BIOLOGICAL - EFFECT OF RECREATIONAL DRUGS ON NEUROTRANSMITTERS

Question 1

recreational drugs: reward pathway

Answer 1

what is the reward pathway?
->when you are being rewarded, the brain is also rewarded
->when we experience pleasure, dopamine is produced in the VTA
->dopamine goes to the amygdala and the nucleus accumbens (motor functions) then to the PFC for actions and attention, and the hippocampus to create memories
->when you experience drugs, your body experiences pleasure and your body wants to do it again

Question 2

recreational drugs: heroin

Answer 2

how does heroin impact neurotransmission?
->heroin binds to the presynaptic neurons that use dopamine as a NT
->heroin acts at the opioid receptor sites in the brain. It changes the action of dopamine in the reward pathway of the brain, releasing more dopamine than usual
->the morphine binds to receptors to reduce the inhibitory effect of GABA on dopamine neurons (those that release dopamine)
->the result is more dopamine activity and increased release of dopamine into the synaptic cleft. If the dopaminergic reward pathway continues to be stimulated, leading to feelings of euphoria

how does the drug change behaviour short term?
->during every day activity, a moderate amount of endorphin is naturally produced, causing the release of dopamine and facilitates the reward system in the brain
->the heroin floods the endorphins (to help dopamine release). Large quantities of dopamine are released, activating the reward system and producing feelings of well-being

what are the long term effects of heroin on neurotransmission?
->over prolonged use, the brain adapts to high levels of dopamine and slows down its own natural production, explaining why higher doses of heroin are needed

Question 3

recreational drugs: amphetamines

Answer 3

how does this drug impact neurotransmission?
->amphetamines temporarily prevent NTs from being recycled. This makes euphoria last longer. Depending on the type of amphetamine and how much is consumed, the euphoric effects can last anywhere from 4-24 hours
->the main impact of this drug on the brain is that it increases the concentration of dopamine in the synaptic gap. It is similar to dopamine in terms of its structure and therefore it is able to enter the terminal button of the synaptic neuron
->amphetamines may also excite dopamine neurones via the glutamate neurones as these NTs are very much linked and interact with one another. Amphetamines may reduce these inhibitory effects that glutamate has on dopamine, thus making the dopamine neuron more readily excitable

how does this drug change behaviour short term?
->when the euphoric effects of the drug end, because the NTs are no longer stimulated, the user can experience depression-like symptoms
->this may cause someone to abuse amphetamines to avoid such feelings, leading to psychological dependence
->this is a perceived need for a substance, which may require rehabilitation, involving being taught skills and coping mechanisms to deal with cravings for a substance

what are the long term effects of amphetamines on neurotransmission?
->over time, dopamine receptors will become damaged/desensitized because of overstimulation
->this will lead to addiction because more dopamine will be required to stimulate the neuron to a normal level

Question 4

evaluation of the effect of recreational drugs on neurotransmission

Answer 4

STRENGTHS:
->research into the biological effects of recreational drugs provides support for other approaches (eg. causes of SZ)
–>amphetamines cause an increase in the NT dopamine, which causes hallucinations. Symptoms of SZ include auditory and visual hallucinations, showing a connection between the two, so SZ is caused by an increase in dopamine
–>therefore, making SZ research more reliable

->Olds and Milner (1954)
–>studied the pleasure centre of the brain in rats by connecting wires to their brains and giving a pleasurable electric shock upon pressing a lever
–>they made an association between the source of pleasure and the rats pulling the lever (C&E)

WEAKNESSES:
->most drug studies use animal studies, which is unethical
–>animal studies should not be conducted unless it is impossible to do so otherwise, but this isn’t the case with drug studies as they can easily be conducted on human volunteers
–>therefore, causing animals unnecessary harm

->not only are animal studies unethical, but they’re also not practical
–>animals are less advanced than humans biologically, so the way animals may react is likely to be different to how humans would react. Humans also live much more complex lives than animals, so the impact of drugs in different every day situations cannot be gauged when we only test on animals
–>therefore, the results are not generalisable to humans