title: Changes in the biochemical profiles of mid-cervically located adenosine A1 receptors after repeated theophylline administration in adult rats.
abstract: OBJECTIVE
  Adenosine A1 receptors localized in the phrenic motoneurons (PMNs), where the axons of the descending bulbospinal respiratory make synaptic contacts, may be involved in theophylline-induced respiratory-related activity in rats. The objective of this study was to characterize the biochemical profiles of adenosine A1 receptors in 2 groups of rats: (a) naïve and (b) theophylline-treated (3-day oral administration).
  
  
  METHODS
  Biochemical binding characteristics of adenosine A1 receptors in the C3 to C5 (PMN) of adult rats were assessed in naïve (n = 6) and theophylline-treated animals (n = 6) using [3H]-DPCPX (10 pmol/L to 30 nmol/L), the specific adenosine A1 receptor antagonist in saturation-binding assays. Competition assays used theophylline as the competing ligand (20 mmol/L to 20 pmol/L), and protein concentration was determined with the Bradford assay using a range of standards (0.016-1.0 mg/mL).
  
  
  RESULTS
  In saturation-binding assays in naïve animals, the A1 receptor was characterized by a single binding site with Bmax and Kd values of 256.00 +/- 32.13 fmol/mg protein and 2.89 +/- 0.45 nmol/L, respectively. Analysis of the isotherm in theophylline-treated animals showed 1 site with Bmax and Kd values of 219.00 +/- 26.3 fmol/mg protein and 0.60 +/- 0.21 nmol/L, respectively, and a second site characterized by Bmax and Kd values of 492.6 +/- 3.15 fmol/mg protein and 14.09 +/- 2.06 nmol/L, respectively.
  
  
  CONCLUSIONS
  Theophylline administration revealed 2 binding sites on receptors (characterized by the specific adenosine A1 antagonist, [3H]-DPCPX) located in the vicinity of phrenic motoneurons (C3-C5). Alteration of the receptor profiles after theophylline may underlie the respiratory-related actions of the drug.
authors.affiliation: Department of Anatomy and Cell Biology, Wayne State University, Detroit, Michigan 48202, USA.
authors.forename: Rubabe S
authors.initials: RS
authors.lastname: Saharan
authors.forename: Kwaku D
authors.initials: KD
authors.lastname: Nantwi
mesh_terms: D000284:Administration, Oral; D000818:Animals; D001665:Binding Sites; D001993:Bronchodilator Agents / Q000008:administration & dosage / Q000494:pharmacology*; D002574:Cervical Vertebrae; D004305:Dose-Response Relationship, Drug; D005260:Female; D009046:Motor Neurons / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D043682:Receptor, Adenosine A1 / Q000378:metabolism*; D012119:Respiration / Q000187:drug effects; D013806:Theophylline / Q000008:administration & dosage / Q000494:pharmacology*
chemical_list: D001993:Bronchodilator Agents; D043682:Receptor, Adenosine A1; D013806:Theophylline