RESUMO
The mechanism by which 5-HT produces relaxations of the rat caecum has been examined. Propranolol and cocaine markedly attenuated the relaxations whereas tetrodotoxin had no effect. Higher doses of propranolol and cocaine (greater than 10(-6) M), as well as reserpinization, converted the relaxations into contractions. There was a residual relaxation resistant to propranolol, cocaine and reserpine treatment. High doses of 5-HT (greater than 10(-5) M) were thus thought to relax the rat caecum indirectly, through the release of noradrenaline from the tissue by a tyramine-like action. The relaxations do not seem to be due only to the release of noradrenaline.
Assuntos
Ceco/fisiologia , Contração Muscular , Relaxamento Muscular , Serotonina/fisiologia , Animais , Ceco/efeitos dos fármacos , Cocaína/farmacologia , Técnicas In Vitro , Contração Muscular/efeitos dos fármacos , Relaxamento Muscular/efeitos dos fármacos , Propranolol/farmacologia , Ratos , Reserpina/farmacologia , Antagonistas da Serotonina , Taquifilaxia , Tetrodotoxina/farmacologiaRESUMO
The inhibitory effects of cryptolepine and its interaction with prostaglandin E (2), indomethacin, adrenaline and acetylcholine have been investigated on the isolated rabbit duodenum. Cryptolepine (10-20 microg ml (-1)) or adrenaline (0.5-1 microg ml (-1)) or indomethacin (10-20 microg ml (-1)) abolished or reduced pendular contractions and relaxed the tissue. Cryptolepine (20 microg ml (-1)) produced an initial contraction before relaxation of the tissue. Cryptolepine (10-20 microg ml (-1)) abolished responses of the duodenum to added prostaglandin E (2) and acetylcholine, but failed to reduce prostaglandin production. The results suggested that cryptolepine antagonises prostaglandin, but has no inhibitory effect on its synthesis or release.
Assuntos
Alcaloides/farmacologia , Indóis , Contração Muscular/efeitos dos fármacos , Músculo Liso/efeitos dos fármacos , Sistema Nervoso Parassimpático/efeitos dos fármacos , Quinolinas , Transmissão Sináptica/efeitos dos fármacos , Animais , Feminino , Cobaias , Íleo/efeitos dos fármacos , Técnicas In Vitro , Alcaloides Indólicos , MasculinoAssuntos
Alcaloides/farmacologia , Cálcio/farmacologia , Indóis , Músculo Liso Vascular/efeitos dos fármacos , Norepinefrina/antagonistas & inibidores , Prostaglandinas E/farmacologia , Quinolinas , Animais , Dinoprostona , Feminino , Técnicas In Vitro , Alcaloides Indólicos , Masculino , Artérias Mesentéricas/efeitos dos fármacos , RatosAssuntos
Antagonistas Adrenérgicos alfa , Alcaloides/farmacologia , Indóis , Contração Muscular/efeitos dos fármacos , Músculo Liso/efeitos dos fármacos , Quinolinas , Animais , Técnicas In Vitro , Alcaloides Indólicos , Masculino , Ratos , Sinapses/efeitos dos fármacos , Ducto Deferente/efeitos dos fármacosAssuntos
Antagonistas Adrenérgicos alfa , Alcaloides/farmacologia , Indóis/farmacologia , Plantas Medicinais , Quinolinas , Animais , Alcaloides Indólicos , Masculino , Contração Muscular , Músculo Liso/efeitos dos fármacos , Norepinefrina/antagonistas & inibidores , Ratos , Ducto Deferente/efeitos dos fármacosRESUMO
Decreasing the concentration of sodium in Meng's solution produced a non-parallel shift of the dose-response of acetylcholine on the intestine of the Giant African Snail Achatina fulica. This decrease in sodium decreases the sensitivity of the tissue to acetylcholine and sensitivity was not restored with several washings. The response to decrease calcium is very similar to that of sodium. In the case of potassium however 10% K+ produced less depression in sensitivity than 25% which even caused less depression of sensitivity compared with 50% potassium. The results show an abundance of spare receptors.
