Some pharmacological studies on the effects of Cerastes vipera (Sahara sand viper) snake venom

Venom effects on monoaminergic systems

The monoamines, dopamine, epinephrine, histamine, norepinephrine, octopamine, serotonin and tyramine serve many functions in animals. Many different venoms have evolved to manipulate monoaminergic systems via a variety of cellular mechanisms, for both offensive and defensive purposes. One common function of monoamines present in venoms is to produce pain. Some monoamines in venoms cause immobilizing hyperexcitation which precedes venom-induced paralysis or hypokinesia. A common function of venom components that affect monoaminergic systems is to facilitate distribution of other venom components by causing vasodilation at the site of injection or by increasing heart rate. Venoms of some scorpions, spiders, fish and jellyfish contain adrenergic agonists or cause massive release of catecholamines with serious effects on the cardiovascular system, including increased heart rate. Other venom components act as agonists, antagonists or modulators at monoaminergic receptors, or affect release, reuptake or synthesis of monoamines. Most arthropod venoms have insect targets, yet, little attention has been paid to possible effects of these venoms on monoaminergic systems in insects. Further research into this area may reveal novel effects of venom components on monoaminergic systems at the cellular, systems and behavioral levels.

Effect of suramin on myotoxicity of some crotalid snake venoms

We investigated the protective effect of suramin, an enzyme inhibitor and an uncoupler of G protein from receptors, on the myotoxic activity in mice of different crotalid snake venoms (A.c. laticinctus, C.v. viridis, C.d. terrificus, B. jararacussu, B. moojeni, B. alternatus, B. jararaca, L. muta). Myotoxicity was evaluated in vivo by injecting im the venoms (0.5 or 1.0 mg/kg) dissolved in physiological saline solution (0.1 ml) and measuring plasma creatine kinase (CK) activity. Two experimental approaches were used in mice (N = 5 for each group). In protocol A, 1 mg of each venom was incubated with 1.0 mg suramin (15 min, 37 degrees C, in vitro), and then injected im into the mice at a dose of 1.0 mg/kg (in vivo). In protocol B, venoms, 1.0 mg/kg, were injected im 15 min prior to suramin (1.0 mg/kg, iv). Before and 2 h after the im injection blood was collected by orbital puncture. Plasma was separated and stored at 4 degrees C for determination of CK activity using a diagnostic kit from Sigma. Preincubation of some venoms (C.v. viridis, A.c. laticinctus, C.d. terrificus and B. jararacussu) with suramin reduced (37-76%) the increase in plasma CK, except for B. alternatus, B. jararaca or L. muta venoms. Injection of suramin after the venom partially protected (34-51%) against the myotoxicity of B. jararacussu, A.c. laticinctus and C.d. terrificus venom, and did not protect against C.v. viridis, L. muta, B. moojeni, B. alternatus or B. jararaca venoms. These results show that suramin has an antimyotoxic effect against some, but not all the North and South American crotalid snake venoms studied here.

Toxins 'R' Us: more pharmacological tools from nature's superstore

Conus venoms from marine cone snails continue to provide novel bioactive components. Two new classes of conopeptide specifically block alpha(1)-adrenoceptors (rho-conopeptide) and noradrenaline transporters (chi-conopeptides). Both classes are small peptides with two disulfide bonds. Rho-conopeptide is structurally similar to alpha-conotoxins, which block nicotinic acetylcholine receptors, whereas the chi-conopeptides are unrelated to other conotoxins. Both types of conopeptides are non-competitive blockers. Because these peptides demonstrate greater selectivity than current drugs in clinical use, they could lead to the development of improved therapeutics.

Purification of a 5-HT uptake inhibitor from the venom of Cerastes vipera

A protein that inhibits the re-uptake of 5-hydroxytryptamine into rat brain synaptosomes was isolated from the venom of the Sahara sand viper (Cerastes vipera) by gel filtration and reverse phase chromatography. It has a molecular weight of 13,739 Da and an IC50 of about 50 nM for blocking uptake of 3H-5-HT into rat brain synaptosomes. It also augmented the responses to 5-HT in a smooth muscle preparation. It has phospholipase A2 activity, but it has no lytic activity as measured by its inability to release lactate dehydrogenase from rat brain synaptosomes. Determination of the N-terminal sequence revealed a similarity with a phospholipase A2 previously isolated from Cerastes cerastes venom.