Ketamine

Ketamine is a dissociative anaesthetic with a glutamatergic mechanism. It produces dissociative and psychedelic effects, along with rapid antidepressant effects, with a downstream action on AMPA and synaptic plasticity. The plate presents it as a molecule that unravels the fabric of the self through glutamatergic blockade rather than a serotonergic route.

Pharmacology

Ketamine is a non-competitive antagonist of NMDA receptors. Preferential blockade of NMDA on GABAergic interneurons lifts inhibition, producing a paradoxical glutamatergic burst onto AMPA. The plate lists:

• NMDA: primary dissociative and anaesthetic target.
• Glutamatergic burst onto AMPA: driver of the rapid antidepressant effect.
• BDNF, TrkB, mTOR cascade: rapid synaptic plasticity.
• Other targets or contributions: opioids (μ/κ), HCN1, sigma-1, and the active metabolites (norketamine, HNK).

It stresses that ketamine does not simply act by lowering glutamate: it paradoxically triggers a downstream glutamatergic surge, which underlies its antidepressant effect.

Effect on brain networks

The specific mechanism is a thalamo-cortical dissociation and a disruption of sensory gating. The plate notes a disruption of the default mode network (DMN), increased connectivity between usually separate networks, a rapid drop in brain entropy, a disruption of the predictive flow, a decoupling of cortex or environment or self-narrative, and a constitutive reorganisation of sensory processing. The frames phenomenon, the bogging-down of the visual flow at dissociative doses, would extend to image freezing and stalling. An EEG signature distinct from serotonergic psychedelics is mentioned.

Functional consequences

The plate describes dissociation, the separation of self, body and environment; an alteration of time and space, with a sense of lateral displacement toward other spaces; frames, a slowed or frozen visual flow while other modalities continue; the K-hole, a replacement of the ordinary frame by an autonomous phenomenological space, of a CIBE or NDE-like type; a possible emotional distance, with access to psychic material with less reactivity and affective grip. A therapeutic window at a controlled dose is noted, with the possibility of insight, cognitive flexibility and mental reorganisation.

Reported subjective effects

Cited are: dissociation and depersonalisation; alternative spaces, immersive inner journeys; K-hole-type experiences, loss of frame (CIBE); strange time, fragmentation or suspension of frames; emotional distance, observation of the self from a remove; rapid antidepressant effect and introspective potential.

Significance detached from the percept

One ketamine regime is finer than dissociation or the K-hole: this world stays entirely visible, but its significance comes unstuck. With the perceptual field held constant (the tiling, the door, the corridor all stay), only one thing varies, the valence, the sense of the place. Everything is there, and yet everything is other.

The mechanism reads within the predictive frame. Normally a weighting layer (a high-level prior about the kind of place one is in, about what is done there, about who may be watching) stays transparent: one perceives through it, never it. By NMDA decoupling, ketamine tears this prior from its anchoring without touching the sensory flux; the sensory stays plugged into the corridor, the weighting has locked onto something else, and the two no longer correct each other. The prior then surfaces as an object of perception: a weight without form or edge, bodily without a body, since it has no sensory channel of its own. It is Heideggerian significance (the worlding, usually the medium and not the object) made available as a quasi-percept.

It is the reverse of the frames: the frames reveal the update freezing, here it is the weighting itself that becomes perceptible (see Bayesian brain). And the afterglow follows differently: not a memory of the place passed through, but a residual access, the delamination that has not quite closed back up, the kept capacity to feel the joint where, for everyone else, there is only a room one sees.

Beyond the white-out

Ketamine is often reduced to a subtraction toward an absence, a via negativa thinning the self down to the void. That is an idealised pole: the dissociative plane is never as bare as the concept would like.

Ketamine has its own positive deposits (geometry, encounters, the K-hole mythos) that superimpose on the subtractive vector. Above all, alongside the monadic blank (a void with no one), it opens another regime: world-transposition. At certain depths the self-model is not cut but displaced; it re-moors to a counterfactual world, with its here, its embryo of a self, its setting. Hence the thin thread of memory that is sometimes possible where the white-out stays mute: there was an active self, however elsewhere, to encode.

Three forms of de-appropriation thus emerge, useful for thinking the three molecules together: mineness can thin out (the ketamine absence, close to the 5-MeO pole), distribute itself (the co-emergence of the N,N-DMT breakthrough) or transpose itself (the dissociative voyage into another world). The ketamine blank is not quite the 5-MeO white-out either: something analogous, without being exactly that, very probably because of the dissociative dimension proper to ketamine. Ownership of experience depends less on the presence or absence of content than on a direction of reference: a from-where, which can empty out, be shared, or be displaced. At a titratable dose, ketamine is therefore the best probe of this seam, with one limit: NMDA antagonism is also the antagonism of encoding, and the deepest descent erases itself as it is reached.

Duration and tolerance

By the intravenous route, near-immediate onset is between 40 and 60 minutes; by the nasal route between 5 and 10 minutes; by insufflation, onset is fast between 5 and 15 minutes for a total duration of 30 to 60 minutes. The oral or sublingual route gives onset of 15 to 30 minutes for a duration of 1 to 3 hours. Sought-after effects are possible (fatigue, floating, brain fog). Fast tolerance, especially in close-spaced use, is underlined: possible dose escalation, effects still perceptible more quickly, and a real risk of psychological dependence, particularly in close-spaced or chronic use.

Harm reduction

The plate highlights ketamine cystitis (ulcerative cystitis, pain, haematuria, irreversible bladder damage in severe chronic use), possible hepatotoxicity or hepatopathy in repeated use, severe dissociations or accidents in case of falls or choking, and a risk of respiratory or cardiovascular depression when combined with other depressants. It also stresses the risk of genuine psychological dependence, especially in close-spaced or chronic use.

Sources

• Calvin Stevens, synthesis of ketamine in 1962 (Parke-Davis patent).
• Edward Domino, the term dissociative anaesthetic and the popularisation of the dissociative concept.
• Clinical research on ketamine and esketamine in treatment-resistant depression (esketamine or Spravato approved by the FDA).
• Literature on the glutamatergic NMDA, AMPA, BDNF, TrkB, mTOR pathway of the rapid antidepressant effect.
• Data on cystitis and uropathy associated with chronic ketamine use.