Differential effects of N-methyl-D-aspartate on Ca2+ homeostasis in developing and adult rat striatum: in vivo microdialysis approach.
This in vivo study concerns developmental differences in the sensitivity of striatal neurons to N-methyl-D-aspartate (NMDA). Changes in calcium homeostasis in adult vs immature rats at postnatal days 8-10, evoked by NMDA, were evaluated by measurements of 45Ca efflux and of Ca2+ taurine and phosphoethanolamine concentrations in striatal microdialysates. The efflux of [14C]sucrose was employed in order to measure changes in extracellular space volume. In adult rats the addition of 5 mM NMDA for 20 min to the perfusion medium resulted in a 30-40% increase in 45Ca efflux, and in a 15% increase in [14C]sucrose efflux. Ten minutes after NMDA perfusion, 45Ca and [14C] sucrose efflux returned to the baseline. No significant changes in Ca2+ or amino acid concentrations were observed in the dialysate of the adult rat striatum. NMDA perfusion in the striatum of immature rats initially induced a transient (5 min) increase in the efflux of 45Ca (by 13%) and [14C]sucrose (by 9%). This was followed by a prolonged (lasting 45-50 min) 45% decrease in 45Ca efflux, an 80% reduction of Ca2+ concentration, and increases in taurine and phosphoethanolamine concentrations in the dialysate, whereas [14C]sucrose efflux recovered within 10 min. These data illustrate differences in the NMDA response between developing and adult rat striatum. Only in developing rats did NMDA induce a large and prolonged influx of extracellular calcium to neurons that may explain the enhanced NMDA neurotoxicity in immature rats.
Lazarewicz
J W
JW
Medical Research Centre, Polish Academy of Sciences, Warsaw.
Puka-Sundvall
M
M
Gadamski
R
R
Sandberg
M
M
Hagberg
H
H
D000375:Aging / Q000502:physiology; D000596:Amino Acids / Q000378:metabolism; D000818:Animals; D002118:Calcium / Q000502:physiology*; D002132:Calcium Radioisotopes; D018690:Excitatory Amino Acid Agonists / Q000494:pharmacology*; D006706:Homeostasis / Q000187:drug effects*; D017551:Microdialysis; D016202:N-Methylaspartate / Q000494:pharmacology*; D017072:Neostriatum / Q000033:anatomy & histology / Q000187:drug effects* / Q000254:growth & development*; D051381:Rats; D017208:Rats, Wistar; D013395:Sucrose / Q000378:metabolism
D000596:Amino Acids; D002132:Calcium Radioisotopes; D018690:Excitatory Amino Acid Agonists; D013395:Sucrose; D016202:N-Methylaspartate; D002118:Calcium