Reward and 2.0 Flashcards
Difference between rewarding and reinforcing?
Reward is a subjective term, reinforcing is objective
Which word is used in place of reward in animals?
Reinforcing
What are symptoms of psychological dependence?
Craving, compul drug use, loss of control
Symptoms of physical dependence?
When stopping a drug causes a withdrawal syndrome
What is tolerance?
When continued use of a drug results in the need for increasing doses for equivalent effect
Who first discovered brain sites where direct electrical stimulation is reinforcing?
Olds and Milner
How did Olds and Milner discover reinforcing brian sites?
Implanted electrodes into different parts of rat brains, Rat was in charge of which parts were stimulated–> idea was that theyd stimulate the reinforcing parts
What is the mesolimbic pathway?
The reward pathway
How were the NTs involved in the mesolimbic pathway determined?
Microdialysis
How does microdialysis work?
Probe is inserted into brain region (tip of probe has dialysis tubing)–> NT that is released from nerve terminals that are where the probe is will enter the tip–> contents are pumped out
Why is dialysis tubing used in NT determination?
It has a semi-permeable membrane
What machine is the solution, acquired as a result of microdialysis, pumped into?
HLPC
Which NT is involved in reward?
Dopamine
Where are the dopaminergic neurones projecting from and to in the mesolimbic pathway?
From the ventral tegmental area to the nucleus accumbens
How does self administration work?
Cannula is implanted into the brain–> anything that is put into the cannula will go straight into the brain, animal can control this
What is the effect of 6-hydroxydopamine?
It is toxic but only to dopaminergic neurons
What happens to animals self-administration of drugs if dopaminergic pathways in the brain are lesioned?
They don’t self administer anymore
What is lesioning a brain pathway?
Using a chemical to turn that pathway off
What happens to animals self-administration of drugs if dopamine D1 or D2 antagonists are used?
They wont self administer anymore
What does an increase of dopamine in the nucleus accumbens feel like?
Euphoric
What does an decrease of dopamine in the nucleus accumbens feel like?
Dysphoric
What was the effect of most drugs of abuse on the amount of dopamine in the nucleus accumbens?
They increased it
Why is it thought that rodents take diazepam?
Reduces their anxiety
How do cocaine and amphetamine increase dopamine levels in the nucleus accumbens?
They are both dopamine reuptake inhibitors
What can amphetamine do that cocaine cant?
Directly cause dopamine release
How is it thought that amphetamine causes dopamine release?
It allows reverse transport through the transporters that usually allow dopamine back into the presynaptic neuron
How do opioids increase the levels of dopamine in the nucleus accumbens?
Inhibit the GABA neurons that would otherwise inhibit the dopaminergic neurons in the ventral tegmental area
How does ethanol increase the amount of dopamine in the nucleus accumbens?
Close K+ channels on the postsynaptic neurons in NA, decreasing hyperpolarisation post one AP meaning APs will fire more frequently
Which class of drugs does ethanol have a similar effect to regarding GABAa receptors?
Benzodiazepines–> it is an allosteric modulator (anxiolytic)
How does nicotine increase dopamine levels in nucleus accumbens?
Nicotine acts on nicotinic ACh receptors on dopaminergic neurons in the VTA, increasing the firing rate so more dopamine is released
How does THC increase dopamine levels in nucleus accumbens?
Acts on cannabinoid receptors which are on GABAergic interneurons–> GI/GO coupled GPCRs–> causes inhibition of the GABAergic neuron so less inhibitory GABA is sent to the dopaminergic neurons in the VTA
