Fibers In Rat Hippocampus Research Articles

Suppressing synchronous firing of epileptiform activity by high-frequency stimulation of afferent fibers in rat hippocampus.

AimsDeep brain stimulation (DBS) is a promising technology for treating epilepsy. However, the efficacy and underlying mechanisms of the high‐frequency stimulation (HFS) utilized by DBS to suppress epilepsy remain uncertain. Previous studies have shown that HFS can desynchronize the firing of neurons. In this study, we investigated whether the desynchronization effects of HFS can suppress epileptiform events.MethodsHFS trains with seconds of duration (short) and a minute of duration (long) were applied at the afferent fibers (ie, Schaffer collaterals) of the hippocampal CA1 region in anesthetized rats in vivo. The amplitude and the rate of population spikes (PS) appeared in the downstream of stimulation were calculated to evaluate the intensity of synchronized firing of neuronal populations between short and long HFS groups. A test of paired‐pulse depression (PPD) was used to assess the alteration of inhibitory neuronal circuits.ResultsThe sustained stimulation of a 60‐s long HFS suppressed the afterdischarges that were induced by a 5‐s short HFS to impair the local inhibitions. During the sustained HFS, the mean PS amplitude reduced significantly and the burst firing decreased, while the amount of neuronal firing did not change significantly. The paired‐pulse tests showed that with a similar baseline level of small PS2/PS1 ratio indicating a strong PPD, the 5‐s HFS increased the PS2/PS1 ratio to a value that was significantly greater than the corresponding ratio during sustained HFS, indicating that the PPD impaired by a short HFS may be restored by a sustained HFS.ConclusionsThe sustained HFS can desynchronize the population firing of epileptiform activity and accelerate a recovery of inhibitions to create a balance between the excitation and the inhibition of local neuronal circuits. The study provides new clues for further understanding the mechanism of DBS and for advancing the clinical application of DBS in treating epilepsy.

The effect of tianeptine on the ability of the learning and memory and cholinergic fibers in hippocampus of rats in depression

目的 观察噻奈普汀(TIA)对抑郁模型大鼠学习记忆能力以及海马胆碱能纤维的作用.方法采用慢性轻度不可预见性的应激和孤养建立大鼠抑郁模型,对模型大鼠行噻奈普汀灌胃4周,Y迷宫测试大鼠的学习记忆能力,用乙酰胆碱脂酶(AChE)的组织化学方法染色,显微镜方格目测计数对大鼠海马AchE阳性纤维的密度行定量分析.结果抑郁模型大鼠经噻奈普汀4周治疗后,学习记忆能力:应激+TIA组[(43.0±4.1)分、(7.9±0.8)分]与应激组[(69.3±8.4)分、(4.6±0.7)分]、应激+生理盐水组[(58.0±9.3)分、(5.3±1.1)分]比较学习记忆能力均有极显著差异(P＜0.01);AchE阳性纤维密度为应激+TIA组[CA1:(54.65±14.29);CA3:(51.00±10.77);DG:(57.63±14.59)],应激组[CA1:(40.68±10.17);CA3:(41.27±9.33);DG:(43.90±11.37)],应激+生理盐水组[CA1:(42.47±11.83);CA3:(48.53±10.75);DG:(50.69±14.59)],应激+TIA组各区AchE阳性纤维密度极显著高于应激组(P＜0.01),应激+TIA组CA1区、DG区AchE阳性纤维密度显著高于应激+生理盐水组(P＜0.05).结论噻奈普汀能有效促进抑郁模型大鼠学习记忆能力的恢复以及海马胆碱能纤维的再生。

In vitro effects of bipathic treatment with antibodies in ultralow doses during long-term post-tetanic potentiation.

We studied the effects of individual or combination treatment with monoclonal antibodies 5F5-B6 in ultralow doses specifically marking mossy fibers in rat hippocampus and antibodies to S100 protein during long-term post-tetanic potentiation in hippocampal slices. The possible mechanisms of changes produced by therapeutic administration of antibodies in ultralow doses were revealed.

Epilepsy induced collateral sprouting of hippocampal mossy fibers: Does it induce the development of ectopic synapses with granule cell dendrites?

In the present study, using Golgi and electron microscopy techniques, experimentally induced epilepsy (kindling and kainate treatment) elicited collateral sprouting of mossy fibers in rat hippocampus. Collateral branches invade the hilus, cross the granule cell layer, and distribute throughout the inner third of the molecular layer. These newly developed collaterals may acquire the typical features of mossy fibers including giant fiber varicosities (mousses), although the mean surface of these mousses was thinner in these collaterals than in terminal branches. Granule cell dendrites may develop giant thorny excrescences, suggesting that the targets of these collaterals are granule cells. Giant synaptic boutons appear in the inner third of molecular layer of epileptic rats. These boutons acquire the morphological features of mossy fiber boutons and made multiple synaptic contacts with dendritic spines. The analysis of the profile types suggests that some of the newly developed collateral mossy fibers made hypotrophic synaptic contacts.

DSP-4 treatment produces abnormal tyrosine hydroxylase immunoreactive fibers in rat hippocampus

DSP-4 has been used as selective toxin for central norepinephrine (NE) systems. The depletion of NE by DSP-4 is thought to result from neurotoxic destruction of locus coeruleus terminals and axons. We have used tyrosine hydroxylase immunocytochemistry (TH-IR), silver stains for neural degeneration, and electron microscopy to examine the morphological effects of DSP-4 treatment on the rat hippocampus. Animal survived for either 2 or 5 weeks after DSP-4 treatment. DSP-4 depleted hippocampal norepinephrine levels to 15% of control values. Abnormally enlarged TH-IR fibers were found in the hippocampus of DSP-4-treated animals. No evidence of fiber degeneration was found following light or electron microscopic examination of the dentate hilus in DSP-4-treated animals. These data suggest that DSP-4 treatment does not destroy NE terminals, but may produce an intraneuronal lesion leading to an accumulation of TH and a depletion of norepinephrine within the terminal fields.