title: Time course of expression and function of the serotonin transporter in the neonatal rat's primary somatosensory cortex.
abstract: Immunocytochemical and autoradiographic techniques were employed to determine the time course of expression of the serotonin (5-HT) transporter (SERT) on thalamocortical afferents in the rat's primary somatosensory cortex (S-I), and to correlate this expression to the transient vibrissae-related patterning of 5-HT immunostaining previously described. In additional in vivo and in vitro experiments, 5-HT and 3H-5-HT were applied directly to the cortices of untreated and 5,7-dihydroxytryptamine-treated (5,7-DHT) rats in order to determine the period during which SERT functions on thalamocortical axons to take up 5-HT. In postnatal rats, SERT immunohistochemistry revealed a somatotopic patterning in S-I that persisted until P-15, which is 6 days after the disappearance of the vibrissae-related 5-HT immunostaining. 3H-citalopram autoradiography revealed a vibrissae-related pattern in layer IV of S-I until at least P-30. Following destruction of raphe-cortical afferents with 5,7-DHT on the day of birth, this binding pattern remained visible until at least P-25, indicating that SERT located on thalamocortical axons is responsible for the 3H-citalopram patterning observed in S-I. Tissue from 5,7-DHT-treated rats that had 5-HT applied directly to their cortices revealed a normal vibrissae-related pattern of 5-HT immunostaining in S-I at P-7 and P-11 but only a faint pattern at P-13 and none at P-14. In addition, 3H-5-HT injected directly into S-I labeled layer IV barrels at P-6 and P-12 but not at P-18. The results of these experiments demonstrate that SERT is expressed by thalamocortical afferents and remains functional long after the vibrissae-related 5-HT immunostaining in cortex disappears.
authors.affiliation: Department of Anatomy and Neurobiology, Medical College of Ohio, Toledo 43614-5804, USA. cboylan@mco.edu
authors.forename: C B
authors.initials: CB
authors.lastname: Boylan
authors.forename: C A
authors.initials: CA
authors.lastname: Bennett-Clarke
authors.forename: N L
authors.initials: NL
authors.lastname: Chiaia
authors.forename: R W
authors.initials: RW
authors.lastname: Rhoades
mesh_terms: D000344:Afferent Pathways / Q000033:anatomy & histology / Q000254:growth & development; D000375:Aging / Q000502:physiology*; D000818:Animals; D000831:Animals, Newborn; D001345:Autoradiography; D001931:Brain Mapping; D002352:Carrier Proteins / Q000502:physiology*; D005260:Female; D008297:Male; D008562:Membrane Glycoproteins / Q000502:physiology*; D026901:Membrane Transport Proteins; D009419:Nerve Tissue Proteins; D051381:Rats; D017207:Rats, Sprague-Dawley; D012701:Serotonin / Q000502:physiology; D050486:Serotonin Plasma Membrane Transport Proteins; D013003:Somatosensory Cortex / Q000033:anatomy & histology / Q000254:growth & development*; D013787:Thalamic Nuclei / Q000033:anatomy & histology / Q000254:growth & development; D014738:Vibrissae / Q000294:innervation
chemical_list: D002352:Carrier Proteins; D008562:Membrane Glycoproteins; D026901:Membrane Transport Proteins; D009419:Nerve Tissue Proteins; D050486:Serotonin Plasma Membrane Transport Proteins; C493232:Slc6a4 protein, rat; D012701:Serotonin