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At least 235 records · Page 13Linked to original sources
PubMed1970

Synaptic potentials recorded by the sucrose-gap method from the rabbit superior cervical ganglion.

1. Compound ganglionic potentials evoked by stimulation of the preganglionic nerves to the superior cervical ganglion of the rabbit were recorded by the sucrose-gap method.2. When the distal part of the ganglion was bathed in flowing isotonic sucrose solution or sodium-deficient solutions, ganglionic action potentials were no longer evoked, only large synaptic potentials.3. The compound synaptic potential, which remained unaltered for more than 1 h, originated in a population of cells at the interface between the Krebs and sucrose solutions. Hexamethonium reduced the size but did not alter the time course of the synaptic potential.4. It is suggested that a higher concentration of sodium ions is required for the generation of ganglionic action potentials than for either conduction in the postganglionic axons or production of synaptic potentials.5. When lithium replaced sodium in the solution bathing the distal part of the ganglion, the synaptic potential was greatly reduced in amplitude. Impulse propagation in the postganglionic axons was only slightly impaired when lithium replaced sodium in the solution bathing the axons.6. A quantitative assessment of the potency of the ganglion-blocking drugs nicotine, pentolinium, hexamethonium and pempidine was made by measuring the depression of the synaptic potentials produced by bathing the distal part of the ganglion in flowing isotonic sucrose solution. The concentrations which produced a 50% depression were 8.1 muM nicotine, 26.5 muM pentolinium, 111 muM hexamethonium and 22.2 muM pempidine.

Animals↗
PubMed1970

Oxotremorine-induced hypertension in the anaesthetized rat.

1. Oxotremorine exerts an action on peripheral cholinoceptors in the anaesthetized rat. After the blockade of peripheral cholinoceptors with the quaternary atropine derivative, atropine methylbromide, oxotremorine produced a rise in arterial blood pressure and tachycardia.2. The rise in arterial pressure and tachycardia was absent in rats that had been pithed or had undergone high spinal cord transection.3. A non-quaternary atropine derivative antagonized these cardiovascular effects.4. Drugs which inhibit activity of the sympathetic nervous system antagonized the oxotremorine-induced hypertension and tachycardia.5. It is concluded that the rise in arterial pressure and tachycardia seen in the anaesthetized rat treated with a quaternary derivative of atropine is due to an action of oxotremorine on the central nervous system at a supraspinal level, resulting in an increase in activity of the efferent sympathetic nervous system.

Adrenal Glands↗
PubMed1970

A pharmacological analysis of the peristaltic reflex in the isolated colon of the guinea-pig or cat.

1. The peristaltic reflex in the colon was elicited by a localized intraluminal stimulus. The contractile response of the longitudinal coat, which consists of two phases, begins before the start of propulsion. Although the contractions of the longitudinal and circular musculature are usually associated, they may be independent of each other. In particular, the longitudinal contraction does not seem to be necessary for propulsion.2. Both the longitudinal reflex contraction and the segmental responses of the circular muscle to distension, namely a contraction above and a relaxation below the bolus, are abolished by tetrodotoxin and ganglion blocking agents.3. In the guinea-pig, longitudinal and circular reflex contractions are usually resistant to antimuscarine, antihistamine and antitryptamine drugs but in the cat they are abolished by antimuscarine drugs. In both species, however, atropine and hyoscine can impair propulsion by blocking selectively the descending inhibition. In the cat, it is possible to find doses which abolish the descending inhibition without affecting the contractile responses of the longitudinal and circular muscle.4. Sympathetic denervation and pretreatment with reserpine do not affect the propulsive activity. The maintenance of the descending inhibition in denervated organs suggests that the inhibitory neurones to the circular muscle are not adrenergic.5. On the basis of the effects of drugs, the possible nervous mechanism subserving the polarity of propulsion has been examined. Such a mechanism seems to require an inhibitory pathway involving muscarinic receptors at some point.6. Pelvic nerve stimulation facilitates propulsive activity. The effect of transmural stimulation is different at low and at high frequencies of stimulation. The inhibitory effect of sympathetic stimulation on the reflex responses seems to be due mainly to an action on intrinsic nervous structures.

Acetylcholine↗
PubMed1972

Effect of physostigmine on ventricular fibrillation and myocardial glycogen in hypothermic dogs.

1. Physostigmine (0.1 mg/kg i.v.) given at 37 degrees C and 25 degrees C rectal temperatures, completely protected the hypothermic dog heart against ventricular fibrillation.2. Pentolinium, atropine, vagotomy and reserpine did not significantly alter the incidence of ventricular fibrillation.3. The incidence of ventricular fibrillation under hypothermia could be significantly increased by ligating the anterior descending branch of the left coronary artery. The incidence of ventricular fibrillation in coronary ligated hypothermic dogs was reduced to half by physostigmine pretreatment.4. Hypothermia produced ventricular glycogen depletion and physostigmine prevented ventricular glycogenolysis under hypothermia. However, in the normothermic state physostigmine itself produced a significant decrease in cardiac glycogen.5. The relation between the antifibrillatory and antiglycogenolytic effects of physostigmine under hypothermia are discussed.

