WK 11 bb Flashcards
Substance abuse is a pattern of drug use in which
people rely on a drug chronically and excessively and not for therapeutic reasons
addiction or dependance =
physically dependant on a drug in addition to abusing it
Reinforcing stimuli have a greater effect if
it occurs immediately after the behaviour
Positive Reinforcement: Neural Mechanisms
- triggers release of dopamine in the nucleus accumbens (NAC)
- process of addiction begins in the mesolimbic dopaminergic system
- produce long term changes in other brain regions, starting with the ventral tegmental area (VTA)
Function of dopamine pathway
- REward (motivation)
- Pleasure, euphoria
- Motor functioning (fine tuning)
- Compulsion
- Perseveration
Function of seotonin pathway
- mood
- memory processing
- sleep
- cognition
changes in VTA leads to
(positive reinforcement process from drugs)
does this happen immediately
what other areas does this affect
increased activation in a variety of regions that receive dopaminergic input from the VTA
Synaptic changes that are responsible for the
compulsive behaviours that characterise addiction occur only after continued use.
- Important changes occur in the dorsal striatum which is part of the basal ganglia
- The basal ganglia plays a critical role in instrumental conditioning
- Withdrawal symptoms
– generally the opposite of the drug itself
– the body may have started to compensate for the
disturbed homeostatic mechanisms
Negative Reinforcement and addiction
potentially maibtains addiction e.g. removes withdrawal symptoms
can start addiction, e.g. remove stressors
Cravings can occur after a long period of abstinence.
* Potentially due to
ong-lasting brain changes
* Drug-related stimuli can elicit classically conditioned responses in substance abusers, both physiologically and subjectively - cravings
Franken (2003) suggests craving and relapse are due to
‘attentional bias’ – cued by cognitive processes and increases in dopamine in response to drug
stimuli.
Drug stimuli as in things related to drug use. even weather can cause a dopamine increase, thus intensifying the cravings
Prefrontal cortex has been implicated in drug abuse e.g.
prefrontal cortex activity decreases as drug use increases
Either way, PFC plays an important rol in drug use through ____ ______ and ____ ________ (Goldstein & Volkow, 2011)
emotion regulation
inhibitory control
_______ is the most commonly abused opiate
and abuse comes with high personal and
societal costs.
Heroin
Systematic administration of opiates
stimulates _____ ______
causing which effects
opiate receptors
- analgesia [pain relief] (periaqueductal grey matter)
- Hypothermia (Preoptic area)
- Sedation (Mesencephalic reticular formation)
- Reinforcement (VTA and nucleus accumbens)
Opiate related stimuli trigger the release of …
dopamine in the nucleus accumbens (NAC)
process of action of Cocaine
Deactivates dopamine transporter proteins, blocking reuptake of dopamine
how do Amphetamines work
also inhibit reuptake of dopamine but directly simulates the release of dopamine from terminal buttons as well
cocaine Likely highly addictive – Bozath & Wise (1985) reported that rats that self-administered cocaine were
3 times more likely to die than rats who self-administered heroin
- Smoking stimulates
nicotinic acetylcholine receptors
Nicotine is associated with the release of … in the … resulting in …
dopamine in the
NAC, reinforcing the behaviour (Jasinka et al., 2014)
- It has also been noted that damage to the ____ disrupts smoking addiction
insula
- Potential effects of Alcohol
– Mild euphoria
– Anxiolytic: reduces the discomfort of anxiety
– Disinhibition
– Alcohol myopia (Steel & Josephs, 1990; MacDonald et
al., 1998)
– Alcohol myopia
- tendency for people to respond to near and immediate cues while ignoring more remote cues and potential consequences
alcohol Increases activity in the dopaminergic neurons of the ______ system
mesolimbic
Two major sites of action alcohol
– Indirect antagonist at NMDA (glutamate) receptors
– Indirect agonist at GABAA
receptors (anxiolytic and sedative effects)
why can alcohol withdrawals kill you
Increased sensitivity of NMDA receptors after suppressive
effect of alcohol is removed can trigger seizures and
convulsions
The reinforcing effect of alcohol is not solely due to the
dopaminergic system
* Alcohol can also trigger the release of
endogenous opioids
Korsakoff syndrome
- Often seen in alcoholics who are
malnourished - Caused by a lack of vitamin B1 in the brain and exacerbated by the toxic effects of alcohol
- Damage to areas of the thalamus and the mammillary bodies- structures important for encoding new memories.
_________ receptors mediatemost of the psychotropic effects of THC
Cannabinoid Type 1 (CB1)
THC also has a stimulating effect on
dopaminergic neurons
CB1 receptors also have a probable role in
the reinforcing effects of other drugs as well as cannabis
Kendler et al. (2003) investigated the
specificity of genetic and environmental risk
factors for use and abuse/dependence of 6
classes of illicit substances
– Interviews of 1,196 male-male twin pairs
FouND
Environment plays a stronger role in Drug use
but
genetics play a stronger role in determining whether the person becomes addicted
It is estimated that __ - __% of the vulnerability to addiction can
be attributed to genetic factors
includes variability in which 2 areas
40-60%
Includes both variability in metabolism of the drug and
variability in the sensitivity to the reinforcing effects
- Environmental factors also influence addiction e.g.
- drug availability,
- low SES,
- poor parental support,
- stress
Opiate addiction is most commonly treated with _________, an orally administered replacement drug
* A newer drug, _______ blocks the effect of opiates and produces only a weak opiate effect.
methadone
buprenorphine
