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The effects of evening primrose oil on nerve function and capillarization in streptozotocin‐diabetic rats: modulation by the cyclo‐oxygenase inhibitor flurbiprofen
Author(s) -
Cameron Norman E.,
Cotter Mary A.,
Dines Kevin C.,
Robertson Sharon,
Cox Dominic
Publication year - 1993
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1111/j.1476-5381.1993.tb13716.x
Subject(s) - nerve conduction velocity , evening primrose oil , medicine , diabetes mellitus , diabetic neuropathy , endocrinology , sciatic nerve , streptozotocin , evening , anesthesia , physics , astronomy
1 The aims of this study were first, to examine whether deficits in nerve conduction in streptozotocin‐diabetic rats could be reversed by a 10% dietary supplement of evening primrose oil. Second, to determine the time‐course of reversal, and third, to assess whether the effects could be blocked by the cylco‐oxygenase inhibitor flurbiprofen (5 mg kg −1 day −1 ). 2 One‐month diabetes produced 20% and 15% deficits in sciatic motor and saphenous sensory conduction velocity respectively, which were maintained over 2 months diabetes. 3 The effect of 1‐month evening primrose oil treatment on abnormalities caused by an initial month of untreated diabetes was examined. Motor and sensory nerve conduction velocity were restored to the non‐diabetic level. 4 Resistance to hypoxic conduction failure was investigated for sciatic nerve trunk in vitro . The 80% conduction failure times were 29% and 55% prolonged by 1‐ and 2‐month diabetes respectively. Evening primrose oil did not reverse the increased hypoxic resistance following 1‐month untreated diabetes. 5 Sciatic nerve endoneurial capillary density was not significantly affected by diabetes, but was 16% increased in diabetic rats with reversal by evening primrose oil treatment for 1 month compared to 2‐month untreated diabetes. 6 Serial motor conduction velocity measurement after 3‐month untreated diabetes revealed complete normalization by evening primrose oil within 4 days. Cessation of treatment resulted in a rapid decline in conduction velocity over 24 h. 7 In a preventive study of 2‐month duration, 6 groups of rats were used. These comprised non‐diabetic controls, diabetic rats, and evening primrose oil‐treated diabetic rats, both with and without flurbiprofen treatment. Flurbiprofen had no significant effect in non‐diabetic rats, but produced an 11% worsening of motor conduction velocity and a 21% reduction of sciatic capillary density in diabetic rats. Evening primrose oil prevented the decreases in conduction velocity and increased hypoxic resistance with diabetes, and caused a 23% increase in capillary density. Flurbiprofen completely blocked the effect of evening primrose oil on conduction velocity, resistance to hypoxia, and capillarization. 8 Six main conclusions were reached. First, evening primrose oil rapidly reverses conduction deficits in diabetic rats. Second, the effects of treatment may be very short‐lived, suggesting a primary metabolic action. Third, evening primrose oil cannot reverse established changes in hypoxic resistance over 1‐month treatment. Fourth, long‐term treatment causes angiogenesis, suggesting a vascular action. Fifth, products of cyclo‐oxygenase‐mediated metabolism are necessary for maintaining vasa nervorum integrity in diabetic rats. Sixth, evening primrose oil probably acts by providing substrate for vasodilator prostanoid synthesis by vasa nervorum.