The effectiveness of antisense oligonucleotides (ODNs) to angiotensinogen on intracerebrovenricularly injected renin induced thirst was investigated. As a corollary, information would be gained about the role of centrally synthesised angiotensinogen in the neural mechanisms subserving water drinking in rats. Stable, easily synthesised phosphorothioate antisense oligonucleotides (18 mer), one of which included the sequence encompassing the translation start site, were injected into the lateral ventricle of rats. The drinking response to a number of dipsogenic stimuli was tested. Antisense significantly reduced (by about 50%) the volume of water drunk in response to intracerebroventricular (icv) renin or isoproterenol but did not reduce drinking in response to the physiological challenge of icv angiotensin II, icv carbachol, intravenous hypertonic saline, water deprivation or subcutaneous injection of polyethylene glycol. Only one out of four antisense probes gave positive results, while mismatch or scrambled oligonucleotides did not inhibit water intake. This finding reduces the probability that the results observed are non-specific. In these experiments, an ODN specific for angiotensinogen was discovered and was produced easily in large enough amounts and stabilised against intracellular nucleases without floss of cellular access or biological effect.