Muscle stimulators

Barium metal and most barium compounds are highly poisonous. A notable exception is barium sulfate which is nontoxic because of its extreme iasolubihty ia water. Barium ion acts as a muscle stimulant and can cause death through ventricular fibrillation of the heart. Therefore, care must be taken to avoid contact with open areas of the skin. Workers must wear respirators (of type approved for toxic airborne particles), goggles, gloves, and protective clothing at all times. The toxic barium aluminate residue obtained from barium production is detoxified by reaction with a solution of ferrous sulfate and converted iato nontoxic barium sulfate. According to OSHA standards, the TWA value for Ba and Ba compounds ia air is 0.5 mg/m. ... 

Caffeine is a mild to potent CNS stimulant, with the degree of its stimulating effect dependent on the dose administered. Caffeine stimulates the CNS at all levels, including the cerebral cortex, die medulla, and the spinal cord. Caffeine has mild analeptic (respiratory stimulating) activity. Other actions include cardiac stimulation (which may produce tachycardia), dilatation of coronary and peripheral blood vessels, constriction of cerebral blood vessels, and skeletal muscle stimulation. Caffeine also has mild diuretic activity. 

Figure 2. Muscle stimulation, a) a single nerve impulse (stimulus) causes a single contraction (a twitch). There is a small delay following the stimulus before force rises called the latent period, b) A train of stimuli at a low frequency causes an unfused tetanus. Force increases after each progressive stimulus towards a maximum, as calcium levels in the myofibrillar space increase. But there is enough time between each stimulus for calcium to be partially taken back up into the sarcoplasmic reticulum allowing partial relaxation before the next stimulus occurs, c) A train of stimuli at a higher frequency causes a fused tetanus, and force is maximum. There is not enough time for force to relax between stimuli. In the contractions shown here, the ends of the muscle are held fixed the contractions are isometric.

Figure 2. Force generation and energy metabolism in human quadriceps femoris muscle stimulated intermittently at 20 Hz, with 1.6 sec tetani with 1.6 sec rest periods between tetani. The upper panel shows force, ATP turnover rate, and pH the middle panel, the concentrations of PCr, P and lactate and the lower panel, ATP, ADP, IMP, H, and calculated H2PO4. From Hultman et al. (1990), with permission from Human Kinetics Publishers.

Juel, C. (1988), Intracellular pH recovery and lactate efflux in mouse soleus muscles stimulated in vitro The involvement of sodium/proton exchange and a lactate carrier. Acta Physiol. Scand. 132,... 

Eighty percent of aqueous humor drains through the trabecular meshwork, which is a lattice of connective tissue that surrounds the anterior chamber. The size of the trabecular meshwork can be altered by the contraction or the relaxation of the ciliary muscle. Stimulation of muscarinic receptors on the ciliary muscle causes contraction, which in turn causes the pores of the trabecular meshwork to open, increasing aqueous humor outflow. 

M Schramm, G Thomas, R Towart, G Frackowiak. (1983). Activation of calcium channels by novel 1,4-dihydropyridines. A new mechanism for positive inotropies of smooth muscle stimulants. Arzneim Forsch 33 1268-1272. 

The short-acting / -agonists (Table 80-1) are the most effective broncho-dilators available. /J2-Adrenergic receptor stimulation activates adenyl cyclase, which produces an increase in intracellular cyclic adenosine monophosphate. This results in smooth muscle relaxation, mast cell membrane stabilization, and skeletal muscle stimulation. 

Blaustein We published a paper a couple of years ago on aortic smooth muscle stimulated with serotonin. Using moderate doses for short periods, which cause modest contraction, we saw no effect on Ca2+ in individual mitochondria. However, a big dose for a longer period causes the muscle to go into contracture, and there is a significant rise in Ca2+ in mitochondria. 

Calcium ions Movement of Ca ions from the extracellular environment into the cytosol is achieved via calcium ion channels. An increase in the number of Ca " ion channels that are open in cells of smooth or cardiac muscles stimulates contraction. Excessive rates of entry can, however, cause problems. For example, increased entry of Ca ions into vascular smooth muscle increases contraction which rednces the diameter of blood vessels which can lead to hypertension (Chapter 22). 

