On 31 May 2007 13:09:38 -0700, jonesmat <jonesmat from physiology.wisc.edu>
wrote:
>On May 31, 9:51 am, Mathias <mathiasDOTfranz... from webDELETEME.de> wrote:
>> I'll answer myself in case someone else is interested in the same
>> question later. I found an article by Olbrich and Braak (1985) in Anat.
>> Embryol. 173:105-110 stating that in the human hippocampal area CA1 less
>> than 10% of the neurons are not pyramidal cells. They also cite similar
>> results for rats and monkeys in the discussion section.
>>>> Thus I think one can estimate that the rat CA1 (of a single hippocampus)
>> has approx. 355.000 pyramidal cells.
>>>> hthsl (hope this helps someone later ;)
>> Mathias
>>>>Mathias,
>>Thanks for those references. They are helpful.
>>I wonder, though, if the small number of interneurons might be a bit
>deceptive, functionally.
>>They make enormous numbers of synapses onto pyramidal cells and each
>other. I think each interneuron may make tens of thousands of
>synapses, spanning several hundred microns, and contacting hundreds or
>thousands of pyramidal cells. I can't remember the exact papers where
>these things were measured in CA1, but I think this is reviewed in the
>big Freund & Buszaki "Interneurons of the Hippocampus" paper.
>>Also, Steve Cobb & Eberhard Buhl (r.i.p.) and colleagues showed that a
>single spike in a single interneuron is capable of synchronizing the
>firing of the field of pyramidal cells that it contacts.
>>Just putting in my usual plug for the importance of inhibitory
>systems. The mouse that roared, as it were...
>
Inhibitory systems are exceptionally capable. Consider the crustacean
stomatogastric system, for example, where inhibition is the leading
player (along with inhibitory rebound excitation plus some electrical
interaction) in producing rather complex patterns of coordinated
rhythmic behavior.
