Individual cells in the raphe nuclei of the medulla oblongata in rat that contain immunoreactivities for both serotonin and enkephalin project to the spinal cord

1989 ◽  
Vol 75 (3) ◽  
Author(s):  
D.E. Millhorn ◽  
T. H�kfelt ◽  
A.A.J. Verhofstad ◽  
L. Terenius
Keyword(s):  
Spinal Cord ◽  
Medulla Oblongata ◽  
Raphe Nuclei ◽  
Raphé Nuclei

scholarly journals Medullary raphe nuclei activate the lumbosacral defecation center through the descending serotonergic pathway to regulate colorectal motility in rats

2018 ◽  
Vol 314 (3) ◽  
pp. G341-G348 ◽  
Author(s):  
Hiroyuki Nakamori ◽  
Kiyotada Naitou ◽  
Yuuki Horii ◽  
Hiroki Shimaoka ◽  
Kazuhiro Horii ◽  
...  
Keyword(s):  
Spinal Cord ◽  
Electrical Stimulation ◽  
Raphe Nuclei ◽  
Lumbosacral Spinal Cord ◽  
Pelvic Nerves ◽  
Medullary Raphe ◽  
Raphé Nuclei ◽  
Type 3 ◽  
Stimulation Of

Colorectal motility is regulated by two defecation centers located in the brain and spinal cord. In previous studies, we have shown that administration of serotonin (5-HT) in the lumbosacral spinal cord causes enhancement of colorectal motility. Because spinal 5-HT is derived from neurons of the medullary raphe nuclei, including the raphe magnus, raphe obscurus, and raphe pallidus, we examined whether stimulation of the medullary raphe nuclei enhances colorectal motility via the lumbosacral defecation center. Colorectal pressure was recorded with a balloon in vivo in anesthetized rats. Electrical stimulation of the medullary raphe nuclei failed to enhance colorectal motility. Because GABAergic neurons can be simultaneously activated by the raphe stimulation and released GABA masks accelerating actions of the raphe nuclei on the lumbosacral defecation center, a GABAA receptor antagonist was preinjected intrathecally to manifest excitatory responses. When spinal GABAA receptors were blocked by the antagonist, electrical stimulation of the medullary raphe nuclei increased colorectal contractions. This effect of the raphe nuclei was inhibited by intrathecal injection of 5-hydroxytryptamine type 2 (5-HT2) and type 3 (5-HT3) receptor antagonists. In addition, injection of a selective 5-HT reuptake inhibitor in the lumbosacral spinal cord augmented the raphe stimulation-induced enhancement of colorectal motility. Transection of the pelvic nerves, but not transection of the colonic nerves, prevented the effect of the raphe nuclei on colorectal motility. These results demonstrate that activation of the medullary raphe nuclei causes augmented contractions of the colorectum via 5-HT2 and 5-HT3 receptors in the lumbosacral defecation center. NEW & NOTEWORTHY We have shown that electrical stimulation of the medullary raphe nuclei causes augmented contractions of the colorectum via pelvic nerves in rats. The effect of the medullary raphe nuclei on colorectal motility is exerted through activation of 5-hydroxytryptamine type 2 and type 3 receptors in the lumbosacral defecation center. The descending serotoninergic raphespinal tract represents new potential therapeutic targets against colorectal dysmotility such as irritable bowel syndrome.

Response properties and functional organization of neurons in midline region of medullary reticular formation of cats

1984 ◽  
Vol 52 (5) ◽  
pp. 961-979 ◽  
Author(s):  
C. T. Yen ◽  
P. S. Blum
Keyword(s):  
Spinal Cord ◽  
Reticular Formation ◽  
Visual Stimuli ◽  
The Body ◽  
Raphe Nuclei ◽  
Auditory Stimuli ◽  
Conduction Velocities ◽  
Medullary Raphe ◽  
The Mean ◽  
Raphé Nuclei

