Which of the following adaptations is most likely in a cholinergic synapse in which there is progressive degeneration of the presynaptic terminal?

Question

BlackTom AI · Accepted Answer

The question centers on what adaptation would occur in a cholinergic synapse when there is progressive degeneration of the presynaptic terminal. In this scenario, the presynaptic side is becoming dysfunctional and less capable of releasing acetylcholine (ACh), which reduces signaling at the postsynaptic membrane. Understanding compensatory mechanisms helps explain why postsynaptic changes might occur.

Option 1: Increased expression of postsynaptic receptors. This is a plausible compensatory response. If less ACh is released from the presynaptic terminal, the postsynaptic neuron may upregulate nicotinic ACh receptors to capture the diminished neurotransmitter more effectively, preserving synaptic efficacy. In other words, receptor upregulation can help maintain the response to the reduced ACh stimulus.

Option 2: Increased activity of monoamine oxidase. Monoamine oxidase (MAO) degrades monoamine neurotransmitters such as dopamine, norepinephrine, and serotonin. Since acetylcholine is not a monoamine, MAO activity is not directly relevant to a cholinergic synapse degeneration. Elevating MAO would not compensate for reduced ACh signaling and could indirectly influence other neurotransmitter systems, but it does not address the cholinergic-specific presynaptic degeneration.

Option 3: Increased expression of dopamine β-hydroxylase. This enzyme converts dopamine to norepinephrine and is part of catecholaminergic pathways, not cholinergic ones. Upregulating dopamine β-hydroxylase would not enhance cholinergic transmission and would misalign with the neurotransmitter system described in the question.

Option 4: Increased activity of catechol-O-methyl transferase. This enzyme degrades catecholamines (dopamine, norepinephrine, epinephrine). Like MAO, it targets monoaminergic transmitters rather than acetylcholine. Upregulating COMT would not directly improve cholinergic transmission and would, in fact, reduce monoaminergic signaling, not compensate for cholinergic loss.

To summarize, among the given options, upregulating postsynaptic receptors is the most sensible compensatory adaptation to presynaptic cholinergic degeneration, because it directly enhances the postsynaptic neuron's sensitivity to the reduced acetylcholine signal. The other options involve enzymes and processes tied to non-cholinergic neurotransmitters and thus do not address the specific cholinergic decline described.

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Which of the following adaptations is most likely in a cholinergic synapse in which there is progressive degeneration of the presynaptic terminal?

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PHRM30002_2025_SM2 PHRM30002 MST 1- Requires Respondus LockDown Browser

Which of the following adaptations is most likely in a cholinergic synapse in which there is progressive degeneration of the presynaptic terminal?

View Explanation

Log in for full answers

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