1. Narcotic drugs introduction
Domina Petric, MD

2. Narcotic drugs and dopamine
Mesolimbic dopaminergic system is the main target for narcotic drugs.
Ventral tegmental area (VTA) sends projections into the nucleus accumbens, amygdala, hippocampus and prefrontal cortex.
Most of the VTA neurons excrete dopamine.
Dopamine release in the mesolimbic dopaminergic system is very important for reward and motivation processing.

3. Reward Motivation Pleasure Euphoria Motor functioning Compulsion
Image source: QUORA
Dopamine pathways:
Reward
Motivation
Pleasure
Euphoria
Motor functioning
Compulsion
Perseveration
Nucleus
accumbens
VTA

4. Narcotic drugs and dopamine
Narcotic drugs activate mesolimbic dopaminergic system (MDS).
MDS is important in discernment between expected and real reward. MDS creates strong signal for learning process.

5. Narcotic drugs classification
that bind on
the Gio-protein
receptors.
Narcotic drugs that act
on the ionotropic
receptors or ion channels.
Narcotics that affect dopaminergic
transporter (DTA).

6. Tolerance Dose of narcotic drugs must be increased
to maintain rewarding effect.
This is called tolerance.
Very fast development
of tolerance is called
tachyphylaxis.

7. Abstinence syndrome
After cessation of taking narcotic drug, usually after relatively short period of time (specific for every drug), abstinence syndrome develops.

8. Addiction
It is characterised with high motivation to get the narcotic drug despite negative consequences.
With time drug abuse becomes compulsive (desire without pleasure).

9. Addiction High risk for relapses
LTP: long term potentiation, activation of NMDA receptors.
LTP
Nucleus
accumbens
Dopamine
Addiction
High risk
for relapses
Genetic
predisposition

10. Katzung, Masters, Trevor.
Clinical pharmacology.