SEARCH · PubMed Health
Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
Parasympathomimetic drugs include (1) acetylcholine and several synthetic choline esters and related derivatives, and (2) naturally occurring cholinomimetic alkaloids and certain related synthetic compounds. Pharmacology of acetylcholine, the prototype parasympathomimetic, is presented, as well as an introduction to other parasympathomimetic drugs and choline esters.
Various parasympathomimetic drugs are discussed, including the choline esters, bethanechol, carbachol, methacholine chloride, and furtrethonium. Other cholinomimetic agents include muscarine, muscarone, arecholine, and pilocarpine. Anticholinesterase agents inhibit or inactivate acetylcholinesterase enzyme and thus result in a prolonged stimulation of cholinergic receptors by endogenous ACh. Bethanechol is the most widely used parasympathomimetic drug in the United States. Its action is mainly muscarinic with activity largely confined to the urinary bladder and to a lesser degree the gastrointestinal tract. It can be administered only subcutaneously or orally, and adequate dosage is necessary for a successful response.
Although the precise mechanism of the cardiovascular effects in man evoked by the venom of the yellow scorpion has yet to be completely elucidated, previous studies indicate that excessive adrenergic activity is present in many of the cases. This report describes two patients in whom yellow scorpion sting was followed by bradyarrhythmia with varying degrees of atrioventricular block which promptly regressed after the administration of atropine; this is consistent with a direct parasympathomimetic effect of the venom or with a central effect producing increased vagal tone. It is suggested that the cardiovascular actions of the venom may represent a wide spectrum of effects on the autonomic nervous system, ranging from the predominantly sympathomimetic to the predominantly parasympathomimetic.
Rats treated with 0.5 mg/kg of reserpine per day for 7 days were anesthetized and submaxillary saliva was collected and analyzed for Na+, K+, Ca++ and protein concentrations. Salivary secretion was elicited by i.p. injections of carbamylcholine (50-100 mug/kg), phenylephrine (5 mg/kg) and isoproterenol (10 mg/rat). Saliva was also collected from untreated controls. Submaxillary glands were excised from both groups of animals at the termination of the secretory response, homogenized and analyzed. Glands from other animals were removed in the resting state and similarly processed. Pretreatment with reserpine resulted in decreased volumes of salvia and in elevated salivary concentrations of Ca++ and protein. Saliva from the reserpine-treated animals secreted in response to carbamylcholine had higher concentrations of Na+ and K+ than control saliva, particularly at the low rates of flow. Saliva secreted after stimulation with the two sympathomimetic secretagogues had lower concentrations of these two ions. Resting glands from the treated animals showed significant elevations in protein and Ca++ content and a significant decrease in K+ content. At the end of the secretory response to the three secretagogues, glands from treated animals showed a significantly higher Na+ content and a significantly lower K+ content than control glands. It is concluded that pretreatment with reserpine alters the secretory response of the rat submaxillary gland to both parasympathomimetic and sympathomimetic stimulation. This alteration results from a toxic lesion caused by reserpine in the salivary cells, which involves changes in their permeability to ions and in their energy resources. These in turn, result in an abnormal stimulus-secretion coupling mechanism. The possibility that the toxic lesion is related to alterations in Ca++ homeostasis is discussed.
The kinetics of K+ release from an in vitro system of rat submaxillary gland slices were studied after stimulation with parasympathomimetic secretagogues. The slices were incubated at 37degreesC in an oxygenated, enriched Krebs-Ringer bicarbonate medium in the presence and in the absence of Ca++ and of ouabain and, in some experiments, in the presence of the specific antagonists atropine (5 x 10(-6) and 2 x 10(-5) M), phentolamine (2 x 10(-5) M) or propranolol (2 x 10(-5) M. K+ release was elicited by the addition of acetylcholine (2 x 10(-5) M), pilocarpine (2 x 10(-5) M) and carbamylcholine (10(-9) to 2 x 10(-5) M). The results demonstrate that: 1) The selective stimulation of cholinergic receptors induces a rapid net release of K+ from the slices. After 10 minutes of incubation, the percent K+ released after a 2 x 10(-5) M dose of each of the three secretagogues was, respectively, 20.8%, 15.5%, and 19%. 2) The response to carbamylcholine does not occur when Ca++ is absent from the medium and is blocked by atropine but not by phentolamine or by propranolol. Atropine (5 x 10(-6) M) causes a 17-fold shift to the right on the dose-response curve to carbamylcholine. 3) The magnitude of K+ release is the ratio of two opposing mechanisms, a passive efflux and an active reuptake. The latter depends on the activity of the ouabain-sensitive Na+-K+-adenosine triphosphatase. 4) The sensitivity of the slice system to carbamylcholine seems to be greater than that to norepinephrine in terms of net K+ release after equimolar doses of 2 x 10(-5) M and also in terms of the dose required to induce a half maximal passive K+ efflux. However, the maximal passive K+ efflux is similar after both types of secretagogue and amounts of approximately 45% of the K+ present in the slices.
