bluuebunny/crossref_metadata_2025_split huggingface dataset:
The effect of catecholamine infusions on myocardial blood flow, metabolic heat production and on general haemodynamics, before and after alprenolol (H56/28), in anaesthetized cats
Authors: PARRATT J. R. , WADSWORTH R. M. 
Published: July 2012

Summary
. In cats anaesthetized with pentobarbitone sodium, infusions of adrenaline, noradrenaline (0·5 μg/kg per min) and isoprenaline (0·25 μg/kg per min) increased myocardial blood flow, myocardial heat production, left ventricular systolic and end‐diastolic pressures, left ventricular +ve and –ve dp/dt max, and calculated cardiac output, effort and oxygen consumption. These effects (apart from the effect of noradrenaline on left ventricular systolic pressure) were markedly reduced by previous administration of alprenolol (0·5 or 1·0 mg/kg).
. Infusions of adrenaline and noradrenaline increased arterial diastolic blood pressure and isoprenaline reduced it. After alprenolol the effects of adrenaline and noradrenaline were potentiated and that of isoprenaline abolished; in some experiments isoprenaline increased arterial diastolic pressure after alprenolol. Alprenolol did not influence the increases in arterial systolic pressure which followed the administration of adrenaline and noradrenaline.
. Isoprenaline‐induced tachycardia was markedly reduced and adrenaline tachycardia was converted to bradycardia after alprenolol. The bradycardia which occurred during noradrenaline infusions was unaffected.
. After blockade by alprenolol, recovery of the effects of isoprenaline on left ventricular dp/dt and on heart rate occurred more quickly than recovery of the effects on arterial diastolic pressure. This suggests that alprenolol has a greater affinity for β2‐ than for β1‐adrenoceptors.
. Intravenous administration of acetylcholine decreased arterial blood pressure, left ventricular pressure and +ve and –ve dp/dt max. During recovery from these effects there was a marked increase in +ve dp/dt max. which was absent after the administration of alprenolol (0·5 mg/kg). Because this dose of alprenolol is thus able to block the effects of reflex sympathetic cardiac nerve stimulation but does not completely antagonize the effects of exogenous adrenaline on dp/dt, it is suggested that alprenolol may have some adrenergic neurone blocking activity.
. Increases in liver and myocardial blood flow and heat production produced by noradrenaline, adrenaline and isoprenaline were reduced after alprenolol.
. Isoprenaline reduced air‐way resistance and this effect was abolished by alprenolol; increases in air‐way resistance produced by adrenaline and noradrenaline were augmented. All three amines inhibited intestinal smooth muscle contractions in vivo. Only the effect of isoprenaline was reduced by alprenolol.
The vascular responses of the spleen to intravenous infusions of catecholamines, angiotensin and vasopressin in the anaesthetized cat
Authors: GREENWAY C. V. , STARK R. D. 
Published: July 2012

Summary
. Splenic arterial flow and splenic weight were recorded in cats anaesthetized with sodium pentobarbitone. The responses of the spleen to catecholamines, angiotensin and vasopressin were investigated.
. Catecholamines caused responses mediated by α‐ and β‐adrenoceptors in the arteriolar smooth muscle, but only insignificant β‐adrenoceptor responses could be elicited from the capsular smooth muscle. The difficulties in elucidating the mechanism of action of catecholamines on arteriolar smooth muscle are discussed.
. Angiotensin caused marked vasoconstriction, but contraction of the capsular smooth muscle was less marked. Vasopressin caused vasoconstriction but had no effect on capsular smooth muscle. Thus these peptides constrict the resistance vessels but produce much weaker contraction of the capsule.
. These responses are discussed in relation to the splenic responses to acute haemorrhage.
Coronary vasodilatation following diazepam (Valium)
Authors: ABEL R. M. , REIS R. L. , STAROSCIK R. N. 
Published: July 2012

Summary
. The effects of diazepam (Valium) on coronary and systemic vascular resistance were studied in anaesthetized dogs on cardiopulmonary bypass under conditions of constant heart rate and aortic pressure.
. Pharmacological doses of diazepam uniformly produced coronary vasodilation lasting 30 min; systemic vascular resistance also decreased, but to a lesser degree.
. When coronary blood flow was maintained constant at physiological levels, diazepam produced no changes in left ventricular contractility, as assessed by peak LV isovolumetric pressure, dp/dt max, force‐velocity, and length‐tension relations, whereas previous experiments had demonstrated a positive inotropic effect in a similar preparation in which coronary blood flow was responsive to alterations in coronary vascular resistance.
. In five dogs, complete separation of the coronary and systemic circulations was accomplished by a double pump‐oxygenator system; direct intracoronary administration of diazepam produced coronary vasodilatation, but coronary pressure and flow were not altered by administration of diazepam to the systemic circulation.
. It is concluded that diazepam augments myocardial contractility by increasing coronary blood flow. This relationship is independent of extracardiac humoral mechanisms, and appears to require the delivery of diazepam to the coronary circulation.
The effect of Arvin on reticulo‐endothelial activity in rabbits
Authors: ASHFORD A. , BUNN D. R. G. 
Published: July 2012

