title: Brain circuits mediating baroreflex bradycardia inhibition in rats: an anatomical and functional link between the cuneiform nucleus and the periaqueductal grey.
abstract: Defence responses triggered experimentally in rats by stimulation of the dorsomedial nucleus of the hypothalamus (DMH) and the dorsolateral periaqueductal grey matter (PAG) inhibit the cardiac baroreflex response (i.e. bradycardia). It has also been proposed that the midbrain cuneiform nucleus (CnF) is involved in active responses. Our aim was to identify the neurocircuitry involved in defence-induced baroreflex inhibition, with a particular focus on the link between DMH, CnF and dorsolateral PAG. Microinjection of the anterograde tracer Phaseolus vulgaris leucoaggutinin into the CnF revealed a dense projection to the dorsolateral PAG. Moreover, activation of neurons in the CnF induced increased expression of Fos protein in the dorsolateral PAG. Inhibition of neurons of the CnF or dorsolateral PAG prevented the inhibition of baroreflex bradycardia induced by DMH or CnF stimulation, respectively. These results provide a detailed description of the brain circuitry underlying acute baroreflex modulation by neurons of the DMH. Our data have shown for the first time that the CnF plays a key role in defence reaction-associated cardiovascular changes; its stimulation, from the DMH, activates the dorsolateral PAG, which, in turn, inhibits baroreflex bradycardia.
authors.affiliation: UPMC/INSERM, UMR-S 975 and CNRS UMR 7225, Faculté de médecine UPMC, Site Pitie-Salpêtrière, Paris F-75013, France.
authors.forename: Florence
authors.initials: F
authors.lastname: Netzer
authors.forename: Jean-François
authors.initials: JF
authors.lastname: Bernard
authors.forename: Anthony J M
authors.initials: AJ
authors.lastname: Verberne
authors.forename: Michel
authors.initials: M
authors.lastname: Hamon
authors.forename: Françoise
authors.initials: F
authors.lastname: Camus
authors.forename: Jean-Jacques
authors.initials: JJ
authors.lastname: Benoliel
authors.forename: Caroline
authors.initials: C
authors.lastname: Sévoz-Couche
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D017704:Baroreflex / Q000187:drug effects; D001919:Bradycardia / Q000378:metabolism / Q000503:physiopathology / Q000517:prevention & control*; D002317:Cardiovascular Agents / Q000008:administration & dosage; D003674:Defense Mechanisms; D025461:Feedback, Physiological; D006339:Heart Rate / Q000187:drug effects; D008297:Male; D020645:Mediodorsal Thalamic Nucleus / Q000503:physiopathology; D008636:Mesencephalon / Q000187:drug effects / Q000378:metabolism / Q000503:physiopathology*; D008845:Microinjections; D009433:Neural Inhibition / Q000187:drug effects; D009434:Neural Pathways / Q000187:drug effects / Q000378:metabolism / Q000503:physiopathology*; D056347:Neuroanatomical Tract-Tracing Techniques; D056325:Neuronal Tract-Tracers / Q000008:administration & dosage; D018377:Neurotransmitter Agents / Q000008:administration & dosage; D010487:Periaqueductal Gray / Q000187:drug effects / Q000378:metabolism / Q000503:physiopathology*; D010835:Phytohemagglutinins / Q000008:administration & dosage; D016760:Proto-Oncogene Proteins c-fos / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D002317:Cardiovascular Agents; D056325:Neuronal Tract-Tracers; D018377:Neurotransmitter Agents; D010835:Phytohemagglutinins; D016760:Proto-Oncogene Proteins c-fos; C100156:leukoagglutinins, plants