II. Long-Term Changes in the Morphology of Aply- 
sia Sensory Neurons In Vitro Due to 5-HT Resem- 
ble Developmental Growth in Being Regulated by 
the Postsynaptic Motor Neuron. 
Process formation of Aplysia sensory neurons in 
dissociated cell culture is regulated by the presence 
of an appropriate target motor neuron. Sensory 
neurons cocultured with the identified motor 
neuron L7 have a more complex morphology than 
do those cultured alone. Moreover, the motor neu- 
rons not only stimulate but also appear to guide 
the outgrowth of processes from the sensory neu- 
rons. D. L. Glanzman, Schacher, and Kandel have 
now found that the postsynaptic cell is also re- 
quired for long-term morphological changes in sen- 
sory neurons in response to a modulatory transmit- 
ter, 5-HT. Application of 5-HT produced an increase 
in the number of varicosities on the neurites of sen- 
sory neurons, but only when they are cocultured 
with motor neurons. This increase is restricted to 
neurites that contacted the major processes of 
motor neurons, suggesting that some signal from 
the postsynaptic motor cell regulates long-term 
changes in the morphology of sensory neurons, 
both during development and with learning and 
memory. 
III. Cloning oi Aplysia Potassium Channel with Ho- 
mology to Drosophila Shaker. 
One of the substrate proteins modulated by 5-HT 
and cAMP during both short- and long-term sensiti- 
zation is the S-type K"*" channel. A K"*" channel from 
PUBLICATIONS 
Aplysia that has high homology to the Drosophila 
Shaker, mouse, and rat channels has been 
cloned, to begin the examination of this modula- 
tion on the molecular level. Homology screening 
was performed by P. Pfaffinger, B. Zhao, M. Knapp, 
J.-F. Brunet, D. Dugan, and Kandel, using the poly- 
merase chain reaction (PCR) on Aplysia total ner- 
vous system RNA. PCR amplified a single DNA band 
of 180 bp, the predicted size based on the other K"*^ 
channel clones. This fragment was sequenced and 
showed >85% amino acid identity to other 
channel clones. Using PCR and specific oligonucle- 
otides to this Aplysia K"*^ channel, Pfaffinger, Zhao, 
Knapp, Brunet, Dugan, and Kandel cloned the 
complete coding region. They have identified five 
different 3' ends, one of which contains a possible 
A kinase phosphorylation site. These 3' ends appar- 
ently are generated by alternative splicing, since 
Southern analysis suggests this is a single-copy 
gene. The domain containing the transmembrane- 
spanning regions has >70% amino acid identity to 
other channels. Efforts to clone the 5' end are now 
under way. In addition, Zhao, Kandel, and Pfaffin- 
ger are now examining the relationship between 
the expression of different K"*" channel isoforms and 
the electrical properties of specific identified neu- 
rons. 
Dr. Kandel is also University Professor, Center for 
Neurobiology and Behavior, Departments of Physi- 
ology and Psychiatry, Columbia University College 
of Physicians and Surgeons, located at the New 
York Psychiatric Institute. 
Books and Chapters of Books 
Glanzman, D., Sweatt, D., Dale, N., Schacher, S., Barzilai, A., Kennedy, T, and Kandel, E.R. 1989. Long-term 
memory in Aplysia-. its characterization by protein synthesis and neuronal growth. In Neuromuscular 
Junction (Sellin, L.C., Libelius, R., and Thesleff, S., Eds.). Amsterdam: Elsevier, pp 489-497. 
Kandel, E.R. , Goelet, R , Castellucci, VE, Montarolo, PG., Dale, N. , and Schacher, S. 1989. Initial steps toward 
a molecular biology of long-term memory. In Molecular Biology in Physiology (Chien, S., Ed.). New York: 
Raven, pp 119-147. 
Volterra, A., Siegelbaum, S.A., Sweatt, J. D., and Kandel, E.R. 1989. Presynaptic inhibition, presynaptic facilita- 
tion, and the molecular logic of second-messenger systems. In Molecular and Cellular Aspects of the Drug 
Addictions (Goldstein, A., Ed.). New York: Springer-Verlag, pp 159-197. 
Articles 
Barzilai, A., Kennedy, TE., Sweatt, J.D., and Kandel, E.R. 1989. 5-HT modulates protein synthesis and the ex- 
pression of specific proteins during long-term facilitation in Aplysia sensory neurons. Neuron 2:1577- 
1586. 
Continued 
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