title: A comparison of pattern formation by thalamocortical and serotonergic afferents in the rat barrel field cortex.
abstract: In the present study we compare the formation of vibrissa-related patterns by thalamocortical afferents from the ventrobasal (VB) nucleus to that by raphe-cortical, serotonergic afferents from the raphe nuclei. In opposite hemispheres of the same brain, 1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate (Dil) labeling of VB afferents and serotonin (5-HT) immunohistochemistry reveal that the pattern of vibrissa-specific patches is first exhibited by thalamocortical axons in barrel field cortex. Shortly thereafter, 5-HT axons form patches in the same locations as the dense concentrations of VB afferents. To assess a possible role of 5-HT afferents in the specification of barrel field cortex, neonatal rat pups were administered p-chloroamphetamine (PCA), a selective 5-HT neurotoxin. The formation of vibrissa-related patterns by thalamocortical and serotonergic afferents was compared in normal and PCA-treated rat pups at various developmental stages. PCA treatment led to a significant decrease in the number of serotonergic axons in barrel field cortex. Despite this decrease, VB afferents segregated in patches over individual barrels. However, a delay in the emergence of the thalamocortical pattern was noted in toxin-treated animals. We conclude that PCA treatment does not prevent formation of a vibrissa-specific pattern by thalamocortical afferents, and discuss the possibility that the 5-HT axons may play a trophic role in the maturation of VB afferents.
authors.affiliation: Kennedy Research Institute, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205.
authors.forename: M E
authors.initials: ME
authors.lastname: Blue
authors.forename: R S
authors.initials: RS
authors.lastname: Erzurumlu
authors.forename: S
authors.initials: S
authors.lastname: Jhaveri
mesh_terms: D000818:Animals; D002232:Carbocyanines; D002540:Cerebral Cortex / Q000166:cytology*; D005260:Female; D006651:Histocytochemistry; D009475:Neurons, Afferent / Q000502:physiology*; D011247:Pregnancy; D011903:Raphe Nuclei / Q000502:physiology; D051381:Rats; D011919:Rats, Inbred Strains; D012701:Serotonin / Q000502:physiology*; D013788:Thalamus / Q000166:cytology*; D014738:Vibrissae / Q000502:physiology; D010133:p-Chloroamphetamine / Q000494:pharmacology
chemical_list: D002232:Carbocyanines; D012701:Serotonin; C024286:3,3'-dioctadecylindocarbocyanine; D010133:p-Chloroamphetamine