title: Dopaminergic modulation of neuropathic pain: analgesia in rats by a D2-type receptor agonist.
abstract: Experimental studies have shown that dopaminergic mechanisms can modulate both nociception and chronic pain perception, but such property is not exploited pharmacologically at the clinical level. We have previously shown that levodopa produces D2-receptor-mediated antiallodynic effects in rats with peripheral mononeuropathy. Here, we test the effects of a D2-type receptor (D2R) agonist, quinpirole, on neuropathic pain in rats. Allodynic responses to cooling and light touch were measured in the hind limbs of rats with chronic constriction injury of one sciatic nerve. Single intraperitoneal injection of quinpirole (1 mg/kg) totally inhibited cold and tactile allodynic responses for over 3 and 48 h, respectively. At that dose, quinpirole had no effect on nocifensive responses to heat. Lumbar intrathecal injection of quinpirole produced short-term inhibition of the responses to cold and tactile stimuli, suggesting that spinal mechanisms may contribute to the antiallodynic activity of quinpirole. Chronic subcutaneous infusion of quinpirole by implanted Alzet pumps (0.025 mg/kg·day) provided a slowly progressing inhibition of cold and tactile allodynic responses, which re-emerged after the pumps were removed. These experiments show the involvement of dopaminergic systems in the modulation of chronic allodynias and provide experimental support for proposing the use of D2R agonists for neuropathic pain relief.
authors: Service of Neurobiology-Research, IRYCIS, Hospital Ramón y Cajal, Carretera de Colmenar km 9, 28034 Madrid, Spain.
authors: Nuria
authors: N
authors: Cobacho
authors: Pain Unit, Hospital Ramón y Cajal, Carretera de Colmenar km 9, 28034 Madrid, Spain.
authors: José Luis
authors: JL
authors: de la Calle
authors: Service of Neurobiology-Research, IRYCIS, Hospital Ramón y Cajal, Carretera de Colmenar km 9, 28034 Madrid, Spain. Electronic address: carlos.paino@hrc.es.
authors: Carlos Luis
authors: CL
authors: Paíno
mesh_terms: D000698:Analgesia; D000818:Animals; D018491:Dopamine Agonists / Q000008:administration & dosage / Q000494:pharmacology / Q000627:therapeutic use*; D006930:Hyperalgesia / Q000188:drug therapy; D007278:Injections, Spinal; D008297:Male; D009437:Neuralgia / Q000188:drug therapy*; D010147:Pain Measurement / Q000187:drug effects; D019257:Quinpirole / Q000008:administration & dosage / Q000494:pharmacology / Q000627:therapeutic use*; D051381:Rats; D017207:Rats, Sprague-Dawley; D017448:Receptors, Dopamine D2 / Q000819:agonists*; D013116:Spinal Cord / Q000187:drug effects*
chemical_list: D018491:Dopamine Agonists; D017448:Receptors, Dopamine D2; D019257:Quinpirole
keywords: Chronic subcutaneous infusion; Cold allodynia; Quinpirole; Spinal delivery; Systemic delivery; Tactile allodynia