On 3 Dec 2001 06:03:23 GMT, dag.stenberg at nospam.helsinki.fi wrote:
>Richard Norman <rsnorman at mediaone.net> wrote:
>> And don't even think about a synapse that actually DEcreases ion
>> permeabilities!
>>Well, but there are synapses that do so indirectly: an axon terminal may
>release a transmitter that binds to a postsynaptic receptor that via a
>G-protein in the membrane induces closure of a K+ channel, which is a
>depolarizing, i.e. excitatory action.
>>Dag Stenberg
Exactly. That makes defining just what is an "excitatory" or an
"inhibitory" synapse very complicated. Let's see, its not the
transmitter -- ACh and NE can do either. Its not depolarization vs
hyperpolarization -- a Cl channel can depolarize but still be
inhibitory. Its not the type of ion involved -- you have given a case
of an excitatory synapse that affects K channels. So it is a little
tricky. That is what makes neurobiology such fun. That is also what
drives newcomers crazy.
