Antisense oligodeoxynucleotide complementary to oxytocin mRNA blocks lactation in rats.

The posterior lobe peptide oxytocin (OT) is known to control lactation and parturition, as well as maternal and sexual behavior. An antisense oligodeoxynucleotide (ODN) directed against the mRNA of OT was injected intracerebroventricularly 6 times in 12 hour intervals to manipulate the transcriptional message of OT in lactating rats. OT immunoreactivity in magnocellular hypothalamic nuclei and in the posterior lobe of the pituitary was reduced in antisense treated animals in comparison to ODN with scrambled base composition and vehicle controls. This decline in OT levels was associated with a decrease of pup weight. Our results demonstrate that central infusions of antisense ODN significantly reduce OT expression in vivo.