title: Neuronal excitability after water intoxication in young rats.
abstract: OBJECTIVE
  Our previous experiments with animal models revealed that water intoxication induces brain oedema and opens plasma membranes. Present study is aimed to determine whether the standard method of hyperhydration can influence cerebral microenvironment also in young rats. Neuronal functions were tested by standard electrical cortical stimulation.
  
  
  METHODS
  Hyperhydration was induced by administration of distilled water (DW) intraperitoneally. Three groups of young rats were used: 12, 25, and 35-day-old. Cortical excitability was tested 19 to 20 hours after DW administration by electrical stimulation of the sensorimotor cortex with intensity necessary to elicit cortical afterdischarges (AD). Water content in the brain was estimated by dry/wet ratio and value of natremia by standard biochemical examination. Control animals of the same age groups were tested in the same way, only they did not receive DW.
  
  
  RESULTS
  Brain water content in hyperhydrated animals was smaller than in controls in all studied age groups. Natremia was the same (normal) in both the hyperhydrated and control animals aged 25 days. Excitability of cortical neurons in young hyperhydrated animals was significantly inhibited in comparison to the same age groups of controls.
  
  
  CONCLUSIONS
  Hyperhydration induced in young rats (12, 25, 35-day-old) had different effects than in adults. Absence of hyponatremia, lower water content in the brain and significant inhibition of cortical excitability can be explained on the basis of ontogenetically dependent aquaporine expression (AQP 4) and different activity of ionic membrane transporters.
authors.affiliation: Institute of Physiology, First Faculty of Medicine, Charles University in Prague, Prague, Czech Republic.
authors.forename: Dana
authors.initials: D
authors.lastname: Maresova
authors.affiliation: Institute of Physiology, First Faculty of Medicine, Charles University in Prague, Prague, Czech Republic.
authors.forename: Petr
authors.initials: P
authors.lastname: Kozler
authors.affiliation: Institute of Physiology, First Faculty of Medicine, Charles University in Prague, Prague, Czech Republic.
authors.forename: Jaroslav
authors.initials: J
authors.lastname: Pokorny
mesh_terms: D000818:Animals; D001834:Body Water / Q000378:metabolism*; D001921:Brain / Q000378:metabolism / Q000503:physiopathology*; D002540:Cerebral Cortex / Q000503:physiopathology; D004195:Disease Models, Animal; D055724:Electrophysiological Phenomena / Q000502:physiology; D008297:Male; D009474:Neurons / Q000502:physiology; D051381:Rats; D017208:Rats, Wistar; D014869:Water Intoxication / Q000139:chemically induced / Q000503:physiopathology*