title: Autoradiographic labelling of P2 purinoceptors in the guinea-pig cochlea.
abstract: Two different radioligands were used to identify extracellular ATP binding sites specific to P2 purinoceptors in guinea-pig cochlear tissue. Deoxyadenosine 5'-(alpha-[35S]thio)triphosphate ([35S]dATP alpha S; 10 nM) provided a high activity probe for the P2y purinoceptor subtype on the basis of selective block by 2-methylthio-ATP (2MeSATP; 100 microM). [3H]alpha, beta-methylene-ATP (10 nM), a high affinity probe for a P2x purinoceptor subtype was selectively blocked by inclusion of the related compound beta, gamma-methylene-ATP (100 microM). Both probes labelled the organ of Corti, stria vascularis and spiral prominence regions. The P2x purinoceptor probe also bound to lateral wall tissue below the spiral prominence and insertion point of the basilar membrane within the scala tympani compartment, a region which failed to show significant binding using [35S]dATP alpha S. Frozen sections of whole cochlea permitted analysis of radioligand binding to the cell body region (spiral ganglion in Rosenthal's canal) of the primary auditory afferents and the auditory nerve itself, which lies within the central region of the modiolus of the cochlea. Both these regions exhibited 2MeSATP blockable [35S]dATP alpha S binding whereas specific [3H]alpha, beta-methylene-ATP binding was absent from spiral ganglion and minimal in the auditory nerve region. These results demonstrate a mixed P2 purinoceptor distribution in cochlear tissues and suggest that complex purine-mediated neurohumoral mechanisms may influence cochlear function at a number of sites.
authors.affiliation: Department of Physiology, School of Medicine, University of Auckland, New Zealand.
authors.forename: B G
authors.initials: BG
authors.lastname: Mockett
authors.forename: X
authors.initials: X
authors.lastname: Bo
authors.forename: G D
authors.initials: GD
authors.lastname: Housley
authors.forename: P R
authors.initials: PR
authors.lastname: Thorne
authors.forename: G
authors.initials: G
authors.lastname: Burnstock
mesh_terms: D000255:Adenosine Triphosphate / Q000031:analogs & derivatives / Q000378:metabolism / Q000494:pharmacology; D000818:Animals; D001345:Autoradiography; D001667:Binding, Competitive; D003051:Cochlea / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D003838:Deoxyadenine Nucleotides / Q000378:metabolism / Q000494:pharmacology; D005260:Female; D005629:Frozen Sections; D006168:Guinea Pigs; D006199:Hair Cells, Auditory, Inner / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D018072:Hair Cells, Auditory, Outer / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D008297:Male; D058919:Purinergic P2 Receptor Antagonists; D011869:Radioligand Assay; D018048:Receptors, Purinergic P2 / Q000378:metabolism*; D013136:Spiral Ganglion / Q000187:drug effects / Q000378:metabolism; D013316:Stria Vascularis / Q000187:drug effects / Q000378:metabolism; D013873:Thionucleotides / Q000378:metabolism / Q000494:pharmacology
chemical_list: D003838:Deoxyadenine Nucleotides; D058919:Purinergic P2 Receptor Antagonists; D018048:Receptors, Purinergic P2; D013873:Thionucleotides; C015109:2'-deoxyadenosine 5'-O-(1-thiotriphosphate); D000255:Adenosine Triphosphate; C002630:alpha,beta-methyleneadenosine 5'-triphosphate; C008501:2-methylthio-ATP