Final answer:
If a neuron has receptors for a particular neurotransmitter, it will respond in a similar way to another agonist for that receptor, as agonists mimic the action of the neurotransmitter. Antagonists, on the other hand, bind to the receptor without activating it, preventing the neurotransmitter's effect. Receptor-neurotransmitter interactions are highly specific, and the effects depend on the receptor type involved.
Step-by-step explanation:
If a neuron has receptors for a particular neurotransmitter, it will respond in a similar way to another agonist for that receptor. Agonists are substances that bind to a receptor and result in a response, therefore mimicking the action of the naturally occurring neurotransmitter. In contrast, antagonists bind to the receptor but do not activate it, which blocks or dampens a biological response.
The interaction between neurotransmitters and receptors is highly specific, akin to a key (neurotransmitter) fitting into a lock (receptor). When a neurotransmitter like acetylcholine binds to its specific receptor, it may cause depolarization or hyperpolarization of the postsynaptic neuron, depending on the receptor type. For instance, acetylcholine acting on a nicotinic receptor causes depolarization as it is a cation channel allowing the influx of Na+ ions, whereas its binding to a muscarinic receptor can have varied effects including both depolarization and hyperpolarization. Conversely, an antagonist for that receptor would not elicit the same effect as the neurotransmitter, but would instead block the receptor's activity.
It is important to note that the presence of receptors for a particular neurotransmitter does not mean the neuron will release that same neurotransmitter from its axon terminals. Neurons can have receptors for multiple neurotransmitters and can release different neurotransmitters than those for which they have receptors.