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Many sensory neurons express different kinds of neurotransmitter receptors that are used to modulate sensory activity based on neural inputs.

In addition to odor receptors located on their dendrites, olfactory neurons in the nasal cavity possess adrenergic receptors. Experiments have shown that applying norepinephrine, a main adrenergic neurotransmitter, to isolated olfactory neurons inhibits their responses to odors. Applying norepinephrine alone, without odors, does not affect olfactory neurons.

Einstein - Created for Copyright 2016. All rights reserved.

In autoimmune diseases, antibodies can sometimes be generated against neurotransmitter receptors. Depending on the extracellular region of the receptor to which the antibody binds, the receptor can be stimulated or inhibited.

Einstein - Created for Copyright 2016. All rights reserved.

You wish to determine whether antibodies that stimulate the adrenergic receptor in other systems, also will stimulate the adrenergic receptors on olfactory neurons, thus inhibiting their responses to odors.

You isolate olfactory neurons from mice, place them into nutrient-rich medium in a dish, and record responses from them. You observe that antibodies that have previously been shown to stimulate the adrenergic receptor inhibit the neuron’s responses to odors.

However, when you inject these same antibodies into a mouse’s vascular system and test the animal’s responses to odors, there is no effect.

Einstein - Created for Copyright 2016. All rights reserved.

Given the information above, the diagrams that illustrate the experiment, and logic, which of the following might explain this finding and should be further explored scientifically?

Select ALL that apply.


The antibodies may not have been administered in high enough concentration to the living animal to influence olfactory neurons.


The antibodies may have bound to other structures in the body so as to not have access to the olfactory neuron dendrites.


The antibodies may not be able to reach the dendritic ends of the olfactory neurons due to the compartmentalization of extracellular space around the olfactory neurons.


There may be bacterial enzymes in the nasal mucus that destroy the antibodies before they can stimulate the neurons.


Some ingredient in the nutrient medium may facilitate the antibody binding to the receptor in the isolated olfactory neuron preparation.

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