Olson lab Group Presentation March 4 th, 2016

Ketamine was discovered in 1962 and has been used primarily as an anaesthetic in emergency and intensive care situations Ketamine possesses some unique properties; Able to induce deep, trance-like state while providing pain relief, sedation, and amnesia Unlike opiates, typically does not depress breathing or blood pressure Has also been used in limited situations as a drug of abuse, however this is less common Has a diverse pharmacology, but operates principally as an NMDA antagonist

As an NMDA antagonist, ketamine is classified as a dissociative anaesthetic Other members of this class include phencyclidine (PCP) and dextromethorphan All share the ability to induce feelings of depersonalization and out-of-body experiences, an effect unique and distinct from the classical psychedelics Vs. ?

A single sub-anaesthetic dose of ketamine can induce a rapid antidepressant effect (~less than 2 hrs) in patients suffering from treatment-resistant major depressive disorder This is in sharp contrast to traditional antidepressant (SSRI) medications which can take from weeks to months for full effect, and hints at a unique mechanism of action

Ketamine Displays Antidepressant Effect in FST Ketamine’s Antidepressant Effect is BDNF Dependent

Ketamine’s Effects Depend on Translation, but not Transcription Anisomycin – Inhibitor of protein synthesis NBQX – AMPA receptor antagonist These data indicate that behavioural antidepressant effects are not elicited by alterations in evoked neurotransmission, but require ketamine-mediated augmentation ofAMPA-receptor activation. mTOR – mammalian Target of Rapamycin. Previously, a link between ketamine activity and mTOR was demonstrated. Data in i are taken at 30 minutes, previous work was 2 hr and 24 hr. mTOR may be responsible for maintenance of effect, rather than rapid induction

Ketamine Inhibits eEF2 Phosphorylation and Permits Protein Synthesis eEF2 is an elongation factor essential for protein synthesis. It is completely inactivated by EF-2 kinase phosphorylation. Ketamine dose-dependently inhibits eEF2 phosphorylation, in the absence of neuronal activity

Ketamine Reduces NMDAR-mEPSCs, Potentiates Hippocampal Field Responses NMDAR-mEPSC – NMDA receptor miniature excitatory post-synaptic currents 1 – Baseline 2 – 45 minutes post ketamine treatment

Ketamine Decreases Hippocampal eEF2 Phosphorylation in vivo Red – p-eEF2 Blue – DAPI Cortical levels of p-eEF2 were unaffected.

Ketamine Increases Synaptic Proteins and Spine Number Arc – activity-regulated cytoskeletal protein Synapsin – Regulates neurotransmitter release PSD95 – Post-synaptic density GluR1 – glutamate receptor 1

Ketamine Enhances mPFC layer V pyramidal cell EPSC responses Ketamine enhances mPFC excitatory post- synaptic currents in response to 5-HT and hypocretin. This response can be blocked with rapamycin (mTOR blocker).

Ketamine-induced Behavioral Effects A – Forced swim test B – Novelty-suppressed feeding test C – learned helplessness due to inescapable stress For A-C, rapamycin was infused ICV. In D and E, rapamycin was infused directly into the mPFC.

Ketamine behavioral effects are reversed by Erk/Akt inhibitors UO126 – Erk inhibitor LY – PI3K/Akt inhibitor (I) – immobility in the FST is reduced by a sub-anaesthetic, but not fully anaesthetic dose of ketamine (duh)