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 language | English (US) |
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Pages (from-to) | 338-349 |
Number of pages | 12 |
Journal | Brain Research |
Volume | 445 |
Issue number | 2 |
DOIs | |
State | Published - 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