Drugs and the Brain

Question 1

Psychoactive Drugs

Answer 1

can affect several processes at the level of the synapse

Question 2

Law of Mass Action

Answer 2

The response is proportional to the fraction of receptors occupied at any given moment. If the drug is in high amounts - tolerance may occur. Homeostatic adjustment.

Question 3

Agonistic Drugs

Answer 3

Mimics the actions of neurotransmitters

Question 4

Antagonistic Drugs

Answer 4

Oppose or block the action of neurotransmitters

Question 5

Acetylcholine

Answer 5

Is a stimulant.
1st neurotransmitter discovered. Neurotransmitter for motor neurons involving voluntary movement (attention, arousal and memory).
- venom of black widow spider: stimulates release of ACh causing massive post synaptic potentials. Symptoms –> massive rigidity in the abdomen and chest.
- botulinum toxin: prevents release of ACh despite neural firing. Symptoms —> weakness and paralysis.

Question 6

Nicotine

Answer 6

Stimulant.

Stimulates some post synaptic ACh receptors.

Question 7

Curare

Answer 7

block post synaptic receptors

depletion of ACh observed for individuals suffering from Alzheimer’s disease.

Question 8

Dopamine (DA)

Answer 8

Neurotransmitter involved with the instructions for the control of voluntary movements and reward centres.
- degeneration of DA neurons leads to Parkinsonism (tremors, rigidity, reduced control)

Question 9

Dopamine

• –> Cocaine
• –> Amphetamines

Answer 9

Cocaine: a stimulant that blocks reuptake producing more post synaptic DA potentials.
Amphetamines: stimulants that both increase release of DA and block reuptake.
Continued use of amphetamines can cause positive symptoms of schizophrenia (hallucinations, paranoia). And continued use causes depletion of naturally produced dopamine.

Question 10

Dopamine and Schizophrenia

Answer 10

Overactive DA synapses —> positive symptoms of schizophrenia (dopamine hypothesis)
anti-psychotic drugs: bind to post-synaptic receptors (eg. chlorpromazine) and reduce post-synaptic potentials. Relieve the positive symptoms of the schizophrenia. Produce parkinsonism symptoms as a side effect.

Question 11

Norepinephrine (NE)

Answer 11

Cocaine and amphetamines also block reuptake at NE synapses.
Implicated as a mechanism for mood disorders.
Increase activity produces mania
Decrease activity produces depression —> accounts for emotional crash after drug abuse.

Question 12

Serotonin

Answer 12

Neurotransmitter involved in the regulation of sleep and wakefulness.
Decrease activity observed during sleep.
Increase activity observed during wakefulness.
Low levels of serotonin –> depression and obsessive-compulsive disorder.
Prozac: anti-depressant drug that interferes with re-uptake of serotonin. Also affects other neurotransmitters (so called dirty drug).

Question 13

GABA Calms

Gamma-aminobutyric acid

Answer 13

GABA produces IPSPs
Receptors widely distributed throughout the brain
GABA activity regulates anxiety by keeping overall neural excitement in check. Reduced levels of GABA activity —> feelings of anxiety and anxiety disorders.
Barbiturates and benzodiazepines: attach to GABA receptors and facilitate the binding of GABA itself. Produces increased IPSPs (ie. sedation and reduced anxiety).