Levels of monoamine and amino acid neurotransmitters in the developing male mouse hypothalamus and in histotypic hypothalamic cultures.
The variation in the levels of the monoamine and amino acid neurotransmitters was studied during the period of neurogenesis in male mouse hypothalamus, from embryonic day 15 until the age of young adult. The results shown in this study demonstrate that the monoamines appear early in the fetal brain and that the maximum expression of the catecholaminergic system, particularly that of dopamine, occurs during the late neonatal period or mouse infancy, when the role played by the catecholamines on the maturation of the neurosecretory systems is more significant. In relation to the amino acid neurotransmitters, glutamate and taurine seem to be the principal transmitters of the hypothalamus since their concentrations were about five-tenfold higher than the levels of glycine and GABA. Both amino acids had the same pattern of variation during development, showing elevated values during the prenatal, late neonatal and early pubertal period. Increased concentrations of the inhibitory neurotransmitter GABA were observed on the day before birth, at the end of the neonatal period and throughout the prepubertal period, suggesting that the influence of GABA on hypothalamic neurogenesis increases by the time when the hypothalamic nuclei have reached maturity and the local circuits have been established. To determine the intrinsic neurotransmitter production, primary hypothalamic histotypic cultures prepared from mice at postnatal days 8-10 were analyzed for their content of neurotransmitters. The in vitro analysis revealed that the hypothalamic neurons intrinsically produce dopamine, glutamate, taurine and glycine in homologable amounts with those of young adult animals. The comparative analysis also showed that about 50% of the GABA content and less than 5% of the hypothalamic epinephrine level are locally produced, while serotonin comes mainly from extrinsically located neurons.
Miranda-Contreras
L
L
Center of Electron Microscopy, University of Los Andes, Mérida, Venezuela.
Mendoza-Briceño
R V
RV
Palacios-Prü
E L
EL
D000818:Animals; D015306:Biogenic Monoamines / Q000378:metabolism*; D046508:Culture Techniques; D005314:Embryonic and Fetal Development / Q000502:physiology; D005865:Gestational Age; D007031:Hypothalamus / Q000196:embryology / Q000254:growth & development / Q000378:metabolism*; D008297:Male; D051379:Mice; D008815:Mice, Inbred Strains; D018377:Neurotransmitter Agents / Q000378:metabolism*
D015306:Biogenic Monoamines; D018377:Neurotransmitter Agents