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Synaptic function and psychopharmacology

The Synapse and Neurotransmitters

  • Connection between neurons involves the action potential and neurotransmitter release.

  • Calcium ions (Ca2+) are crucial for neurotransmitter release in synaptic transmission.

Communication in the Central Nervous System

  • Each neuron receives thousands of synaptic inputs.

  • Generates simple outputs (Action Potentials).

  • Plays a role in neural computation.

Types of Neurotransmitters

  • Variety of neurotransmitters exist, including:

    • Acetylcholine: First known neurotransmitter; excita tory, key in memory formation, At nerve-muscle connections of all voluntary & many involuntary muscles, low levels in Alzheimer's.

    • Noradrenalin: Involved in regulating processes like heart rate, BP and mood regulation; associated with arousal, alertness, and concentration, cocaine influences the activity of noradrenaline in the brain or body.

    • Dopamine: Critical for movement, attention, learning, affected in Parkinson's Disease.

    • Serotonin: Versatile functions including mood regulation; associated with various mental disorders.

    • GABA: Major inhibitory neurotransmitter; implicated in epilepsy, affected by substances like benzodiazepines.

Neurotransmitter Mechanisms

  • Drug interactions can occur at various points in neurotransmitter function:

    • Synthesis, release, receptor interaction, reuptake, and inactivation.

  • Agonists mimic neurotransmitters while antagonists block their effects.

Clinical Disorders - Parkinson’s Disease

  • Symptoms include tremors, rigidity, poor balance, and cognitive effects.

  • Treatment often involves L-Dopa, a precursor of dopamine; however, side effects may occur from peripheral conversion.

Treatment - Alzheimer’s Disease

  • Characterized by ACh depletion and neuronal degeneration.

  • Current treatments aim to inhibit degradation (AChE inhibitors) or enhance ACh release.

Pharmacological Treatments in Mental Health

  • Includes neuroleptics, MAOIs, SSRIs, benzodiazepines, and beta-blockers.

  • Some debates exist on their efficacy and the chemical imbalance theory.

Psychoactive Drugs: Uses & Abuses

  • Categories of psychoactive drugs:

    • Sedatives: (e.g., benzodiazepines, alcohol)

    • Opiates: (e.g., morphine, heroin)

    • Stimulants: (e.g., amphetamines, cocaine)

    • Psychedelics: (e.g., LSD, psilocybin)

Cannabis: Effects and Uses

  • Cannabis consists of THC and other cannabinoids, can induce bronchodilation, anti-emetic effects, and has applications in glaucoma treatment.

  • Two primary types of cannabinoid receptors (CB1 and CB2) affect various physiological processes.

Addiction vs. Dependence

  • Differences between addiction (compulsive behavior) and dependence (physiological adaptation).

  • Tolerance development involves up-regulation or down-regulation of receptors affecting sensitivity.