ANTISENSE OLIGODEOXYNUCLEOTIDES FOR IN-VIVO TARGETING OF CORTICOTROPIN-RELEASING HORMONE MESSENGER-RNA - COMPARISON OF PHOSPHOROTHIOATE AND3'-INVERTED PROBE PERFORMANCE

Antisense DNA has been successfully used in vivo to selectively inhibi t expression of proteins in the brain. However, stressful side effects after oligodeoxynucleotide (ODN) application have been observed, but not carefully characterized. An attempt was made to establish an anima l model of reduced corticotropin-releasing hormone (CRH) activity, usi ng antisense DNA corresponding to the start coding region of rat CRH m RNA with either 3'-3' inverted internucleotidic linkage or with all-ph osphorothioate modification. Probes were injected intracerebroventricu larly (i.c.v.) twice, 12-hours apart. After phosphorothioate sense ODN injection serum corticosterone levels were significantly elevated com pared to vehicle (aCSF) or 3'-3' end inverted sense ODN controls. This increase was also apparent but less pronounced in phosphorothioate an tisense treated animals compared with the corresponding sense group. A fter exposure to ether vapour, both phosphorothioate and inverted anti sense ODN injected rats showed a markedly diminished stress induced co rticosterone secretion compared to the corresponding sense or vehicle injected rats. These results indicate that a) stress induced corticost erone release is suppressed by i.c.v. CRH antisense treatment, b) phos phorothioate ODNs exert an unspecific, chronic stress-like activation of the HPA-axis and c) this effect is partly inhibited by phosphorothi oate antisense directed against CRH mRNA.