Final answer:
Increased neurotransmitters lead to more binding at the postsynaptic receptors, potentially altering the electrochemical potential and causing either excitation or inhibition depending on the neurotransmitter type. Agonist drugs can further enhance this effect.
Step-by-step explanation:
When neurotransmitters are increased in the synaptic gap, they become more likely to bind to receptors on the postsynaptic cell membrane. This can result in changes to the electrochemical potential of the postsynaptic neuron, potentially leading to the generation of an action potential if the effect is excitatory. For example, increased levels of acetylcholine in the neuromuscular junction can lead to depolarization and an excitatory postsynaptic potential (EPSP), making the postsynaptic neuron more likely to fire an action potential. Conversely, neurotransmitters like GABA tend to cause hyperpolarization of the postsynaptic membrane, which results in an inhibitory postsynaptic potential (IPSP), making it less likely to fire an action potential. Additionally, drugs classified as agonists can enhance neurotransmitter activity by various mechanisms, which might influence the number of neurotransmitter molecules released during exocytosis and therefore alter neurological responses and behaviors.