Observations of synaptic efficacy and paired-pulse facilitation in area CA1 of hippocampal slices from coriaria lactone-kindled rats

Phytochemistry and Biology of Loranthus parasiticus Merr, a Commonly Used Herbal Medicine

Loranthus parasiticus Merr (L. parasiticus) is a member of Loranthaceae family and is an important medicinal plant with a long history of Chinese traditional use. L. parasiticus, also known as Sang Ji Sheng (in Chinese), benalu teh (in Malay) and baso-kisei (in Japanese), is a semiparasitic plant, which is mostly distributed in the southern and southwestern regions of China. This review aims to provide a comprehensive overview of the ethnomedicinal use, phytochemistry and pharmacological activity of L. parasiticus and to highlight the needs for further investigation and greater global development of the plant's medicinal properties. To date, pharmacological studies have demonstrated significant biological activities, which support the traditional use of the plant as a neuroprotective, tranquilizing, anticancer, immunomodulatory, antiviral, diuretic and hypotensive agent. In addition, studies have identified antioxidative, antimutagenic, antiviral, antihepatotoxic and antinephrotoxic activity. The key bioactive constituents in L. parasiticus include coriaria lactone comprised of sesquiterpene lactones: coriamyrtin, tutin, corianin, and coriatin. In addition, two proanthocyanidins, namely, AC trimer and (+)-catechin, have been recently discovered as novel to L. parasiticus. L. parasiticus usefulness as a medicinal plant with current widespread traditional use warrants further research, clinical trials and product development to fully exploit its medicinal value.

A new rat model of acute seizures induced by tutin

Coriaria Lactone (CL) is a mixture that has been used to establish animal models of epilepsy. In this study, we focused on the epileptogenic action of tutin, a pure chemical component derived from CL. Rats were implanted with a guide cannula for microinjection of tutin into either of the lateral cerebral ventricles. Behavioral and electroencephalographic (EEG) changes were investigated for at least 2 h after tutin administration. Injected animals presented behavioral seizures: initially, facial and limbic clonus, and subsequently, tonic-clonic seizures that eventually progressed to status epilepticus. Accompanying the behavioral activities, a variety of EEG patterns were recorded. Spike-and-wave complexes occurred continuously at 3 Hz, with a mean amplitude of approximately 295 microV. Multiple spikes and slow waves occurred repetitively and became more frequent and intense. The amplitude of this EEG pattern was low (approximately 85 microV) at onset and gradually increased to approximately 200 microV. Spikes (8 Hz, approximately 555 microV) and slow waves (3 Hz, approximately 670 microV) occurred periodically at the onset of grand mal seizures. Behavioral and EEG changes induced in rats by tutin demonstrated that this is a potent convulsant, by which a new animal model of status epilepticus was established. This acute seizure model is productive and would be optional for investigation of seizures or status epilepticus.

Simultaneous expression of excitatory postsynaptic potential/spike potentiation and excitatory postsynaptic potential/spike depression in the hippocampus

Tetanic stimulation of afferents in the stratum radiatum of the CA1 area of the rat hippocampus results in long-term potentiation of excitatory synaptic responses in pyramidal cells. Previous studies have reported a greater increase in the population spike amplitude following the induction of long-term potentiation than could be accounted for by the increase of the slope of the population excitatory postsynaptic potential. Two hypotheses have been proposed to explain this phenomenon (called excitatory postsynaptic potential/spike potentiation): a modification of the firing threshold and/or a modification of the inhibitory drive. Previous studies have not, however, addressed the question of possible changes in spike threshold in association with long-term depression. This paper examines whether the concomitant long-term potentiation of pharmacologically isolated N-methyl-D-aspartate receptor-mediated excitatory postsynaptic potentials, reported previously, is also associated with a change in spike threshold. When the amplitude of the population spike is plotted as a function of the slope of the population excitatory postsynaptic potential (excitatory postsynaptic potential/spike curve), excitatory postsynaptic potential/spike potentiation (depression) is seen as a shift of the excitatory postsynaptic potential/spike curve to the left (right) following a conditioning stimulus. In this study, using kainic acid lesioned hippocampus, we have shown that tetanic stimulation produced excitatory postsynaptic potential/spike potentiation of the control synaptic response and excitatory postsynaptic potential/spike depression of the isolated N-methyl-D-aspartate receptor-mediated responses.