Animals↗
PubMed1972

Augmentation of drug-induced blood pressure increases in rats by amorbarbital.

The effects of amobarbital anaesthesia on blood pressure responses to angiotensin and noradrenaline were determined in rats with chronically implanted venous and aortic catheters. Responses were tested twice on the same day in each rat, first in the conscious state and then during anaesthesia. Blood pressure rises produced by noradrenaline and angiotensin were larger when the rats were anaesthetized with amobarbital than when they were conscious. This enhancement was not characteristic of general anaesthesia since urethane, instead of enhancing, depressed the pressor responses.Blockade of acetylcholine receptors with atropine also increased the response to pressor drugs. However, amobarbital in anaesthetic doses did not affect the response to acetylcholine, indicating that removal of compensatory parasympathetic reflexes was not a major cause of its enhancing effect. The effects of amobarbital on arterial pressure and heart rate were similar to those of the ganglion blocking drug pentolinium. When pressor responses were increased by amobarbital, autonomic ganglia were depressed as indicated by the loss of the response to nicotine. These findings suggest that amobarbital enhances blood pressure responses to noradrenaline and angiotensin by blocking autonomic ganglia.

Acetylcholine↗
PubMed1978

Effect of parathyroidectomy on cardiovascular reactivity in rats with mineralocorticoid-induced hypertension.

Previous work has shown that parathyroidectomy protected Sprague-Dawley rats against mineralocorticoid hypertension. 2 In order to explain this protection, we studied vascular reactivity to noradrenaline and angiotensin II in several groups of rats with and without their parathyroid and thyroid glands. Work was performed in vagotomized, anaesthetized rats after ganglionic blockade with pentolinium, and atropine sulphate. 3 The reactivity to noradrenaline was significantly lower in parathyroidectomized rats, especially at the beginning of mineralocorticoid treatment. 4 Autotransplantation of parathyroid glands in thyroparathyroidectomized rats re-established normal cardiovascular reactivity and development of hypertension. 5 Cardiovascular reactivity to angiotensin II was not affected in parathyroidectomized rats and was lowered in thyroparathyroidectomized thyroxine-treated rats.

Angiotensin II↗
PubMed1985

Pressor sensitivity to exogenous vasopressin in conscious, adult rats treated neonatally with capsaicin.

Pressor responses to exogenous arginine vasopressin were assessed in adult rats that had been treated neonatally with capsaicin or its vehicle. Measurements were made under control conditions, after inhibition of baroreflexes (with pentolinium), and after inhibition of baroreflexes (with pentolinium) and the production of angiotensin II (with captopril). Resting arterial blood pressures and pressor sensitivities to exogenous arginine vasopressin were similar in capsaicin-treated and vehicle-injected rats. Sixty minutes after the administration of pentolinium, systolic and diastolic blood pressures were reduced in both groups of rats and the pressor responses to arginine vasopressin were similarly and significantly enhanced. In both groups of rats 60 min after administration of pentolinium and captopril, systolic and diastolic blood pressures were lower than in the presence of pentolinium alone, but pressor responses were not different from those seen in control conditions. The possibility that the present results are explicable in terms of baroreflexes, the renin-angiotensin system and endogenous vasopressin interacting to influence the pressor sensitivity to exogenous vasopressin is discussed. From the present findings, it seems that our previous observation of impaired, vasopressin-mediated blood pressure recovery following acute hypotension in capsaicin-treated rats cannot be attributed to a reduced pressor sensitivity to the hormone.

Animals↗
PubMed1985

The influence of neonatal treatment with capsaicin on the control of blood pressure in adult rats in water-replete and water-deprived states.

Arterial blood pressures and heart rates were measured in water-replete and in water-deprived (48 h) conscious, adult rats that had received capsaicin (50 mg kg-1) or its vehicle neonatally. Resting arterial blood pressures and heart rates in capsaicin-treated rats were not different from the controls in either the water-replete or the water-deprived state. Inhibition of the vascular actions of vasopressin (with 1-beta-mercapto,-beta, beta-cyclopentamethylenepropionic acid, 8-D-arginine vasopressin, (d(CH2)5DAVP] had no significant effect on blood pressures in the water-replete animals but caused a significant hypotension in water-deprived rats; the magnitude of the hypotension was the same irrespective of whether the animals had received capsaicin or its vehicle. During angiotensin converting enzyme inhibition (with captopril) and ganglion blockade (with pentolinium), the vasopressin-mediated blood pressure recovery was more gradual in the capsaicin-treated animals than in the controls, but after 60 min blood pressures were similar in all groups. Collectively the results indicate that although the full development of vasopressin-dependent mechanisms following acute hypotension takes longer when a large proportion of unmyelinated afferent fibres have been destroyed by neonatal treatment with capsaicin, 48 h of water deprivation results in a normal involvement of vasopressin-dependent mechanisms in the maintenance of blood pressure.

