The Bezold-Jarisch in the conscious dog.

Zucker, Irving H.; Cornish, Kurtis G.

doi:10.1161/01.res.49.4.940

Cited by 51 publications

(24 citation statements)

References 25 publications

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“…considered to be a result of the activation of the BezoldJariszh reflex [21]. RVEDP of 4 live dogs remained at a significantly low level until 30 min after injection, whereas LVSP, LVEDP, and LV dp/dt increased gradually, and CO returned to normal 30 min after injection.…”

mentioning

confidence: 94%

Hemodynamic Alterations in Dogs with Shock Induced by Intravenous Injection of Heartworm Extract.

Kitoh¹,

Mikami²,

Kitagawa³

et al. 2001

The Journal of Veterinary Medical Science

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ABSTRACT. To elucidate one way of the shock mechanisms, the hemodynamic alterations were examined in 7 dogs with heartworm (HW) extract-induced shock. The first alteration observed after injection of HW extract was a decrease in right ventricular end-diastolic pressure (RVEDP). After that, left ventricular (LV) end-diastolic pressure, LV systolic pressure, and LV dp/dt fell significantly, followed by a decrease in the cardiac output of all dogs to below the detectable level (1.00 l/min). Since RVEDP depends on blood flow into the right ventricle, the decrease in RVEDP means a reduction in venous return. Therefore, this study showed that the first trigger of a decrease in blood pressure in HW extract-induced shock is the reduction in venous return.KEY WORDS: heartworm, hemodynamics, shock.J. Vet. Med. Sci. 63(2): 179-182, 2001 It is well known that the administration of prophylactics for Dirofilaria immitis (heartworm, HW), such as diethylcarbamazine (DEC) [1,14], milbemycin D [15], and ivermectin [5], induces shock in dogs with microfilaremic HW infection (mf-induced shock). In human beings, treatment of onchocerciasis and lymphatic filariasis with DEC and ivermectin also induces shock, which leads to the failure of many control programs [3,12]. On the other hand, shock resulting from HW adult worms occurs clinically when such worms are injured during surgical treatment of the host [6,7]. However, to the authors' knowledge, the mechanisms of these shocks in both veterinary medicine and human medicine have not yet been clarified. Thus, there is a need to elucidate the mechanisms of such shocks in order to improve prophylaxis and treatment of filariasis, not only in veterinary but also in human medicine. We have previously reported that intravenous injection of HW extract induces shock in dogs irrespective of HW infection [8][9][10]. The clinicopathologic and pathologic findings of HW extractinduced shock were fundamentally similar to those associated with mf-induced shock [8][9][10]. Therefore, investigation of the mechanisms of HW extract-induced shock would be useful in elucidating the mechanisms of shock due to injured adult worms and mf-induced shock.The main clinical findings of HW extract-induced shock were hyperemia of the mucous membranes, palpitation, and tachypnea observed immediately after intravenous injection of HW extract, followed by collapse due to a sudden decrease in blood pressure 5 to 30 min after injection [9]. During collapse, clinical signs indicating circulatory failure such as paleness of the mucous membranes, weak heart sounds, dyspnea, and cold skin were observed. In the shock-related pathologic findings, centralobular congestion in the liver, and congestion and hemorrhage in mucous membranes of the gastrointestinal tract were observed during collapse [8]. These pathologic findings and the collapse disappeared simultaneously. The cardiac muscle and vessels in dogs with shock were normal in the morphologic findings. Moreover, hemorrhage and edema, which suggested a decrease in circula...

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confidence: 94%

Hemodynamic Alterations in Dogs with Shock Induced by Intravenous Injection of Heartworm Extract.

Kitoh¹,

Mikami²,

Kitagawa³

et al. 2001

The Journal of Veterinary Medical Science

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“…In conscious dogs with intact baroreceptors, large doses of veratridine elicit classic Bezold-Jarisch reflex responses of hypotension and bradycardia (Zucker & Cornish, 1981). However, the doses of veratrine that we administered decreased BP only 10 mmHg and did not significantly change HR when the baroreceptors were in continuity with the circulation.…”

Section: Effect Of Intracoronary Veratrine On the Baroreflexmentioning

confidence: 71%

“…These findings suggest that in anaesthetized dogs stimulation of both mechanoreceptors and chemoreceptors causes an attenuation of the baroreflex, whereas stimulation of mechanoreceptors, alone, does not. In conscious dogs, stimulation of mechanoreceptors by increasing left ventricular pressure causes an attenuation of baroreflex control of HR (Holmberg & Zucker, 1986) (Thoren, 1977 (Oberg & Thoren, 1973;Zucker & Cornish, 1981). Our experitnents included a demonstration that the observed attenuation of the baroreflex by intracoronary veratrine also was mediated through the autonomic nervous system.…”

Section: Mechanism Of Veratrine's Effect On the Baroreflexmentioning

confidence: 91%

Intracoronary veratrine attenuates carotid baroreceptor reflex regulation of blood pressure in conscious dogs.

