Hypothermia inhibits pentylenetetrazol kindling and prevents kindling-induced deficit in shuttle-box avoidance

In this study, we evaluated the effects of hypothermic exposure on pentylen etetrazol (PTZ) kindling and the resulting deficit of shuttle-box avoidance learning in rats. Additionally, to acknowledge neuronal cell loss, we esti mated the number of toluidine blue-positive cells in different brain region s after PTZ kindling and hypothermia exposure in comparison to different no rmothermic and hypothermic controls. To obtain hypothermic conditions over a period of up to about 3 h, 30 min after PTZ application the animals were treated with 5 mg/kg chlorpromazine (CP) and 25 min later exposed to 15 deg rees C cold water for 5 min. Under these conditions the rectal and the stri atal temperature were reduced up to a maximum of 5 degrees C. The additiona l injection of CP did not influence the development of PTZ kindling. Animal s treated with PTZ/CP and exposed to hypothermia did not reach the criterio n for kindling. Furthermore, this group of animals did not demonstrate any learning deficit. Forty-eight hours after the last kindling application the number of toluidine blue-stained cells was decreased in the investigated b rain regions (hippocampal CA1 and CA3 sector, hilus, and cingular cortex) o f kindled rats. Hypothermia protected from cell damage in the hippocampal C A3 sector and in the hilus. Results suggest that the inhibiting effect of h ypothermia on the development of kindling and the following learning defici t possibly resulted from the suppression of cell damage in distinct brain s tructures on PTZ-kindled rats. (C) 1999 Elsevier Science Inc.