cobra

cobra

(records of Guangxi Traditional Chinese Medicine)

[synonym] distended necked snake (Xue de? Systematic zoology), bat snake, five venomous snake, flat headed wind, Pipa snake (vertebrate taxonomy), blown snake, blown turtle, rice shovel head, rice spoon head, Wan snake (Guangxi Chinese medicine records).

[collection] all the viscera of Cobra were removed.

[animal form] Cobra

The total length is about 120 cm. The head is not very big. The ribs between the neck can move, making the neck suddenly expand. The width ratio of snout scale is 1 / 2 times larger than that of other scales. The scales between nose and eyes are not connected. Buccal scales absent. The third and seventh part of the upper lip. There are 8 scales on the lower lip. The nasal scales are divided into anterior and posterior parts with nostrils between them. There are 1 anterior scale and 2-3 posterior scales. The scales on the neck are 24-27 rows, 19-21 rows in the middle of the body and 13-15 rows in front of the anus. There are 164-178 pairs of abdominal scales, 2 pairs of anal scales and 41-51 pairs of inferior caudal scales. There are many variations in all colors and patterns. There are typical white or light yellow eyeglass like markings on the back of the neck; the color of the back of the body is brown, black brown, gray black and dark black; there are 15-16 narrow white or light yellow ring markings on the back and tail. The abdomen is gray or gray black, with small black spots.

It lives in plain and hilly areas, mostly near villages. Every night. It preys on frogs, fish, lizards, scorpions, snakes, rats and birds. When irritated, the front part of the body stands up, the neck expands, and the voice is "whistling". It has strong neurotoxicity. It is distributed in Zhejiang, Fujian, Taiwan, Hunan, Jiangxi, Guangdong, Guangxi, Yunnan, etc.

[collection] before and after the beginning of winter. After catching, laparotomy, remove internal organs and teeth, swab and dry.

[chemical constituents] cobra venom is mainly neurotoxic and has hemolytic effect. In the early years, a crystalline snake venom component, called crotoxin, was isolated, which has the functions of neurotoxin and hemolysin. It is a solid mixture. Its neurotoxin part has been isolated and purified, which is called cobra neurotoxin. It is a small molecular weight protein with sedimentation coefficient of 1.4s and molecular weight of 11000. It is relatively heat-resistant. The cysteine in the molecule is bound to cystine group by - s-s-bond, and it is toxic if it is reduced The toxicity can be recovered after oxidation. In addition, the low molecular weight highly toxic component (LD50 of mice is 0.03 mg / kg) and a heat-resistant component of snake venom (which can not be damaged at 100 ℃ for 30 minutes, but can not tolerate 120 ℃) may be this kind of cobra venom. The hemolysin in snake venom was purified and proved to be lecithinase a. Snake venom also contains cytotoxin, cardiotoxin, a component causing local necrosis (1 mg can produce necrosis 12-23 mm in diameter), cobra factor (an activating factor of complement C "3 pathway in serum), anticoagulant factor, various enzymes (such as cholinesterase, ribonuclease, adenosine triphosphatase), nucleoside acid, cholinesterase inhibitor, etc.

[pharmacological action] ① toxicity to nervous system

Naja naja atra Venom is a mixture of neurotoxins for human and animals. Its effects on the nervous system are extensive and complex, and often have two-way effects, that is, due to different doses, individual differences in animals, or differences in the sensitivity of the nervous system, it shows excitatory or inhibitory effects. The first is the paralysis of ventilator energy, which is the main cause of death. When the breath stops, the heartbeat will continue for several minutes; if the animal is given artificial respiration, the heartbeat can continue for more than 1-2 hours. The reason of respiratory paralysis is that the crude snake venom may have a direct effect on the respiratory center; the refined pure neurotoxin has a peripheral effect. According to the different principles of action, the latter can be divided into three categories: the first category is cobra neurotoxin and a type of snake venom, whose principle of action is the same as that of curare, that is, blocking the effect of acetylcholine on the receptor on the motor end plate; the second category is acetylcholine Two kinds of snake venom act on the presynaptic motor nerve endings, and the third kind is cobra venom, which has both the above two kinds of effects. Snake venom also has significant and extensive effects on autonomic nervous system, especially on carotid sinus chemoreceptors. In carotid sinus perfusion test, low concentration of snake venom can cause short-term respiratory excitation, and then long-term inhibition, and block the response of acetylcholine; high concentration of snake venom can block the response of potassium cyanide. This inhibition may play an important role in the cause of respiratory depression caused by snake venom poisoning. It can excite the cholinergic receptor of adrenal medulla and make adrenaline secrete in large quantity. This may be closely related to the increase of blood pressure, body temperature and blood sugar. When the concentration is high, it can paralyze the sensory nerve endings (the bitten part has numbness) and reduce or block the impulse conduction of the nerve trunk. It can also increase the tension of isolated intestinal muscle and inhibit the isolated heart, which indicates that snake venom also has certain effect on muscarinic receptor. In the experiment of acetylcholine synthesis, snake venom can inhibit choline acetylase and exert toxic effect on central nervous system. It can block the reaction of rectus abdominis muscle to acetylcholine, which is more than two times stronger than that of tubuline chloride. Neostigmine can eliminate this effect.

