Toxicology Quiz: Insecticides and Na Channel

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Questions and Answers

What is the treatment for OP intoxication?

Pralidoxime (2-PAM) only

Atropine and pralidoxime (2-PAM) (correct)

Decontamination only

Atropine only

What is the effect of 2-PAM on aged enzyme?

It has no effect on the enzyme

It regenerates the enzyme

It is not effective in regenerating the enzyme (correct)

It accelerates the enzyme's activity

What is the mechanism of action of pyrethrum and pyrethrins?

Voltage-gated calcium channels only

Voltage-gated sodium, calcium, and chlorine channels, as well as benzodiazepine receptor (correct)

GABA agonist action only

Voltage-gated sodium channels only

What is the example of a biological insecticide?

Pyrethrum Signup and view all the answers

What is the treatment for convulsions in OP poisoning?

Diazepam (5 to 10 mg, IV) Signup and view all the answers

Why are oximes not effective in antagonizing the toxicity of carbamoyl ester inhibitors?

They even aggravate the toxicity Signup and view all the answers

What is the primary mechanism of action of pyrethroids in insects?

Keeping Na channels open for a long time Signup and view all the answers

Why are pyrethroids relatively non-toxic to animals and humans?

Because of their rapid detoxification and lack of accumulation Signup and view all the answers

What is the primary effect of rotenone on the respiratory system?

Initial respiratory stimulation followed by depression Signup and view all the answers

What is the mode of action of rotenone on nerve conduction?

Blockage of electron transport in mitochondria Signup and view all the answers

What is the primary mode of action of chlorophenoxy compounds in plants?

Mimicry of auxins, leading to uncontrolled growth Signup and view all the answers

What is the combination of 2,4-D and 2,4,5-T commonly known as?

Agent orange Signup and view all the answers

What is the primary effect of paraquat on the lungs?

Formation of reactive oxygen species (ROS) Signup and view all the answers

What is the primary mode of action of bipyridyl derivatives in plants?

Uncoupling of oxidative phosphorylation Signup and view all the answers

What is a major difference between Organophosphate (OP) insecticides and Organochlorine insecticides?

OP insecticides do not bioaccumulate in tissue or organisms Signup and view all the answers

What is the result of the inhibition of AchE by Organophosphate insecticides?

Accumulation of Ach leading to stimulation of cholinergic synapses Signup and view all the answers

What is the treatment for life-threatening OCl insecticide poisoning?

General decontamination and supportive treatment, along with Diazepam or Phenobarbital Signup and view all the answers

What is the reason behind the increasing use of Pyrethrins as pesticides?

Due to the high toxicity of Organophosphate compounds Signup and view all the answers

What is the effect of repetitive stimulation of the CNS in OCl insecticide poisoning?

Interference with respiratory function and resulting acidosis Signup and view all the answers

Which of the following is NOT an Organophosphate insecticide?

Carbaryl Signup and view all the answers

What is the MOA of Organophosphate and Carbamate insecticides?

Inhibition of AchE Signup and view all the answers

What is the result of the phosphorylation of AchE by Organophosphate insecticides?

Formation of a stable, phosphorylated, and largely unreactive enzyme Signup and view all the answers

Study Notes

Insecticides and Herbicides

Pyrethroids keep Na channels open, causing persistence depolarization
Pyrethroids have low toxicity in animals and humans due to:
- Little storage or accumulation
- Efficient detoxification
- Differences in Na channels, making them more toxic to insects

Rotenone

Causes acute poisoning in animals, characterized by:
- Initial respiratory stimulation
- Followed by respiratory depression
- Ataxia and convulsions
- Death by respiratory arrest
Blocks electron transport in mitochondria by inhibiting oxidation linked to NADH2
Causes nerve conduction blockade
Rare cases of human intoxication

Herbicides

Defined as compounds that can kill or severely injure plants
Used to eliminate plant growth or kill plant parts
Examples:
- Chlorophenoxy compounds (2,4-D, 2,4,5-T, and their salts and esters)
- Bipyridyl derivatives (paraquat and diquat)

Chlorophenoxy Compounds

2,4-D and 2,4,5-T are used to destroy broadleaf weeds
Can be used in combination as Agent Orange
Mimic the action of auxins, hormones that stimulate growth
Uncouple oxidative phosphorylation and decrease oxygen consumption
Less effective in non-target organs

Bipyridyl Derivatives

Paraquat: a non-selective contact herbicide
Highly toxic to lungs
Toxicity is due to formation of reactive oxygen species (ROS)
Diquat: another bipyridyl derivative

Organophosphate (OP) Insecticides

Chronic effect: delayed neurotoxicity (OPIDN)
Treatment: atropine and pralidoxime (2-PAM)
General supportive measures: decontamination, gastric lavage, artificial respiration, and treatment of convulsions with diazepam

Insecticides of Biological Origin

Pyrethrum: extracts from the chrysanthemum flower
Pyrethrins: synthetic derivatives of pyrethrin
Rotenone: extracts from leguminaceae genera

Mechanism of Action

Voltage-gated sodium, calcium, and chlorine channels are possible targets
Benzodiazepine receptor (GABA antagonist action) is also a target

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Description

This quiz covers the mechanisms of toxicology, specifically in relation to insecticides and the sodium channel. Topics include the effects of pyrethroids and rotenone on animals and humans.