Alterations in calmodulin content in fractions of rat hippocampal slices during tetanic- and calcium-induced long-term potentiation.
The content of cytosolic and membrane-bound calmodulin was radioimmunologically determined in fractions of rat hippocampal slices 5 min to 7 hours after long-term potentiation (LTP) had been induced by tetanization or exposure of slices to 4 mM Ca++. In light of concepts presuming multistage dynamics in LTP development as reflecting different cellular mechanisms, similar patterns of calmodulin alterations were observed with both models: The alterations in calmodulin content occurred during the early phase(s) of LTP development and continued for two and one hours during tetanic- and calcium-induced LTP, respectively. Thus, 5-30 min after LTP elicitation, membrane-bound calmodulin increased while cytosolic calmodulin diminished and, inversely, 30 min later an increase in cytosolic and decrease in membrane-bound calmodulin were observed. Consequently, the present results indicate that calmodulin was involved in the early phases(s) of LTP development in terms of a two-step translocation sequence. Hence, calmodulin translocation within both intracellular compartments may reflect the involvement of Ca++-calmodulin-dependent intraneuronal metabolic processes which might induce and/or temporarily maintain neuronal functional changes occurring immediately after repeated or intense stimulation of synaptic functions.
Popov
N S
NS
Institut für Pharmakologie und Toxikologie, Medizinischen Akademie, Magdeburg, German Democratic Republic.
Reymann
K G
KG
Schulzeck
K
K
Schulzeck
S
S
Matthies
H
H
D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D002118:Calcium / Q000494:pharmacology*; D002147:Calmodulin / Q000032:analysis*; D002462:Cell Membrane / Q000032:analysis; D003600:Cytosol / Q000032:analysis; D006624:Hippocampus / Q000032:analysis* / Q000502:physiology; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains
D002147:Calmodulin; D002118:Calcium