Japanese journal of pharmacology
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The pressor response to the intracisternal (i.c.) injection of carbachol (1 mug) in anesthetized rats was analyzed. This response was significantly reduced by the intravenous (i.v.) injection of guanethidine (5 mg), hexamethonium (10 mg) or phentolamine (5 mg), and conversely, potentiated by i.v. desmethylimipramine (0.3 mg), while propranolol (0.5 mg) i.v. selectively inhibited the enlargement of pulse pressure and the tachycardia following i.c. carbachol (1 mug). ⋯ The pressor response to i.c. carbachol (1 mug) remained unchanged after sectioning of the bilateral cervical vagal nerves but disappeared after sectioning of the spinal cord (C7-C8). From the above result it is suggested that the pressor response to i.c. carbachol ortral and peripheral adrenergic mechanisms, and that the sympathetic trunk is the main pathway.
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A new theory is presented to describe the effect of functional antagonism on the competitive antagonism between adrenergic beta-mimetics and beta-blockers. According to this theory the shape of the log (dose ratio-1) vs.--log [B] curve and the apparent pA2 value in competitive antagonism should be affected by functional antagonism when the agonist is taken up by the saturable uptake process, and this was experimentally confirmed. ⋯ The log (dose ratio-1) vs. --log [B] curve is ISO-Prop competitive antagonism was shifted variously depending on the concentration of a spasmogen used. Theoretical predictions and experimental results were in good parallel.