大鼠海马癫痫电网络重建中爆发式放电神经元的活动

Electrical activities of bursting-firing neurons in epileptic network reestablishment of rat hippocampus

本文探讨双侧海马(hippoeampus,HPC)神经网络中爆发式放电神经元(bursting-firing neurons,BFN)的活动规律及其与海马癫痫网络重建的关系。实验用雄性SD大鼠140只(150-250 g),急性强直电刺激(60 Hz,2 s,0.4-0.6 mA)右后背HPC CAl区(acute tetanization of the posterior dorsal hippocampus,ATPDH),同步记录同侧或对侧前背HPC单位放电和深部电图;强直电刺激右前背HPC(acute tetanization of the anterior dorsal hippocampus,AT-ADH),同步记录双侧前背HPC单位放电。实验共记录了13.8％(19/138)双侧前背HPC的BFN,其中13个为刺激诱发性BFN,6个为自发性BFN。强直电刺激引起的诱发反应包括:(1)ATPDH明显调制同侧前背HPC的BFN,产生规则的节律性爆发式放电,刺激后串内动作电位间期(bursting interspike interval,BISI)减小(P<0.001);(2)AT-PDH引起对侧前背HPC的BFN出现抑制后轻度调制效应,刺激后动作电位间期(interspike interval,ISI)增大(P<0.001);(3)ATADH后易化对侧前背HPC的自发性BFN节律,增加ISI(P<0.001)和IBI(P=0.01);(4)ATPDH诱导双侧前背HPC的BFN产生规则的节律性爆发式放电,伴有同步或非同步性网络癫痫的形成。上述实验结果提示,ATPDH沿同侧HPC长轴,跨大脑半球诱发前背HPC单个BFN的形成。

The purpose of our present work was to study the discharge of bursting - firing neurons (BFNs) in ipsilateral or contralateral hippocampus (HPC) , and its relations to the reestablishment of local epileptic networks. The experiments were performed on 140 Sprague Dawley male rats (150 -250 g). A-cute tetanization (60 Hz, 2 s, 0.4-0.6 mA) of the right posterior dorsal hippocampus (ATPDH) was administered to establish rat epilepsy model. The single unit discharges and the depth electrographs were simultaneously recorded from ipsilateral or contralateral HPC. In other experimental rats, acute tetanization of the right anterior dorsal HPC (ATADH) was used. Extracellular unit discharges in the CA1 region were simultaneously recorded from bilateral anterior dorsal hippocampi. Analysis of hippocampal BFN firing patterns before or after administration of the tetanization was focused on according to their location in the HPC epileptic networks in vivo. Single unit discharges of 138 hippocampal neurons were recorded from ipsilateral and/or contralateral anterior dorsal HPC. Of the 138 neurons recorded, 19 were BFNs. 13 BFNs were tetanus - evoked and the remaining 6 were spontaneous ones. The evoked reactions of the single hippocampal neuron induced by the tetanization mainly included: ( 1 ) the firing patterns of the BFNs in ipsilateral anteri- or dorsal HPC were obviously modulated by the ATPDH from tonic firing into rhythmic bursting. The bursting interspike intervals (BISI) decreased. (2) There were mild modulations of the firing patterns of the BFNs in contralateral anterior dorsal HPC following post - inhibition of the firing rate of single neuron induced by the ATPDH. The interspike intervals (ISI) increased obviously. (3) Post-facilitation of rhythmic bursting - firing of the BFNs in contralateral anterior dorsal HPC was induced by ATADH; both the ISI and the IBI increased. (4) Synchronous or asynchronous rhythmic bursting -firing of the BFNs and the network epileptiform events ipsilateral or contralateral anterior dorsal HPC were elicited by the ATPDH. The results obtained suggest that bursting - firing of single BFNs is produced by the ATPDH in the anterior dorsal HPC along the longitudinal axis of the ipsilateral HPC or across the hemisphere to the opposite HPC. Rhythmic activities of the BFN may be implicated in the epileptic network reestablishment of the HPC. On the other hand , synaptic modulation of the BFN temporal series might be responsible for pathophysiologcal information transmission in the HPC-epileptic network.