Long-term potentiation in hippocampus involves sequential activation of soluble guanylate cyclase, cGMP-dependent protein kinase, and cGMP-degrading phosphodiesterase.
Previous studies indicate that cGMP is involved in long-term potentiation (LTP). However, the effects of application of tetanus to induce LTP on cGMP content and the mechanisms by which cGMP may modulate LTP have not been reported. The aim of this work was to study the time course of the changes in cGMP content and of the activity of soluble guanylate cyclase (sGC) (the enzyme that synthesizes cGMP) during LTP. Moreover, we also studied how the changes in cGMP affect cGMP-dependent protein kinase (PKG) and cGMP-degrading phosphodiesterase and the possible role of these changes in LTP. Application of tetanus induced a rise in cGMP, reaching a maximum 10 sec after tetanus. cGMP content decreased below basal levels 5 min after tetanus and remained decreased after 60 min. Activity of sGC increased 5 min after tetanus and returned to basal at 60 min. Tetanus increased the activity of cGMP-degrading phosphodiesterase at 5 and 60 min. GMP, the product of degradation, was increased at 5 and 60 min. Activation of phosphodiesterase and a decrease in cGMP were prevented by inhibiting PKG with Rp-8-bromoguanosine-cGMPS (Rp-8-Br-cGMPS). Inhibition of sGC [with ODQ (oxadiazolo quinoxalin-1-one) or NS 2028 (4H-8-bromo-1,2,4-oxadiazolo(3,4-d)benz(b)(1,4)oxazin-1-one)], of PKG (with Rp-8-Br-cGMPS), or of cGMP-degrading phosphodiesterase [with zaprinast or MBAM (4-[[3',4'-(methylenedioxy)benzyl]amino]-6-methoxyquinazoline) ] impairs LTP. The results indicate that induction of LTP involves transient activation of sGC and an increase in cGMP, followed by activation of cGMP-dependent protein kinase, which, in turn, activates cGMP-degrading phosphodiesterase, resulting in long-lasting reduction of cGMP content.
Monfort
Pilar
P
Instituto de Investigaciones Citológicas, Fundación Valenciana de Investigaciones Biomédicas, 46010, Valencia, Spain.
Muñoz
María-Dolores
MD
Kosenko
Elena
E
Felipo
Vicente
V
D015106:3',5'-Cyclic-GMP Phosphodiesterases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D000818:Animals; D006152:Cyclic GMP / Q000031:analogs & derivatives* / Q000378:metabolism / Q000494:pharmacology; D017869:Cyclic GMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D004558:Electric Stimulation; D004789:Enzyme Activation / Q000187:drug effects / Q000502:physiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D019706:Excitatory Postsynaptic Potentials / Q000187:drug effects / Q000502:physiology; D006162:Guanylate Cyclase; D006624:Hippocampus / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D066298:In Vitro Techniques; D017774:Long-Term Potentiation / Q000187:drug effects / Q000502:physiology*; D008297:Male; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors; D051381:Rats; D017208:Rats, Wistar; D018160:Receptors, Cytoplasmic and Nuclear / Q000037:antagonists & inhibitors / Q000378:metabolism*; D016194:Receptors, N-Methyl-D-Aspartate / Q000037:antagonists & inhibitors; D000071756:Soluble Guanylyl Cyclase; D013873:Thionucleotides / Q000494:pharmacology
D004791:Enzyme Inhibitors; D018691:Excitatory Amino Acid Antagonists; D018160:Receptors, Cytoplasmic and Nuclear; D016194:Receptors, N-Methyl-D-Aspartate; D013873:Thionucleotides; C083763:8-bromoguanosino-3',5'-cyclic monophosphorothioate; D019001:Nitric Oxide Synthase; D017869:Cyclic GMP-Dependent Protein Kinases; D015106:3',5'-Cyclic-GMP Phosphodiesterases; D006162:Guanylate Cyclase; D000071756:Soluble Guanylyl Cyclase; D006152:Cyclic GMP