A new cyclitol was isolated using the flowers of the Salpianthus arenarius, and its chemical structure was determined (2-methoxy-5hydroxymethyl cyclopentane-1,3,4-triol). The contractile effects of acetylcholine (Ach), Atropine, Pilocarpine, Adrenaline and Cyclitol were studied in rat ileum. Such cyclitol proves to have parasympathomimetic activity.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
The effects of carbachol, propranolol and isoproterenol on tonin concentrations in rat saliva have been investigated. The results suggest that the activity of this enzyme in rat saliva is dependent on activity of beta-adrenergic receptors.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
1. Seminal vesicle reactivity to cholinergic agents, plasma testosterone, luteinizing hormone (LH) and follicle stimulating hormone (FSH) concentrations and seminal vesicle testosterone concentrations were determined in adult male rats treated during the first 6 h of life with 1.0 ml peanut oil (oil-treated), 1.0 mg testosterone propionate (TP-treated) or 1.2 mg 19-nor-testosterone homofarnesate (19-NT-treated). 2. At 90-100 days of age, the neonatally treated animals presented atrophied accessory genital organs and increased (TP-treated, N = 10) or unchanged (19-NT-treated, N = 11) pD2 values for acetylcholine (vehicle: 5.18 +/- 0.06, N = 10; TP-treated: 5.26 +/- 0.06, N = 10; 19-NT-treated: 5.14 +/- 0.09, N = 11), and acetyl-beta-methylcholine (vehicle: 5.19 +/- 0.07; TP-treated: 5.43 +/- 0.06; 19-NT-treated: 5.25 +/- 0.07). The relative intrinsic activity, alpha, of acetyl-beta-methylcholine increased after both hormonal treatments (vehicle: 0.85 +/- 0.03; TP-treated: 0.95 +/- 0.02; 19-NT-treated: 0.92 +/- 0.03). 3. No variation in mean adult plasma testosterone concentration was observed after neonatal treatment with either TP or 19-NT (vehicle: 752.93 +/- 273.66, N = 8; TP-treated: 459.05 +/- 88.32, N = 8; 19-NT-treated: 836.86 +/- 113.08, N = 7). However, testosterone content of seminal vesicles of adult rats was decreased in the animals treated with TP (N = 5) and 19-NT (N = 6) compared to controls. 4. These results indicate a specific effect of neonatal hormone treatment on androgen metabolism which is demonstrable in the adult.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
The effects of Mono sodium glutamate on smooth muscles were studied using the guinea-pig isolated ileum. Mono sodium glutamate produced spasmogenic effect. Atropine blocked the contractile response elicited by Mono sodium glutamate whereas mepyramine and hexamethonium failed to do so. These findings suggest a cholinergic involvement at post ganglionic site of action.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Mechanisms underlying urethral pressure changes at the external sphincter region after administration of neuropharmacologic agents were investigated with cystosphincterometric studies and electromyography of the external urethral sphincter in adult patients with spinal cord injury and control male subjects. Bethanechol chloride, propantheline or phentolamine were administered to 37 spinal cord injury men and 3 normal controls. After cystectomy 3 additional spinal cord injury patients were subjected to bethanechol studies. The results of these studies suggested that the pressure changes in the external sphincter zone were caused predominantly by the concurrent changes produced in the detrusor and/or the smooth muscle components of the proximal urethra and of the external sphincter zone.