Summary
. Arvin stimulated the reticulo‐endothelial uptake of colloidal carbon in rabbits. The onset of effect after intravenous administration was immediate and the minimum stimulant dose by this route was very low—0·05 unit/kg (0·1 μg protein/kg).
. Carbon opsonized in vitro with serum taken 4 h after an intravenous injection of Arvin was cleared more rapidly than carbon treated with control serum. Serum collected 10 min after Arvin did not promote carbon uptake.
. Reticulo‐endothelial block with Thorotrast or excess carbon did not prevent the stimulant effect of Arvin but prevented the stimulant effect of opsonization with 4 h serum.
. The reticulo‐endothelial stimulant effect of Arvin appears to be unrelated to its coagulant action on fibrinogen. The mechanism may involve a direct action on phagocytic cells and an effect on colloidal particles via serum opsonins.
The effects of caerulein on insulin secretion in anaesthetized dogs
Authors: BERTACCINI G. , DE CARO G. , MELCHIORRI P. 
Published: July 2012

Summary
. Insulin concentration changes in pancreatico‐duodenal venous plasma were studied in anaesthetized dogs injected with caerulein.
. Rises in insulin concentration were elicited by rapid intravenous injection of caerulein, as well as by intravenous infusion. Threshold doses were 10 ng/kg and 0·5–1 (ng/kg)/min respectively.
. At the highest dose used (500 ng/kg by rapid intravenous injection and (25 ng/kg)/min by intravenous infusion) the increase in immuno‐reactive insulin release was approximately 7 to 9 times the base levels.
. Adrenalectomy potentiated the effects of intravenous infusion of caerulein.
. On a molar basis, caerulein was 2–3 times as active as pancreozymin.
. It is concluded that caerulein is a potent stimulant of pancreatic islets in the dog and that it may be considered as a model peptide, capable of being substituted for pancreozymin in any experiment.
. The mechanism of the insulin stimulating effect of caerulein is discussed. The possibility of a direct “β‐cytotropic” effect of the peptide is suggested.
Effects of morphine and pentobarbitone on acetylcholine synthesis by rat cerebral cortex
Authors: SHARKAWI M. 
Published: July 2012

Summary
. The synthesis of carbon‐14‐labelled acetylcholine (14C‐ACh) from carbon‐14 uniformly labelled glucose (U‐14C‐D‐glucose) under different conditions was studied.
. The ability of cerebral cortex slices and minces from morphine‐treated and pentobarbitone‐treated rats incubated in 4 mm K+ medium to form 14C‐ACh was markedly reduced as compared with those from control animals.
. The ability of slices from drug‐treated and control animals incubated in 31 mm K+ medium to form 14C‐ACh was similar.
. Cerebral cortex homogenates from both groups of animals in either 4 or 31 mm K+ medium formed similar amounts of 14C‐ACh.
. These findings add further support to the hypothesis that the concentration of ACh at the site of synthesis governs the rate of formation of the neurotransmitter.
Drug receptor sites in the rabbit saphenous nerve
Authors: WATSON P. J. 
Published: July 2012

Summary
. The actions of acetylcholine, carbachol, methacholine, pilocarpine, nicotine, tetramethylammonium, 1,1‐dimethyl‐4‐phenylpiperazinium, histamine, 5‐hydroxytryptamine, angiotensin, bradykinin and potassium chloride were investigated on the sensory endings of the rabbit saphenous nerve.
. By means of specific antagonists the presence of separate receptor sites sensitive to acetylcholine, histamine, 5‐hydroxytryptamine and bradykinin were demonstrated.
. The cholinoceptive receptors were shown to be predominantly nicotinic, but there was evidence of the existence of at least a small population of muscarinic receptors.
. Catecholamines of both α and β types exhibited some stimulatory activity on administration. It is unlikely that this was due to either vasomotor effects or to any action involving the arrectores pilorum muscles.
. The α‐receptor stimulants modified the response to acetylcholine in a biphasic way. There was a brief enhancement of effect followed by a more prolonged depression. β‐receptor stimulation only produced a prolonged enhancement of acetylcholine‐evoked activity.
. The discharge generated by acetylcholine was augmented by anticholinesterases and blocked by ganglion blocking agents. None of these drugs in reasonable doses affected the response to stroking the fur. The results therefore support earlier evidence against a sensory cholinergic synaptic link.
A method for investigating the effects of drugs on the exploratory behaviour of mice
Authors: SHILLITO ELIZABETH E. 
Published: July 2012

