Rapid maturation of synaptic functions of prenatal serotoninergic neurons in short-term cultures: absence of sex differences and hormone effects.
Serotonin is believed to modulate neuronal differentiation during early stages of brain development. In order to assess basic functional requirements for such a role, it was investigated how early serotoninergic neurons mature with respect to transmitter storage and stimulus-secretion coupling. Dissociated cell cultures were raised from embryonic rat rhombencephalon obtained at gestational day 14 and cultured for 3-8 days, which may roughly correspond to the prenatal period in vivo. Because of a possible involvement of serotonin in processes leading to sexual differentiation of the brain, gender-specific cultures were raised in addition and treated with sex steroids. Sensitivity of [3H]serotonin uptake to fluoxetine could already be observed at 3 days in vitro. Vesicular storage as probed with reserpine and nigericin, and the capability of releasing preaccumulated serotonin in a Ca2+-dependent manner were also present as early as 3 days in vitro. Seven per cent of the pre-accumulated transmitter could be released per minute upon stimulation with 54 mM K+. Immunocytochemical and autoradiographic preparations demonstrated that, after the same short culture period, the neurons had formed large fiber networks. No differences could be detected regarding any of the above parameters between female and male serotonin neurons and between cultures treated with and without estradiol, testosterone and dihydrotestosterone. It is concluded that, in contrast to other neuronal phenotypes, serotoninergic neurons are functionally mature when or shortly after they are taken into culture, i.e. around gestational day 14. The functional competence of prenatal serotonin systems should be a prerequisite for their suspected role in modulating neural development at pre and postsynaptic sites. The present results provide no evidence for the occurrence of a sexual dimorphism of serotonin neurons at this early developmental stage.
Reisert
I
I
Abteilung Anatomie und Zellbiologie, Universität Ulm, F.R.G.
Han
V
V
Hartwig
S
S
Ahnert-Hilger
G
G
Pilgrim
C
C
D000818:Animals; D002478:Cells, Cultured; D005314:Embryonic and Fetal Development; D005260:Female; D005865:Gestational Age; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains; D012249:Rhombencephalon / Q000196:embryology / Q000378:metabolism*; D012701:Serotonin / Q000493:pharmacokinetics* / Q000502:physiology; D012737:Sex Factors
D012701:Serotonin