Thursday, 28 August 2008

Can one neuron release more than one neurotransmitter?

Go here to find out!

One question for pondering: why does the brain use so many different neurotransmitters? If their purpose is simply to transmit information (in a sort of analogue way, as opposed to the more digital action potentials), why can't you just have one, or at best two (one excitatory, one inhibitory) type of neurotransmitter to do all the work? Hmm...


  1. Although there are many neurotransmitters in the central nervous system, the peripheral nervous system has only two: acetylcholine and norepinephrine. Why are there so many brain neurotransmitters? Because the functions performed by brain neurotransmitters are not as uniform as they might superficially appear. Some (like glutamate) are excitatory, whereas others (like GABA) are primarily inhibitory. In many cases (as with dopamine) it is the receptor which determines whether the transmitter is excitatory or inhibitory. Receptors can also determine whether a transmitter acts rapidly by direct action on an ion channel (eg, nicotinic acetylcholine receptors) or slowly, by a second-messenger system that allows for synaptic plasticity (eg, muscarinic acetylcholine receptors). Speed & mechanism of transmitter inactivation after the signal has been sent is also a factor. There are probably also costs & benefits involved in synthesizing, transporting and recycling various neurotranmitters in the differing chemical mileus of the brain.

    From here.

  2. Yes, I think that's a good start.

    Don't much buy the receptor variation red herring though - that only seems to bolster my point. If a receptor is able to vary considerably, then there is even LESS need for the neurotransmitters to do so. (You could work the argument the other way too, of course!)

    I liked the points about:
    (a) speed and mechanism of transmitter inactivation
    (b) costs/benefits differing in different brain regions

    ... these seem to have promise, even if they are rather speculative and broad. In general, it's HARD to find the bewildering number of neurotransmitters explained anywhere, don't you think?