Extracellular single-unit recordings were made in the anesthetized cat from neurons within the medullary raphe nuclei and nearby reticular formation. The descending axons from some of these neurons were characterized in terms of length, conduction velocity, and location within the white matter of the spinal cord. The sensory properties were characterized following somatic, baroreceptor, visual, and auditory stimuli. The mean conduction velocities of the descending axons from neurons in the medullary raphe nuclei and in the magnocellular tegmental field (26 m/s) were significantly slower than the mean conduction velocities of units in the regions immediately dorsal to them (50 m/s). Action potentials in neurons in the medullary raphe nuclei and in the magnocellular tegmental field were evoked by anti-dromic stimulation from the dorsolateral portion of the spinal cord (30 of 43, 70%), whereas neurons located in more dorsal regions along the midline and in the reticular formation projected into the ventral columns (18 of 25, 72%). Neurons were most easily activated by a tap stimulus to the body surface. This stimulus activated 84% of the neurons tested. The receptive fields were large, often including the four limbs, back, and head. Tap-sensitive neurons were found throughout the regions investigated. Stimulation of hair receptors activated 37% of neurons tested, whereas 19% responded to a high-intensity cutaneous stimulus (pinch), 35% responded to baroreceptor stimuli, 32% responded to visual stimuli, and 33% responded to auditory stimuli. Neurons responsive to pinch were likely to respond to baroreceptor stimuli and unlikely to respond to visual stimuli. Neurons responsive to visual stimuli were likely to respond to auditory stimuli.

Effect of Treadmill Exercise on Serotonin Immunoreactivity in Medullary Raphe Nuclei and Spinal Cord Following Sciatic Nerve Transection in Rats

2009 ◽  
Vol 35 (3) ◽  
pp. 380-389 ◽  
Author(s):  
Arthiese Korb ◽  
Leandro Viçosa Bonetti ◽  
Sandro Antunes da Silva ◽  
Simone Marcuzzo ◽  
Jocemar Ilha ◽  
...  
Keyword(s):  
Spinal Cord ◽  
Sciatic Nerve ◽  
Treadmill Exercise ◽  
Raphe Nuclei ◽  
Nerve Transection ◽  
Sciatic Nerve Transection ◽  
Medullary Raphe ◽  
Serotonin Immunoreactivity ◽  
Raphé Nuclei

Gigantocellular vasodepressor area is tonically active and distinct from caudal ventrolateral vasodepressor area

1997 ◽  
Vol 272 (3) ◽  
pp. R731-R742 ◽  
Author(s):  
S. A. Aicher ◽  
D. J. Reis
Keyword(s):  
Spinal Cord ◽  
Reticular Formation ◽  
Kynurenic Acid ◽  
Sympathetic Nerve Activity ◽  
Raphe Nuclei ◽  
Ventrolateral Medulla ◽  
Medullary Reticular Formation ◽  
Nerve Activity ◽  
System 2 ◽  
Raphé Nuclei

The gigantocellular depressor area (GiDA) is a functionally defined subdivision of the medullary gigantocellular reticular formation where vasodepressor responses are evoked by glutamate microinjections (Aicher, S. A., D. J. Reis, D. A. Ruggiero, and T. A. Milner. Neuroscience 60: 761-779, 1994). The present experiments sought to determine whether the GiDA 1) tonically inhibits the sympathetic nervous system; 2) is necessary for baroreflex function; and 3) is functionally distinct from adjacent vasodepressor regions in the medullary reticular formation, including the midline raphe nuclei and the caudal ventrolateral medulla (CVL). Excitotoxic lesions of the GiDA abolished the baroreflex and significantly increased sympathetic nerve activity in anesthetized rats. Equivalent injections into the midline raphe nuclei elevated sympathetic activity but did not alter baroreflex responses. Therefore, the GiDA is functionally distinct from the raphe nuclei, although both contain tonically active sympathoinhibitory neurons. Because the effects of GiDA lesions were identical to those seen after lesions of the CVL, further studies were required to demonstrate that the GiDA and CVL are functionally and anatomically distinct. First, intramedullary injections of kynurenic acid produced hypertension and blocked the baroreflex when placed in the CVL, but not when placed in the GiDA. Second, muscimol inactivation of the RVL blocked the hypertension produced by excitotoxic lesions of the CVL, but failed to block the hypertension produced by similar lesions of the GiDA. Third, CVL neurons project to the RVL but not the spinal cord, whereas GiDA neurons project to the spinal cord but not the RVL. These studies show that the CVL and GiDA are both tonically sympathoinhibitory regions, but they are distinct with regard to their functional connectivity with other autonomic regions.

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