Summary
. Exploratory behaviour in mice was observed when they were put on a wooden board to which twelve tunnels were fixed. The number of different tunnels entered (indicating exploration) and the total entries into tunnels were recorded over 5 min on 2 successive days.
. Untreated mice entered more different tunnels in the first minute on the second day on the tunnel board, and this difference in behaviour was taken as an indication that exploration had occurred on the first day. When the behaviour of the treated mice on the second day was similar to that of inexperienced mice on the first day it was inferred that drug treatment had adversely affected exploration.
. Haloperidol 4 mg/kg, chlorpromazine 8 mg/kg and thioridazine 16 mg/kg adversely affected exploration at doses which almost immobilized the mice.
. Amphetamine at 8 mg/kg disrupted exploratory behaviour in the mice, although the mice were observed to move round the board very quickly.
. With tranylcypromine 2 mg and nialamide 100 mg, increased exploratory behaviour by comparison with controls was recorded in the mice when they were tested 24 h after drug treatment.
. Imipramine at 20 mg/kg reduced the total number of tunnels entered by the mice on the first day, but on the second day the mice behaved in a similar way to mice treated with monoamine oxidase inhibitors.
Ascorbic acid deficiency and pituitary adrenocortical activity in the guinea‐pig
Authors: HODGES J. R. , HOTSTON R. T. 
Published: July 2012

Summary
. Guinea‐pigs kept on a diet deficient in ascorbic acid lost weight and became moribund in about 24 days.
. The adrenal ascorbic acid concentration fell rapidly during the first 2 weeks, and the plasma corticosteroid concentration and 17‐oxogenic steroid excretion rose sharply in the third week of ascorbic acid deficiency.
. Both histamine and corticotrophin increased the plasma corticosteroid concentration when injected during the second week but failed to change the pre‐existing high concentration of the steroid in the third week of ascorbic acid deficiency.
. The observations confirm that ascorbic acid is not involved in corticoidogenesis and that scurvy is a severe stress which increases adrenocortical activity to such an extent that the rate of synthesis of corticosteroids is incapable of matching the rate of their release.
The relationship between the level of cholinesterase in plasma and the action of suxamethonium in animals
Authors: HOBBIGER F. , PECK A. W. 
Published: July 2012

Summary
. The neuromuscular blocking action of suxamethonium, given by intravenous injection, and the effect upon it of iso‐OMPA (tetraisopropyl pyrophosphoramide) in doses which produced marked selective inhibition of cholinesterase in blood were studied in anaesthetized rats and cats, and in mice.
. In cats experiments were also carried out in which suxamethonium was given by intravenous infusion until an effect which remained constant with time was achieved. From the degree of neuromuscular block (under equilibrium conditions) obtained with different infusion rates the infusion rate for 50% reduction in twitch tension of the indirectly stimulated soleus and gastrocnemius muscles (IR50) was calculated. The effect on it of raising the suxamethonium hydrolysing capacity of blood and of selectively reducing the level of cholinesterase in blood by various doses of iso‐OMPA was then investigated.
. At relevant stages of each experiment cholinesterase activity in blood was determined with butyrylcholine or benzoylcholine and where appropriate with suxamethonium as substrate.
. The results obtained show that in rats and cats the effectiveness of suxamethonium is unrelated to the level of cholinesterase activity in blood and that raising the suxamethonium hydrolysing capacity in the blood up to 22‐fold (in cats) only reduces the IR50 by a factor of 1.6.
. The enhancement of the effectiveness of suxamethonium in the three species (2‐ to 3‐fold in rats, 2‐ to 4‐fold in mice and 7‐ to 8‐fold in cats under the conditions used for comparison) which follows the administration of iso‐OMPA is attributable to inhibition of cholinesterase in the tissues.
. It is concluded that the results obtained clearly indicate that the species studied do not give information as regards suxamethonium and its metabolism which is applicable to man.
A simple method for measuring a picogram of acetylcholine using the clam (Mya arenaria) heart
Authors: COTTRELL G. A. , POWELL B. , STANTON M. 
Published: July 2012

