Kindling in spontaneous hypertensive rats.

Vasopressin is a neurohormone and neuromodulator with many effects on behavior. Rats lacking vasopressin have been found to develop kindled seizures more slowly with amygdala stimulation. In the present study the spontaneous hypertensive (SH) rat and rats from the parent strain, the Wistar-Kyoto (WKY) rat received amygdala and pyriform kindling. The SH rat has been reported to have increased plasma vasopressin and increased brain vasopressin release. Plasma vasopressin, osmolality and hematocrit were also measured in blood samples obtained through chronic, indwelling catheters implanted in SH, WKY normal and Sprague-Dawley rats. SH rats were found to kindle with fewer afterdischarges than WKY normal rats with both amygdala and pyriform cortex stimulation. The total afterdischarge duration required to reach each kindling stage was significantly shorter in the SH rat. Plasma osmolality and vasopressin were significantly higher in the SH rats compared to WKY normal rats and Sprague-Dawley rats. These findings provide additional evidence that vasopressin may influence the establishment of enduring behaviors such as kindled seizures.