Dissociation of the plasticity of 5-HT1A sites and 5-HT transporter sites

To study the early effects of neonatal 5,7-dihydroxytryptamine lesions on 5-hydroxytryptamine_1A (5-HT_1A) receptors, we measured regional [³H]8-OH-DPAT-labeled 5-HT_1A sites in binding assays and compared them to our previous studies of [³H]paroxetine-labeled 5-HT transporter sites during the first month in the same rats. While there were significant time- and dose-dependent effects of 5,7-DHT on 5-HT transporter sites, there were no significant changes in 5-HT_1A sites in cortex, hippocampus, diencephalon, brainstem, cerebellum, or spinal cord. 5,7-DHT lesions also did not alter the K_i of Gpp(NH)p at brainstem 5-HT_1A sites or the K_i of 5-HT in cortex or brainstem in the presence or absence of GTPS or Gpp(NH)p. There were significant regional differences between the density of 5-HT_1A sites and 5-HT transporter sites. The ontogeny of brainstem 5-HT_1A sites was a pattern of increases until three weeks postnatal, and 5,7-DHT lesions did not alter the ontogeny of 5-HT_1A sites. These data suggest differential plasticity of 5-HT_1A and 5-HT transporter binding sites during the first month after neonatal 5,7-DHT lesions.