(from Latin, raphe: seam) The raphe nuclei form a column of neurons (see NEURON) along the MIDLINE of the BRAINSTEM. The raphe is divisible into component nuclei with projections to virtually all parts of the CENTRAL NERVOUS SYSTEM: the more posterior nuclei have descending projections while the more anterior nuclei have ascending projections. SPINAL CORD, BRAINSTEM, CEREBELLUM and virtually all parts of the MIDBRAIN, DIENCEPHALON and FOREBRAIN have serotonin inputs. The various raphe nuclei are all associated with populations of SEROTONIN-containing neurons, labeled as cell groups B1– B9 in the CLASSIFICATION OF DAHLSTRÖM AND FUXE.
The various raphe nuclei and serotonin cell groups are as follows: nucleus raphe pallidus (B1); nucleus raphe obscurus (B2); NUCLEUS RAPHE MAGNUS (B3); MEDIAN RAPHE NUCLEUS (pontine portion) (B5); DORSAL RAPHE NUCLEUS, pontine portion (B6); dorsal raphe nucleus, midbrain portion (B7); median raphe nucleus, midbrain portion (B8). Cell group B4 is in the CENTRAL GREY (the portion in the MEDULLA OBLONGATA) and B9 in the MEDIAL LEMNISCUS; the NUCLEUS RAPHE PONTIS incorporates elements of both B5 and B6. Functionally, the raphe nuclei have been associated with many processes: the dorsal and medial nuclei, and the nucleus raphe magnus (important in pain suppression) have been the most closely investigated. The dorsal and medial raphe nuclei have both been associated with SLEEP (especially SLOW-WAVE SLEEP): lesions in these structures, or local inhibition of serotonin synthesis, produce INSOMNIA. The dorsal raphe also has a role in the regulation of HIPPOCAMPAL THETA, which is prominent during the waking state. In addition, the dorsal raphe has connections with the BASAL GANGLIA: it sends serotonin containing afferents to the SUBSTANTIA NIGRA pars compacta, GLOBUS PALLIDUS and STRIATUM.
This is the complete article, containing 278 words
(approx. 1 page at 300 words per page).
