Neurotransmitters are ligands (a chemical that attaches itself to a larger entity) of two major types of receptors.

  • Ionotropic: opens channel for ions to flow in to or out of cell
    • Otherwise known as ligand-gated ion channels, or, channel proteins
    • Fast communication
    • Takes longer time to revert back to normalcy after being artificially stimulated
    • GABA-A receptors
    • Nicotinic acetylcholline receptors
  • Metabotropic: after binding to receptor, create transduction (continuance of message, chain-reaction) down through the cell
    • Unlike activation of ionotropic receptors, metabatropic receptors never directly open ion channels on the post-synaptic neuron
    • Otherwise known as g-protein coupled receptors, or, signal proteins
    • Slower
    • Has “second messenger”: G-protein
    • GABA-B receptors
    • Muscarinic acetylcholline receptors
    • Can indirectly open ion channels, acting similarly to ionotropic neurons
      • Occurs from action inside the neuron
      • Caused by the second messenger
      • Seen below

And, one more time:

  • The image next image shows how a more structurally realistic metabotropic receptor looks like
    • Signal proteins look like strings criss-crossing the cell membrane several times, with part of it projecting into the synapse
    • We see which loops and parts of the string various neurochemicals bind to
  • G-protein coupled receptors usually create a more complex chain of events via the second messenger
    • GDP molecule exchanged for GTP molecule, which detaches from inner-cell complex
    • A large variety of other interactions can the take place
    • Reaction makes its way to the cell body (soma) (where RNA and DNA are located)
    • Transcription factors (involved in RNA prodcution) may interact with the soma
    • Signal transduction (propagating the signal on to another neuron occurs

The image below depicts the sequence in a similar manner

One more:

Things can get damn complicated…

ScholarPedia is a peer-reviewed Wikipedia-esque website that describes theses processes in much more detail.

Sources: Dr. Kevin Davis, Biopsychology,