Mapping patterns of c-fos expression in the central nervous system after seizure

A dramatic and specific induction of c-fos was observed in identifiable neuronal populations in vivo after administration of the convulsant Metrazole. This effect was time- and dose-dependent and was abolished by prior treatment with the anticonvulsant drugs diazepam or pentobarbital. About 60 minutes after administration of Metrazole, c-fos messenger RNA reached a maximum and declined to basal levels after 180 minutes. A further decrease below that in normal brain was observed before a return to basal levels after 16 hours. While Metrazole still elicited seizures during this period, reinduction of c-fos was largely refractory. At 90 minutes, c-fos protein was observed in the nuclei of neurons in the dentate gyrus, and in the pyriform and cingulate cortices. Subsequently, c-fos protein appeared throughout the cortex, hippocampus, and limbic system. Thus, seizure activity results in increased c-fos gene expression in particular subsets of neurons.     

Impairment of muscle stretch reflexes in tick paralysis

Experiments with tick-paralyzed dogs and woodchucks have shown impairment of stretch reflexes in addition to partial paralysis at the neuromuscular junction. Stretch reflexes disappear very early during paralysis, whereas nociceptive reflexes do not appear to be directly affected. The early incoordination and the ascending nature of the paralysis may be related to impairment of stretch reflex pathways.     

Postsynaptic versus presynaptic inhibition in antagonistic stretch reflexes

Motoneurons of the cat gastrocnemius-soleus muscle were studied intracellularly with conventional glass micropipettes. Each of these motoneurons was made to fire repetitively by stretch of its own muscle (gastrocnemius-soleus), and by current injected through the impaling microelectrode. By comparing the amount of inhibitory influence from antagonistic stretch of posterior biceps on the repetitive firing in these two different situations, an estimate could be obtained of the relative contribution of postsynaptic inhibition in this type of antagonistic stretch reflex. Even when the experimental conditions were such as to favor presynaptic inhibition, only strong postsynaptic inhibitory effects were seen; presynaptic inhibition was not found.     

出生前山羊脑和脊髓的生长发育规律

测量了6～21周山羊胎儿脑和脊髓的相关指标,并绘制生长曲线.结果表明:山羊胎儿脑和脊髓生长发育具有快慢交替的阶段性变化规律.发育早期脑的生长速度要快于同期脊髓的生长速度.出生前,山羊大脑在长、宽、高3个方向上的发育表现出不均衡的特点.脊髓不同节段的生长高峰期出现的时间、数量和增长趋势都不一致,可能与脊髓内不同组份发育先后次序有关.     

Testosterone regulation of sexual reflexes in spinal male rats

Castrated male rats with complete midthoracic spinal transections were maintained on exogenous testosterone; they showed intermittent clusters of genital responses consisting of erections, quick flips, and long flips of the penis when gentle pressure was con stantly applied to its base. The number of these genital responses per 30-minute test was markedly influenced by withdrawal or administration of testosterone.     

Stress-induced analgesia in humans: endogenous opioids and naloxone-reversible depression of pain reflexes

The cumulative effects of a repetitive stress induced by anticipation of pain (noxious foot shock) were studied on the threshold of a nociceptive flexion reflex of the lower limb. The threshold of the nociceptive reflex progressively increased with the repetition of the stress. This effect was reversed by naloxone, which even produced hyperalgesia, since a rapid and significant decrease in this threshold, below the initial values, was noted. Tha data provide evidence for involvement of endogenous opioids in the phenomenon of stress-induced analgesia in normal man.     

自噬在脊髓细胞中的作用与机制研究进展

脊髓损伤(spinal cord injury,SCI)是脊柱外科常见的复杂神经系统疾病,尽管不同脊髓损伤存在病理生理差异,但在许多方面损伤机制相似。损伤引起的一系列生化变化为继发性损伤,存在自噬迹象,但自噬的机制仍不清楚。综述了脊髓损伤后自噬在不同类型细胞中作用机制的研究进展及自噬对受损组织的影响。     

Protective role of ATP-sensitive potassium channels in hypoxia-induced generalized seizure

Adenosine triphosphate (ATP)-sensitive potassium (K(ATP)) channels are activated by various metabolic stresses, including hypoxia. The substantia nigra pars reticulata (SNr), the area with the highest expression of K(ATP) channels in the brain, plays a pivotal role in the control of seizures. Mutant mice lacking the Kir6.2 subunit of K(ATP) channels [knockout (KO) mice] were susceptible to generalized seizures after brief hypoxia. In normal mice, SNr neuron activity was inactivated during hypoxia by the opening of the postsynaptic K(ATP) channels, whereas in KO mice, the activity of these neurons was enhanced. K(ATP) channels exert a depressant effect on SNr neuronal activity during hypoxia and may be involved in the nigral protection mechanism against generalized seizures.     

Reproductive patterns in the deep-sea benthos

The reproductive condition of a variety of benthic invertebrates from the bathyal San Diego Trough was monitored periodically. In this physically seasonless, deep-sea environment most species reproduce throughout the year, and only a few display highly synchronous, annual reproductive cycles. These few are not typical deep-sea species; they are known from shallow water and belong to groups which are relatively unimportant in abyssal depths. Of the 11 species examined, 3 bivalves, 2 ophiuroids, 2 isopods, 1 amphipod, and 1 polychaete breed year-round, and 1 brachiopod and 1 scaphopod spawn seasonally.     

狗脊髓灰质内动脉构筑

将明胶墨汁溶液注入到15例狗脊髓动脉系统内,观察其灰质内动脉构筑,结果如下:供应脊髓灰质内的动脉分别自脊髓背外侧动脉、沟动脉和周缘支发出。背角内侧动脉和背角外侧动脉分布于背角的头和颈部。中间外侧动脉发出分支到灰质侧角。供应灰质腹角的动脉有腹角外侧、腹侧和内侧动脉。中间内侧动脉分布于灰质中间带的内侧2/3。背连合动脉供应背侧灰质连合。在中央管两侧各有一条中央管旁动脉,纵向将各沟连合动脉串连一起。分布于灰质内的相邻各动脉间均存在吻合,构成灰质内动脉网。     

Endogenous anticonvulsant substance in rat cerebrospinal fluid after a generalized seizure

Cerebrospinal fluid taken from rats subjected to electroshock-induced seizures and injected into the cerebral ventricles of rats that had not been shocked increased the seizure threshold of the recipients. The anticonvulsant activity of the donor cerebrospinal fluid was antagonized by opioid antagonists and enhanced by peptidase inhibitors. These results suggest the existence of an endogenous anticonvulsant substance in rat cerebrospinal fluid, possibly opioid in nature, which is activated as a consequence of a seizure and which may play a critical role in postseizure inhibition.     

NMDA antagonists differentiate epileptogenesis from seizure expression in an in vitro model

In an electrographic model of seizures in the hippocampal slice, both of the N-methyl-D-aspartate (NMDA) antagonists 2-amino-5-phosphonovaleric acid and 5-methyl-10,11-dihydro-5H-dibenzo(a,d)cyclohepten-5,10-imine maleate (MK-801) prevented the progressive development of seizures but did not block previously induced seizures. Thus, a process dependent on the NMDA receptor-ionophore complex establishes a long-lasting, seizure-prone state; thereafter the seizures depend on non-NMDA receptor-ionophore mechanisms. This suggests that there is an important distinction between epileptogenesis and seizure expression and between antiepileptogenic and anticonvulsant pharmacological agents.