Ornithine α-ketoglutarate supplementation influences motor activity in healthy rats

Background: Ornithine α-ketoglutarate (OKG) improves nutritional status in malnourished patients. Published and unpublished data suggest OKG may have effects on the central nervous system that may contribute to its action. Objective: We investigated the effect of an OKG-enriched diet on behaviour in healthy rats. Design: Thirty male Wistar rats were randomised in three groups: the OKG group was fed for 5 days (D0–D5) at 90% of spontaneous food intake with an OKG-enriched diet (5 g/kg/d). The non-essential amino acids (NEAA) group was fed similarly with a regimen enriched with NEAA (glycine, alanine, histidine and serine) to be isonitrogenous to OKG group. The ad libitum (AL) group had no treatment and was fed ad libitum with a standard regimen throughout. Rats were tested at D4 for motor activity by actimetry, and at D5 first for spontaneous alternation behaviour measured in the Y-maze, and then for exploratory behaviour measured using the open-field test (stressful environment). Results: We found that OKG supplementation enhanced global motricity by actimetry (AL 772±55, NEAA 811±54 vs. OKG 966±24 arbitrary units, P<0.05) and total numbers of arms visited in the Y-maze (AL 26±2, NEAA 30±3 vs. OKG 38±3, P<0.05). The lack of any effect of the OKG-enriched diet in the open-field test shows that the enhancement of locomotion activity was most probably not due to an increase in anxiety or fear in the rats. Conclusion: An OKG-enriched diet can induce beneficial stimulant effects that may be involved in the mechanism of action of OKG.