Objectives: To investigate changes in CSF concentrations of inhibitory and excitatory neurotransmitters in dogs with confirmed idiopathic epilepsy, and to evaluate them with regard to the clinical characteristics of the sample population and of the seizures.
Animals: 13 (8 male and 5 female) drug-naive dogs with an initial generalized seizure, 6 (4 male and 2 female) drug-naive dogs with an initial partial seizure, and 10 clinically normal (5 male and 5 female) control dogs.
Procedure: At least 24 hours after the last observed seizure, CSF was collected aseptically from the cisterna cerebellomedullaris, and a portion was immediately aliquoted into vials, placed on dry ice, then stored at -80 C. The CSF glutamate (GLU) and gamma-aminobutyric acid (GABA) concentrations were estimated by use of HPLC with electrochemical detection. Cerebellomedullary cisternal CSF glutamate and GABA values were analyzed in dogs with noninduced idiopathic epilepsy. Comparisons were determined for differences attributable to weight, sex, age at first seizure, seizure type, and total time of past seizure history.
Results: Mean (range) age at onset of the first seizure was 3.33 (0.1 to 11), 3.5 (0.1 to 11), and 3.25 (0.5 to 9) years for all dogs, dogs with initial partial seizure, and dogs with initial generalized seizure, respectively. Low GABA and high GLU values were found in the CSF of epileptic dogs, and were independent of time elapsed between the first observed seizure and CSF sample collection. The GABA value was inversely related to body weight in epileptic dogs, independent of age. Changes in GABA and GLU concentrations were not related to seizure type.
Conclusions: Altered GABA and GLU values in CSF might be indicative of a state of chronic overexcitation in the brain of dogs with primary or idiopathic epilepsy.
Clinical relevance: CSF GABA and GLU may serve as important markers in epileptic dogs for potential response to antiepileptic drugs.