Irrespective of where, when and how neuromodulators are released, eventually they are detected by some receptors in the membrane of a target neuron (typically G protein–coupled receptors)

Neurotransmitter receptors are typically distributed on the dendrite and the soma of a neuron (and only occasionally on the axon):

  • at excitatory synapses (more distal)
  • at inhibibitory synapses (more proximal)

Does this rule of thumb also hold for neuromodulator receptors:

  • excitatory → more distal
  • inhibitory → more proximal

And are they clustered (like ligand-gated ion channels at synapses)?

  • $\begingroup$ There is a basic misunderstanding here: neurohormones are nothing more than hormones released by a neuron. Have a look here: biology.stackexchange.com/q/67048/24284 $\endgroup$ – user24284 Dec 4 '17 at 10:26
  • $\begingroup$ Thanks for the hint, I'll rephrase the question accordingly. $\endgroup$ – Hans-Peter Stricker Dec 4 '17 at 10:28
  • $\begingroup$ Do you have evidence that excitatory synapses/receptors are overall more distally distributed than inhibitory synapses? What is certainly true is that there are very few excitatory synapses on the soma. But at least when considering input densities, further out from the soma excitatory and inhibitory input densities are of roughly the same magnitude in the cortex: doi.org/10.3389/fnana.2016.00124. What you suggest, although unlikely, may still be right, but I can't think of any evidence from the top of my head. As for neuromodulator synapses/receptors, they are probably even less well studied. $\endgroup$ – vkehayas Dec 4 '17 at 11:38
  • $\begingroup$ Now that you ask me: no, I have no evidence, it's just a vague impression I gained: that inhibition - for regulatory (damping) purposes - occurs preferrably near the soma. For "calculatory" (finer tuned) purposes (concurring with excitatory synapses on an equal footing) it may occur also more distally. $\endgroup$ – Hans-Peter Stricker Dec 4 '17 at 11:47
  • $\begingroup$ Now think of neuromodulators performing more regulatory tasks (slow, unpronounced), even though not necessarily damping. Nearer to the soma they might perform these tasks more efficiently. $\endgroup$ – Hans-Peter Stricker Dec 4 '17 at 11:52

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