title: Developmental plasticity of central serotonin neurons after 5,7-dihydroxytryptamine treatment.
abstract: Systemic administration of 5,7-HT to newborn rats produces an altered development of the 5-HT neurons in the central nervous system, with marked regional differences. 5,7-Hydroxytryptamine can enter the brain and elicit its neurotoxic actions after systemic administration in the neonatal stage due to an incompletely developed blood-brain barrier, which for 5,7-HT is elaborated between postnatal Days 5 and 7. Treatment with 5,7-HT at birth produces marked and permanent 5-HT denervation in the cerebral cortex and spinal cord, whereas hyperinnervation occurs in the 5-HT cell body-near regions (mesencephalon-pons-medulla). The latter effect is seen within the first week postnatally. Treatment with 5,7-HT also affects NA neurons in a similar manner, although the action is exerted preferentially on 5-HT neurons. A selective effect on 5-HT neurons can be achieved by DMI pretreatment, after which both NA and DA neurons develop normally. No signs of any interaction among growing 5-HT, NA, and DA neurons can be observed. Studies of the postsynaptic 5-HT receptor in vitro with [3H]-5-HT and [3H]LSD binding indicate that this receptor develops independently of presynaptic 5-HT nerve terminals. Neither 5-HT denervation nor 5-HT hyperinnervation was accompanied by any change in receptor-binding characteristics or receptor density. The results available are compatible with the view that the consequences for 5-HT neurons that occur after neonatal 5,7-HT administration are mainly due to a "pruning effect." The developing 5-HT neurons seem to be programmed to produce a certain quantity of nerve terminal arborizations, which they try to conserve after 5-HT-induced injury, leading to the observed rearrangement of 5-HT nerve terminals.
mesh_terms: D015116:5,7-Dihydroxytryptamine / Q000494:pharmacology*; D000375:Aging; D000818:Animals; D000831:Animals, Newborn; D002490:Central Nervous System / Q000166:cytology / Q000187:drug effects*; D004102:Dihydroxytryptamines / Q000494:pharmacology*; D008238:Lysergic Acid Diethylamide / Q000378:metabolism; D009474:Neurons / Q000166:cytology / Q000187:drug effects*; D051381:Rats; D011985:Receptors, Serotonin / Q000187:drug effects / Q000378:metabolism; D012701:Serotonin / Q000502:physiology*
chemical_list: D004102:Dihydroxytryptamines; D011985:Receptors, Serotonin; D015116:5,7-Dihydroxytryptamine; D012701:Serotonin; D008238:Lysergic Acid Diethylamide