On the distribution and morpho-functional characteristics of 5-HT-immunoreactive cells in the hypothalamus of fetuses and neonatal rats.
This study attempted to visualize serotonin (5-HT)-immunoreactive (IR) neurons in the hypothalamus of intact fetuses (E18) and neonatal rats (P9) as well as after their pretreatment with some drugs interfering with the 5-HT metabolism and uptake in the serotoninergic neurons (L-tryptophan, pargyline, 5-hydroxytryptophan, fluoxetine). The 5-HT-IR cells were not observed in the hypothalamus of normal, untreated fetuses and neonatal rats. However, two large accumulations of 5-HT-IR neurons appeared in the anterolateral hypothalamus and in the dorsomedial nucleus after the subsequent injections of the monoamine oxidase inhibitor, pargyline, and the amino acid precursor of the 5-HT synthesis, L-tryptophan. A significantly less intensive reaction was observed after injections either of the second precursor of the 5-HT synthesis, 5-hydroxytryptophan instead of L-tryptophan, or pargyline only. Immunostaining, provoked by the pargyline and L-tryptophan pretreatment, was completely blocked by the injection of the specific 5-HT uptake inhibitor, fluoxetine. It means that the 5-HT immunostaining of the hypothalamic neurons may be accounted for by their capacity to take up specifically 5-HT from the environment rather than by its intraneuronal synthesis from L-tryptophan. Nevertheless, the 5-HT synthesis from 5-hydroxytryptophan in these cells cannot be excluded. The uptake of extracellular 5-HT into catecholaminergic neurons can be excluded as nomifensine, the specific inhibitor of the uptake to these neurons, did not modify the immunostaining.
Ugrumov
M V
MV
Laboratory of Hormonal Regulations, U.S.S.R. Academy of Sciences, Moscow.
Taxi
J
J
Steinbusch
H W
HW
Tramu
G
G
Mitskevich
M S
MS
D000818:Animals; D000831:Animals, Newborn; D005314:Embryonic and Fetal Development; D007031:Hypothalamus / Q000196:embryology / Q000254:growth & development / Q000378:metabolism*; D010293:Pargyline / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D012701:Serotonin / Q000378:metabolism* / Q000502:physiology; D014364:Tryptophan / Q000494:pharmacology
D012701:Serotonin; D014364:Tryptophan; D010293:Pargyline