Antagonistic effect of L-aspartic acid on decrease in body weight, and food and fluid intake, and naloxone reversible rectal temperature depression caused by D-aspartic acid.

Seventy-five rats, divided into five groups, were given D-aspartic acid (D-Asp), L-Asp and D + L-Asp in ratio 1/1 or 1/2 for one week. The body weight, food and fluid intakes, and rectal temperature of the rats received D-Asp or D + L-Asp in 1/1 ratio significantly decreased. The decrease in rectal temperature was antagonized by naloxone. L-Asp given together with D-Asp in 1/2 ratio prevented D-Asp-caused decrease in body weight, food and fluid intakes, and rectal temperature. Although D-amino acids, as antipeptidases have some effects through endorphinergic systems, D-Asp (an inhibitor of L-asparaginase) seems to act at the level of L-asparaginase presumably by increasing the level of endorphins since L-Asp antagonizes the inhibitory effect of both D-Asp and morphine.