Ketamine effects on somatosensory cortical single neurons and on behavior in rats.
I M Patel, J K Chapin
Anesthesia & Analgesia June 1990 DOI: 10.1213/00000539-199006000-00010 (opens in new tab)
Study at a glance
AI-extracted from the abstract| Characteristics | Observational study (single-neuron electrophysiology in awake rats) Peer reviewed |
|---|---|
| Population | Unanesthetized rats behaving in a treadmill movement paradigm |
| Intervention | Ketamine |
| Dose | 5 to 20 mg/kg (subanesthetic) and 30-50 mg/kg, intramuscularly |
| Topics | Esketamine Ketamine |
| Key findings | Ketamine produced two separable cortical effects: strong inhibition of somatosensory responsiveness in nearly all recorded neurons and a tonic excitatory influence on a subgroup (27%) of neurons. The authors propose this coexistence of excitation and sensory suppression may partly explain dissociative anesthesia and hallucinatory side effects seen in humans emerging from ketamine anesthesia. |
Abstract
The neurophysiological effects of ketamine were studied at the single-neuron level in the somatosensory cortex of unanesthetized rats behaving in a treadmill movement paradigm. Chronically implanted 25-microns microwire electrodes were used to record spontaneous discharge, sensory responses, and sensorimotor-correlated activity of single neurons before and after ketamine administration. Extracellular action potentials of up to six single neurons were simultaneously recorded for several days, allowing ketamine effects to be tested repeatedly on the same neurons. Videotaped recordings obtained during each experiment were used to measure both the sensorimotor properties of the neurons and the changes in these measures caused by different doses of ketamine. Behaviorally, ketamine produced restless-hyperactive behavior at subanesthetic doses from 5 to 20 mg/kg (intramuscularly). At higher doses (30-50 mg/kg) the rats became cataleptic and immobile after the initial hyperactive period. Whereas the spontaneous rates of most neurons were reduced or unchanged after subanesthetic doses, a subgroup (27% of the total) exhibited markedly increased firing rates. This excitation was of a tonic nature, persisting for a dose-dependent duration in a manner that was not correlated with any of the behavioral effects of the drug. In further analyses, ketamine suppressed the sensory responses of virtually all of the recorded neurons. In particular, low doses of ketamine suppressed "sensorimotor" firing (mainly proprioceptive responses) of neurons in relation to active limb movement. It also suppressed virtually all neuronal sensory responses to the sudden onset of treadmill movement, although the time-course of this effect varied from neuron to neuron. These results reveal two separable effects of ketamine: (a) a strong inhibition of all somatosensory responsiveness in this area and (b) a tonic excitatory influence expressed heterogeneously on a subgroup of neurons. This coexistence of cortical neuronal excitation and sensory suppression in the same cortical region may explain in part the mechanism of dissociative anesthesia and hallucinatory side effects observed in humans during emergence from ketamine anesthesia.
Comparable studies
Other preclinical and animal studies on ketamine, most cited first.
| Study | Year | Design | Participants |
|---|---|---|---|
| mTOR-Dependent Synapse Formation Underlies the Rapid Antidepressant Effects of NMDA Antagonists Rats | 2010 | Observational study | |
| Activation of Glutamatergic Neurotransmission by Ketamine: A Novel Step in the Pathway from NMDA Receptor Blockade to Dopaminergic and Cognitive Disruptions Associated with the Prefrontal Cortex Conscious rats | 1997 | Dose-response study with microdialysis and behavioral testing | |
| NMDAR inhibition-independent antidepressant actions of ketamine metabolites Mice | 2016 | Preclinical study | |
| The dissociative anaesthetics, ketamine and phencyclidine, selectively reduce excitation of central mammalian neurones by N‐methyl‐aspartate Spinal neurons in decerebrate or pentobarbitone-anaesthetized cats and rats | 1983 | Experimental study | |
| R-ketamine: a rapid-onset and sustained antidepressant without psychotomimetic side effects Mice | 2015 | Experimental study |
Citations in the library
Cited by 3
- Neural assemblies coordinated by cortical waves are associated with waking and hallucinatory brain states. Cell Reports April 23, 2024
- Cortical Mechanisms Contributing to Ketamine-Induced Dissociation The Neuroscientist December 26, 2025
- Neural Dynamics in Primate Cortex during Exposure to Subanesthetic Concentrations of Nitrous Oxide. eNeuro 2021