Influence of triiodothyronine (L-T3) on the morphological and biochemical development of fetal brain acetylcholinesterase-positive neurons cultured in a chemically defined medium.
In cerebral hemisphere cultures initiated from 15-day-old rat embryos, the number of acetylcholinesterase-positive (AChE+) cells increased from 6.8 +/- 1.6 cells/well on day 3 to 112 +/- 16 cells/well on day 15. With time in culture, AChE+ cells increased both in size of the perikarya and neurite length. The addition of L-triiodothyronine (L-T3) at a concentration of 3 x 10(-8) M at the initiation of the culture had no effect on the number of AChE+ cells but significantly increased the size and neurite length of AChE+ neurons after 5 days in vitro. These morphological effects are associated with biochemical effects. L-T3 increased AChE activity in both a dose- and time-dependent manner (the stimulatory effect of L-T3 becomes significant between day 8 and day 15). Since a major part of AChE+ cells may be cholinergic neurons, we have also measured the effect of L-T3 on ChAT activity. L-T3 also increased ChAT activity in a dose and time dependent manner. Furthermore, treatment of cultures with L-T3 at different times in culture demonstrated the presence of a critical period which occurs in vitro around day 20, since the stimulatory effect of L-T3 on ChAT activity is lost after 20 days in vitro. Studies of the time necessary for L-T3 to increase both ChAT and AChE activities show that 2 days and 15 days, respectively, are required for L-T3 to significantly stimulate both enzyme activities. This in vitro analysis demonstrated the morphological effect of L-T3 on the size and the neurite length of AChE+ cells. These effects are associated with biochemical effects on ChAT and AChE activities. Thus, it appears that thyroid hormones regulate several steps of neuronal maturation.
Garza
R
R
Laboratoire de Recherches en Ontogénèse et Génétique Moléculaires, Centre Hospitalier de l'Université Laval, Ste-Foy, Qué, Canada.
Dussault
J H
JH
Puymirat
J
J
D000110:Acetylcholinesterase / Q000378:metabolism*; D000818:Animals; D001921:Brain / Q000166:cytology* / Q000187:drug effects / Q000201:enzymology; D002478:Cells, Cultured; D002795:Choline O-Acetyltransferase / Q000378:metabolism; D002799:Cholinergic Fibers / Q000166:cytology* / Q000187:drug effects / Q000201:enzymology; D003470:Culture Media / Q000494:pharmacology*; D003712:Dendrites / Q000187:drug effects; D051381:Rats; D011919:Rats, Inbred Strains; D013997:Time Factors; D014284:Triiodothyronine / Q000494:pharmacology*
D003470:Culture Media; D014284:Triiodothyronine; D002795:Choline O-Acetyltransferase; D000110:Acetylcholinesterase