Developmental changes in purinergic calcium signalling in rat neocortical neurones.
The changes in cytoplasm free calcium concentration ([Ca2+]i transients) were measured in Fura-2/AM loaded pyramidal neurones of sensorimotor cortex in acutely prepared slices isolated from 14 days (P14) and 30 (P30) days old rats. Ni2+ (50 microM) diminished the [Ca2+]i transients evoked by 50 mM KCl bath application by 47%+/-8% in neurones of the P14 group and only by 15%+/-6% in those of P30 group (P<0.002). Nifedipine and verapamil in concentration 100 microM reduced the calcium transients amplitude triggered by depolarization to about the same extent in both groups of neurons-on average by 50% and 35%, respectively. The amplitude of [Ca2+]i transients induced by application of 100 microM ATP reached 103+/-6 nM in P14 neurones and 72+/-8 nM in the P30 ones. The ATP-[Ca2+]i induced transient could be evoked in Ca2+-free external solution, indicating the presence of metabotropic (P2y) purinoreceptors. Almost all (90%) P14 neurones were endowed with such receptors. At the same time only 1/3 of the tested (n=42) P30 neurones presented responses to ATP applications in Ca2+-free solution. The share of ionotropic (P2x) purinoreceptors in generation of calcium signal was the same in both groups of neurons. No caffeine-induced Ca2+-release has been observed in the P14 neurons. To the contrary, in 28 cells from 42 investigated neurones of the P30 group application of 40 mM caffeine for 10 s induced considerable [Ca2+]i transients, which did not disappear in calcium-free solution. A conclusion is made about substantial changes in the expression of Ca2+-handling mechanisms which are occurring in neocortical neurones at the third-fourth week of postnatal development.
Lalo
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U
Bogomoletz Institute of Physiology, National Academy of Sciences of Ukraine, Bogomoletz St., 4, 252024 Kyiv-24, Ukraine. lalo@serv.biph.kiev.ua
Kostyuk
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P
D000375:Aging / Q000502:physiology*; D000818:Animals; D000831:Animals, Newborn / Q000254:growth & development* / Q000502:physiology; D002110:Caffeine / Q000494:pharmacology; D015220:Calcium Channels / Q000502:physiology; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology*; D002462:Cell Membrane / Q000378:metabolism; D002540:Cerebral Cortex / Q000166:cytology / Q000502:physiology*; D009474:Neurons / Q000502:physiology; D011687:Purines / Q000378:metabolism*; D051381:Rats; D011983:Receptors, Purinergic / Q000502:physiology
D015220:Calcium Channels; D011687:Purines; D011983:Receptors, Purinergic; D002110:Caffeine