Contributions of the Medullary Raphe and Ventromedial Reticular Region to Pain Modulation and Other Homeostatic Functions

Abstract

The raphe magnus is part of an interrelated region of medullary raphe and ventromedial reticular nuclei that project to all areas of the spinal gray. Activation of raphe and reticular neurons evokes modulatory effects in sensory, autonomic, and motor spinal processes. Two physiological types of nonserotonergic cells are observed in the medullary raphe and are thought to modulate spinal pain processing in opposing directions. Recent evidence suggests that these cells may modulate stimulus-evoked arousal or alerting rather than pain-evoked withdrawals. Nonserotonergic cells are also likely to modulate spinal autonomic and motor circuits involved in thermoregulation and sexual function. Medullary serotonergic cells have state-dependent discharge and are likely to contribute to the modulation of pain processing, thermoregulation, and sexual function in the spinal cord. The medullary raphe and ventromedial reticular region may set sensory, autonomic, and motor spinal circuits into configurations that are appropriate to the current behavioral state.

Central neural distribution of immunoreactive Fos and CRH in relation to plasma ACTH and corticosterone during sepsis in the rat

“…The distribution after CLP was restricted to the area shown in Fig. 7A that receives projections from other Fospositive areas including the preoptic region (Murphy et al, 1999), the bed nucleus of the stria terminalis, the central nucleus of the amygdala, the dorsal and lateral hypothalamic areas, the ventrolateral periaqueductal gray, the parabrachial nuclei, and the subcoeruleus area (Hermann, et al, 1997;Mason, 2001). This restricted area also projects to the preoptic area (Murphy, et al, 1999) and is the source of multisynaptic sympathetic pathways to brown fat and to blood vessels in the tail that induce fever (Smith et al, 1998).…”

Long-term deficits of preterm birth: Evidence for arousal and attentional disturbances

“…However, virtually all Preterm neonates are affected by various forms of stress. In experimental animals, these stressors have led to changes in arousal and attention (Mason 2001). Alterations in arousal (pre-attentional processes) and attention in human subjects are associated with learning disabilities and cognitive difficulties.…”

Estimulação do córtex motor e antinocicepção: envolvimento da via de analgesia serotonérgica descendente.

“…Confirmando a participação dos neurônios serotonérgicos do NMR no aumento do limiar nociceptivo induzido pela ECM, observamos um aumento na imunomarcação para 5HT no NMR após estimulação cortical. Com isso ressaltamos que a 5HT pode estar contribuindo com o efeito antinociceptivo induzido pela estimulação cortical, já que a inibição dos neurônios de projeção nociceptivo na CPME depende desse suporte serotonérgico (MASON, 2001). Na CPME o aumento da marcação dos proto-oncogenes está associado com a marcação de neurônios nociceptivo ativados (HUNT et al, 1987).…”

“…Todas estas estruturas possuem inervações diretas para a CPME (ALMEIDA; ROINZENBLATT;TUFIK, 2004;BRAZ;ENQUIST;BASBAUM, 2009;HEINRICHER, 2006;MASON, 2001;MILLAN, 1999;ROSENFELD, 1994;SANDKUHLER, 1996). O núcleo dorsal da rafe (NDR) tem sido incluído neste grupo por agir relevantemente na modulação nociceptiva (WANG; NAKAI, 1994), modulação esta que é provavelmente mediada através da sua conexão direta com o NMR ou indireta com a CPME ou com o tálamo (PALAZZO et al, 2006) …”

“…Dentre os núcleos do RVM implicados no mecanismo de supressão da dor destacam-se o NMR, rico em neurônios serotonérgicos, e os neurônios da formação reticular adjacente que recebem projeções oriundas da PAG, do hipotálamo posterior e do LC, rico em neurônios noradrenérgicos (FIELDS; BASBAUM, HEINRICHER, 2006;MASON, 2001;ROSENFELD, 1994;SANDKUHLER, 1996;). Neurônios da NMR projetam-se diretamente para a medula espinhal, onde inibem a transmissão nociceptiva FIELDS, 1984;MASON, 1991).…”