title: Excitatory effects of adenosine 5'-triphosphate on rat locus coeruleus neurones.
abstract: Pontine slices of the rat brain were used for extracellular recording of the frequency of spontaneous action potentials of locus coeruleus (LC) neurones. In the absence of 8-cyclopentyl-1,3-dipropylxanthine (DPCPX), alpha,beta-methyleneadenosine 5'-triphosphate (alpha,beta-meATP; 0.3-30 mumol/l) and 2-methylthio ATP (0.3-100 mumol/l), but not ATP (1-100 mumol/l) increased the firing rate. In the presence of DPCPX 0.1 mumol/l, all three purinoceptor agonists were active, the potency order being alpha,beta-meATP greater than 2-methylthio ATP = ATP. Preincubation of the slices with tetrodotoxin (TTX) 0.5 mumol/l decreased the spike discharge but did not alter the percent facilitatory effect of alpha,beta-meATP 30 mumol/l. There was no desensitization to alpha,beta-meATP 10 mumol/l on repeated or continuous application. Suramin 100 mumol/l selectively depressed the effect of alpha,beta-meATP 30 mumol/l without interfering with the effect of equiactive concentrations (10-100 mumol/l) of glutamic acid. The concentration-response curve of alpha,beta-meATP was shifted in a parallel manner to the right by suramin 10 mumol/l. While DPCPX 0.1 mumol/l facilitated firing, suramin 100 mumol/l did not change it. In conclusion, LC neurones may possess P2-purinoceptors of an unidentified type, which share some P2x characteristics.
authors.affiliation: Department of Pharmacology, University of Freiburg, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Tschöpl
authors.forename: L
authors.initials: L
authors.lastname: Harms
authors.forename: W
authors.initials: W
authors.lastname: Nörenberg
authors.forename: P
authors.initials: P
authors.lastname: Illes
mesh_terms: D000200:Action Potentials / Q000187:drug effects; D000255:Adenosine Triphosphate / Q000031:analogs & derivatives / Q000494:pharmacology*; D000818:Animals; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D008125:Locus Coeruleus / Q000187:drug effects* / Q000502:physiology; D008297:Male; D009474:Neurons / Q000187:drug effects / Q000502:physiology; D051381:Rats; D011919:Rats, Inbred Strains; D011983:Receptors, Purinergic / Q000187:drug effects / Q000502:physiology*; D013498:Suramin / Q000494:pharmacology; D013779:Tetrodotoxin / Q000494:pharmacology; D013873:Thionucleotides / Q000494:pharmacology; D014970:Xanthines / Q000494:pharmacology
chemical_list: D011983:Receptors, Purinergic; D013873:Thionucleotides; D014970:Xanthines; D013779:Tetrodotoxin; D013498:Suramin; D000255:Adenosine Triphosphate; C051360:1,3-dipropyl-8-cyclopentylxanthine; C002630:alpha,beta-methyleneadenosine 5'-triphosphate; C008501:2-methylthio-ATP