Animals↗
PubMed1985

Comparison of the action of cholinomimetics and pentagastrin on gastric secretion in dogs.

Stimulation of acid secretion by muscarinic cholinomimetic agents depended on the periodic interdigestive activity of the stomach. This explains the peak and following fade. Pentagastrin stimulated gastric secretion after a fixed interval and did not depend on the interdigestive activity. Neither gastrin nor methacholine directly contracted the gallbladder in the doses used. A sustained secretion of gastric acid and pepsin, such as follows a meal, required both hormonal stimulation and gastric distension. The magnitude of the acid response from Heidenhain pouches following meals suggested that pentagastrin doses commonly used experimentally greatly exceed the physiological.

Animals↗
PubMed1987

Nicotine cue in rats: effects of central administration of ganglion-blocking drugs.

In rats trained to discriminate nicotine from saline, a single intraventricular injection of a small dose of the quaternary ganglion-blocking drug chlorisondamine blocked the response to nicotine for four weeks. pentolinium was only weakly active and hexamethonium was inactive as a nicotine antagonist under the conditions used, even in doses that were just below those producing myoclonic jerks. Chlorisondamine had no blocking effect in rats trained to discriminate the non-nicotinic drugs midazolam or morphine from saline. Intraventricular injections of chlorisondamine have a specific and unusually persistent nicotine-blocking action, the mechanism of which requires further investigation.

Animals↗
PubMed1990

Characterization of histamine H3-receptors in guinea-pig ileum with H3-selective ligands.

1. The effect of the selective histamine H3-receptor agonist R-(alpha)-methylhistamine has been investigated on the contractile responses of the longitudinal smooth muscle of guinea-pig ileum elicited by electrical field stimulation of acetylcholine release from myenteric nerve endings. 2. R-(alpha)-methylhistamine produced a concentration-dependent (EC50 = 1.4 +/- 0.2 x 10(-8) M) inhibition of the response to electrical field stimulation which was insensitive to inhibition by mepyramine (1 microM) and tiotidine (2.4 microM). 3. This response to R-(alpha)-methylhistamine could be inhibited in a competitive fashion by a range of H3-receptor antagonists including thioperamide (KB = 1.1 nM), impromidine (KB = 65 nM), norburimamide (KB = 380 nM) and SKF 91486 (KB = 34 nM). Burimamide was also a potent inhibitor of this response but the Schild slope obtained (1.3) was significantly greater than unity. 4. The estimated KB values were all within a factor of three of those values reported for the histamine H3-receptor mediating inhibition of histamine release in rat cerebral cortex. 5. These data suggest that the histamine receptor mediating inhibition of cholinergic neurotransmission by R-(alpha)-methylhistamine in guinea-pig ileum is the same as the H3-receptor present in rat cerebral cortex.

Animals↗
PubMed1992

Haemodynamic and abdominal motor reflexes elicited by neurotensin in anaesthetized guinea-pigs.

1. Single intraperitoneal (i.p.) injections of neurotensin (NT) (0.14- 140 nmol kg-1) in anaesthetized guinea-pigs were found to trigger transient abdominal wall contractions (TAWC) accompanied by relatively sustained increases of systemic blood pressure (BP) and heart rate (HR). The modification of the latter NT effects by various drugs and surgical manipulations was examined to obtain some insight into the nature of, and possible relationship between, these responses. 2. The abdominal motor response (i.e. TAWC) to i.p. NT (14 nmol kg-1) was inhibited by prior i.v. injection of the guinea-pigs with pancuronium (0.27 mumol kg-1), morphine (1.5 and 15 mumol kg-1), clonidine (0.34 mumol kg-1), by concomitant i.p. injection of procaine 2% w/v, or by acute spinalization. It was potentiated by naloxone (2.8 and 28 mumol kg-1), but not affected by i.v. injection of autonomic drugs (i.e. pentolinium, prazosin, yohimbine and atropine), by capsaicin desensitization, or by acute bilateral cervical vagotomy. In spinalized animals a sustained abdominal wall contraction (SAWC) was unmasked, which was resistant to i.v. morphine, clonidine or baclofen but suppressed by i.v. pancuronium or i.p. lignocaine 2% w/v. 3. Haemodynamic responses to i.p. NT were not affected by i.v. pancuronium, morphine, naloxone, atropine, or by vagotomy. They were inhibited by i.v. pentolinium or clonidine (BP, HR), i.v. prazosin (BP), i.p. procaine 2% w/v (BP, HR), capsaicin desensitization or acute spinalization (BP, HR). Yohimbine (i.v.) potentiated BP and HR increases caused by i.p. NT.4. These results suggest that: (1) the haemodynamic and TAWC responses to i.p. NT in this animal model, are two independent, neurally-mediated reflexes which are likely to originate from the abdominal cavity and require a functionally intact spinal cord for their full expression; (2) the neural pathways subserving both types of responses appear to be different from each other. The nature and time-response characteristics of the reflexes caused by i.p. NT, raise the possibility that i.p. NT is a noxious stimulus, at least in guinea-pigs.

Animals↗