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Neurons in the caudal ventrolateral medulla mediate the sympathoinhibitory effects of CCK
Author(s) -
Sartor Daniela M,
Verberne Anthony JM
Publication year - 2006
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.20.4.a771-b
Subject(s) - rostral ventrolateral medulla , reflex , medulla , baroreflex , endocrinology , medulla oblongata , medicine , baroreceptor , cholecystokinin , chemistry , blood pressure , central nervous system , heart rate , receptor
The gastrointestinal hormone cholecystokinin (CCK) inhibits a subset of presympathetic neurons in the rostroventrolateral medulla (RVLM) that may be responsible for driving the sympathetic vasomotor outflow to the gastrointestinal circulation. We tested the hypothesis that the central neurocircuitry of this novel reflex is similar to that of other sympathoinhibitory reflexes that utilise a relay in the caudal ventrolateral medulla (CVLM). Blood pressure, heart rate and splanchnic sympathetic nerve discharge (SSND) were monitored in anesthetised (1.5% halothane in 100% O 2 ), paralysed male Sprague‐Dawley rats. After electrophysiological localisation of a barosensitive RVLM neuron, a pressure microinjector was inserted into the medulla 1.6mm caudal and 0.4 mm dorsal to this site. The effects of phenylephrine (PE, 10 μg/kg i.v.; baroreflex activation), phenylbiguanide (PBG, 10 μg/kg i.v.; von Bezold‐Jarisch reflex) and CCK (4 μg/kg, i.v.) on SSND, were tested before and after bilateral injection of 50‐100 nl of muscimol (1.75 mM; n=6) or kynurenate (55 mM; n=6) into the CVLM. In control experiments (n=8), these agents were injected outside the CVLM. CVLM injections abolished the sympathoinhibitory responses to PE, PBG and CCK whereas control injections had no effect. These results implicate CVLM neurons in the gastrointestinal reflex responsible for the sympathoinhibitory responses to CCK.