Modulation of mechanically induced calcium waves in hippocampal astroglial cells. Inhibitory effects of alpha 1-adrenergic stimulation.
The effects of different adrenoceptor agonists were investigated on mechanically induced Ca2+ waves in astroglial cells in astroglial-neuronal mixed cultures from rat hippocampus. In the initial part of the study some properties of the waves were characterized. The results show that the initiation of the Ca2+ waves was not critically dependent on extracellular Ca2+ but both the calcium signal and the propagation area of the calcium wave were significantly reduced when the experiments were performed in Ca2+-free buffer. In addition, using the phospholipase C (PLC) inhibitor U-73122 (1 microM) and the gap junction uncoupler octanol (1 mM), the results showed that the Ca2+ wave propagation required PLC activation and functional gap junctions. Further, the data also showed that the protein kinase C (PKC) activator phorbol-12-myristate-13-acetate (PMA 150 nM) reduced the spreading of the waves. The adrenoceptor agonists isoproterenol (iso; beta), phenylephrine (phe; alpha1) and clonidine (clon; alpha2) were evaluated for their short-term (<30 s) effects on the wave propagation. The propagation area was persistently decreased 1, 3 and 5 min after removal of phe. No effects were observed after incubation with iso or clon. Furthermore, using U-73122 or PMA together with phe, shortly incubated, the experiments showed that PLC was a central regulator in the initial phase of the initiation procedure of wave propagation. However, under these conditions PKC was shown not to be involved. Instead it appeared that PKC exerted its inhibitory action on the Ca2+ waves in a latter phase, after prolonged phe exposure. Taken together, the results show that the propagation of Ca2+ waves between astroglial cells in primary cultures can be inhibited/regulated in two principally different ways which involve a pronounced time component. The results also further point out the adrenergic signaling system as an important mediator of dynamic neuron-astroglial information exchange.
Muyderman
H
H
Department of Neurology, Institute of Neurobiology and Institute of Clinical Neuroscience, Göteberg University, Göteborg, Sweden. hakan.muyderman@anatcell.gu.se
Nilsson
M
M
Blomstrand
F
F
Khatibi
S
S
Olsson
T
T
Hansson
E
E
Rönnbäck
L
L
D020003:1-Octanol / Q000494:pharmacology; D058646:Adrenergic alpha-1 Receptor Agonists; D058668:Adrenergic alpha-1 Receptor Antagonists; D000818:Animals; D001253:Astrocytes / Q000166:cytology / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism* / Q000502:physiology; D002478:Cells, Cultured; D003000:Clonidine / Q000494:pharmacology; D004789:Enzyme Activation / Q000187:drug effects; D004963:Estrenes / Q000494:pharmacology; D017629:Gap Junctions / Q000187:drug effects / Q000502:physiology; D006624:Hippocampus / Q000166:cytology / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism*; D007545:Isoproterenol / Q000494:pharmacology; D010656:Phenylephrine / Q000494:pharmacology; D011493:Protein Kinase C / Q000502:physiology; D011760:Pyrrolidinones / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D018340:Receptors, Adrenergic, alpha-1 / Q000502:physiology; D010738:Type C Phospholipases / Q000037:antagonists & inhibitors / Q000502:physiology
D058646:Adrenergic alpha-1 Receptor Agonists; D058668:Adrenergic alpha-1 Receptor Antagonists; D004963:Estrenes; D011760:Pyrrolidinones; D018340:Receptors, Adrenergic, alpha-1; C060229:1-(6-((3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl)-1H-pyrrole-2,5-dione; D010656:Phenylephrine; D011493:Protein Kinase C; D010738:Type C Phospholipases; D007545:Isoproterenol; D003000:Clonidine; D020003:1-Octanol; D002118:Calcium