Exogenous Chemicals Alter Synaptic Transmission by Blocking or Enhancing Signals
- Synaptic transmission can be influenced by a variety of exogenous chemicals, such as pesticides, drugs, and other substances.
- These chemicals can either block or enhance the transmission of signals across synapses, affecting the normal functioning of the nervous system.
Neonicotinoids Disrupt Insect Synapses by Prolonged Receptor Activation
How Neonicotinoids Work
- Neonicotinoids are synthetic compounds resembling nicotine.
- They target cholinergic synapses, which use acetylcholine as a neurotransmitter.
- Neonicotinoids bind to nicotinic acetylcholine receptors, much like acetylcholine (the natural neurotransmitter), but they do not get broken down by acetylcholinesterase, leading to prolonged receptor activation.
This blockage causes paralysis and death in insects, making neonicotinoids effective insecticides.
Why Neonicotinoids Are Selective
- Neonicotinoids are more toxic to insects than mammals because:
- Insects have a higher proportion of cholinergic synapses.
- Neonicotinoids bind more strongly to insect receptors than mammalian ones.
Result
- The prolonged activation leads to an interruption in normal synaptic signaling, which can paralyze and kill insects.
- However, the impact on the nervous system of insects can cause death, and exposure to humans and other animals may also lead to harmful effects, particularly in large amounts.
- Students often assume neonicotinoids are harmless to all non-insect species.
- However, their impact on pollinators like bees has raised significant ecological concerns.
Real-World Implications
- Neonicotinoids are widely used in agriculture, but their effects on non-target species, such as bees, have sparked controversy.
- The disruption of synaptic transmission in bees can lead to colony collapse, affecting pollination and ecosystems.
Cocaine Blocks Dopamine Reuptake
How Cocaine Affects Synapses
- Cocaine targets synapses that use dopamine, a neurotransmitter involved in reward and pleasure pathways.
- Cocaine works by blocking the reuptake of dopamine at the synapse.
- Normally, dopamine is released into the synapse and then reabsorbed by the presynaptic neuron through dopamine transporters.
- Cocaine inhibits these transporters, resulting in prolonged dopamine activity in the synapse.
This overstimulation leads to the intense feelings of euphoria associated with cocaine use.