Summary
. A simple and reliable method is described for assaying 1 pg or less of acetylcholine (ACh) using a strip of clam (Mya arenaria) heart.
. Clam heart preparations generally are extremely selective for ACh. The preparation described is at least 105 times less sensitive to the following: acetyl coenzyme A, adrenaline, choline, dopamine, γ‐aminobutyric acid, glutamic acid, histamine, 5‐hydroxytryptamine and noradrenaline.
. Because this preparation is one of the most sensitive known for detecting ACh, it should prove useful for assaying particularly low levels of this substance in biological extracts.
Effects of angiotensin and noradrenaline on discharge in fibres of the cervical sympathetic nerve in cats and dogs
Authors: MORRISON J. F. B. , PICKFORD MARY 
Published: July 2012

Summary
The effects of angiotensin and noradrenaline on discharge frequency in single and few‐fibre preparations of the cervical sympathetic nerve of cats and dogs have been compared.
When equal changes in blood pressure were produced by intravenous infusion of these drugs, the changes found in sympathetic discharge were similar both in anaesthetized animals and in a decerebrate one.
Angiotensin and noradrenaline also have similar effects on discharge in sympathetic nerve fibres following complete denervation of the baroreceptor and chemoreceptor nerves.
It is concluded that when the blood pressure is raised to 200 mmHg by angiotensin, the drug has no central stimulant action on the sympathetic nervous system.
Pyrrolizidine alkaloids: actions on muscarinic receptors in the guinea‐pig ileum
Authors: POMEROY A. R. , RAPER C. 
Published: July 2012

Summary
Eleven pyrrolizidine alkaloids have been tested on the isolated guinea‐pig ileum preparation.
Platyphylline, supinine, heleurine and cynaustraline were more potent in antagonizing responses to acetylcholine and carbachol than responses to histamine. Their anticholinergic activity appeared to involve a competitive mechanism.
Lasiocarpine, monocrotaline, spectabiline, sarracine, 7‐angelylheliotridine, heliotrine and senecionine had similar antagonistic potencies against responses to both acetylcholine and histamine.
The alkaloids had no appreciable activity as antagonists of acetylcholine in the isolated toad rectus abdominis preparation.
These results are discussed with respect to interactions of the alkaloids at receptor sites involved in anticholinergic activity at the muscarinic receptor.
Hypothermia produced in mice by histamine acting on the central nervous system
Authors: SHAW GRAHAM G. 
Published: July 2012

Summary
In mice 1–10 μg histamine injected intraventricularly produces hypothermia.
This hypothermia was not antagonized by chlorcyclizine administered subcutaneously or intraventricularly, but chlorcyclizine injected intraventricularly was effective in antagonizing the hypothermia produced by a subcutaneous injection of histamine.
Pretreatment with atropine was without effect on the hypothermia produced by an intraventricular injection of 10 μg histamine.
Amphetamine and tranylcypromine not only effectively reduced the intensity of, or abolished, the hypothermia but also reversed the response to an intraventricular injection of 10 μg histamine so that hyperthermia was produced. Pargyline was without effect.
Tolazoline strongly potentiated the hypothermia produced by the intraventricular injection of 10 μg histamine, but phentolamine did not.
It is concluded that at least part of the hypothermia produced by a subcutaneous injection of histamine arises as a result of an action on the central nervous system.
The possible mechanisms by which histamine acting on the central nervous system produces hypothermia and the suggestion that histamine may have a physiological role in thermoregulation are discussed in the light of these findings.
Effect of electrical stimulation and high potassium concentrations on the efflux of [14C] glycine from slices of spinal cord
Authors: HOPKIN JUDY , NEAL M. J. 
Published: July 2012

Summary
The effects of electrical stimulation and solutions containing a high concentration of potassium on the efflux of [14C] glycine from slices of rat spinal cord have been studied.
Slices of cord were incubated with [14C] glycine which rapidly accumulated in the tissue. The slices were then superfused in a small chamber and the radioactivity released from the tissue was measured. After superfusion for 60 min, 98% of the radioactivity remaining in the tissue was present as unchanged glycine.
The spontaneous efflux of [14C] glycine consisted of an initial rapid phase followed by a much slower release of [14C] glycine. After superfusion for 60 min, more than 65% of the radioactivity taken up during the incubation period was retained by the tissue.
When the slices were depolarized by electrical stimulation or by solutions containing a high concentration of potassium (40 mm), a striking increase in the efflux of [14C] glycine was produced. This effect was not reduced by the absence of calcium ions in the superfusion medium.
Electrical stimulation produced similar increases in the efflux of [3H] GABA and [14C] glutamate from slices of cord but had no significant effects on the efflux of [3H] alanine or [14C] urea.
The results are consistent with the suggestion that glycine may be an inhibitory synaptic transmitter substance in the mammalian spinal cord.
Modification of the vascular response to isoprenaline by cholinomimetic drugs
Authors: HAMILTON T. C. 
Published: July 2012