② Toxicity to circulatory system

Although respiratory paralysis is the first cause of death caused by cobra bite, most of the patients with mild poisoning or respiratory depression have presented myocardial damage and ECG changes of myocarditis. Moreover, the patients with severe cobra bite poisoning have developed severe shock even before respiratory depression. Therefore, the toxicity to the circulatory system is also poisoning The important factor of death can not be ignored. After the injection of snake venom into dogs, the change of blood pressure can be roughly divided into three stages: early stage - the rapid decline of blood pressure. This may be due to the formation of lysophosphatidase after the phospholipase contained in snake venom enters the body, leading to the rupture of tissue cells and the release of histamine, bradykinin, serotonin and adenosine. A large amount of histamine is released, which causes pulmonary vasoconstriction, pulmonary arterial pressure rise and pulmonary circulation resistance increase. In addition, histamine and bradykinin cause capillary dilation, resulting in relatively insufficient circulating blood volume and reduced cardiac output. In the early stage, snake venom can strengthen and accelerate cardiac contractility, which may be a kind of compensation rather than a real cardiotonic effect. As for the direct excitatory effect on isolated rabbit heart and frog heart (so-called digitalis like effect), it is estimated that there is no significant effect on the whole. Medium term - due to the body's anti damage effect, play compensation, make blood pressure gradually rise, at this time, respiratory and circulatory functions are in a relatively stable state. In the late stage, respiration is inhibited and gradually turns to paralysis. Due to hypoxia, blood pressure often rises briefly. Under the condition of artificial respiration, cardiac contractility gradually weakens, heart rate slows down, blood pressure continues to drop, arrhythmia occurs and heart failure dies. The cause of heart failure is the direct toxicity of snake venom to the heart. In the early stage of ECG, myocardial damage such as ST segment depression, T wave flat or inverted, QT interval prolongation and R wave low voltage can be found. In the late stage, severe arrhythmias such as atrial or ventricular premature contraction, bundle branch block, ventricular paroxysmal tachycardia, ventricular rhythm or ventricular pause can also be found. The pathological section showed the pathological changes of acute interstitial myocarditis, such as extensive myocardial edema, focal necrosis, subendocardial hemorrhage. Cobra venom can dilate coronary artery. The pure "cardiotoxin" isolated from Naja naja atra Venom is a kind of strong basic polypeptide with high content, accounting for 25-40% of the dry weight of the snake venom. It is extremely toxic to the heart of mammals, but its lethality is only 1 / 20 of the neurotoxicity. Its primary effect is depolarization of cell membrane, which makes the heart stop during systole.

③ The role of enzymes

Snake venom itself contains many enzymes, which can cause serious toxicity to the body. The important ones are lecithinase, which can cause hemolysis and histamine release, invade capillary wall cells, cause pulmonary hemorrhage and ventricular fiber tremor to tetanic contraction, directly damage nervous system (respiratory depression, coma), etc.; proteolytic enzyme, which can damage vascular wall, cause severe hemorrhage, tissue damage, and even cause bone tissue necrosis. At the same time, it can release histamine and other substances, and affect nerve function. Phosphatase and phosphodiesterase can hydrolyze adenosine triphosphate in the body, leading to its deficiency and so on. In addition, snake venom can also inhibit the activities of some important enzyme systems.

④ Effects on blood

There were no significant changes in erythrocyte, hemoglobin and hematocrit in dogs and rabbits died of cobra venom poisoning, indicating that there was no blood concentration. Cobra venom can prolong the clotting time of experimental animals (rabbits), and the clotting time is more significantly prolonged by adding snake venom in vitro, which can explain the bleeding tendency of patients bitten by snakes. For the whole animals, cobra venom can increase the fragility of red blood cells, but there is no hemolysis phenomenon, and it has no effect on the production of oxyhemoglobin. It can increase blood glucose in dogs, cats, rabbits and mice, which may be related to the release of epinephrine, but it can decrease blood glucose in rats. It has no constant effect on the total number and score of leukocytes in animals. In clinic, some cases seem to have increased eosinophils. In the glass dish, the hemolytic concentration of Naja atra Venom was 0.0 million 00001 (rabbit) or 0.0 million 001 (dog).

⑤ Effect on endocrine

Snake venom poisoning can cause significant changes in the adrenal cortex. For example, taking the LD50 of mice as the index, all kinds of adrenal cortical preparations can effectively improve the tolerance of animals to naja atra Venom, but the tolerance of adrenalectomized animals is significantly decreased. The supplement of corticosteroids can increase the tolerance to the level of normal animals, and the addition of chlorpheniramine can further improve the tolerance

Chinese PinYin : Yan Jing She