A facilitatory role of endogenous somatostatin in long-term potentiation of the mossy fiber-CA3 system in guinea-pig hippocampus.
To estimate the functional role of endogenous somatostatin in the production of long-term potentiation (LTP) in mossy fiber-CA3 system, an influence of depletion of somatostatin on the magnitude of it was examined in guinea-pig hippocampal slices. Administration of cysteamine (200 mg/kg, s.c.), a depletor of somatostatin, to guinea-pigs 13 h prior to preparing slices resulted in a significant decrease in the magnitude of LTP of population spikes in mossy fiber-CA3 system, being associated with a significant depletion of the content of somatostatin in the hippocampus. Furthermore, bath-applied somatostatin (1-14) at a concentration, at which the substance did not influence LTP in slices prepared from saline-treated animals, significantly augmented LTP in slices from cysteamine-treated animals. Cyclo-somatostatin (0.32 and 3.2 microM), a putative antagonist of somatostatin receptors, failed to affect the magnitude of LTP of mossy fiber-CA3 system when applied alone; however, the combined application of cyclo-somatostatin with somatostatin (0.32 microM) significantly inhibited the augmenting action of somatostatin on LTP. From these observations, it is suggested that endogenous somatostatin plays a facilitatory role in the production of LTP in mossy fiber-CA3 system in guinea-pig hippocampus.
Department of Pharmacology, Faculty of Pharmaceutical Sciences, Kyoto University, Japan.
N
N
Matsuoka
S
S
Kaneko
M
M
Satoh
D000818:Animals; D003543:Cysteamine / Q000494:pharmacology; D004558:Electric Stimulation; D005071:Evoked Potentials / Q000502:physiology*; D006168:Guinea Pigs; D006624:Hippocampus / Q000166:cytology / Q000502:physiology*; D066298:In Vitro Techniques; D008297:Male; D008624:Mercaptoethylamines / Q000494:pharmacology; D009474:Neurons / Q000502:physiology*; D013004:Somatostatin / Q000378:metabolism / Q000502:physiology*
D008624:Mercaptoethylamines; D013004:Somatostatin; D003543:Cysteamine