Spinal cord monoaminergic system response to age and cold-acclimatization in Muscovy duckling

The effect of age and cold acclimatization on the regional distribution of monoamines in duckling spinal cord was studied. In thermoneutral controls ( TN), the high dopamine (DA) to norepinephrine (NE) ratios (0.25 at 4 weeks of age and 0.15 at 6 weeks of age) suggest the presence of specific (non pr ecursor) dopaminergic pools in cervical spinal cord. DA levels and the rati o of DA to NE were lowered by age and cold exposure in the cervical cord. I n TN ducklings, serotonin (5-HT) and its metabolite 5-hydroxyindole acetic acid (5-HIAA) showed a decline with age in the spinal cord, indicating that this system is affected with development, whereas cold exposure prevents t his decrease. The contents of 5-HT (+58%), 5-HIAA (+93%) and the ratio of 5 -HIAA to 5-HT (+50%) are higher in the cervical spinal cord of cold acclima ted than in TN ducklings. These results indicate that central monoaminergic systems are markedly affected by age and cold exposure.