Electron microscopy techniques employed to explore mitochondrial defects in the developing rat brain following ketamine treatment.
Trisha Eustaquio, Cheng Z Wang, Christopher K Dugard, Nysia I George, Fang Liu, William Slikker, Merle G. Paule, Paul C Howard, Angel M Paredes
Experimental cell research October 18, 2018 DOI: 10.1016/j.yexcr.2018.10.009 (opens in new tab)
Study at a glance
AI-extracted from the abstract| Characteristics | Pilot experimental animal study Pilot study Peer reviewed |
|---|---|
| Sample size | 12 |
| Population | Postnatal day 7 Sprague-Dawley rats (n=6 ketamine, n=6 saline), frontal cortex neurons |
| Intervention | Ketamine |
| Dose | 20 mg/kg (6 subcutaneous injections at 2-h intervals); saline 10 ml/kg for controls |
| Duration | 6 injections over 10 hours, with a 6-h withdrawal period after the last injection |
| Measures | Transmission electron microscopy (TEM), serial block-face scanning electron microscopy (SBF-SEM) |
| Topics | Ketamine Esketamine |
| Keywords | Brain Animals Rats, sprague-dawley Analgesics Microscopy, electron, scanning Microscopy, electron, transmission Image processing, computer-assisted Female Mitochondrial membranes Apoptosis Tem Developmental neurotoxicology Sbf-sem |
| Key findings | Repeated ketamine exposure (6 × 20 mg/kg) induced significant mitochondrial swelling in developing rat frontal cortex neurons, confirmed in 3D by SBF-SEM, which also suggested possible mitochondrial fission not visible with 2D TEM. Ketamine-treated mitochondria appeared to have significantly larger volumes per unit surface area than untreated mitochondria. The authors state these ultrastructural changes support ketamine's proposed neurotoxicity mechanism. |
Abstract
Ketamine, an FDA-approved N-methyl-D-aspartate (NMDA) receptor antagonist, is commonly used for general pediatric anesthesia. Accumulating evidence has indicated that prolonged exposure to ketamine induces widespread apoptotic cell death in the developing brains of experimental animals. Although mitochondria are known to play a pivotal role in cell death, little is known about the alterations in mitochondrial ultrastructure that occur during ketamine-induced neurotoxicity. The objective of this pilot study was to utilize classic and contemporary methods in electron microscopy to study the impact of ketamine on the structure of mitochondria in the developing rat brain. While transmission electron microscopy (TEM) was employed to comprehensively study mitochondrial inner membrane topology, serial block-face scanning electron microscopy (SBF-SEM) was used as a complementary technique to compare the overall mitochondrial morphology from a representative treated and untreated neuron. In this study, postnatal day 7 (PND-7) Sprague-Dawley rats were treated with ketamine or saline (6 subcutaneous injections × 20 mg/kg or 10 ml/kg, respectively, at 2-h intervals with a 6-h withdrawal period after the last injection, n=6 each group). Samples from the frontal cortex were harvested and analyzed using TEM or SBF-SEM. While classic TEM revealed that repeated ketamine exposure induces significant mitochondrial swelling in neurons, the newer technique of SBF-SEM confirmed the mitochondrial swelling in three dimensions (3D) and showed that ketamine exposure may also induce mitochondrial fission, which was not observable in the two dimensions (2D) of TEM. Furthermore, 3D statistical analysis of these reconstructed mitochondria appeared to show that ketamine-treated mitochondria had significantly larger volumes per unit surface area than mitochondria from the untreated neuron. The ultrastructural mitochondrial alterations demonstrated here by TEM and SBF-SEM support ketamine's proposed mechanism of neurotoxicity in the developing rat brain.
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 |