Effects of phosphodiesterase inhibitors on spontaneous electrical activity (slow waves) in the guinea-pig gastric muscle.

AUTOR(ES)

Tsugeno, M

RESUMO

1. The effects of the phosphodiesterase inhibitors caffeine, theophylline, isobutylmethylxanthine (IBMX) and rolipram on spontaneous electrical activity (slow waves) were studied in the circular muscle of the guinea-pig gastric antrum. 2. All the inhibitors reduced slow wave frequency without changing the membrane potential and the slow wave configuration, but at higher concentrations they blocked the slow waves and caused membrane hyperpolarization. In the presence of the inhibitors a low level of irregular electrical activity could be observed in many preparations. 3. Isoprenaline, forskolin, dibutyryl cAMP and 8-bromo-cAMP all produced effects essentially similar to those of phosphodiesterase inhibitors. K+ (12 mM) and removal of K+ both depolarized the membrane and these were not affected by IBMX (1-3 microM). A decrease in frequency caused by IBMX was also not significantly affected by 12 mM K+ or K+ removal and only partially antagonized by TEA or 4-aminopyridine. 4. These results suggest that an increase in intracellular cAMP inhibits pacemaker activity of slow waves. An increase in K+ conductance does not seem to be a major factor in this inhibition. Slow waves appear to be a compound electrical activity in a group of muscle cells and are likely to be disintegrated by xanthine derivatives.

Documentos Relacionados

• Role of K+ channels in spontaneous electrical and mechanical activity of smooth muscle in the guinea-pig mesotubarium.
• The effects of vasopressin on electrical activity in the guinea-pig supraoptic nucleus in vitro.
• Spontaneous electrical and contractile activity correlated to 86Rb+ efflux in smooth muscle of guinea-pig mesotubarium.
• Effect of extracellular calcium on contractile activation in guinea-pig ventricular muscle.
• The effects of papaverine on the electrical and mechanical activity of the guinea-pig ureter.