Premium
Responses of neurones in the medullary raphe nuclei to inputs from visceral nociceptors and the ventrolateral periaqueductal grey in the rat
Author(s) -
Snowball RK,
Dampney RA,
Lumb BM
Publication year - 1997
Publication title -
experimental physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.925
H-Index - 101
eISSN - 1469-445X
pISSN - 0958-0670
DOI - 10.1113/expphysiol.1997.sp004041
Subject(s) - raphe , nucleus raphe magnus , medulla oblongata , nociceptor , rostral ventrolateral medulla , neuroscience , stimulation , dorsal raphe nucleus , splanchnic , raphe nuclei , anatomy , nociception , noxious stimulus , periaqueductal gray , medicine , serotonergic , central nervous system , biology , midbrain , serotonin , blood flow , receptor
The ventrolateral periaqueductal grey matter (PAG) is believed to have a role in mediating cardiovascular responses to noxious visceral stimuli. The present study was carried out as a first stage in establishing whether the ventrolateral PAG may exert these influences after a relay in the caudal medullary raphe nuclei (nucleus raphe obscurus and nucleus raphe pallidus). Single unit extracellular recordings were made from neurones in the caudal raphe nuclei and, for comparison, in the more rostral nucleus raphe magnus in Saffan‐anaesthetized and paralysed rats. Neurones in the mid‐line medulla were tested for their responses to electrical stimulation at chemically identified depressor sites in the ventrolateral PAG and to noxious visceral stimuli (distensions of the urinary bladder and electrical stimulation of the greater splanchnic nerve). Fifty‐two per cent of caudal and 74% of rostral mid‐line neurones gave short latency excitatory responses to stimulation of depressor sites in the ventrolateral PAG. Of the neurones that were also tested with noxious visceral stimuli, 5% of the caudal and 47% of the rostral neurones responded to bladder distension, while 33 and 35%, respectively, of caudal and rostral neurones responded to splanchnic nerve stimulation. These results indicate that many mid‐line medullary neurones receive inputs from both the ventrolateral PAG and visceral nociceptors and may, therefore, be part of the output pathway by which the ventrolateral PAG produces integrated physiological responses to noxious visceral stimuli.