l-arginine treatment early in life influences NADPH-diaphorase neurons in visual cortex of normal and early-malnourished adult rats

Do the accelerating actions of tianeptine and l-arginine on cortical spreading depression interact? An electrophysiological analysis in young and adult rats

In the rat, we previously demonstrated that serotonin-enhancing drugs impair cortical spreading depression (CSD) and that l-arginine (arginine) treatment enhances CSD. Here, we investigated the interaction between topical application of the serotonin uptake enhancer tianeptine and systemic arginine administration on CSD. From postnatal day 7-28, female Wistar rats (n=40) received by gavage 300mg/Kg/day arginine (n=20) or water (n=20). Half of the arginine- or water-treated rats underwent CSD recording at 30-40days of age (young), while the other half was recorded at 90-120days (adult). Following baseline recording (four episodes of CSD), we applied tianeptine solution (10mg/ml) to a rectangular portion of the intact dura mater for 10-min and then elicited CSD. This procedure was repeated three times. Compared to baseline values, CSD velocities and amplitudes following tianeptine application increased, and CSD duration decreased significantly (p<0.05) in both young and adult rats, regardless of treatment group. CSD acceleration caused by systemic treatment with arginine is in agreement with previous findings. Topical cortical application of tianeptine replicated the effect of systemic application, suggesting a cortically based mechanism for tianeptine's action. However, the absence of interaction between arginine and tianeptine treatments suggests that they probably act through separate mechanisms.

Differential effects of physical exercise and L-arginine on cortical spreading depression in developing rats

OBJECTIVE

We investigated the effect of early-in-life administration of L-arginine, combined with physical exercise, on cortical spreading depression (CSD) in young and adult rats.

METHODS

L-arginine (300 mg/kg/day, n = 40) or distilled water (vehicle, n = 40) was given to the rats during postnatal days 7-35 by gavage. Physical exercise (treadmill) was carried out during postnatal days 15-35 in half of the animals in each gavage condition described above. The other half (non-exercised) was used for comparison. When the animals reached 35-45 days (young groups) or 90-120 days of age (adult) CSD was recorded on two cortical points during 4 hours and CSD propagation velocity was calculated.

RESULTS

L-arginine-treated + exercised rats had increased body weight, but not brain weight, in adult age compared to L-arginine + non-exercised ones (P < 0.05). In both young and adult animals, L-arginine increased, whereas exercise decreased the CSD propagation velocity. Analysis of variance revealed a significant interaction between gavage treatment and age (P < 0.001), and also between gavage treatment and exercise (P = 0.004), but not between age and exercise. An additional control group of young rats, treated with 300 mg/kg of L-histidine, presented CSD velocities comparable to the corresponding water-treated controls, suggesting that the CSD acceleration seen in the L-arginine group was an L-arginine-specific effect, rather than an effect due to a non-specific amino acid imbalance.

DISCUSSION

L-arginine and exercise affect CSD differentially (L-arginine accelerated, while exercise decelerated CSD), and both effects did interact. Probably, they depend on developmental plasticity changes associated with the treatments.

Exercise and food ad libitum reduce the impact of early in life nutritional inbalances on nitrergic activity of hippocampus and striatum

Nutritional imbalances were produced by varying litter size pups per dam: 3 (small), 6 (medium), and 12 (large). On the 21st day, 4 subjects of each litter, were sacrificed and the remaining were grouped, 2 per cage, with or without running wheels, with food and water ad libitum. Adult subjects were tested in water maze, their brains processed for NADPH-diaphorase histochemistry and quantified by densitometry. No differences were detected in water maze. At 21st day, S and L compared with M presented reduced NADPH-d in the stratum molecular of dentate gyrus (DG), stratum lacunosum of CA1 and in all CA3 layers but not in the striatum. On the 58th day, actvity remained low in S and L in CA3 and striatum and L in CA1 and DG. Voluntary exercise increased NADPH-d in DG, CA1, CA3, and striatum in S, and in the stratum lacunosum of CA1 and CA3 in L.