Denison

Stephenson

Hull

et al. 1992

The Journal of Physiology

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SUMMARY1. The effect of activation of left ventricular cardiac receptors on carotid baroreflex control of blood pressure, heart rate, cardiac output, and total peripheral resistance was determined in conscious dogs. Previous studies in conscious subjects assessed only the effect on baroreflex control of heart rate.2. Dogs with denervated aortic baroreceptors were equipped with aortic flow probes, cardiac pacing electrodes, and catheters in the aorta, vena cava, and left circumflex coronary artery. Both carotid sinus regions were prepared for reversible vascular isolation.3. Left ventricular receptors were stimulated by an infusion of veratrine (0-1-1P0 gug kg-' min-') into the left circumflex coronary artery. 4. Veratrine infusion decreased control blood pressure only 10+2 mmHg, but it decreased the range of baroreflex control of blood pressure by 50% and decreased maximum baroreflex gain by 42 %. Both the cardiac output and total peripheral resistance components of the baroreflex were attenuated.5. Baroreflex control of blood pressure was unaffected by intravenous veratrine or by intracoronary infusion of vehicle.6. Intracoronary veratrine had no effect after autonomic ganglionic blockade. 7. When cardiac output was kept nearly constant (by ,-adrenergic and cholinergic receptor blockade or by fl-blockade and cardiac pacing), intracoronary veratrine still attenuated baroreflex control of blood pressure and total peripheral resistance. Veratrine impaired the ability of the baroreflex to utilize cz-adrenergic mechanisms to control total peripheral resistance.8. We conclude that activation of ventricular receptors attenuates baroreflex regulation of blood pressure in conscious dogs through an attenuation of baroreflex control of both cardiac output and total peripheral resistance.

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“…The slope of the HR/MABP relationship was not significantly different after vagotomy, suggesting that in the newborn, there is also an efferent vagal component to this reflex. The HR response to the infusion of nitroprusside after vagotomy is difficult to interpret because the BJ reflex-induced bradycardia is indeed mediated in part by vagal efferents, being attenuated by muscarinic blockade (12,39). Therefore, the HR response after vagotomy must be influenced by either withdrawal of cardiac sympathetic tone or circulating neurohumoral factors.…”

Section: Discussionmentioning

confidence: 99%

Autonomic Adjustments to Severe Hypotension in Fetal and Neonatal Sheep

et al. 2001

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In fetal sheep, severe hypotension causes heart rate (HR) slowing. Studies during development have also shown that a reflex bradycardia and hypotension can be elicited after chemostimulation with veratridine and is dependent on the age of the animal. In adults, a vagally mediated depressor reflex characterized by bradycardia, hypotension, and withdrawal of efferent sympathetic activity can be observed after stimulation of chemosensitive or mechanosensitive cardiac receptors with veratridine or in circumstances of reduced cardiac filling. This reflex, known as the Bezold-Jarisch reflex, plays a role in disease states such as myocardial ischemia and hemorrhage. The objectives of our study were to determine whether a sympathoinhibitor depressor reflex, along with the bradycardia, is observed during pharmacologically induced hypotension in fetal and newborn lambs. In both fetal and newborn lambs, HR and renal sympathetic nerve activity (RSNA) initially increased (p Ͻ 0.05) in response to nitroprusside infusion to reach a maximum value. The range (or "plateau") of mean arterial blood pressure over which maximum RSNA was maintained constant before withdrawal of sympathetic tone started to be observed was significantly (p Ͻ 0.05) smaller in fetuses (0.3 Ϯ 0.3 mm Hg) than newborn (6 Ϯ 1 mm Hg) lambs. Similarly, the plateau over which maximum HR was maintained before onset of bradycardia was significantly smaller in fetuses (4 Ϯ 1 versus 11 Ϯ 2 mm Hg). The mean arterial blood pressure level ("threshold") at which a depressor reflex was triggered was significantly (p Ͻ 0.05) lower in fetal than newborn sheep (35 Ϯ 2 versus 53 Ϯ 3 mm Hg for HR and 35 Ϯ 2 versus 57 Ϯ 2 mm Hg for RSNA). The rates of fall (slopes) for both HR and RSNA were also significantly (p Ͻ 0.05) more pronounced in fetuses (1.85 Ϯ 0.27 and 6.08 Ϯ 2.45%/mm Hg) than in newborns (1.21 Ϯ 0.16 and 1.97 Ϯ 0.32%/mm Hg). Bilateral vagotomy significantly increased the plateau of mean arterial blood pressure over which maximum RSNA and HR were maintained constant. Vagotomy also decreased the threshold for both RSNA and HR and the slope of the RSNA response to the nitroprusside infusion in newborn lambs. Results from this study show that activation of the arterial baroreflex during nitroprusside-induced hypotension is followed by withdrawal of sympathetic tone and bradycardia and that this depressor reflex is more pronounced in late-gestation fetuses than newborn lambs and is significantly attenuated after bilateral vagotomy in newborn lambs. (Pediatr Res 49: 56-62, 2001) Abbreviations: AP, amniotic pressure BJ, Bezold-Jarisch HR, heart rate MABP, mean arterial blood pressure RSNA, renal sympathetic nerve activityIn fetal sheep, in contrast to the tachycardic response to moderate hypotension (1, 2), severe hypotension causes HR slowing (2-4). This reflex bradycardia can be observed in response to hemorrhage (2), vena caval obstruction (5, 6), and vasodilator infusion (7). In adults, hypotension and bradycardia can be elicited after stimulation of mechanical or che...

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The Bezold-Jarisch in the conscious dog.

Cited by 51 publications

References 25 publications

Hemodynamic Alterations in Dogs with Shock Induced by Intravenous Injection of Heartworm Extract.

Hemodynamic Alterations in Dogs with Shock Induced by Intravenous Injection of Heartworm Extract.

Intracoronary veratrine attenuates carotid baroreceptor reflex regulation of blood pressure in conscious dogs.

Autonomic Adjustments to Severe Hypotension in Fetal and Neonatal Sheep

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