老ラットのseizure susceptibilityについて—pentylenetetrazolおよび扁桃核キンドリングによるけいれんの検討

Seizure Susceptibility in Aged Rats : Pentylenetetrazol-induced Seizures and Amygdaloid Kindling Seizures

　脳の老化過程におけるseizure susceptibilityを検討する目的で，老ラット群（A群，21-25カ月齢）のpentylenetetrazol（PTZ）けいれん反応および扁桃核キンドリング（AMK）形成を対照群ラット（C群，3—4カ月齢）と比較検討した。PTZ 70mg／kg（s．c．）投与後60分間に，A群ではC群と比較してgeneralizedconvulsion（GC）の出現回数が多く，また，1回のGC持続時間が有意に延長していた。A群のAMK形成はC群と比較して著しい遅延を示し，とくにstage1-2（部分発作）が長く持続した。しかし，A群ではstage3を飛び越えてstage4-5（全般発作）に急速に進展し，また，A群のstage5の発作症状は対照群よりもviolentであった。A群の後発射持続時間はAMKの全経過を通して対照群よりも延長しており，また，後発射は速やかに対側扁桃核に波及した。以上の所見から，老ラットでは，てんかん原性は獲得されにくいがけいれんは起こりやすいと考えられる。

Seizure susceptibility in male aged rats (21-25 mo. of age) was investigated by pentyleneterazol (PTZ) -induced seizures and amygdaloid kindling seizures. Male adult rats ( 3 - 4 mo. of age) were used as the control group. During 60 min. after the administra-tion of PTZ (70 mg/kg, s. c.), the aged rats had a higher incidence and a significantly longer duration of generalized convulsion than the control group. On the other hand, the kindling rate of the aged rats was significantly slower than that of the control. The aged rats remained longer at stage 1- 2 indica-tive of partial seizures. However, the aged rats skipped stage 3 on their way to stage 4 - 5 (genera-lized seizures) , and showed a more violent stage 5 seizure than the control group. They had a longer duration of afterdischrges (AD) through the kindling process with a significantly faster propagation of AD to the contralateral amygdala as compared with the control group. The present study suggests that aged rats are prone to convulsion, while they have a difficulty in aquisition of epileptogenesis.