Do brain fluid ion concentrations change in hydrocephalus? A study on potassium and calcium in rats with congenital hydrocephalus.

Potassium and calcium have been measured in cerebrospinal fluid (CSF), brain interstitial fluid (ISF) and in plasma of congenitally hydrocephalic rats (H-Tx strain) and the results compared with a previous study on control, non-hydrocephalic, rats (CFY strain). Ion-selective microelectrodes were used to determine [K+] at 1-2 and 5 days and [Ca2+] at 1-2, 5, 10 and 20 days after birth. Total [Ca] was measured in plasma and CSF samples with atomic absorption spectrometry. In addition, K+ homeostasis has been studied in CSF and ISF during plasma hyperkalaemia at 5 days after birth. Apart from a raised [Ca2+] immediately after birth, hydrocephalic rats had similar CSF and ISF potassium and calcium concentrations to those found in control rats at the same age. The degree of CSF and ISF K+ homeostasis was also similar in hydrocephalic and control rats.