Lack of pressor effect of dopamine in the pentobarbital-anesthetized rat

The blood pressure and heart rate responses to intravenous dopamine infusion at 2.5, 5.0 and 10.0 micrograms.min-1 X 100 g-1 were studied in conscious and pentobarbital-anesthetized Sprague-Dawley rats. In the conscious rats, dopamine caused a significant dose-related increase in the mean arterial blood pressure which was abolished in the anesthetized rats. The heart rate increased significantly only at the highest dose infused. The responses to equipressor doses of noradrenaline (40 ng.min-1 X 100 g-1) and phenylephrine (1.0 micrograms.min-1 X 100 g-1) were also suppressed in the anesthetized rats. The results suggest that pentobarbital anesthesia depresses the blood pressure response to dopamine infusion in the rat through a depression of activation of alpha-adrenoceptors.     

Lack of pressor effect of dopamine in the pentobarbital-anesthetized rat

Summary The blood pressure and heart rate responses to intravenous dopamine infusion at 2.5, 5.0 and 10.0 g·min^–1·100 g^–1 were studied in conscious and pentobarbital-anesthetized Sprague — Dawley rats. In the conscious rats, dopamine caused a significant dose-related increase in the mean arterial blood pressure which was abolished in the anesthetized rats. The heart rate increased significantly only at the highest dose infused. The responses to equipressor doses of noradrenaline (40 ng·min^–1·100 g^–1) and phenylephrine (1.0 g·min^–1·100 g^–1) were also suppressed in the anesthetized rats. The results suggest that pentobarbital anesthesia depresses the blood pressure response to dopamine infusion in the rat through a depression of activation of alpha-adrenoceptors.16 June 1986     

Effect of dibutyryl cyclic AMP on cerebral energy charge and electrocorticographic activity in rats under asphyxic hypoxia]

In Rats anesthetized with pentobarbital and submitted to brief asphyxic episodes, intracerebroventricular administration of dibutyryl cyclic AMP inhibits the decrease of energy charge, delays the disappearance of electrocorticographic activity (E Co G) and shortens the recovery time of E Co G.     

D-ala2-Metenkephalinamide blocks the synaptically elicited cortical spreading depression in rats

Spreading depression (SD) was elicited in rats anesthetized with pentobarbital by a train of 8 electrical pulses (0.1 ms, 10 Hz) applied to parietal cortex. Local application of 50 micrograms of D-ala2-metenkephalinamide (DAME) on the stimulated area evoked one or two SD waves followed by an increase of SD threshold from 40 V to 90 V. This effect could be partly prevented by naloxone (1 mg/kg i.p.) and reversed by local application of 4-aminopyridine (10(-3) M, 2 microliters), which reduced SD threshold to 5 and 20 V in normal and DAME-treated cortex, respectively. It is argued that DAME exerts an inhibitory effect on cortical neurons and that the initial SD facilitation is due to initial blockade of inhibitory neurons in the superficial cortical layers.     

The effect of urethane and pentobarbital anaesthesia and hepatic portal vein catheterization on liver blood flow in the rat

Summary The effect of urethane and pentobarbital anaesthesia and hepatic portal vein catheterization on liver blood flow was investigated in the rat. Liver blood flow with pentobarbital anaesthesia was 40% greater than with urethane. Hepatic portal vein catheterization had no effect under pentobarbital anaesthesia whereas it produced an 18% fall in liver blood flow with urethane.Acknowledgments. This work was supported by grants from ICI Pharmaceuticals and Mersey Regional Health Authority (Research Scheme No. 338). We wish to thank Mr P.J. Roberts for much skilled assistance and Evans Medical Ltd for the kind gift of drugs.     

Dämpfung des Kältezitterns durch Pentobarbital und Pethidin bei Ratten

Summary In rats, shivering was induced by cooling. Shivering started at 36.6°C in unanaesthetized rats and at 36.0°C in animals with light pentobarbital anaesthesia (5 mg/kg i.V.). Pethidine (2 mg/kg) lowered the onset of shivering in unanaesthetized rats to 35.3 °C and in anaesthetized animals to 33.0°C. The results suggest that the effect of pethidine upon shivering is potentiated by pentobarbital.     

Das hypoxiebedingte EEG-Arousalstadium unter dem Einfluss von Pentobarbital und Urethan

Summary The influence of pentobarbital and urethan on the hypoxia induced EEG arousal was studied in adult rats and rabbits. A depression of this EEG reaction by pentobarbital was found, while the arousal was unchanged by urethan. A possible mechanism for these findings is discussed.     

