Behavior in the open field predicts the number of KCl-induced cortical spreading depressions in rats

Anxiety disorders are known to be comorbid with migraine, and cortical spreading depression (CSD) is the most likely cause of the migraine aura. To search for possible correlations between susceptibility to CSD and anxiety we used the open field test in male Sprague-Dawley rats chronically treated with the preventive anti-migraine drugs valproate or riboflavin. Animals avoiding the central area of the open field chamber and those with less exploratory activity (i.e. rearing) were considered more anxious. After 4 weeks of treatment CSDs were elicited by application of 1 M KCl over the occipital cortex and the number of CSDs occurring over a 2 hour period was compared to the previously assessed open field behaviour. Higher anxiety-like behaviour was significantly correlated with a higher frequency of KCl-induced CSDs. In saline-treated animals, fewer rearings were found in animals with more frequent CSDs (R= −1.00). The duration of ambulatory episodes in the open field center correlated negatively with number of CSDs in the valproate group (R= −0.83; p