Attenuation of the baroreceptor reflex by general anesthetic agents in the normotensive rat

Flückiger, Jean-Pierre; Sonnay, Mireille; Boillat, Nicole; Atkinson, Jeffrey

doi:10.1016/0014-2999(85)90545-x

Cited by 104 publications

(47 citation statements)

References 10 publications

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“…In our research the baroreflex function was evaluated in conscious rats, since baroreflex activity is blunted under anesthesia 25,26 reducing the range of HR, which outcomes in an analysis of a restricted portion of the baroreflex response. Our investigation provides valid information regarding the discrepancy of baroreflex function among rats of the same strain, in this case the WKY strain.…”

Section: Discussionmentioning

confidence: 99%

Intra-strain variations of baroreflex sensitivity in young Wistar-Kyoto rats

Valenti

Imaizumi²,

Abreu³

et al. 2009

CIM

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Clin Invest Med 2009; 32 (6): E251-E257. AbstractPurpose: To compare baroreflex sensitivity among conscious rats of the same strain. Methods: Male WKY rats (eight weeks old) were studied. Cannulas were inserted into the abdominal aortic artery through the right femoral artery to measure mean arterial pressure (MAP) and heart rate (HR). Baroreflex gain was calculated as the ratio between variation of HR in function of the MAP variation (ΔHR/ΔMAP) tested with a depressor dose of sodium nitroprusside (SNP, 50µg/kg, iv) and with a pressor dose of phenylephrine (PE, 8µg/kg, iv). We divided the rats into four groups: 1) Low bradycardic baroreflex (LB), BG between -1 and -2 bpm/mmHg tested with PE; 2) High bradycardic baroreflex (HB), BG < -2 bpm/mmHg tested with PE; 3) Low tachycardic baroreflex (LT), BG between -1 and -2 bpm/mmHg tested with SNP and; 4) High tachycardic baroreflex (HT), BG < -2 bpm/ mmHg tested with SNP. Significant differences were considered for p<0.05.Results: Approximately 82% of the rats presented reduced bradycardic reflex while 22 showed attenuated tachycardic reflex. No alterations were noted regarding basal MAP and HR, tachycardic and bradycardic peak and HR range. Conclusions: There was alteration in baroreflex sensitivity among rats of the same strain. Care should be taken when interpreting studies employing WKY as a control for the SHR.In 1963, Okamoto and Aoki 1 reported that they had selectively bred Wistar rats to be spontaneously hypertensive. Established as an inbred strain in 1969 at the National Institutes of Health (NIH), the spontaneously hypertensive rat (SHR) remains the most widely studied animal model of essential hypertension (i.e., persistent high blood pressure of unknown causation), and the strain presents similar characteristic to hypertension in humans. As controls for the SHR, most workers have employed normotensive descendants of Wistar rats that NIH investigators obtained in 1971 from the colony in Kyoto from which the SHR strain was originally derived (Wistar-Kyoto rats, WKY). 2 Baroreflex function is one of the body's homeostatic mechanisms to sustain arterial pressure. It offers a negative feedback loop in which the increased arterial pressure reflexively causes blood pressure to de-

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Section: Discussionmentioning

confidence: 99%

Intra-strain variations of baroreflex sensitivity in young Wistar-Kyoto rats

Valenti

Imaizumi²,

Abreu³

et al. 2009

CIM

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“…Although the directions of MAP and HR responses of the present versus the aforementioned study are the same, the extent and the time course of responses are different. The use of general anesthesia, which affects central neuronal activity including baroreflex function, 16 as well as the use of 95% ethanol as the vehicle by Laurent et al 10 may contribute to the different results. In Wistar-Kyoto rats under urethane anesthesia, 9 nifedipine, diltiazem, or verapamil administered on the dorsal surface of the brain stem at the obex decreased BP and HR.…”

Section: Discussionmentioning

confidence: 99%

Sympathoinhibitory Effects of Central Nifedipine in Spontaneously Hypertensive Rats on High Versus Regular Sodium Intake

