N'Gouemo P, Faingold C L
Department of Pharmacology, Southern Illinois University School of Medicine, Springfield 62794-1222, USA.
Neuroscience. 1998 May;84(2):619-25. doi: 10.1016/s0306-4522(97)00551-4.
The ventrolateral periaqueductal gray is implicated as a component of the neuronal network for audiogenic seizure. This implication is based on immunocytochemical labeling of the proto-oncogene, c-fos, and microinjection studies in the severe substrain of genetically epilepsy-prone rats that exhibits tonic seizures. The present study examines changes in acoustically evoked neuronal responses within the periaqueductal gray in the awake and behaving genetically epilepsy-prone rat as compared to normal Sprague Dawley rats. Two populations of neuronal response were observed in the periaqueductal gray of both genetically epilepsy-prone and normal rats. Most of the neurons exhibited long latencies (>10 ms) and lower thresholds, and were more responsive to the acoustic stimulus. The remainder of the periaqueductal gray neurons exhibited short latencies (<10 ms) and higher thresholds, and exhibited minimal responsiveness to the acoustic stimulus. The mean threshold of periaqueductal gray acoustically evoked neuronal firing of short-latency neurons was significantly higher than normal in the genetically epilepsy-prone rat. The number of acoustically evoked action potentials was significantly elevated in the genetically epilepsy-prone rat, particularly at the highest acoustic intensity and at a repetition rate of 1/2 s. In the genetically epilepsy-prone rat, the number of action potentials exhibited adaptation (habituation) at 1/s as compared to 1/2 s across stimulus intensities. Habituation in normal rats was observed primarily at high intensities (95 dB sound pressure level or above). During wild running and tonic seizures in the genetically epilepsy-prone rat, periaqueductal gray neurons. which had diminished firing rates due to habituation, exhibited a tonic firing pattern. Just (1-5 s) prior to the onset of tonic convulsive behaviors, an increase in the rate of periaqueductal gray tonic firing was observed. These patterns of abnormal neuronal firing suggest that periaqueductal gray neurons may be involved in generation of the tonic seizure behavioral component of audiogenic seizure in the genetically epilepsy-prone rat, which will need confirmation in other audiogenic seizure models.
腹外侧导水管周围灰质被认为是听源性癫痫神经网络的一个组成部分。这一观点基于原癌基因c-fos的免疫细胞化学标记以及对表现出强直性癫痫发作的遗传性癫痫易感大鼠严重亚系的微量注射研究。本研究检测了清醒且有行为活动的遗传性癫痫易感大鼠与正常斯普拉格-道利大鼠相比，导水管周围灰质内听觉诱发神经元反应的变化。在遗传性癫痫易感大鼠和正常大鼠的导水管周围灰质中均观察到两类神经元反应。大多数神经元表现出长潜伏期（>10毫秒）和较低阈值，对听觉刺激反应更强。其余导水管周围灰质神经元表现出短潜伏期（<10毫秒）和较高阈值，对听觉刺激反应极小。遗传性癫痫易感大鼠中，短潜伏期神经元的导水管周围灰质听觉诱发神经元放电的平均阈值显著高于正常大鼠。遗传性癫痫易感大鼠中听觉诱发动作电位的数量显著增加，尤其是在最高声强和1/2秒的重复率时。在遗传性癫痫易感大鼠中，与1/2秒相比，动作电位数量在1/秒时随刺激强度表现出适应性（习惯化）。正常大鼠的习惯化主要在高声强（95分贝声压级及以上）时观察到。在遗传性癫痫易感大鼠的狂奔和强直性癫痫发作期间，因习惯化而放电率降低的导水管周围灰质神经元表现出强直性放电模式。就在强直性惊厥行为发作前（1 - 5秒），观察到导水管周围灰质强直性放电率增加。这些异常神经元放电模式表明，导水管周围灰质神经元可能参与了遗传性癫痫易感大鼠听源性癫痫强直性癫痫发作行为成分的产生，这需要在其他听源性癫痫模型中得到证实。
