Central nervous system , insecticides action

The tobacco compound nicotine has been used as an insecticide for over 200 years. It is especially effective against sucking insects, such as aphids, and has excellent contact activity. Related compounds are neonicotinoids (e.g., imidacloprid), which have similar insecticidal activity, but are less toxic to mammals. Nicotine and imidacloprid mimic the action of acetylcholine, which is the major excitatory neurotransmitter in an insect s central nervous system. The action of acetylcholine is stopped by the enzyme acetylcholinesterase, which rapidly breaks down acetylcholine. Nicotine and imidacloprid are also neuroexcitatory, but do so persistendy, since they are not affected by acetylcholinesterase. Overstimulation of the nervous system often leads to convulsions, paralysis, and death. 

Neonicotinoids are potent broad-spectrum insecticides that exhibit contact, stomach and systemic activity. Acetamiprid, imidacloprid, nitenpyram, thiamethoxam and thiacloprid are representatives of the neonicotinoid insecticides (Figure 1). The mechanism of action is similar to that of nicotine, acting on the central nervous system causing irreversible blocking of postsynaptic nicotinic acetylcholine receptors (nAChR). Neonicotinoid insecticides are often categorized as antagonists of the... 

Lindane, the y-isomer of HCH, is a potent insecticide. Its insecticidal action is due to a hyperexcitatory effect on the insect s central nervous system induced by accumulation of acetylcholine in the synaptic region 73). We prepared a number of analogs in which some of the chlorine atoms are replaced by other substituents while maintaining the -configuration and determined their insecticidal activity against mosquitos74,). 

In spite of the smaller ratio of nicotinic to muscarinic receptors in the brain, nicotine and lobeline (Figure 7-3) have important effects on the brainstem and cortex. The mild alerting action of nicotine absorbed from inhaled tobacco smoke is the best-known of these effects. In larger concentrations, nicotine induces tremor, emesis, and stimulation of the respiratory center. At still higher levels, nicotine causes convulsions, which may terminate in fatal coma. The lethal effects on the central nervous system and the fact that nicotine is readily absorbed form the basis for the use of nicotine as an insecticide. Dimethylphenylpiperazinium (DMPP), a synthetic nicotinic stimulant used in research is relatively free of these central effects because it does not cross the blood-brain barrier. 

The powerful action of some natural products on the central nervous system may suggest their potential value in insect control. If their mammalian toxicity can be reduced by structural modification they may be useful insecticides. Cartap, a rice insecticide, is a bisthiocarbamate. Its structure was based on that of the natural product, nereistoxln, a neurotoxin isolated from shellfish, and it is likely that an in vivo metabolic conversion of cartap to nereistoxln or related compound is responsible for its activity (11). 

Etofenprox is an insecticide with an action similar to pyrethroids, which act predominantly on the central nervous system. It may be hazardous if swallowed. Do not inhale spray mist. Avoid skin contact wear protective gloves, clean protective clothing and a face mask (surgical type) when handling the product. Wash hands and exposed skin thoroughly after using. 

Many pyridazine derivatives were tested for analgesic activity,162,487,834-840 for antimicrobial,841-845 tuberculostatic,846,847 and hypoglycemic activity as antidiabetics,848,849 for activity on the central nervous system,850 for anticoccidial,851 insecticidal.852 and fugicidal activity,853 for inhibition of mitochondrial monoamine oxidase,854 for their action on the metabolism of rat cerebral cortex slices,855,856 and against the enzyme... 

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