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The present data on the extracts of C. procera indicate a direct action on the myocardium, stimulatory effect on smooth muscle motility, and relaxant action on skeletal muscle contraction. Chemical constituents could directly affect the cell membrane probably through receptors coupling to G proteins. They regulate the ion channel physiology as in the myocardium.

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1 The effect of Egyptian cobra (Naja haje) venom on the normal electrical activity of the cardiac muscles (ECG) and arterial blood pressure of envenomated rats were investigated in this study. 2 Rats were divided into three groups. The first group was injected im with saline and considered as control group. Rats of the second and third groups were injected IM with 0.02 μg and 0.04 μg cobra venom/ gim b.wt, respectively. 3 Mean blood pressure (MBP), heart rate (HR) and four different ECG parameters (PR and QT intervals, R and T wave amplitudes) were measured over 1 h following envenomation. 4 The low dose (0.02 μg/g) of N. haje venom caused hypotension accompanied by an increase in the HR, whereas hypertension and bradycardia developed after injection of the high dose (0.04 μg/g) of venom. 5 There was a decrease in the P-R interval after administration of the low dose and prolongation of it after the high dose. The Q-T interval and R-wave amplitude were significantly increased after injection of both doses. T-wave amplitude was significantly elevated only after injection of the high dose. 6 The present results indicate that the Egyptian cobra (N. haje) venom significantly alters the arterial blood pressure and ECG parameters of envenomated rats. This suggests that impairment of the electrical activity of cardiac muscle may be one of the reasons why victims of cobra bite die.

The Buthid scorpion Leiurus quinquestriatus is divided into two sub-species whose region of contact occurs at the Suez Isthmus. L.q. quinquestriatus, found in the North Africa is distinguished from L.q. hebraeus by minor differences in morphology. Despite the very high similarity in body plan, out of the 24 toxins isolated from this species none is common to both sub-species, suggesting a degree of molecular divergence not apparent at the morphological level. We show, by comparison with two sets of reference proteins from humans and Old-World monkeys, that divergence of toxins with common structures and functions in these two subspecies has occurred under conditions of strong negative selection.