Effects of neurotransmitters on astrocyte glycogen stores in vitro.
We have used receptor binding assays to determine the presence of three neurotransmitter receptors in a crude membrane fraction derived from neonatal rat cortical astrocyte cultures and subsequently determined the effects of transmitter receptor activation on astrocyte glycogen content in vitro. beta-Adrenergic (KD = 88 pM; Bmax = 51 fmol/mg of protein), serotonin (KD = 70 nM; Bmax = 44 pmol/mg of protein), and muscarinic cholinergic receptors (KD = 79 pM; Bmax = 44 fmol/mg of protein) were found to be present on astrocyte membranes using [3H]dihydroalprenolol, [3H]serotonin, and [3H]quinuclidinyl benzilate, respectively, as ligands. Astrocyte cultures exposed to noradrenaline but not specific alpha- and beta-receptor agonists contained 33% less glycogen than controls. Neither serotonin nor carbachol caused alterations in astrocyte glycogen content under normal conditions. Reserpine-treated cultures, however, responded to serotonin with a 28% decrease in glycogen content and contained higher levels of glycogen than non-reserpine-treated controls (a 55% increase). These results show that both noradrenaline and serotonin can evoke astrocyte glycogenolysis and that noradrenergic control of glycogen metabolism is probably exerted through both alpha- and beta-receptors. Neurotransmitter control of astrocyte glycogen turnover may represent a form of neuron-astrocyte signalling in addition to that provided by changes in external potassium concentration.
D000818:Animals; D000831:Animals, Newborn / Q000378:metabolism; D001253:Astrocytes / Q000187:drug effects / Q000378:metabolism*; D003994:Bucladesine / Q000494:pharmacology; D002217:Carbachol / Q000494:pharmacology; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000166:cytology*; D005576:Colforsin / Q000494:pharmacology; D004082:Dihydroalprenolol / Q000378:metabolism; D006003:Glycogen / Q000378:metabolism*; D007545:Isoproterenol / Q000494:pharmacology; D018377:Neurotransmitter Agents / Q000494:pharmacology*; D009638:Norepinephrine / Q000494:pharmacology; D010656:Phenylephrine / Q000494:pharmacology; D011813:Quinuclidinyl Benzilate / Q000378:metabolism; D011869:Radioligand Assay; D051381:Rats; D011941:Receptors, Adrenergic / Q000378:metabolism; D011976:Receptors, Muscarinic / Q000378:metabolism; D011985:Receptors, Serotonin / Q000378:metabolism; D012110:Reserpine / Q000494:pharmacology; D012701:Serotonin / Q000378:metabolism / Q000494:pharmacology
D018377:Neurotransmitter Agents; D011941:Receptors, Adrenergic; D011976:Receptors, Muscarinic; D011985:Receptors, Serotonin; D005576:Colforsin; D010656:Phenylephrine; D012701:Serotonin; D004082:Dihydroalprenolol; D003994:Bucladesine; D011813:Quinuclidinyl Benzilate; D012110:Reserpine; D002217:Carbachol; D006003:Glycogen; D007545:Isoproterenol; D009638:Norepinephrine