Cardiorespiratory reflexes in a working heart-brainstem preparation of the house musk shrew, Suncus murinus.
In this study, we adapted the working heart-brainstem preparation (WHBP) from rodents to the Insectivore, Suncus murinus. Suncus WHBPs had a baseline heart rate of 333 +/- 8 beats min(-1), a perfusion pressure of 69 +/- 2 mm Hg and a respiratory cycle length of 6.5 +/- 0.7 s. Administration of atropine produced an increase in heart rate of 26 +/- 9 beats min(-1) indicative of the presence of cardiac vagal tone. Activation of baroreceptors produced pressure-dependent reflex falls in heart rate and reduced respiratory cycle length. The baroreceptor reflex sensitivity in Suncus WHBP was a decrease in heart rate of 8.1 +/- 1.4 beats min(-1) mm Hg(-1). Activation of peripheral chemoreceptors with aortic injections of sodium cyanide (0.1-12.5 microg) produced a dose-dependent reflex fall in heart rate and reduced respiratory cycle length. The reflex falls in heart rate evoked by baroreceptor and peripheral chemoreceptor stimulation were both atropine-sensitive. We conclude that viable WHBP can be prepared from Suncus and that Suncus WHBP is a novel non-rodent model in which to study brainstem-mediated reflexes.
Smith
J E
JE
Department of Physiology, St. George's Hospital Medical School, London, UK. jesmith@sghms.ac.uk
Paton
J F
JF
Andrews
P L
PL
D000818:Animals; D001285:Atropine / Q000494:pharmacology; D017704:Baroreflex / Q000187:drug effects / Q000502:physiology*; D001933:Brain Stem / Q000502:physiology*; D002628:Chemoreceptor Cells / Q000502:physiology; D003679:Deglutition / Q000502:physiology; D003714:Denervation; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D006321:Heart / Q000294:innervation*; D006339:Heart Rate / Q000187:drug effects / Q000502:physiology; D007823:Laryngeal Nerves; D008297:Male; D010276:Parasympatholytics / Q000494:pharmacology; D010791:Phrenic Nerve / Q000502:physiology; D012119:Respiration; D012788:Shrews / Q000502:physiology*; D012966:Sodium Cyanide / Q000494:pharmacology
D004791:Enzyme Inhibitors; D010276:Parasympatholytics; D001285:Atropine; D012966:Sodium Cyanide