Effects of Exogenous Chemicals
Neonicotinoids
- Neonicotinoids are synthetic compounds similar to nicotine that are commonly found in pesticides
- Neonicotinoids can block synaptic transmission at cholinergic synapses in insects by binding to acetylcholine receptors
- This binding is irreversible, as acetylcholinesterase cannot break down neonicotinoids
- As the acetylcholine receptors are blocked, acetylcholine is unable to bind, which stops impulses from being transmitted across synapses
- This leads to paralysis and death in insects
- Neonicotinoids are considered to be especially suitable as pesticides because they're not toxic to humans and other mammals
- A much larger proportion of synapses in insects are cholinergic compared to mammals
- Neonicotinoids bind much more strongly to acetylcholine receptors in insects
- There is a great deal of controversy over the use of neonicotinoid pesticides because of the impact that they are thought to have on essential pollinators such as bees
Cocaine
- Cocaine is a drug which blocks the reuptake of neurotransmitters into the presynaptic knob
- Primarily cocaine affects reuptake of dopamine as it binds to the dopamine transporter protein
- This prevents dopamine from binding to the transporter so it is not able to move through the membrane back into the presynaptic neurone
- As a result dopamine builds up in the synapses which can lead to feelings of pleasure
- Cocaine also blocks the neurotransmitters serotonin and norepinephrine which enhances feelings of confidence and energy
- In regular users of cocaine, the brain responds by increases numbers of dopamine receptors to respond to the high levels of dopamine
- Once levels return to normal, more dopamine receptors results in increased sensitivity and depression