The role of glycine and NMDA glutamate receptor on central

Glycine is an inhibitory neurotransmitter in central nervous system and plays a certain role in food intake in mammalian. The purpose of the present study was to investigate the role of glycine in central regulation of feed intake of broiler cockerels (Ross 308) during six sequential phases. At 1, 2 and 3 phases, glycine (50, 100 and 200 nmol), NFPS (inhibitor of glycine transporter at 25, 50 and 100 nmol) and hydrochloride strychnine (competitive antagonist of presynaptic of glycine at 10, 50 and 250 nmol) were injected intracerebroventriculary (ICV). At 4, 5 and 6 phases, the effect of pretreatment of NFPS (100 nmol), strychnine (250 nmol) and DL-AP5 (antagonist of glutamate NMDA receptors, 5 nmol) on cumulative feed intake induced by glycine was evaluated. During this study, the control group was injected ICV by sterile physiological serum. Thereafter, Cumulative feed intake was measured at 15, 30, 60, 120 and 180 min after injection. According to the results, ICV injection of 200 nmol glycine significantly reduced the feed intake (p<0.05). Moreover, the injection of NFPS at 50 and 100 nmol, significantly increased the feed intake (p<0.05), while strychnine had no effect. Additionally, pretreatment with NFPS and DL-AP5 significantly attenuated the feed intake induced by glycine (p<0.05), whereas strychnine had no effect (p>0.05). These results showed that the inhibitory effect of glycine on feed intake is not associated with neurotransmitory function of glycine, but is due to its neuromodulatory effect which is probably mediated via NMDA glutamate receptors in birds.