Mechanism of the decline in vagal cardiac acceleration in dogs in neuroleptanaesthesia

“…The second phase shows a slow further increase in heart rate to a maximum, representing a VCA reflex response to the concomitant increase in MAP. As we have previously shown ( Roossien et al . 1995 ), each dog has its characteristic maximum VCA activity, reproducible within narrow limits in spite of a large interindividual variation, ranging between 27 and 92 beats min −1 in the present study.…”

Section: Discussionsupporting

confidence: 83%

“…197 9) a residual sympathetic component in heart rate control seems highly improbable. Besides, the maximum VCA activity in nicotinic blocked dogs has been shown not to be different from the maximum VCA activity in dogs in which vagotomy was substituted for the nicotinic blockade ( Roossien et al . 1995 ).…”

Section: Discussionmentioning

confidence: 99%

“…1970 , Hill et al . 1993 , Roossien et al . 1995 ), whereas PVT can be evoked by stimulation of about 10 Hz.…”

Section: Discussionmentioning

confidence: 99%

“…In the control experiments, the maximum VCA activity in each dog was determined by measuring the heart‐rate response to successive β ‐adrenergic, muscarinic, and ganglionic nicotinic receptor blockade. The maximum VCA activity is quantified as the difference between the maximum heart rate after the muscarinic blockade, always reached within 10 min after the blockade, and the intrinsic rate assessed by the subsequent ganglionic blockade ( Roossien et al . 1995 ).…”

Section: Methodsmentioning

confidence: 99%

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The vagal cardiac accelerator system in the reflex control of heart rate in conscious dogs

Roossien

Brunsting

Zaagsma

et al. 2000

Acta Physiologica Scandinavica

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The reactions of the vagal cardioaccelerator (VCA) system to changes in mean arterial pressure (MAP) were studied in five beta-adrenoceptor blocked conscious dogs. An increase in MAP was obtained by administration of vasopressin or methoxamine, a decrease by doxazosin or nitroprusside. In the first series of experiments the MAP changes were induced after muscarinic receptor blockade, in a second series both before and after muscarinic blockade. Prior to these experiments, the maximum VCA activity, defined as the difference between maximum heart rate after muscarinic blockade and the rate after additional nicotinic blockade, was determined. We hypothesized that this quantity, as a measure of VCA activity, depends on the prevailing vagal tone. In the first series of experiments, a rise in MAP evoked an increase in heart rate, a fall in MAP indicated decrease. In the second series, when prior to muscarinic blockade the vagal tone was reflexly raised, the subsequent VCA reflex response to the rise in MAP was attenuated. Prior to the muscarinic blockade the vagal tone was reflexly lowered, the VCA reflex response was enhanced. Direct chronotropic effects of MAP-varying drugs were ruled out by the absence of a heart-rate response in experiments on vagotomized animals. We concluded that the vagal cardioaccelerator system is involved in the reflex control of heart rate. Both the VCA reflex response to changes in systemic blood pressure and the maximum VCA activity however, are determined by the prevailing vagal tone.

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β3-Adrenoceptors in the heart

Conrath¹

2002

Cardiovascular Research

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Mechanism of the decline in vagal cardiac acceleration in dogs in neuroleptanaesthesia

Cited by 6 publications

References 22 publications

An investigation into the physiological relevance of the vagal tachycardia in the anaesthetized dog

An investigation into the physiological relevance of the vagal tachycardia in the anaesthetized dog

The vagal cardiac accelerator system in the reflex control of heart rate in conscious dogs

β3-Adrenoceptors in the heart

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