The plant alkaloid strychnine is a poison that occurs at high levels in a partic
ID: 99859 • Letter: T
Question
The plant alkaloid strychnine is a poison that occurs at high levels in a particular deciduous tree found in India. It is an effective poison for killing rodents and other small vertebrates. In small doses, it has been used illegally by athletes as a stimulant. Strychnine is an antagonist of the glycine receptor, which is a ligand-gated chloride channel. Explain the general role of glycine in neuron transmission. How does chloride fit in to this explanation? Explain why strychnine has the effects it has (described above). Your answer must include what is happening at the cellular level (think channels and ions) and you must address both scenarios-rodents and athletes-and why the effects are different.Explanation / Answer
As a neurotransmitter, glycine is inhibitory in nature which means it acts in the central nervous system parts including spinal cord, brainstem and retina in inhibitory way. On activation of the glycine receptors, there is occurrence of inhibitory post synaptic potential which makes the post synaptic neuron to generate and produce less action potential that may interfere with the signal transmission. Glycine is present in forebrain and is the major inhibitory neurotransmitter in brainstem and spinal cord. It helps in various motor and sensory functions. Chloride definitely fits in the whole discussing related to glycine as neurotransmitters as on activation of the glycine receptors, the chloride enters the neuron via the ionotrophic receptors.
In cases of Rodents - Strychnine is a plant alkanoid which is an antagonist of glycine receptors which is consumed as stimulant by atheletes and leads to rodent death. The inhibitory glycine receptors are blocked by strychnine leading to poisoning leading to muscular contractions and tetany. It causes glycinergic disinhibition and over excitation which activates the chloride ion conductance due to glycine activation. This leads to hyper polarisation of neuronal membrane causing death in rodents. The consumption causes muscular convulsions and leads to death due to asphyxia when consumed by rodents.
In case of Humans - However, consuming the same in small doses by athletes acted as stimulant and enhanced performance. It has convulsant effect and small doses enhance the performance due to high degree of excitement. Being an antagonist to glycine inhibitor, it binds to the glycine receptor and prevents inhibitory effects of glycine on post synaptic neuron. Low dose helps in excitement due to immediate muscle spasm aimed at improving performance by athletes.
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