Huang¹,

Leenen²

1999

Hypertension

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Abstract-The putative central sympathoinhibitory actions of the dihydropyridine calcium antagonist nifedipine and the effect of dietary sodium on these actions were investigated in spontaneously hypertensive rats (SHR). Regular or high dietary salt was administered from 4 to 8 weeks of age. At 8 weeks, blood pressure (BP), heart rate (HR), and renal sympathetic nerve activity were recorded in conscious rats at rest as well as in response to intravenous (50 g/kg) and intracerebroventricular (5 and 50 g/kg) injections of nifedipine and intracerebroventricular injections of vehicle. Resting mean arterial pressure was higher in SHR on high versus regular salt (159Ϯ3 versus 135Ϯ4 mm Hg; PϽ0.05). Nifedipine administered intracerebroventricularly decreased BP as well as renal sympathetic nerve activity and HR in a dose-related manner. The responses reached their peak at 3 to 5 minutes and lasted Ϸ30 minutes. Peak decreases in BP, renal sympathetic nerve activity, and HR in response to both doses of nifedipine were significantly larger in SHR on high versus regular salt. Nifedipine administered intravenously also decreased BP but, in contrast, caused (reflex) increases in renal sympathetic nerve activity and HR. On both diets, intracerebroventricular vehicle did not affect mean arterial pressure, renal sympathetic nerve activity, or HR. These data indicate that in contrast to its peripheral vasodilator effect, centrally administered nifedipine may decrease sympathetic outflow and therefore BP and HR. The enhanced sympathoinhibitory and depressor responses to nifedipine in SHR on high versus regular salt suggest that the sympathetic hyperactivity induced by high salt intake is dependent on neuronal calcium influx via L-type channels. (Hypertension. 1999;33:32-35.)Key Words: nifedipine Ⅲ dihydropyridines Ⅲ nervous system, sympathetic Ⅲ hypertension Ⅲ rats, inbred SHR Ⅲ sodium, dietary A n increase in Ca 2ϩ influx triggers a variety of cellular functions, such as increased cardiac and smooth muscle contractility, endocrine gland secretion, and neurotransmitter release. 1 Dihydropyridines such as nifedipine inhibit Ca 2ϩ influx through voltage-sensitive calcium channels. 2 The effects of calcium antagonists on sympathetic activity have thus far been related mainly to reflex responses after rapid lowering of blood pressure (BP) induced by rapidly acting calcium antagonists 3 and perhaps presynaptic effects. 4 Although receptors for calcium antagonists 5 as well as calcium antagonist-sensitive calcium channels 6 have been demonstrated in the brain, little is known regarding direct central effects of Ca 2ϩ antagonists on sympathetic activity and central control of circulation.In vitro, dihydropyridine-sensitive Ca 2ϩ channels exist in rat hypothalamus. 6 The stimulus-induced high-frequency activity in brain cells is carried by L-type but not T-type Ca 2ϩ channels, 7 and a dihydropyridine such as nifedipine is a potent L-but not T-type channel antagonist. 8 Although centrally administered calcium antagonists have been reported ...

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“…(Pegram et al, 1984;Nagura et al, 1986). The rats were studied while conscious and unrestrained in order to avoid the influence of anaesthesia or stress on the cardiovascular activity (Fluckiger et al, 1985). Their aortic BP was continuously recorded and analysed for long periods of time by means of our previously described computerized technique (Cerutti et al, 1985).…”

Section: Drugsmentioning

confidence: 99%

“…Finally, the sensitivity of the cardiac baroreflex was carefully assessed in freely moving animals, which is of special importance in the measurement of reflex mediated responses (Fluckiger et al, 1985). It was demonstrated that, 1 h after the 5th injection of either 100 or 200 fig kg-' of PY 108-068 and PN 200-1 10, the cardiac baroreflex response was increased by both drugs but not significantly.…”

Section: Drugsmentioning

confidence: 99%

Cardiovascular effects of two new calcium antagonists, PY 108‐068 and PN 200‐110, in conscious spontaneously hypertensive rats

Barrès

Cerutti

Morin

et al. 1988

British J Pharmacology

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1 The acute cardiovascular effects of PY 108-068 and PN 200-110 were studied by means of a computerized analysis of the intra-aortic blood pressure (BP) recorded continuously for 26 h in conscious unrestrained spontaneously hypertensive rats. Both compounds were studied at three doses (50, 100 and 200 lgkg-') and each dose was administered intravenously 5 times (09hOOmin, 14 hOOmin, 19hOOmin, 24hOOmin and 09hOOmin). Baroreflex sensitivity was measured 1 h following the last injection. 2 The two compounds were found to induce rapid (3 min) and dose-dependent falls in BP. After the first administration, these decreases reached -20% and -35% for systolic BP (SBP) and diastolic BP (DBP) respectively with PY 108-068 (200pgkg-') and -25% and -45% for SBP and DBP respectively with PN 200-110 (200 pg kg-'). 3 The duration of the reduction in BP increased with the dose and was much longer for PN 200-110 (180 min for SBP) than for PY 108-068 (20 min for SBP). 4 A tachycardia was associated with the decrease in BP which did not differ at 200 pg kg-' between PY 108-068 (+ 108 beats min-') and PN 200-110 (+ 103 beats min' ). Baroreflex sensitivity was not significantly increased by either drug. 5 The 5 repeated injections of PY 108-068 and PN 200-110 evoked similar responses. 6 In conclusion, both compounds exhibited marked hypotensive properties. PN 200-110 appeared to be more suitable for further development since its effects were found to be greater and much longer lasting than those of PY 108-068.

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Attenuation of the baroreceptor reflex by general anesthetic agents in the normotensive rat

Cited by 104 publications

References 10 publications

Intra-strain variations of baroreflex sensitivity in young Wistar-Kyoto rats

Intra-strain variations of baroreflex sensitivity in young Wistar-Kyoto rats

Sympathoinhibitory Effects of Central Nifedipine in Spontaneously Hypertensive Rats on High Versus Regular Sodium Intake

Cardiovascular effects of two new calcium antagonists, PY 108‐068 and PN 200‐110, in conscious spontaneously hypertensive rats

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