Characterisation of ATP-induced facilitation of transmission in rat hippocampus.
Superfusion of rat hippocampal slices with ATP induces a form of facilitation that has been poorly characterised. The present study has confirmed that at low concentrations of ATP (10 microM or less), an initial depression of evoked potential size is followed by a rebound facilitation which is not reproduced by alphabeta-methyleneATP, betagamma-methyleneATP, or the dinucleotide P1,P6-diadenosine hexaphosphate. The post-ATP facilitation could be prevented by the adenosine A1 receptor antagonists 8-phenyltheophylline or 1,3-dipropyl-8-cyclopentyltheophylline (50 nM), or superfusion of adenosine deaminase. The adenosine A2A receptor antagonist 8-(chlorostyryl)-caffeine did not affect the inhibition but prevented the post-ATP facilitation. The NMDA receptor antagonist 2-amino-5-phosphonopentanoic acid prevented the establishment of post-ATP facilitation. The post-ATP facilitation was also blocked by suramin at a concentration (50 microM) that does not block glutamate receptors. Suramin prevented the induction but not the maintenance phase of the post-ATP facilitation. The repeated induction of post-ATP facilitation by bursts of electrical stimulation designed to saturate the normal mechanisms of long-term potentiation prevented the induction of post-ATP facilitation. However, repeated applications of ATP to achieve saturation of its receptor did not prevent the subsequent induction of electrically evoked long-term potentiation. It is concluded that ATP can induce a form of synaptic facilitation which resembles only partially that induced by electrical stimulation and which may require the simultaneous activation of P1 and P2 receptors.
O'Kane
E M
EM
Institute of Biomedical and Life Sciences, West Medical Building, University of Glasgow, Glassgow G12 8QQ, Scotland, UK.
Stone
T W
TW
D000243:Adenosine Deaminase / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000031:analogs & derivatives* / Q000494:pharmacology*; D000818:Animals; D002110:Caffeine / Q000031:analogs & derivatives* / Q000494:pharmacology; D015226:Dinucleoside Phosphates / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004558:Electric Stimulation; D005071:Evoked Potentials / Q000187:drug effects; D006624:Hippocampus / Q000187:drug effects* / Q000502:physiology; D066298:In Vitro Techniques; D017774:Long-Term Potentiation / Q000187:drug effects; D008297:Male; D058915:Purinergic P1 Receptor Antagonists; D011732:Pyridoxal Phosphate / Q000031:analogs & derivatives* / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D013498:Suramin / Q000494:pharmacology; D009435:Synaptic Transmission / Q000187:drug effects*; D013806:Theophylline / Q000031:analogs & derivatives* / Q000494:pharmacology
D015226:Dinucleoside Phosphates; D058915:Purinergic P1 Receptor Antagonists; C081320:8-(3-chlorostyryl)caffeine; C077792:pyridoxal phosphate-6-azophenyl-2',4'-disulfonic acid; D002110:Caffeine; C070070:diadenosine 5',5''''-P1,P6-hexaphosphate; D011732:Pyridoxal Phosphate; D013498:Suramin; D000255:Adenosine Triphosphate; D013806:Theophylline; C028322:8-phenyltheophylline; D000243:Adenosine Deaminase; C002630:alpha,beta-methyleneadenosine 5'-triphosphate