Effects of clycine, chlorpromazine and apomorphine on brain monoamines and free amino acids in rats

Abstract

Summary Rats were orally given glycine (Gly) (3 g/k/day) and chlorpromazine (CPZ) (2 mg/k day) both separately and in combination for four days, after which time a number from each group were injected i.p. with 0.025 mg of apomorphine (AP). 25 min after the injection the rats were killed and the levels of DA, NA, 5-HT and free amino acids (FAA's) were determined in the brain. Gly treatment resulted in an increase in DA, NA, 5-HT and FAA levels and AP antagonized this effect with respect to levels of DA and FAA's. Although CPZ potentiated the effect of Gly on the level of DA, it inhibited the Gly-related increase in FAA levels, apparently through the blockade of DA receptors. In the case of rats, given both Gly and CPZ, AP injection decreased the level of DA to the control value, possibly due to the inhibition of DA metabolism, and release by means of the stimulation of presynaptic DA receptors. This, together with the blockade of DA receptors by CPZ, resulted in a further decrease, below control values, in FAA levels. In the light of the previous and present findings the authors draw some conclusions some of which are following: 1. At appropriate concentration Gly causes an increase in DA metabolism and release. 2. The experiments support the claim that DA has a regulating effect on FAA levels in the brain.