Effects of salt-loading hypertension on nociception in rats

• Published in: Journal of pain research 2013-01, Vol.6 (default), p.387-392
• Main Authors: Afolabi, Ayobami Oladele, Mudashiru, Saheed Kolade, Alagbonsi, Isiaka Abdullateef
• Format: Article
• Language: English
• Subjects: Analysis; Blood pressure; Care and treatment; Causes of; Complications and side effects; formalin test; Hypertension; Nociception; Original Research; Pain; Rodents; tail-flick test
• ISSN: 1178-7090; 1178-7090
• DOI: 10.2147/JPR.S44206

There is on going controversy on the effect of experimentally induced hypertension on nociception. The effect of salt-loading-induced hypertension on pain was studied in male rats. Twenty-four male Sprague-Dawley rats (160-280 g) were divided into two groups. Group A (n = 12) was treated with normal-feed diet (control), while group B (n = 12) was treated with 8% salt-loaded diet for 10 weeks. After 10 weeks of the treatment, six rats each from groups A and B were used for blood pressure measurement, while the remaining six rats were used for both the tail-flick and formalin tests. Thermal and chemical pain test were assessed using tail immersion test (tail flick) and formalin test pain paradigms at onset of salt-loading diet and after 10 weeks of salt loading. Chronic administration of salt-loading diet caused significant increases (P < 0.001) in systolic blood pressure, diastolic blood pressure, and mean arterial blood pressure. Moreover, salt-loading-induced hypertension was found to significantly reduce pain sensitivity in the tail-immersion test (P < 0.001) and in the early and late phase of the formalin test (P < 0.01). However, the hypoalgesia was higher in the late phase (94.8%) than in the early phase (56.8%) of the formalin test. The present study suggests that high salt-loading-induced hypertension causes hypoalgesia in rats, which might be due more to reduction in inflammatory response.