Gamma-aminobutyric acid-induced calcium signalling in rat superior collicular neurones.
Ionotropic gamma-aminobutyric acid (GABA) receptors are known to mediate excitation in neonatal neurones as a crucial developmental factor. In the present study we employed calcium imaging techniques with the calcium indicator Fura-2-AM to study the pharmacology of GABA-induced calcium responses in cultures prepared from neonatal rat superficial superior colliculus (SC), after immunocytochemical labelling confirmed the presence of GABA(C) rho(1) subunits in 35% of neurones. Rises in neuronal intracellular calcium were obtained in response to GABA and also to the subtype-specific GABA(A) agonist 4,5,6,7-tetrahydroisoxazolo[5,4-c]pyridin-3-ol. However, the GABA(C) agonist cis-4-aminocrotonic acid induced calcium response only at unspecifically high concentrations (500 microM). Co-application of GABA antagonists revealed that both GABA(A&C) agonists' actions could be blocked by the GABA(A) antagonist bicuculline but not the GABA(C) antagonists 1,2,5,6-tetrahydro-(pyridin-4-yl) methylphosphinic acid. This suggests that activation of GABA(A) but not GABA(C) receptors contributes to excitatory GABA responses and related calcium signals in neonatal SC neurones.
White
Anne-Marie
AM
Department of Biomedical Sciences, Institute of Medical Sciences, Foresterhill, University of Aberdeen, Aberdeen, AB25 2ZD, Scotland, UK.
Platt
Bettina
B
D000818:Animals; D001640:Bicuculline / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002478:Cells, Cultured; D003561:Cytarabine / Q000031:analogs & derivatives* / Q000494:pharmacology; D018755:GABA Agonists; D018756:GABA Antagonists / Q000494:pharmacology; D007150:Immunohistochemistry; D007555:Isoxazoles / Q000494:pharmacology; D009474:Neurons / Q000187:drug effects / Q000378:metabolism*; D010721:Phosphinic Acids / Q000494:pharmacology; D011725:Pyridines / Q000494:pharmacology; D051381:Rats; D018079:Receptors, GABA / Q000187:drug effects / Q000378:metabolism*; D013477:Superior Colliculi / Q000187:drug effects / Q000378:metabolism; D005680:gamma-Aminobutyric Acid / Q000187:drug effects / Q000378:metabolism*
C101879:(1,2,5,6-tetrahydropyridin-4-yl)methylphosphinic acid; D018755:GABA Agonists; D018756:GABA Antagonists; D007555:Isoxazoles; D010721:Phosphinic Acids; D011725:Pyridines; D018079:Receptors, GABA; D003561:Cytarabine; C055054:N(4)-chloroacetylcytosine arabinoside; D005680:gamma-Aminobutyric Acid; C015542:gaboxadol; D002118:Calcium; D001640:Bicuculline