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Characteristics of 3H-substance P binding sites in rat brain membranes |
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| Authors: | C H Park V J Massari R Quirion Y Tizabi C W Shults T L O'Donohue |
| Affiliation: | 1. Department of Pharmacology, College of Medicine, Howard University 520 W. Street, N.W., Washington, D.C. 20059 USA;2. Experimental Therapeutics Branch, National Institute of Neurological and Communicative Disorders and Stroke, Bethesda, MD 20205 USA;3. Section on Brain Biochemistry, Clinical Neuroscience Branch, National Institute of Mental Health Bethesda, MD 20205 USA |
| Abstract: | Binding characteristics of 3H-Substance P (SP) were studied with rat brain membranes using a method applied to peripheral tissues by Lee and Snyder [15]. This method was well applicable to central nervous system (CNS) tissues. The results in the present study indicate that specific 3H-SP binding reaches a plateau only after 20 minutes of incubation, and the binding sites are saturable at a relatively low concentration of 3H-SP. Scatchard analysis of specific binding data reveals a single class of binding sites with a high affinity (Kd = 0.30 nM) and a low density (Bmax = 27.7 fmol/mg protein) in rat brain membranes. A Hill plot of the displacement curve of 3H-SP with unlabelled SP showed no indication for cooperativity (nH = 0.83). The relative potencies of binding of various SP fragments at 3H-SP binding sites were fairly parallel to the length of the C-terminal fragments. Neurotransmitters not structurally related to SP produced no effect on 3H-SP binding even when used at micromolar concentrations. |
| Keywords: | Rat brain membranes Specific binding |
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