Organisms using a single neurotransmitter

[Pietr Hitzig]

rcb1 at LEX.LCCC.EDU (Ron Blue) wrote:
>On Wed, 13 Mar 1996, Sandra L Wegert wrote:
>> On 12 Mar 1996, JONES MICHAEL STEPHEN wrote:
>> > Is anyone aware of an organism that uses only a single
>> > neurotransmitter? 
>> 
>> Cool question, but it seems that if an organism HAS nerves, it
>> usually uses many of the same NT's that we do.  I searched that
>> jumbled mess in my head for an answer, and the only thing I came
>> up with was - get this- slime molds.  Yep.  They use cAMP to 
>> aggregate.  This doesn't really "count" as a NT-like function, but
>> I think that's the only chemical messenger they use (please check, 
>> though).  My two pesos...  :)
>> ----------------------
>> sandraw at U.Arizona.EDU
>cAMP is a NT and was recently connected to pain perception.
>So slime molds could have started the whole ball of wax by using
>cAMP to emit reflex responses to danger.  The gene code could
>have been picked up by bacteria.  Ron Blue <rcb1 at lex.lccc.edu

CAMP may now be a NT but doesn't mean in the ur-organism that it served 
that role. It may be a spandrel but spandrels get modified for other uses 
(Daniel Dennett, Darwin's Dangerous Idea, responding to Stephen Gould)

I believe that the idea of a single neurotransmitter organism is as 
fantastic as an arm without the triceps to balance the biceps, or insulin 
without glucagon or somatostatin without growth hormone.  

I am proposing that the "primal regulators" (??NT's) are DA and 5-HT or 
better, the metabolism of tryptophan (and probably the other aromatic 
amino acids, phenylalanine and tyrosine.)  

All other regulatory systems are derived from these ancient opposing 
monomamines.