Summary
Pilocarpine and other cholinomimetic drugs convert isoprenaline to a vasoconstrictor and pressor agent.
This effect of pilocarpine was abolished by atropine; it is thus an acetylcholine‐like response. It was not dependent on the integrity of the central nervous system or the adrenal glands and was not abolished by ganglionic blockade.
The constrictor action of isoprenaline after pilocarpine was abolished by propranolol; this action of isoprenaline is thus on the β‐adrenoceptor. Another β‐adrenoceptor stimulating agent, salbutamol, resembled isoprenaline in this situation, though papaverine and acetylcholine did not.
The constrictor action of isoprenaline after pilocarpine was abolished by phenoxybenzamine, guanethidine and cocaine; the effect did not appear after reserpine pretreatment.
These results suggest an action of cholinomimetic drugs at adrenergic nerve endings which permits the uptake of β‐adrenoceptor stimulating agents resulting in the release of neuronal transmitter.
5‐Hydroxytryptamine metabolism in sheep
Authors: BARTLET A. L. 
Published: July 2012

Summary
5‐Hydroxytryptamine (5‐HT) (10 mg) administered intravenously to sheep was mostly excreted in the urine as 5‐HT‐O‐glucuronide (705 ± 162 μg, mean from six wethers ± s.e.m.) and 5‐hydroxyindolylacetic acid (5‐HIAA) (6,850 ± 1,538 μg). Oral administration of 5‐HT (100 mg) led to the excretion of 590 ± 212 μg 5‐HT‐O‐glucuronide (mean from five wethers ± s.e.m.) and 7,394 ± 2,093 μg 5‐HIAA in the urine.
After administration of dl‐5‐hydroxytryptophan (dl‐5‐HTP) (20 mg i.v. or 200 mg orally) sheep excreted about 5 mg 5‐HT in the urine together with 5‐HT‐O‐glucuronide and 5‐HIAA. The excretion of 5‐HT suggests that some DL‐5‐HTP perfused the liver and the lungs before being decarboxylated.
Twenty‐four hour specimens of control urine contained 335 ± 45 μg 5‐HT, 909 ± 90 μg 5‐HT‐O‐glucuronide and 3,352 ± 362 μg 5‐HIAA (seven sheep in each instance). Thus endogenous 5‐HT seemed to be conjugated with glucuronic acid to a greater extent than administered 5‐HT.
Although urinary 5‐HIAA was reduced after a single dose of isocarboxazid (20 mg/kg daily) the 5‐HT‐O‐glucuronide content of the specimens was not increased until two or three doses of the drug had been given.
Carbon tetrachloride (4 ml orally) reduced the urinary excretion of 5‐HT‐O‐glucuronide. Although the conjugation of 5‐HT with glucuronic acid was inhibited after administration of carbon tetrachloride the excretion of 5‐HT and 5‐HIAA was not increased. This observation suggests that carbon tetrachloride impaired the formation or clearance of endogenous 5‐HT in sheep.
Blockade of the reticulospinal inhibitory pathway by anaesthetic agents
Authors: FRANK G. B. , OHTA M. 
Published: July 2012

Summary
Adult cats were decerebrated at the intercollicular level. The effect of the anaesthetic agents, pentobarbitone, paraldehyde, tribromethanol, chloralose and procaine on the reticulospinal inhibitory pathway, which produced inhibition of segmental reflex potentials, was analysed.
The doses which blocked this inhibitory pathway did not exceed the doses required to produce surgical level anaesthesia with any of the drugs.
After the reticular inhibition of the reflex potentials was abolished, the reflex potentials were augmented by reticular stimulation with a higher intensity. This was thought to be due to spread of current to the excitatory pathways which were not completely depressed by the anaesthetic agent.
The resistance of the reticular facilitation of the reflex potentials to inhibition by these drugs after abolition of inhibition corresponded in general to the degree of excitement in intact mice produced by the same drugs.
These findings seem to indicate that the preferential block of the reticulospinal inhibitory pathway may be an important neural mechanism for the excitement stage of anaesthesia.