fMRI in monkeys also revealed hyperactivity in entorhinal cortex, striatum regions, but hypoactivity in midbrain and visual cortex (Yu et al., 2012). In the higher primate, chronic treatment of ketamine induced changes of apoptotic markers in the prefrontal cortex and abnormal behavior in movement, walking, jumping, and climbing (Sun et al., 2012). The damage on the nervous system included neuronal loss, synaptic changes, changes in functional magnetic resonance imaging (fMRI) activities, and the formation of mutated tau protein in neurons as described in models of rodents and monkeys (Yeung et al., 2010a Sun et al., 2011 Yu et al., 2012). Unfortunately, ketamine has now become an abusive drug in many parts of the world and chronic and prolonged usage led to damages of many organs in experimental animals (Yeung et al., 2009 Chan et al., 2011 Tan et al., 2011a Wai et al., 2012 Wong et al., 2012).
![resonance refers to an effect in which the resonance refers to an effect in which the](https://d3i71xaburhd42.cloudfront.net/a84d9d7a891868441aab667985d304eba431f813/5-Table3-1.png)
Being one of the noncompetitive NMDA receptor antagonists like phencyclidine and MK801, it would produce schizophrenia like psychosis in human (Dickerson and Sharp, 2006).
![resonance refers to an effect in which the resonance refers to an effect in which the](https://aip.scitation.org/action/showOpenGraphArticleImage?doi=10.1063/5.0041132&id=images/medium/5.0041132.figures.online.highlight_f1.jpg)
Medically, ketamine has also been proposed for anticonvulsive control (Dickenson and Ghandehari, 2007) and for controlling injury after stroke via it action on the glycine, zinc, and magnesium components of the glutamate binding sites (Collins et al., 1989) thus, protecting neuronal loss after stroke (Meldrum et al., 1987) and preventing of the spread of depolarization after injury (Hertle et al., 2012). Ketamine employed in prescribed medical conditions had its advantages as it did not increase intracranial pressure during neurosurgery (Schmittner et al., 2007) and had no postoperative neurological damage when used in cardiopulmonary bypass patients (Smith et al., 2006). Ketamine, a known antagonist of N-methyl-D-aspartic (NMDA) glutamate receptors, had been used as an anesthetic, particularly for pediatric or for cardiac patients. Such study confirmed that many brain regions in the human were susceptible to chronic ketamine injury and presented a diffuse effect of ketamine on the brain which might differ from other central nervous system (CNS) drugs, such as cocaine, heroin, and methamphetamine. Cortical atrophy was usually evident in the frontal, parietal or occipital cortices of addicts. Twenty-one ketamine addicts were recruited and the results showed that the lesions in the brains of ketamine addicts were located in many regions which appeared 2–4 years after ketamine addiction. This paper described for the first time via employing magnetic resonance imaging (MRI) the changes in ketamine addicts of 0.5–12 years and illustrated the possible brain regions susceptible to ketamine abuse. However, no studies on possible damages in the brains induced by chronic ketamine abuse have been documented in the human via neuroimaging. Unfortunately, ketamine has become an abusive drug in many parts of the world while chronic and prolonged usage led to damages of many organs including the brain. Hydrogen nucleus is shielded in the case of #CH_4# and therefore, the peak appears on the lower ppm side.Ketamine, a known antagonist of N-methyl-D-aspartic (NMDA) glutamate receptors, had been used as an anesthetic particularly for pediatric or for cardiac patients.
![resonance refers to an effect in which the resonance refers to an effect in which the](https://webartacademy.com/wp-content/uploads/2011/01/Dead-Christ-by-Andrea-Mantegna--300x251.jpg)
Let us compare the chemical shift of #CH_4# protons and #CH_3Cl# protons.Ĭhlorine atom is an electronegative atom that will pull the electron density toward it ( electron withdrawing ), resulting in a deshielding of the hydrogen nucleus an edit will fell higher external magnetic field #B_0# increasing the resonance frequency and therefore, shifting to higher ppms.
![resonance refers to an effect in which the resonance refers to an effect in which the](https://ars.els-cdn.com/content/image/1-s2.0-S1385894721027509-ga1.jpg)
How would this affect the H NMR spectrum? Because the proton experiences higher external magnetic field, it needs a higher frequency to achieve resonance, and therefore, the chemical shift shifts downfield (higher ppms). If the electron density around a nucleus decreases, the opposing magnetic field becomes small and therefore, the nucleus feels more the external magnetic field #B_0#, and therefore it is said to be deshielded. Because the proton experiences lower external magnetic field, it needs a lower frequency to achieve resonance, and therefore, the chemical shift shifts upfield (lower ppms). The higher the electron density around the nucleus, the higher the opposing magnetic field to #B_0# from the electrons, the greater the shielding. In this case we say that electrons are shielding the nucleus from #B_0#. The basic principle of NMR is to apply an external magnetic field called #B_0# and measure the frequency at which the nucleus achieves resonance.Įlectrons orbiting around the nucleus generate a small magnetic field that opposes #B_0#.