ISSN:
1471-4159
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Medicine
Notes:
Abstract: Intracerebral microdialysis combined with a sensitive and specific radioimmunoassay was used to monitor the neuronal release of somatostatin (somatostatin-like immunoreactivity, SLI) in the dorsal hippocampus of freely moving rats. The sensitivity of the radioimmunoassay was optimized to detect 〈1 fmol/ml. The basal concentration of SLI in 20-min dialysate fractions (5 μl/min) collected 24 h after probe implantation was stable over at least 200 min. The spontaneous efflux dropped by 54 ± 6.4% (p 〈 0.05) when Ca2+ was omitted and 1 mM EGTA added to the Krebs-Ringer solution and by 65.5 ± 3.2% (p 〈 0.05) in the presence of 1 μM tetrodotoxin. Depolarizing concentrations of the Na+ channel opener veratridine (6.25, 25, 100 μM) induced 11 ± 2 (p 〈 0.05), 17 ± 2 (p 〈 0.05), and 21 ± 5 (p 〈 0.01) fold increase in SLI concentration, respectively, during the first 20 min of perfusion. The effect of 100 μM veratridine was blocked by coperfusion with 5 μM tetrodotoxin (p 〈 0.01) and reduced by 79% (p 〈 0.01) in the virtual absence of Ca2+. Neuronal depolarization by 20 min of perfusion with Krebs-Ringer solution containing 25 and 50 mM KCl and proportionally lowered Na+ increased the dialysate SLI 4.4 ± 1 (p 〈 0.05) and 17 ± 3 (p 〈 0.01) fold baseline, respectively. Ten micromolar ouabain, a blocker of Na+,K+-ATPase, increased the dialysate SLI 15-fold baseline, on average (p 〈 0.05), during 80 min of perfusion. The results demonstrate the suitability of brain microdialysis for monitoring the neuronal release of SLI and for studying its role in synaptic transmission.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1111/j.1471-4159.1993.tb03200.x
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