This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Nervous System, Subject name: Physiology
[{'content': 'All are features of neurotransmitters except: \nSelect and explain. \nA. Released from presynaptic cleft, B. Degraded from presynaptic cleft, C. Exogenous administration will not have any effect, D. Produced in neurons only', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Ans: C (exogenous admin...) Ref: Ganong, 22nd ed, p. 85, 94Exogenous administration does have effects, for example when adrenaline (which is a neurotransmitter) is administered; it produces a number of effects like tachycardia, increase in BP etc.Mechanism of neurotransmission* Nerve endings convert electrical energy into chemical energy by means of neurotransmitters.* These neurotransmitters are stored in synaptic vesicles and released by nerve impulses into the synaptic cleft.* These neurotransmitters then act on the post synaptic membrane which results in conduction of impulse.* After their action they are rapidly removed from synaptic cleft by diffusion, metabolism or by re- uptake into the presynaptic neuron.* Exogenous administration of the neurotransmitter can also cause effects similar to its endogenous counterpart. Noradrenaline (which is a neurotransmitter) is given in shock to raise BP.', 'role': 'assistant'}]