Increases in seizure latencies induced by subcutaneous docosahexaenoic acid are lost at higher doses.

Docosahexaenoic acid (DHA) is a polyunsaturated fatty acid (PUFA) which has been found to have anticonvulsant properties. Our group has previously reported in a pilot study that the acute administration of subcutaneous (s.c.) DHA increases seizure latencies in the maximal pentylenetetrazole (PTZ) seizure test, however it loses its effect at higher doses. The purpose of the present experiments was (1) to confirm that DHA loses its effect at higher doses, (2) to correlate the anticonvulsant properties of DHA with DHA levels in the different lipid pools of serum and (3) to evaluate whether an anticonvulsant dose of DHA resulted in an increase in DHA release from the brain phospholipids following induction of seizure. In the first experiment, male Wistar rats were injected s.c. with 200, 300, 400 or 600 mg/kg of DHA, or 400mg/kg oleic acid (OA, isocaloric control), and seizure tested with the maximal PTZ test 1h post injection (Experiment 1). In a second experiment, subjects received either: (1) an effective dose of DHA (400mg/kg), (2) a higher, non-effective dose (600 mg/kg; based on the findings of Experiment 1), or (3) OA (400mg/kg). Subjects were sacrificed 1h post injection and blood was collected for fatty acid analysis (Experiment 2). In the third experiment, subjects were injected with either the effective dose of DHA (400mg/kg) or OA (400mg/kg). One hour post lipid injection, animals received either PTZ or saline, and animals were euthanized via microwave fixation. Brain were extracted and unesterified fatty acid concentrations were measured (Experiment 3). Experiment 1 confirmed that DHA loses its effects at higher doses in the maximal PTZ test. The 400mg/kg dose was maximally effective but effects were lost at 600 mg/kg. Experiment 2 showed that only the unesterified DHA pool in serum was statistically increased by an acute injection of s.c. DHA (P<0.05, as compared to OA), whereas esterified DHA pools were unchanged (P>0.05). Curiously, unesterified DHA levels were similar in both the 400mg/kg and 600 mg/kg dosage groups. Experiment 3 showed that an anticonvulsant dose of DHA (400mg/kg) did not increase DHA release from brain phospholipids following seizure induction (P>0.05). In conclusion, DHA has anticonvulsant properties when injected s.c., but these properties are lost at higher doses. The anticonvulsant effects of DHA are accompanied by increased levels of unesterified DHA in the serum, but not in increased DHA release from brain phospholipids.

Assessing the metabolic and toxic effects of anticonvulsant doses of polyunsaturated fatty acids on the liver in rats.

Polyunsaturated fatty acids (PUFA), at high doses, have been demonstrated to possess anticonvulsant properties in animal seizure models. Little is known, however, about the possible metabolic or adverse effects of PUFA at these high, anticonvulsant doses. The goal of the present study was to assess the metabolic and potential adverse effects of high-dose PUFA administration to rats. Adult male rats received a fatty acid mixture containing alpha-linolenic and linoleic acid in a 1 to 4 ratio, intraperitoneally, for 3 wk. After sacrifice, livers were isolated and analyzed for fatty acid composition and for mRNA expression of HMG-CoA lyase, catalase, and glutathione S-transferases A1 and A4, markers for ketosis, antioxidant defense, and phase II xenobiotic metabolism, respectively. Chronic administration of the PUFA mixture decreased hepatic levels of total lipids--and several fatty acids within total lipids--without altering mRNA expression of HMG-CoA lyase, a metabolic marker of ketosis. The PUFA mixture did not affect mRNA expression of catalase or glutathione S-transferases A1 and A4, which are involved in antioxidant defense and phase II xenobiotic metabolism. These findings suggest that PUFA, given for 3 wk at anticonvulsant doses, result in significant changes in liver lipid metabolism, but do not alter measured genetic markers of liver toxicity.