Antihypertensive and other cardiovascular effects of 2-(3-pyridyl)- and 2-(4-pyridyl)-4-trifluoromethylimidazoles.

2 new 4-trifluoromethylimidazole derivatives were found which lowered mean arterial pressure in renal and spontaneously hypertensive (SH) rats by the oral route. In SH rats, compounds A and B were 0.1 and 0.3 times, respectively, as potent as hydralazine. No tolerance development was observed in SH rats with either compound over a 1-week period. In anesthetized dogs, both compounds lowered arterial pressure and peripheral vascular resistance but increased cardiac output. By intraarterial administration, both compounds increased femoral arterial blood flow. These findings represent discovery of a new class of vasodilator durgs.     

Antihypertensive and other cardiovascular effects of 2-(3-pyridyl)- and 2-(4-pyridyl)-4-trifluoromethylimidazoles

Summary 2 new 4-trifluoromethylimidazole derivatives were found which lowered mean arterial pressure in renal and spontaneously hypertensive (SH) rats by the oral route. In SH rats, compounds A and B were 0.1 and 0.3 times, respectively, as potent as hydralazine. No tolerance development was observed in SH rats with either compound over a 1-week period. In anesthetized dogs, both compounds lowered arterial pressure and peripheral vascular resistance but increased cardiac output. By intraarterial administration, both compounds increased femoral arterial blood flow. These findings represent discovery of a new class of vasodilator drugs.Deceased, May 31, 1978.     

L-arginine and pancreatic islet blood flow in anesthetized rats

The aim of the present study was to see if L-arginine, which induces insulin release and is a precursor of the endothelial-derived relaxing factor nitric oxide, affects whole pancreatic and/or islet blood flow. For this purpose, anesthetized male Sprague-Dawley rats were injected intravenously with either saline or L-arginine (25, 100 or 250 mg/kg body weight). All doses of arginine caused a slight increase in blood glucose concentration, while the highest dose (250 mg/kg body weight) also increased insulin concentration. However, no changes in either mean arterial blood pressure, whole pancreatic or islet blood flow could be discerned with any of the doses of arginine used. It is concluded that insulin release is not necessarily associated with an increased islet blood perfusion.     

Some species differences in cardiovascular responses to intravenously injected leucine-enkephalin

Studies were conducted to determine the cardiovascular responses to leucine-enkephalin (L-enk) in three different species of animals; rabbit, dog and monkey. All animals were anesthetized with pentobarbital sodium after sedation with ketamine. Mean blood pressure (MBP) and heart rate (HR) were simultaneously monitored. The pressor and HR responses to bilateral carotid occlusion (BCO) were determined before injection of L-enk. Increased MBP and HR due to BCO in monkey were significantly greater than in the other two animal groups. Following i.v. injection of L-enk (5-30 micrograms/kg), a significant fall in MBP occurred in all groups in a dose-dependent manner; however, the time course of changes in MBP in rabbits was significantly shorter than that in the other animal groups. Significant decreases in HR after the injection of L-enk occurred in rabbits and dogs, whereas increases in HR occurred in monkeys. These results show that some cardiovascular responses to L-enk may be species dependent. These different cardiovascular responses to L-enk may be at least partly related to species differences in baroreceptor reflex sensitivity.     

Enhanced reactivity towards flunarizine in cerebrovascular bed of spontaneously hypertensive rats

Cerebral blood flow (CBF) was measured and cerebrovascular resistance (CVR) was calculated in anesthetized spontaneously hypertensive rats (SHR) and normotensive rats (NR) following the administration of incremental dosages of i.v. flunarizine or papaverine. CBF and CVR changes following papaverine were the same in both groups of rats irrespective of the dose of the drug. The effect of flunarizine was much more pronounced in SHR than in NR. The results point out the greater dependency of basal cerebrovascular tone in SHR upon Ca2+ influx into vascular smooth muscle cells.     

Neural discharge can be modulated by carotid arterial injection of gastrin-17 in rat hypothalamic paraventricular nucleus

Neural discharge in the hypothalamic paraventricular nucleus (PVN) was examined after gastrin-17 injection into the carotid artery in anesthetized rats. Neural discharge was increased by gastrin-17 injection into the carotid artery close to the cranium, and the response due to the gastrin was dose-dependent. No discharge response was seen when gastrin was injected into the jugular vein. These results suggest that gastrin circulating in the arterial blood can penetrate the blood brain barrier, and modulate neural PVN activity which is responsible for gastric acid secretion.     

