Host serotonin axons innervate intrastriatal ventral mesencephalic grafts after implantation in newborn rats.
This study investigated the potential of immature and adult serotonin (5-HT) neurons for axonal growth into intrastriatal grafts of ventral mesencephalic tissue. Implantation of dissociated fetal (embryonic days 14-15) ventral mesencephalic tissue was carried out in immature [postnatal days (P) 5-14] and adult rat neostriatum. The brains were processed 2-6 months later for dopamine and 5-HT immunocytochemistry. A few grafts implanted into adult and P7 recipients contained small numbers of cotransplanted 5-HT cell bodies. These also displayed a rich network of 5-HT axons, even in adult rats prelesioned with 5,7-dihydroxytryptamine, indicating the graft origin of these axons. All other grafts were totally devoid of 5-HT cell bodies. After implantation in adults, such grafts contained rare 5-HT axons. In contrast, in P5-P7 recipients, they displayed many 5-HT fibres, which were uniformly distributed. Such was no longer the case after implantation in P14 recipients, which showed minimal 5-HT innervation, as in adult recipients. Processing of naïve rat brain at different ages for 5-HT immunocytochemistry showed that 5-HT axons were still clearly less numerous in the neostriatum at P21 than in adults, whereas in the substantia nigra the 5-HT innervation developed more rapidly and was comparable, at P21, to that of adults. It was concluded that 5-HT axons are able to grow into ventral mesencephalic grafts, but mainly at the fetal stage and with decreasing capacity after birth.(ABSTRACT TRUNCATED AT 250 WORDS)
Mounir
A
A
Département de pathologie, Faculté de médecine, Université de Montréal, Québec, Canada.
Chkirate
M
M
Vallée
A
A
Pierret
P
P
Geffard
M
M
Doucet
G
G
D015116:5,7-Dihydroxytryptamine / Q000633:toxicity; D000818:Animals; D000831:Animals, Newborn / Q000502:physiology; D001369:Axons / Q000502:physiology*; D016380:Brain Tissue Transplantation / Q000502:physiology*; D004298:Dopamine / Q000378:metabolism / Q000502:physiology; D005260:Female; D016332:Fetal Tissue Transplantation / Q000502:physiology*; D007150:Immunohistochemistry; D008297:Male; D008636:Mesencephalon / Q000166:cytology / Q000378:metabolism / Q000637:transplantation*; D017072:Neostriatum / Q000166:cytology / Q000378:metabolism / Q000502:physiology*; D016627:Oxidopamine; D011903:Raphe Nuclei / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D012701:Serotonin / Q000378:metabolism / Q000502:physiology*; D013378:Substantia Nigra / Q000502:physiology
D015116:5,7-Dihydroxytryptamine; D012701:Serotonin; D016627:Oxidopamine; D004298:Dopamine