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Brain: Nucleus raphe magnus
Section of the medulla oblongata at about the middle of the olive. (Raphe nuclei not labeled, but 'raphe' labeled at left.)
Latin nucleus raphes magnus
nucleus raphe magnus, located directly rostral to the raphe obscurus, is afferently stimulated from axons in the spinal cord and cerebellum.
This makes the magnus a likely candidate for part of the
motor system; however, it seems to participate in the endogenous analgesia system.
The magnus receives descending afferents from the
periaqueductal gray, the paraventricular hypothalamic nucleus, central nucleus of the amygdala, lateral hypothalamic area, parvocellular reticular nucleus and the prelimbic, infralimbic, medial and lateral precentral cortices .
All of these brain areas influence the main function of the raphe magnus.
The main function of the magnus is mostly pain mediation; in fact it sends projections to the dorsal horn of the spinal cord to directly inhibit pain.
periaquiductal gray, the epicenter of analgesia, sends efferent connections to the nucleus raphe magnus in when it is stimulated by opiates (endogenous or otherwise).
Electrical stimulation of the PAG produces
analgesia, as well as administration of morphine to the PAG or n.r. magnus.
antinociceptic affects of electrical stimulation of the PAG can be blocked by administering naloxone, an opiate antagonist, to the n.r. magnus.
All of this seems to indicate that the magnus is part of the endogenous opiate system, and acts to inhibit pain in the spinal cord.
↑ Hermann, Dirk M. et al. Afferent projections to the rat nuclei raphe magnus, raphe pallidus and reticularis gigantocellularis pars demonstrated by iontophoretic application of choleratoxin (subunit b). Journal of Chemical Neuroanatomy Volume 13, Issue 1 , June 1997, Pages 1-21
Brain: rhombencephalon (hindbrain)
surface: Locus ceruleus
Trigeminal lemniscus ( Dorsal trigeminal tract, Ventral trigeminal tract)
cranial nuclei: GSA: Principal V/ Spinal V - VIII-c ( Dorsal, Anterior)/ VIII-v ( Lateral, Superior, Medial, Inferior) - SVE: Motor V - VII - GSE: VI - GVE: VII: Superior salivary nucleus
MLF, III, IV and VI ( vestibulo-oculomotor fibers, medial vestibulospinal tract)
sensory/ascending: Trapezoid body/VIII - Superior olivary nucleus
Inferior cerebellar peduncle ( Vestibulocerebellar tract)
motor/descending: Apneustic center • Pneumotaxic center ( Medial parabrachial nucleus) - Lateral parabrachial nucleus
Middle cerebellar peduncles ( Pontocerebellar fibers) - Pontine nuclei motor/descending: Corticospinal tract - Corticobulbar tract - Corticopontine fibers
Reticular formation ( Caudal, Oral, Tegmental, Paramedian) • Raphe nuclei ( Median)
surface: Posterior median sulcus - Postero-lateral sulcus - Area postrema
cranial nuclei: GVA: VII,IX,X: Solitary/ tract • SVA: Gustatory nucleus • GSE: XII • GVE: IX,X,XI: Ambiguus • SVE: X: Dorsal • IX: Inferior salivatory nucleus - MLF, III, IV and VI
sensory/ascending: Gracile nucleus • Cuneate nucleus ( Accessory cuneate nucleus) • Sensory decussation • Medial lemniscus
motor/descending: Dorsal respiratory group
motor/descending: Ventral respiratory group - Pyramid ( Motor decussation) - Inferior olivary nucleus ( Olivocerebellar tract, Rubro-olivary tract) surface: Anterior median fissure - Antero-lateral sulcus - Arcuate nucleus of medulla - Olivary body
Reticular formation ( Gigantocellular, Parvocellular, Ventral, Lateral, Paramedian) • Raphe nuclei ( Obscurus, Magnus, Pallidus)