Binding of [3H]prazosin and [3H]p-aminoclonidine to α-adrenoceptors in rat spinal cord

Rosa Maria Ademe Simmons, David J. Jones

Research output: Contribution to journalArticle

25 Scopus citations

Abstract

α-Adrenoceptors in spinal cord appear to play a role in a number of physiologic processes including the control of blood pressure, pain and motor function. In order to evaluate more clearly these potential roles, the characteristics of binding of [3H]prazosin ([3H]PRZ) to spinal α1 adrenoceptors and [3H]p-aminoclonidine ([3H]PAC) to spinal α2 adrenoceptors were determined. Binding of each ligand to their respective adrenoceptors was saturable and Scatchard analysis revealed binding of each to a single class of adrenoceptors with characteristics of [3H]PRZ binding of Bmax = 78 fmol/mg protein and Kd = 0.75 nM and [3H]PAC binding Bmax = 70 fmol/mg protein and Kd = 1.39 nM. Whereas [3H]PRZ specific binding (Bmax) was unaltered by guanine nucleotides, [3H]PAC binding was increased with addition of 10 μM guanosine triphosphate (GTP) (P < 0.05) and decreased with either 50 μM GTP or guanyl-5′-yl-imidodiphosphate [Gpp(NH)p] (P < 0.01). Competition for specific [3H]PRZ and [3H]PAZ binding by various α1and α2 adrenoceptor vs 4300 nM for yohimbine) and [3H]PAC defines α2 adrenoceptors (Ki = 1.06 nM for yohimbine vs 15480 nM for prazosin). Regional spinal cord studies demonstrated that dorsal spinal cord in the lumbar region contains the highest density of both [3H]PRZ (Bmax = 93 ± 14 fmol/mg protein) and [3H]PAC (Bmax = 101 ± 6 fmol/mg protein). In contrast, lowest binding was evident in thoracic cord with equal levels in both dorsal and ventral regions (Bmax = 44-48 fmol/mg protein). The regional distribution of both α1and α2 adrenoreceptors in spinal cord compares to the localization previously classified functional utilizing various pharmacological agonists and antagonists at norepinephrine receptors.

Original languageEnglish (US)
Pages (from-to)338-349
Number of pages12
JournalBrain Research
Volume445
Issue number2
DOIs
StatePublished - Apr 5 1988

Keywords

  • Adrenoceptor
  • Cyclic adenosine monophosphate
  • Development
  • Noradrenaline
  • Spinal cord
  • Uptake

ASJC Scopus subject areas

  • Neuroscience(all)
  • Molecular Biology
  • Clinical Neurology
  • Developmental Biology

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