Modulatory effects of diltiazem on inotropic responses to amrinone on rabbit isolated atria.

The effect of pretreatment with graded concentration of diltiazem on the inotropic responses to amrinone were studied on isolated atria of rabbit. The responses to amrinone were modified by diltiazem in a biphasic manner; initial potentiation followed by inhibition. The potentiation is proposed to be due to synergistic rise in cytosolic calcium ion concentration by diltiazem and amrinone. The inhibition by diltiazem in higher concentration may be due to blockade of calcium ion influx and depletion of intracellular calcium ion from storage sites.

Interaction of ciprofloxacin with diclofenac and paracetamol in relation to it's epileptogenic effect.

A number of fluoroquinolones have shown convulsive potential. The effect of Ciprofloxacin was studied in electroconvulsive seizures in mice using the tonic extensor phase as end point and seizure threshold as observational parameter. Its interaction with diclofenac and paracetamol was also studied. It was found that Ciprofloxacin produced a significant epileptogenic effect. This was potentiated by diclofenac but paracetamol had no such effect. Though the exact mechanisms involved in this effect are conjectural, role of GABA inhibitory mechanisms is a possibility.

Noradrenaline release by nicotinic acid.

In doses (from 100 mug to 1 mg) nicotinic acid produced positive inotropic and chronotropic action on isolated frog heart. This effect was blocked by pronethalol and guanethidine administration. This effect was not observed in reserpinised frogs. Repeated administration of the same dose of nicotinic acid caused development of tachyphylaxis, in frog's heart preparation. The observations indicate that nicotinic acid induced a release of noradrenaline in frog's heart. On other preparations, such as isolated rabbit heart, rabbit's intestine and guinea pig seminal vesicles, nicotinic acid produced a nonspecific direct depressant action.