Narcotic drugs introduction Domina Petric, MD

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.

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

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.

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).

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

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

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

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

Katzung, Masters, Trevor. Clinical pharmacology.