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Diseases of the Nervous System
Published in George Feuer, Felix A. de la Iglesia, Molecular Biochemistry of Human Disease, 2020
George Feuer, Felix A. de la Iglesia
Swines kept on a vitamin B6-free diet for 9 to 10 weeks exhibit demyelinization of peripheral nerves and degeneration of axons.116 In rats, brain development, particularly myelination, was affected by deficiency of vitamin B6 prior to and including the period of rapid myelination. Maternal deficiency of vitamin B6 in the rat resulted in decreased myelination of the central nervous system in the progeny.418 Five weeks of pyridoxine deficiency was sufficient to produce a deficit in active avoidance learning in postweaning rats when the brain development had been almost completed. The active avoidance learning was restored to normal within 1 week by reversal of the pyridoxine deficiency.547
The Stress System
Published in Len Wisneski, The Scientific Basis of Integrative Health, 2017
In the 1980s, researchers made a distinction between opioid and nonopioid forms of stress. Yehuda Shavit, who began this work as a graduate student in psychology at UCLA, showed that, depending on the length and intensity of the stressor, the body responds with either an opioid-mediated or a nonopioid-mediated form of analgesia. Rats exposed to prolonged intermittent foot shock (inescapable shock) demonstrated an opioid-mediated route of analgesia (ascertained by its ability to be blocked by the opioid antagonist, naloxone). These experiments caused an “escape or avoidance learning deficit” or “learned helplessness” (Shavit, 1991). However, rats exposed to brief but continuous foot shock, given for the same cumulative amount of time, elicited a nonopioid analgesic response to a degree comparable with that of the opioid-mediated analgesia.
MRCPsych Paper A1 Mock Examination 1: Answers
Published in Melvyn WB Zhang, Cyrus SH Ho, Roger Ho, Ian H Treasaden, Basant K Puri, Get Through, 2016
Melvyn WB Zhang, Cyrus SH Ho, Roger CM Ho, Ian H Treasaden, Basant K Puri
Explanation: This phenomenon is known as operant conditioning, specifically negative reinforcement. Escape and avoidance learning are two examples of negative reinforcement. The removal of the unpleasant stimulus leads to reinforcement of the behaviour. In operant conditioning, the reinforcer (reduction in anxiety levels) is presented only after the behaviour (going home) is executed, which is why Option D is incorrect.
Dual-target ligand discovery for Alzheimer’s disease: triphenylphosphoranylidene derivatives as inhibitors of acetylcholinesterase and β-amyloid aggregation
Published in Journal of Enzyme Inhibition and Medicinal Chemistry, 2023
Marwa El-Hussieny, Mansoura A. Abd-El-Maksoud, Fouad M. Soliman, Marwa A. Fouad, Mohamed K. El-Ashrey
The central cholinergic neurons have a role in passive avoidance learning, while the hippocampus is principally in charge of controlling the learning response49. The step-down passive avoidance test was used to assess compound 8c’s ability to guard against memory loss. Figure 8 shows that the transfer latency time (TLT) of the scopolamine-treated group was substantially shorter than that of the control group (27.2 s, at #p = 0.01). Comparable to donepezil at a dose of 1 mg/kg for each, treatment with compound 8c (TLT = 45.2 s) demonstrated a substantial increase in TLT compared to the model group (*p = 0.01). These in vivo results demonstrated that compound 8c could cross the blood–brain barrier (BBB), hence enhancing scopolamine–induced cognitive impairment.
Overnight fasting affects avoidance learning and relief
Published in Nutritional Neuroscience, 2023
Silvia Papalini, Laura Neefs, Tom Beckers, Lukas Van Oudenhove, Bram Vervliet
We examined the effects of overnight fasting on avoidance learning, fear extinction, and relief pleasantness. We found that overnight fasting (1) overnight fasting optimized avoidance decisions by selectively reducing unnecessary avoidance actions during learning and by reducing a general return of avoidance after fear extinction, and (2) reduced relief pleasantness to signaled threat omissions during extinction learning. Furthermore, the reduction in unnecessary vs necessary avoidance was mediated by a reduction in differential relief pleasantness during avoidance learning (3). The effect of fasting on avoidance learning contributed to a persistent reduction of avoidance after fear extinction (4a); while (4b) the reduction in general avoidance at test 1 in the fasting group was mediated by the reduction in differential relief pleasantness during avoidance learning.
Maternal overnutrition leads to cognitive and neurochemical abnormalities in C57BL/6 mice
Published in Nutritional Neuroscience, 2019
Christian Wolfrum, Daria Peleg-Raibstein
During conditioning, the subjects were placed in the box and were exposed to 60 avoidance trials which were administered at variable ITIs. The number of avoidance responses in successive blocks of 10 trials was expressed as percentage avoidance responses. This was used as an index of avoidance learning.