Enhanced reactivity towards flunarizine in cerebrovascular bed of spontaneously hypertensive rats

Summary Cerebral blood flow (CBF) was measured and cerebrovascular resistance (CVR) was calculated in anesthetized spontaneously hypertensive rats (SHR) and normotensive rats (NR) following the administration of incremental dosages of i.v. flunarizine or papaverine. CBF and CVR changes following papaverine were the same in both groups of rats irrespective of the dose of the drug. The effect of flunarizine was much more pronounced in SHR than in NR. The results point out the greater dependency of basal cerebrovascular tone in SHR upon Ca²⁺ influx into vascular smooth muscle cells.     

D-ala2-Metenkephalinamide blocks the synaptically elicited cortical spreading depression in rats

Summary Spreading depression (SD) was elicited in rats anesthetized with pentobarbital by a train of 8 electrical pulses (0.1 ms, 10 Hz) applied to parietal cortex. Local application of 50 g of D-ala²-metenkephalinamide (DAME) on the stimulated area evoked one or two SD waves followed by an increase of SD threshold from 40 V to 90 V. This effect could be partly prevented by naloxone (1 mg/kg i.p.) and reversed by local application of 4-aminopyridine (10^–3 M, 2 l), which reduced SD threshold to 5 and 20 V in normal and DAME-treated cortex, respectively. It is argued that DAME exerts an inhibitory effect on cortical neurons and that the initial SD facilitation is due to initial blockade of inhibitory neurons in the superficial cortical layers.supported by the European Training Program in Brain and Behavior Research.     

Some species differences in cardiovascular responses to intravenously injected leucine-enkephalin

Summary Studies were conducted to determine the cardiovascular responses to leucine-enkephalin (L-enk) in three different species of animals; rabbit, dog and monkey. All animals were anesthetized with pentobarbital sodium after sedation with ketamine. Mean blood pressure (MBP) and heart rate (HR) were simultaneously monitored. The pressor and HR responses to bilateral carotid occlusion (BCO) were determined before injection of L-enk. Increased MBP and HR due to BCO in monkey were significantly greater than in the other two animal groups. Following i.v. injection of L-enk (5–30 g/kg), a significant fall in MBP occurred in all groups in a dose-dependent manner; however, the time course of changes in MBP in rabbits was significantly shorter than that in the other animal groups. Significant in HR after the injection of L-enk occurred in rabbits and dogs, whereas increases in HR occurred in monkeys. These results show that some cardiovascular responses to L-enk may be species dependent. These different cardiovascular responses to L-enk may be at least partly related to species differences in baroreceptor reflex sensitivity.     

Die Wirkung von Desoxycorticosteron auf den aktiven Kationenaustausch an Rattenblutzellen

Summary Cold-stored blood cells of rats, which were depleted of potassium and had gained an equivalent amount of sodium instead, were incubated with 500 mg% glucose at 37°C in serum. Under these conditions an extrusion of sodium from and a re-entry of potassium into the cells could be observed. Desoxycorticosterone, when added in a concentration of 1 mg per ml, was able to slow down the rate of this exchange to three fifths of the rate of untreated cells. With blood of adrenalectomised rats, the same effect of DOC was observed, although the rate without DOC was somewhat lower than in the blood of normal animals. There was no statistically significant difference between the DOC-effect in blood of normal and adrenalectomised rats.     

Methyleugenol as a surgical anesthetic in rodents

Summary Methyleugenol, suspended in Tween-80 or cremophor EL, at the dose 200–275 mg/kg i.p., is a safe anesthetic agent in rats and mice submitted to surgical procedures in the brain, without some of the inconvenience of sodium pentobarbital.     

Histamine release in dogs by Emulphor EL620.

A vehicle containing ethanol and Emulphor EL620 lowers blood pressure and increases heart rate in morphine-chloralose anesthetized dogs. These effects are associated with histamine release caused by Emulphor EL620.     

Comportamento dell allossanain vivo

Summary The author describes a microprocedure, based on the o-phenylenediamine reaction, for the determination of alloxan in blood and tissuesin vivo. With this method he has been able to determine alloxan in blood, liver, kidney, muscle, and pancreas of rats treated with diabetogenous doses of alloxan. This substance has been found in the blood and tissues during an hour and a half after the injection and in the urine collected directly from the ureter a quarter of an hour after the injection.