DEVELOPMENTAL AND STIMULUS-SPECIFIC EXPRESSION OF THE IMMEDIATE-EARLYGENE ZIF268 IN RAT SPINAL-CORD

Expression of the cellular immediate-early gene, zif268, was investiga ted using immunocytochemical methods in cervical spinal cord of neonat al and adult rats. The postnatal expression of zif268 follows a specif ic temporal and spatial sequence in the spinal dorsal horn. Neurons im munoreactive for Zif268 protein were not present in cervical spinal co rd before postnatal day (P) 6. At P6 they were occasionally observed i n Rexed's lamina I. By P11, a few additional, faintly labeled, Zif268- positive neurons appeared in lamina III. Around P16, however, many imm unoreactive neurons were found in laminae I-III and a few in laminae I V-VII. The number of Zif268-immunoreactive neurons decreased markedly by P21 and was further reduced by P26 to become virtually absent in ad ult rats. In adults, surgical exposure of peripheral nerves alone enha nced Zif268 expression, but this effect largely disappeared in less th an 6 h. Electrical stimulation of the nerves with high-frequency long trains, typical of those known to elicit long-term neural plasticity, induced a marked increase in Zif268 expression in the dorsal horn. Sti mulation with single pulses had a much weaker effect. Zif268 may thus play a role in stimulus-induced, long-term neural plasticity in the sp inal cord.