Neurotransmission

Neurotransmission

1. Number and Classification of Neurotransmitters:

There are currently about 40 known neurotransmitters. They are divided into two main groups:

• Small molecule group: Includes substances with non-peptide structures, usually act quickly and cause most of the acute responses of the nervous system.

• Large molecule group: Includes peptides, act slower but stronger and have prolonged effects.

2. Small Molecule Neurotransmitters:

• Acetylcholine: Neurotransmitter acting through M1, M2 and N receptors in the central nervous system.

• Noradrenaline: Influences learning, memory and sleep-wake cycle. Acts through ?2 and ?2 receptors in the central nervous system.

• Dopamine: Inhibitory neurotransmitter in the diffuse nervous system, plays an important role in the activity of the central nervous system, associated with mental excitement and inhibition. Acts through dopaminergic receptors.

• Dopaminergic system abolishers: Reduce agitation, delusions and increase negative symptoms such as slow thinking, difficulty, dry, cold emotions.

• Dopaminergic system strengtheners: Increase manic symptoms.

• Serotonin: Inhibitory neurotransmitter, plays a role in sleep, pain perception, depression, sexual desire. Acts through serotoninergic receptors.

• Antidepressants: Inhibit serotonin reuptake, also affect thermoregulation and are associated with pituitary hormone release.

• Glutamic acid and aspartic acid: Excitatory amino acid neurotransmitters, primarily act through the N-methyl-d-aspartate (NMDA) receptor. This receptor is inhibited by ketamine.

• GABA: Important inhibitory neurotransmitter in the brain and spinal cord.

• Sedative hypnotics derived from benzodiazepine and barbiturates, anesthetics: Facilitate GABA transmission by binding to the ?GABA?_A receptor.

• GABA antagonists: Convulsants such as pentylentetrazol, picrotoxin.

• Glycine: Major inhibitory neurotransmitter in the spinal cord.

• Glycine inhibitors: Cause excitation (e.g., strychnine).

3. Large Molecule Neurotransmitters:

• Endorphin, enkephalin, dynorphin, vasopressin, substance P…: These peptides have stronger and longer effects than small molecule neurotransmitters.

4. Mechanism of Action of Drugs on the Central Nervous System:

• Change ion flow through transmembrane ion channels: Most drugs acting on the central nervous system do so by changing the flow of ions through transmembrane ion channels.

5. Classification of Ion Channels:

• Voltage-gated channels: Opening and closing are regulated by changes in membrane potential. Examples: Na+, Ca++, K+ channels.

• Ligand-gated channels: Opening and closing are regulated by the interaction between neurotransmitters and receptors.

6. Effects of Drugs on the Central Nervous System:

• Effects on ligand-gated channels: Drugs mainly act on receptors at nerve synapses, altering the production, accumulation, release, uptake or metabolism of chemical neurotransmitters.

7. Groups of Drugs Acting on the Central Nervous System:

• Central nervous system depressants: Anesthetics, analgesics, sedatives-hypnotics, central analgesics, antiepileptics.

• Groups treating mental disorders: Antipsychotics, antidepressants, mood stabilizers.