The effects of gaboon viper (Bitis gabonica) venom on voltage-clamped single heart cells.

The effects of crude B. gabonica venom on single ventricular myocytes from guinea-pig hearts were studied using the patch clamp technique in the 'whole cell' mode. Irreversible effects on the membrane currents, which became prominent within 15 min of venom application, were: (1) a decrease in the time invariant current (associated with the inward rectifying K+ current), most clearly seen over a voltage range negative to the resting membrane potential; and (2) a decrease in the peak inward current (associated with the Ca2+ current) elicited by steplike depolarizations from a holding potential of -40 mV.

The effects of Gaboon viper (Bitis gabonica) venom on the electrical and mechanical activity of the guinea-pig myocardium.

The effects of Bitis gabonica venom were tested on guinea-pig heart, using both Langendorff preparations and isolated atrial strips or papillary muscles. In the self-paced whole heart, a single passage of 50 micrograms of venom per ml produced in sequence: irregularities of the A-V conduction and decrease of the contractile strength, progressive failure to relax and systolic arrest of the heart. Pretreatment with atropine reduced but did not abolish these effects.

[Postnatal variations in the electrophysiological characteristics of the mouse heart].

Electrocardiograms were recorded in 13 mice, from birth up to 57 days of age; during this period the heart rate, at rest, showed a marked increase (from 310 to 797 beats/min), occurring in two waves. Recordings of the intracellular electrical activity in the atria disclosed a different temperature dependence of the resting membrane potential, action potential duration and Vmax in the neonatal mouse as compared with the adult one. The results are consistent with the suggestion that a decrease of the 'slow inward' conductance/K+ outward conductance ratio still occurs during a postnatal period.

Effect of Bitis gabonica venom on the action potentials of guinea-pig heart. Preliminary results.

The effect exerted by different doses (50 to 500 mg/kg body weight, or 1 or perfusing solution) of the lyophilised secretion of B. gabonica venom glands has been studied -by intracellular electrodes- on the electrical activity of atrial and ventricular cells from guinea-pigs hearts, by using both open-chested animals and isolated preparations. Noticeable changes in the features and duration of the repolarization phase of the action potentials precede the abolition (reversible, after washing) of the contractile activity.

Calcium-dependent action potentials elicited in the lizard ventricle by a prolonged hypothermic incubation.

After a prolonged hypothermic incubation (48 h at 4 degrees C), lizard ventricles perfused with a solution containing 15 mM k+ and 1 mM Ca2+ exhibit slow responses, which are similar (prescinding from their noticeable greater duration) to the responses which can be elicited, in the same depolarizing solution, by increasing the external calcium concentration or by adding catecholamines to the perfusing medium. The phenomenon is transient, and vanishes within 90 min from the end of the hypothermia.