RESUMEN
Intravenous injection of substance P (SP) increases blood pressure in normotensive rats by stimulating sympathetic ganglia. This study compared the effects of SP to increase renal nerve firing and blood pressure in normotensive and hypertensive rats treated with chlorisondamine. The increase in renal nerve firing was greatest in spontaneously hypertensive rats (SHR), intermediate in Wistar rats, and least in Wistar-Kyoto (WKY) rats. Blood pressure was increased more in SHR than in Wistar rats. Blood pressure was not increased in WKY rats. Responses to the ganglionic stimulant 1,1-dimethyl-4-phenylpiperazinium were the same in the three strains. These results suggest that there is a selective increase in the action of SP on sympathetic ganglia of SHR and that ganglion responsiveness to SP is correlated with its effect on blood pressure.
Asunto(s)
Ganglios Simpáticos/fisiología , Riñón/inervación , Sustancia P/fisiología , Animales , Presión Sanguínea/efectos de los fármacos , Presión Sanguínea/fisiología , Yoduro de Dimetilfenilpiperazina/farmacología , Estimulantes Ganglionares/farmacología , Frecuencia Cardíaca/efectos de los fármacos , Frecuencia Cardíaca/fisiología , Inyecciones Intravenosas , Masculino , Ratas , Ratas Endogámicas WKY , Ratas Wistar , Especificidad de la Especie , Sustancia P/farmacologíaRESUMEN
Secretin and VIP stimulate cardiac adenylyl cyclase activity and exert a positive inotropic action in several mammalian species. This study examined positive inotropic activity and cAMP levels in rat papillary muscle. Isoproterenol and secretin increased contractions by 150+/-31% and 129+/-27%, respectively. VIP increased contraction by 30+/-21% only at 10 microM. Isoproterenol significantly increased cAMP levels by 82%, whereas increases by secretin (58%) and VIP (56%) were not significant. These results are consistent with reports that secretin and VIP stimulate cardiac adenylyl cyclase in the rat, but suggest that cAMP tissue levels cannot totally explain the positive inotropic responses to secretin and VIP.
Asunto(s)
Cardiotónicos/farmacología , AMP Cíclico/análisis , Músculos Papilares/efectos de los fármacos , Secretina/farmacología , Péptido Intestinal Vasoactivo/farmacología , Animales , Relación Dosis-Respuesta a Droga , Femenino , Isoproterenol/farmacología , Masculino , Contracción Miocárdica/efectos de los fármacos , Ratas , Ratas Sprague-DawleyRESUMEN
Intravenous injection of 3-33 nmol/kg of substance P (SP) caused pressor and tachycardic responses in anesthetized rats. The responses were not blocked by a ganglion nicotinic receptor antagonist or by pithing. Pretreatment with reserpine blocked both responses. beta-Adrenoceptor blockade attenuated only the tachycardic response, and alpha-adrenoceptor blockade attenuated only the pressor response. These findings indicated that the effects of SP to increase blood pressure and heart rate are due to sympathetic ganglion stimulation. Studies with adrenalectomized rats showed that stimulation of the adrenals by SP contributes to both responses but makes a greater contribution to the tachycardic response. These observations raise the possibility that the tachykinin innervation of sympathetic ganglia and the adrenal medulla may be involved in the local regulation of blood pressure and heart rate.
