (Rmc), located lateral to NRM and ventral to Rgc, has an overlapping projection with NRM, but the projection is ipsilateral. This difference between Rmc and Rgc is correlated with cytoarchitectural features of the two regions. The possibility that the raphe‐spinal pathway in the DLF mediates opiate and brain stimulation‐produced analgesia is discussed.

Analysis of the circuitry responsible for primary afferent depolarization in the trigeminal spinal nucleus caudalis of cats.

Depth analysis was performed on the field potential evoked by stimulation of the infraorbital nerve in the trigeminal spinal nucleus caudalis and the subjacent lateral reticular formation of cats. It was shown by dye marking of the recording positions that each subnucleus of the nucleus caudalis (subnucleus marginalis, gelatinosus and magnocellularis) and the reticular formation could be differentiated from one another by the characteristics of the peripherally evoked field potentials. Responses of neurons were extracellularly recorded in the subnuclei gelatinosus and magnocellularis of the nucleus caudalis and in the reticular formation to stimulation of the trigeminal sensory branches (the frontal, infraorbital and lingual nerves), the nucleus ventralis posteromedialis of the thalamus and the cerebral cortex. The properties of the neurons were studied in relation to their thresholds, latencies, receptive fields (sensory branches effective for spike generation) and frequency-following capacities. These responses were then compared with properties of the PAD induced in the fibers terminating in the nucleus caudalis by similar peripheral and central stimulation. It was found that the neurons in the subnucleus magnocellularis were the most likely candidates for the interneurons mediating the peripherally evoked disynaptic PAD in the trigeminal nerve fibers terminating in the nucleus caudalis.

Primary afferent depolarization in the trigeminal spinal nucleus of cats.

Intra-axonal recordings were made from trigeminal primary afferent fibers in the trigeminal spinal nuclei oralis and caudalis of cats. Primary afferent depolarization (PAD) was evoked in these afferents by stimulation of the trigeminal peripheral sensory branches (the frontal, infraorbital and lingual nerves), the cerebral cortex and the trigeminal spinal nucleus caudalis. The properties of the PAD, including the threshold, latency, receptive field (sensory branches effective for PAD induction) and frequency-following capacity, were studied with the following results: The results are discussed in relation to the neuronal circuitry responsible for induction of the trigeminal PAD.

Effect of Fentanyl, A Narcotic Analgesic, on Two Components of the Jaw Opening Reflex

An action of fentanyl, a short-acting narcotic, on the reflex discharge in the digastric nerve induced by the inferior alveolar nerve stimulation was investigated in α-chloraiose anesthetized cats. In the ipsilateral digastric reflex discharge, there were an early phase induced by stimulus exciting Aα fibers and a late phase appearing when Aδ fibers were also stimulated. Following dorso-lateral cordotomy at the obex level, an isolation of the spinal trigeminal nucleus caudalis, a total area in the digastricreflex discharge decreased, while its first peak amplitude was little affected, indicating a disappearance of the late phase and a preservation of the early phase. Fentanyl depressed both the total discharge area and the first peak amplitude. After dorsolateral cordotomy, the depression of the area decreased considerably, whereas that of the amplitude decreased slightly. Results indicate that fentanyl depressed both the early phase which is activated by the Aα fiber stimulation, not via the subnucleus caudalis and the late phase which is activated by the Aδ fiber stimulation via the subnucleus caudalis or its surroundings. The latter action would be related to the analgesic action of fentanyl.

The motor nucleus of the facial nerve in the opossum (Didelphis marsupialis virginiana). Its organization and connections.

AbstractThe organization of the facial nucleus was studied in the opossum by localizing neurons which stin poorly for acetylcholinesterase activity following transection of identified facial rami. The caudal auricular representation is limited to the ventromedial extreme of the nucleus, whereas the neurons contributing to the cervical ramus are situated dorsally and medially. The zygomatic representation extends throughout the intermediate portion of the nucleus, apparently overlapping with that of the palpebral and rostral auricular muscles which is limited to the ventral extreme of the intermediate zone. The buccolabial area is particularly large in the opossum and encompasses most of the lateral facial enlargement.Midbrain‐facial projections were identified from the superior colliculus, the midbrain tegmentum (particularly caudal ventromedial areas) and the red nucleus. The location of terminal degeneration in the facial nucleus following lesions within each of these areas was plotted and interpreted in light of facial organization. Of particular note is the fact that the fibers of rubral origin distribute preferentially to the zygomatic and, to some extent, buccolabial areas, whereas the ventromedial tegmental system distributes most strongly to the areas of caudal auricular, cervical, palpebral and rostral auricualar representation. The medial and intermediate regions of the facial nucleus receive a denser midbrain projection than does the lateral (buccolabial) area. In contrast, evidence was obtained for an extensive facial projection from the parvocellular reticular formation and the caudal spinal trigeminal nucleus which strongly favors the buccolabial enlargement. The possibility exists that the medial pontine and medullary reticular formation as well as portions of the dorsal column nuclei also have a facial projection. Spino‐facial fibers arise rostral to the cervical enlargement and show a predilection for the medial facial enlargement (cervical and caudal auricular areas). Although some systems distribute preferentially to specific areas of the facial nucleus, overlap is present suggesting considerable integration.

Sensory mechanisms in mammalian teeth and their supporting structures.

Sensory mechanisms in mammalian teeth and their supporting structures.

Four aspects of trigeminal nucleus and a paradox.

Four aspects of trigeminal nucleus and a paradox.