[The effect of atrial natriuretic peptide on intracranial pressure in a congenital hydrocephalic model].

Atrial natriuretic peptide (ANP), which was discovered from rat atria, has been implicated in the regulation of systemic water and electrolyte balances. Recently, ANP and that specific receptor was identified in rat brain. These observations suggest the additional central effect of ANP. In this study, the effect of ANP on the intracranial pressure, brain water content and brain sodium concentration was studied with congenital hydrocephalus rats (HTX strain). This strain of rat has a high incidence of congenital hydrocephalus (50%), and the survival period of hydrocephalic rat was 4-5 weeks. Using this hydrocephalic HTX rats, the intracranial pressure was measured through the fine needle of 26 gauge which was placed in the ventricle stereotaxically. The water content was measured by dry-weight method. The brain tissue sodium concentration was measured with atomic absorption spectrophotometer (Shimazu Corp., AA-670). Because ANP did not pass through the blood-brain barrier, ANP was administered into the cerebral ventricle with direct puncture. Intraventricular administration of 2 micrograms of alpha-hANP decreased the intracranial pressure significantly (p less than 0.01), from 5.25 +/- 0.60 (mean +/- SEM) mmHg to 3.00 +/- 0.35 mmHg (n = 10), from 7.38 +/- 1.13 mmHg to 5.20 +/- 1.32 mmHg (n = 5) after 40 minute in both 21 and 28 days HTX rats, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)