In vivo release of somatostatin from rat hippocampus and striatum.
Rats were implanted with microdialysis probes in hippocampi and striata, and somatostatin-like immunoreactivity (SS-LI) was measured in outflows obtained from awake, freely moving animals 48 and 72 h post implantation. SS-LI was measurable in all dialysates under basal conditions; concentrations were stable and within a narrow range, about 3-6 fmol/ml. Cysteamine (300 mg/kg, s.c.) markedly reduced basal SS-LI concentrations in outflows from hippocampus (P < 0.00001). KCl (100 mM, 10 min) or veratridine (50 microM, 10 min) infusion elevated hippocampal SS-LI output by 55 and 106%, respectively (P's < 0.05). EGTA (10 mM) or tetrodotoxin (2 microM) infusion inhibited the SS-LI release elicited by KCl and veratridine, respectively, without affecting the basal SS-LI outflow. Thus, our results demonstrate that SS-LI is released from rat hippocampus and striatum in vivo, and provide evidence that the peptide may be released in hippocampus by both action potential dependent and independent processes.
Mathé
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AA
Department of Psychiatry, St. Göran's Hospital, Stockholm, Sweden.
Nomikos
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GG
Svensson
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TH
D000818:Animals; D003342:Corpus Striatum / Q000187:drug effects / Q000378:metabolism*; D003543:Cysteamine / Q000494:pharmacology; D003956:Dialysis; D006624:Hippocampus / Q000187:drug effects / Q000378:metabolism*; D066298:In Vitro Techniques; D008297:Male; D011189:Potassium Chloride / Q000494:pharmacology; D011863:Radioimmunoassay; D051381:Rats; D017208:Rats, Wistar; D013004:Somatostatin / Q000378:metabolism*; D013779:Tetrodotoxin / Q000494:pharmacology; D014701:Veratridine / Q000494:pharmacology
D013779:Tetrodotoxin; D013004:Somatostatin; D003543:Cysteamine; D011189:Potassium Chloride; D014701:Veratridine