States of consciousness

Prof. dr. Anton M.L. Coenen

NICI – Department of Biological Psychology

Radboud University Nijmegen

The Netherlands

a.coenen@nici.ru.nl

States of consciousness

• Lecture 4. Psychoactive drugs modulating consciousness

PSYCHOACTIVE SUBSTANCES AND CONSCIOUSNESS

THREE MAIN GROUPS OF DRUGS MODULATE CONSCIOUSNESS

CENTRAL STIMULANTS

AMPHETAMINES – COCAINE – CAFFEINE - NICOTINE

HYPNOTICS – SEDATIVES – ANXIOLYTICS

BARBITURATES – BENZODIAZEPINES

PSYCHODELICS (MIND-ALTERING DRUGS)

ALCOHOL - MESCALINE – LSD – PSYLOCYBINE – OPIATES

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BALANCE BETWEEN EXCITATORY AND INHIBITORY SYSTEMS

HYPNOTICS AND SEDATIVES  

BARBITURATESSince 1903 Fischer and von Mering - efficient drugs - high toxicity - modulate chloride channels

  

BENZODIAZEPINESSince1960 Sternbach – safe and efficient – modulate GABA-system

  

HYPNOS

EFFECT

DEATH

COMA

ANESTHESIA

SLEEP

DOSE

BENZODIAZEPINES

BARBITURATEN

Leo Sternbach

(1908)

The valium structure

EEFFECTS OF BENZODIAZEPINES         SEDATIVE / HYPNOTIC        ANXIOLYTIC        MUSCLE RELAXANT        ANTI-CONVULSIVE        AMNESTIC        EEG-CHANGES           TOLERANCE          DEPENDENCY

 

The AIM model may be used to think about the state of the brain in conditions other than sleep. For example, when all three state values fall and the AIM points move to the left lower front corner, the result is coma. Hallucination would be the effect when the internal stimulus strength increases during waking, and AIM moves to the right upper front corner. AIM moves to the left upper rear corner when external stimulus strength is increased, as in electroshock therapy. Whether or not these assumptions are correct can now be tested experimentally.

Natives of Amazon prepare a brew of ‘ayahuasca’ (‘vine of the dead, or souls’). With this tea containing powerful hallucinogenic alkoloids, interior sounds are commonly heard, often triggering spontaneous vocalisations.

ALCOHOL

Alcohol

• invades all parts of the body (molecules are small and soluble in both fat and water)

• inhibits the flow of sodium across the membranes

• expands the surface of membranes • facilitates response by the GABAA receptor• blocks glutamate receptors• increases dopaminergic activity

NICOTINE

• Nicotine binds to a nicotinic receptor, one of the two subtypes of acetylcholine receptors.

• When nicotine binds to a nicotinic receptor, it opens Na+-channels, allowing sodium to flow into the cell.

• This depolarises the cell membrane leading to a fast excitation.

MARIJUANA

COCAINE

Cocaine

Dopamine

Cocaine

Central effects

When Coca-Cola was first produced, there was a clear reason why it relieved fatigue: It contained cocaine.

HEROIN AND MORPHINE

Opiates: narcotic analgesics

Pain relief

Sedation

Euphoria

Miosis

Impaired peristalsis

Respiratory depression

Inhibition cough reflex

a- Opium anta- NaloxonMorphineHeroineMethadon ……

Local Anesthetics

Gate Control TheoryMelzack and Wall

• Three classes of psycho-active drugs interfere with consciousness: central stimulants (enhancing), central depressants (diminishing) and psychodelics (‘changing’).

• Central stimulants activate acetylcholine (nicotine), block GABA (caffeine) or inhibit dopamine re-uptake (amphetamine).

• Central depressants open chloride channels (barbiturates), or facilitate GABA (benzodiazepines)

• Psychodelics (‘hallucinogenics’) induce ‘altered states of consciousness (ASC)’, including hallucinations and distorted perception (amphetamine, cocaine, MDMA (ecstacy), LSD).

• A deep brain depression causes anaesthesia, by opening Cl-channels (barbiturates), by agonistic action on GABA (benzodiazepines) or by antagonistic action on glutamate.

• Powerful analgetics (pain killers) are morphine and heroine, interfering with opiate receptors and endorphines.

• The fact that psycho-active drugs modulate neurotransmitter-systems in relation to consciousness pleads for a monistic view of consciousness.