S. Schacher et al., CAMP AND ARACHIDONIC-ACID SIMULATE LONG-TERM STRUCTURAL AND FUNCTIONAL-CHANGES PRODUCED BY NEUROTRANSMITTERS IN APLYSIA SENSORY NEURONS, Neuron, 10(6), 1993, pp. 1079-1088
The efficacy of the synapses between the sensory and motor cells of Ap
lysia, as well as the number of presynaptic sensory cell varicosities
in vitro, can undergo long-term increases and decreases, respectively,
following application of the facilitatory modulator serotonin or the
inhibitory modulator FMRFamide. We here report that cAMP and arachidon
ic acid, two second messenger systems mediating some of the short-term
actions of serotonin and FMRFamide on sensory cells, reproduce some o
f the long-term changes in the structure of the sensory cells, and the
se structural changes in turn parallel the long-term changes in the fu
nctional effectiveness of the synapses. cAMP enhances the strength of
the connections between the sensory and motor cells and increases the
number of sensory varicosities. Conversely, arachidonic acid decreases
the strength of the connections and decreases the number of sensory v
aricosities. Thus, each of the modulatory neurotransmitters may activa
te the same intracellular second messenger system to establish both sh
ort and long lasting functional changes in synaptic efficacy, as well
as to produce enduring structural changes in neuron connectivity.