Influence of Adenosine Intrathecally and its alpha-2-Adrenergic Spinal Interactions of Allodynia After Spinal Nerve Ligation in Rats

Erwin Schrödinger Fellowship J 1991 Spinal action of adenosine in neuropathic rats Andreas SANDER- KIESLING 09.10.2000 This study will test mechanisms responsible for the greater potency of adenosine intrathecally in removing tactile hyperalgesia than in blocking acute nociceptive input. First, we want to determine if incubation of dorsal spinal cord synaptosomes with adenosine can inhibit capsaicin-induced glutamate (GLU) release and whether this inhibition differs between normal and spinal nerve ligated rats. Crude synaptosome solutions will be prepared by homogenization and stepwise centrifugation from lumbar dorsal spinal cords of male 200-250g Sprague-Dawley rats. After preloading with [3H]-GLU, release from C fiber afferent terminals will be stimulated by incubation with 30 M capsaicin and inhibition of this release tested with incubation with the mixed A1/A2 adenosine agonist, 5`- N-ethylcarboxamide (NECA). Receptor subtype involved will be determined by incubation with 10-9 to 10-4 M of the adenosine receptor antagonists: 8-cyclopentyl-1,3-dipropylxanthine (A1), or 3,7-dimethyl- 1 - propargylxanthine (A2). Following rapid filtration, remaining bound [3H]-GLU will be detected using a Beta Scintillation Counter. Second, we want to determine the effect of adenosine receptor stimulation on norepinephrine (NE) release from primary afferent nerve terminals of normal and spinal nerve ligated rats, using a spinal slice perfusion system. Lumbar dorsal horns of 250g male rats will be sliced into 0.1 to 0.5 mm sections and loaded on filters of superfusion chambers. After equilibration and determination of basal NE, the slices will be superfused by 10-9 to 10-4 M of NECA alone or with 8-cyclopentyl-1,3dipropylxanthine, or 3,7-dim ethyl- I -propargylxanthine, and NE in the perfusates analyzed by HPLC.