GABA-mediated Ca2+ signalling in developing rat cerebellar Purkinje neurones.
1. Cellular responses to GABA(A) receptor activation were studied in developing cerebellar Purkinje neurones (PNs) in brain slices obtained from 2- to 22-day-old rats. Two-photon fluorescence imaging of fura-2-loaded cells and perforated-patch recordings were used to monitor intracellular Ca2+ transients and to estimate the reversal potential of GABA-induced currents, respectively. 2. During the 1st postnatal week, focal application of GABA or the GABA(A) receptor agonist muscimol evoked transient increases in [Ca2+]i in immature PNs. These Ca2+ transients were reversibly abolished by the GABA(A) receptor antagonist bicuculline and by Ni2+, a blocker of voltage-activated Ca2+ channels. 3. Perforated-patch recordings were used to measure the reversal potential of GABA-evoked currents (E(GABA)) at different stages of development. It was found that E(GABA) was about -44 mV at postnatal day 3 (P3), it shifted to gradually more negative values during the 1st week and finally equilibrated at -87 mV at around the end of the 2nd postnatal week. This transition was well described by a sigmoidal function. The largest change in E(GABA) was -7 mV x day(-1), which occurred at around P6. 4. The transition in GABA-mediated signalling occurs during a period in which striking changes in PN morphology and synaptic connectivity are known to take place. Since such changes were shown to be Ca2+ dependent, we propose that GABA-evoked Ca2+ signalling is one of the critical determinants for the normal development of cerebellar PNs.
Eilers
J
J
Abteilung Neurophysiologie, Max-Planck-Institut für Hirnforschung, 60528 Frankfurt, Germany. eilers@mpih-frankfurt.mpg.de
Plant
T D
TD
Marandi
N
N
Konnerth
A
A
D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001640:Bicuculline / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology*; D002531:Cerebellum / Q000166:cytology / Q000254:growth & development; D018756:GABA Antagonists / Q000494:pharmacology; D006096:Gramicidin / Q000494:pharmacology; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D009532:Nickel / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D011689:Purkinje Cells / Q000187:drug effects / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D011963:Receptors, GABA-A / Q000378:metabolism; D005680:gamma-Aminobutyric Acid / Q000494:pharmacology*
D000900:Anti-Bacterial Agents; D018756:GABA Antagonists; D011963:Receptors, GABA-A; D006096:Gramicidin; D005680:gamma-Aminobutyric Acid; D009532:Nickel; D002118:Calcium; D001640:Bicuculline