Nucleus raphe obscurus
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The nucleus raphe obscurus, despite the implications of its name, has some very specific functions and connections of afferent and efferent nature. The raphe obscurus projects to the cerebellar lobes VI and VII and to crus II along with the nucleus raphe pontis (Brodal, A. Neurological Anatomy in relation to Clinical Medication 3rd ed. Oxford Press. 1981). This so called obscure nucleus has also been implicated in the modulation of the hypoglossal nerve. It has been observed that the ablation of this nucleus causes a change in the firing pattern in the XII nerve (Peever JH, Necakov A, Duffin J., "Nucleus raphe obscurus modulates hypoglossal output of neonatal rat in vitro transverse brain stem slices." Journal of Appl Physiol. 2001 Jan;90(1):269-79). In addition, the raphe obscurus mediates expiration via the inhibitory effect of serotonin and depresses periodic synaptic potentials (Lalley PM, Benacka R, Bischoff AM, Richter DW, "Nucleus raphe obscurus evokes 5-HT-1A receptor-mediated modulation of respiratory neurons". Brain Research Volume 747, Issue 1 , 30 January 1997, Pages 156-159). It has also been shown that this nucleus stimulates gastrointestinal motor function, microinjections of 5-HT into the n.r. obscurus increase gastric movement (Krowicki, ZK and Hornby, PJ. "Serotonin microinjected into the nucleus raphe obscurus increases intragastric pressure in the rat via a vagally mediated pathway", Pharmacology and Experimental Therapeutics. Volume 265, Issue 1, pp. 468-476, 04/01/1993).
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