Drug addiction and the brain reward system

組員:Sam Wang王煜豪
Pony Lien連顥庭
Reward-- positive value of an internal
physical state
Incentive motivation (Brain’s dopamine
(Incentive salience)
Incentive salience
Psychological reward
Modulation by drugs
modification of behavior
sensory properties of rewards.
more effective than punishment in enforcing
positive behavior
mesolimbic pathway
mesocortical pathway
Region near the base of the brain
Inputs of the reward system
Releasing Dopamine
mesolimbic pathway
Inhibitory neuron
Dopamine releasing VTA neuron
Cerebral neuron of reward pathway
stimulate (D1 Receptor)
inhibit (D2 Receptor)
increase the dopamine release
 Arises psychological drug tolerance ,
Psychological drug tolerance
 CREB protein
 delta FosB
activating genes causes sensitization.
intense cravings (associated with drug
extend the peripheral cues of drug use
Impulsive, destructive behavior medication
Can’t help taking medicine
3 major reasons to lead to drug addiction
1.Hyperactive incentive system
2.Uncomfortable withdrawal symptoms
3.Permanent change in incentive system
Most of drugs can lead to hyperactive
incentive system.
They act on Brain’s dopamine system directly ,
so they can make mesolimbic pathway more
Tolerance:need more medicaine to reach the
general level of joy.
Withdrawal: the unpleasant effects of getting
used to not taking a drug that they have
become dependent on
Neural sensitization: dopamine nerve cells
were activated easily by drugs.
obtained from the leaves of the coca plant
stimulant of the central nervous system, an
appetite suppressant, and a topical anesthetic
The decreased dopaminergic signaling after
chronic cocaine use may contribute to
depressive mood disorders and sensitize this
important brain reward circuit to the
reinforcing effects of cocaine
•psychostimulant drug
•increased wakefulness and focus
•decreased fatigue and appetite
•vesicular level
•dopamine transporter DAT
•reverse tolerance
•sensitization to psychological
Cocaine binds directly to the DAT transporter, inhibiting reuptake with
more efficacy than amphetamines which phosphorylate it causing
internalization; instead primarily releasing DAT (which cocaine does not
do) and only inhibiting its reuptake as a secondary, and much more
minor, mode of action than cocaine and in another manner: from the
opposite conformation/orientation to DAT.
from morphine
μ-opioid agonists morphine
a strong analgesic
name from the Greek god of dreams
is a potent opiate analgesic medication
Can be used as an analgesic to relieve
can be taken orally, rectally, subcutaneously,
intravenously, intrathecally or epidurally