What are the effects of strychnine on glycine receptors?

Sourav PanSeptember 23, 2024

Answered

Strychnine is a potent antagonist of glycine receptors, which are a type of inhibitory neurotransmitter receptor in the central nervous system. Here are the key effects of strychnine on glycine receptors:

1. Inhibition of Glycine Action:

• Blocking Glycine Binding: Strychnine binds to glycine receptors and prevents glycine, the natural neurotransmitter, from activating these receptors. This blockade inhibits the normal inhibitory effects of glycine in the spinal cord and brainstem.

2. Increased Neural Excitability:

• Reduced Inhibition: By blocking glycine receptors, strychnine reduces the inhibitory neurotransmission that glycine normally provides. This leads to an overall increase in neuronal excitability, as the balance between excitatory and inhibitory signals is disrupted.

3. Hyperreflexia and Startle Responses:

• Exaggerated Reflexes: The inhibition of glycine-mediated synaptic transmission results in exaggerated startle responses and hyperreflexia (increased reflex responses). This is because the inhibitory control over motor neurons is diminished, leading to uncontrolled muscle contractions.

4. Seizures and Muscle Spasms:

• Severe Toxicity: At high doses, strychnine can lead to severe symptoms, including uncontrollable seizures and muscle spasms. The lack of inhibition can cause sustained muscle contractions and spasms, particularly in respiratory muscles, which can be life-threatening.

5. Mechanism of Action:

• Competitive Antagonism: Strychnine acts as a competitive antagonist at glycine receptors, meaning it competes with glycine for binding to the receptor sites. This prevents the opening of chloride channels that would normally lead to hyperpolarization of the postsynaptic neuron, thus inhibiting its activity.