Proline is formally an imino acid, but is usually called an amino acid. It is not an essential amino acid, since proline is biosynthetically derived from the amino acid L-glutamate. Food intake was mildly stimulated by low levels of intracerebroventricular (i.c.v.) injection of L-proline, but was suppressed by high levels in chicks. L-Proline was decreased in the telencephalon and diencephalon under several different stressors including restraint with isolation-induced and fasting stress. Central L-proline induced sedative and hypnotic effects in a dose-dependent manner, suggesting that L-proline may have an important role in attenuating the stress response in the central nervous system of chicks. The central effects of L-proline, D-proline and trans-4-hydroxy-L-proline were investigated by using the acute stressful model with neonatal chicks. Sedative and hypnotic effects were induced by all compounds, while plasma corticosterone release under isolation stress was only attenuated by L-proline. To clarify the mechanism by which L-proline and D-proline induce sedative and hypnotic effects, the contribution of the strychnine-sensitive glycine receptor (glycine receptor) and N-methyl-D-aspartate glutamate receptor (NMDA receptor) were further investigated. The glycine receptor antagonist strychnine was co-injected i.c.v. with L-proline or D-proline. The suppression of isolation-induced stress behavior by D-proline was attenuated by strychnine. However, the suppression of stress behavior by L-proline was not attenuated. The NMDA receptor antagonist (+)-MK-801 was co-injected i.c.v. with L-proline. The suppression of stress behavior by L-proline was attenuated by (+)-MK-801. These results indicate that L-proline and Dproline differentially induce sedative and hypnotic effects through NMDA and glycine receptors, respectively. Using microdialysis, the effect of Lproline on monoamine release in the medio-rostral neostriatum/hyperstriatum ventrale (MNH) of freely moving and restricted chicks was investigated. A 30 min handling stress resulted in significant increases of extracellular homovallinic acids (HVA), a dopamine metabolite, and 5- hydroxyindoleacetic acid (5-HIAA), a serotonin metabolite, in the MNH. LProline, perfused through a microdialysis probe in the MNH during the stressed condition, significantly attenuated the average dialysate concentration of HVA produced by handling-stress. Handling-stress resulted in a significant increase in 5-HIAA levels in the control group, which were attenuated by profusion with L-proline. These results show that perfusion of L-proline decreased the release of dopamine and serotonin in the MNH caused by handling-stress.
|Title of host publication||Proline|
|Subtitle of host publication||Biosynthesis, Regulation and Health Benefits|
|Publisher||Nova Science Publishers, Inc.|
|Number of pages||23|
|Publication status||Published - Mar 1 2013|
All Science Journal Classification (ASJC) codes
- Biochemistry, Genetics and Molecular Biology(all)