Long-term regulation of neuronal high-affinity glutamate and glutamine uptake in Aplysia.
An increase in transmitter release accompanying long-term sensitization and facilitation occurs at the glutamatergic sensorimotor synapse of Aplysia. We report that a long-term increase in neuronal Glu uptake also accompanies long-term sensitization. Synaptosomes from pleural-pedal ganglia exhibited sodium-dependent, high-affinity Glu transport. Different treatments that induce long-term enhancement of the siphon-withdrawal reflex, or long-term synaptic facilitation increased Glu uptake. Moreover, 5-hydroxytryptamine, a treatment that induces long-term facilitation, also produced a long-term increase in Glu uptake in cultures of sensory neurons. The mechanism for the increase in uptake is an increase in the V(max) of transport. The long-term increase in Glu uptake appeared to be dependent on mRNA and protein synthesis, and transport through the Golgi, because 5,6-dichlorobenzimidazole riboside, emetine, and brefeldin A inhibited the increase in Glu uptake. Also, injection of emetine and 5,6-dichlorobenzimidazole into Aplysia prevented long-term sensitization. Synthesis of Glu itself may be regulated during long-term sensitization because the same treatments that produced an increase in Glu uptake also produced a parallel increase in Gln uptake. These results suggest that coordinated regulation of a number of different processes may be required to establish or maintain long-term synaptic facilitation.
Levenson
J
J
University of Houston, Department of Biology and Biochemistry, 4800 Calhoun Road, Houston, TX 77204-5513, USA.
Endo
S
S
Kategaya
L S
LS
Fernandez
R I
RI
Brabham
D G
DG
Chin
J
J
Byrne
J H
JH
Eskin
A
A
D000818:Animals; D001048:Aplysia / Q000378:metabolism*; D002352:Carrier Proteins / Q000378:metabolism; D018698:Glutamic Acid / Q000378:metabolism*; D005973:Glutamine / Q000378:metabolism*; D009474:Neurons / Q000378:metabolism*; D013997:Time Factors
D002352:Carrier Proteins; D005973:Glutamine; D018698:Glutamic Acid