Carbachol is a powerful cholinic ester that stimulates both muscarinic and nicotinic receptors, as well as exhibits all of the pharmacological properties of acetylcholine while in addition resulting in vasodilation, a decrease in heart rate, an increase in tone and con-tractability of smooth muscle, stimulation of salivary, ocular, and sweat glands as well as autonomic ganglia and skeletal muscle. For this reason, use of carbachol, like acetylcholine, is limited. The exception is that it is used in ophthalmological practice and post-operational intestines and bladder atony. Upon administration in the eye, the pupil constricts and the intraocular pressure is reduced. It is used for severe chronic glaucoma. Synonyms of this drag are doryl and miostat. 

Caffeine and the related dimethylxanthines have similar pharmacological or therapeutic effects and similar toxic effects. The primary actions include stimulation of the central nervous system, relaxation of bronchial muscles, mild cardiac muscle stimulation, and diuretic effects on the kidney. 

Aetinidine (9a) has been identified as an anal gland product of three species of dolichoderine ants in the genera Conomyrma and Iridomyrmex (Table I). The venoms of ants of the Myrmecia species are rich in histamine (136) (Table VIII), which can act as a defensive substance, together with hemolytic, smooth-muscle-stimulating, and histamine-releasing components. 

A slow intravenous injection of histamine produces marked vasodilation of the arterioles, capillaries, and venules. This causes a fall in blood pressure whose magnitude depends on the concentration of histamine injected, the degree of baroreceptor reflex compensation, and the extent of histamine-induced release of adrenal catecholamines. Vasodilation of cutaneous blood vessels reddens the skin of the face, while a throbbing headache can result from vasodilation of brain arterioles. Vasodilation is mediated through both Hj- and Hj-receptors on vascular smooth muscle. Stimulation of Hj-receptors produces a rapid and short-lived response, whereas stimulation of H2-receptors produces a more sustained response that is slower in onset. Stimulation of Hj-receptors on sympathetic nerve terminals inhibits the release of norepinephrine and its associated vasoconstriction. 

Skeletal muscle stimulant activity. Ethanol (95%) extract of the seed, at a concentration of 10 mg/mL, was inactive on frog rectus abdominus muscle . 

Mechanism of Action A xanthine derivative that acts as a bronchodilator by directly relaxing smooth muscle of the bronchial airway and pulmonary blood vessels similar to theophylline. Therapeutic Effect Relieves bronchospasm, increases vital capacity, produces cardiac, and skeletal muscle stimulation. 

Beta 2 Postsynaptic effector cells, especially smooth muscle and cardiac muscle Stimulation of adenylyl cyclase and increased cAMP. Activates cardiac G under some conditions. 

Before the identification of 5-hydroxytryptamine (5-HT), it was known that when blood is allowed to clot, a vasoconstrictor (tonic) substance is released from the clot into the serum. This substance was called serotonin. Independent studies established the existence of a smooth muscle stimulant in intestinal mucosa. This was called enteramine. The synthesis of 5-hydroxytryptamine in 1951 permitted the identification of serotonin and enteramine as the same metabolite of 5-hydroxytryptophan. 

Ergot Alkaloid a Adrenoceptor Dopamine Receptor Serotonin Receptor (5-HT2) Uterine Smooth Muscle Stimulation... 

Analgesic efficacy and clinical use Pethidine (Clark et al.,1995 Latta et al., 2002) is used for the treatment of moderate to severe pain including labor pain. It is also used as preoperative medication and as an adjunct to anesthesia. Due to its anti-muscarinic properties, it has a weaker muscle stimulant activity than other opioids and does not increase biliary pressure, which makes it suitable for the treatment of pain associated with pancreatitis or biliary colic. 

Insulin-resistant rats muscle Stimulation Liu et al., 2007b... 

Acetylcholine is a neurotransmitter that functions in conveying nerve impulses across synaptic clefts within the central and autonomic nervous systems and at junctures of nerves and muscles. Following transmission of an impulse across the synapse by the release of acetylcholine, acetylcholinesterase is released into the synaptic cleft. This enzyme hydrolyzes acetylcholine to choline and acetate and transmission of the nerve impulse is terminated. The inhibition of acetylcholineasterase results in prolonged, uncoordinated nerve or muscle stimulation. Organophosphorus and carbamate pesticides (Chapter 5) along with some nerve gases (i.e., sarin) elicit toxicity via this mechanism. 

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