NAVAL MEDICAL RESEARCH INSTImTE

  NATIONAL NAVAL MEDICAL CENTER
   BETHESDA, MARYLAND - 20014

Feb.22,1972

Dr. Marshall Nirenburg
Bldg.lO,Rm.GD-18
NIH,Bethesda,Md.

Dear Dr. Nirenburg,

   I attended your recent seminar at our Tnstitute. Your
experimental. data and their implications are most interesting.

   If I understand correctly, you found that B-type cells
which contain Acetylcholine Esterase and respond to electrical
stimulations with local potentials. A-qype cells can respond
to electrical stimulation with action pgtentials. Your findings
remind me of the basic differences between the so-called synaptic
membrane which has acetylcholine receptors or chemoreceptors
and the nonsynaptic membrane which has no chemosensitivity.
I wonder whether the differentiation between the A-type cells
and B-type cells also depends upon the presence of chemoreceptors.
The synaptic membrane has the following properties:(l) it is
chemically excitable,(2) it only generates local and graded
potential responses,  (3) it contains chemoreceptors. The nonsynaptic
membrane has the following characteristics:(l) it is electrically
excitable,(2) it is not chemically excitable,(3) it can generate
action potentials which are regenerative and propagated events.

   It seems to me that the B-type cell membrane may he chemically
excitable, which indicates the presence of chemoreceptors. To
test this, one may use intracellular and extracellular iontopho-
resis to eject acetylcholine or other transmitters to the surface
of the cells and record cell membrane potential changes. If you
are interested in these experimentscand techniques, I would be glad
to be helpful. I am sure the electr>hysiologists in your lab can
do these experiments easily. Your lecture was very stimulating
and I enjoyed lkistenfng to you.

Co dially yours,
if m  +M /LL
ne H. Hu,Ph.D.
Research Neurophysiologist
Bldg.17,Rm.206
Tel: 295-0013