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Neurogenesis occurs in the adult brain throughout the lives of all mammals. The dentate gyrus (DG) of the hippocampus and the subventricular zone (SVZ) of the lateral ventricles have been established as the primary sites of adult neurogenesis, and recent studies have shown that inflammation has a modulating effect on adult neurogenesis. However, only limited studies have investigated how neurogenesis is affected during sepsis and sepsis-associated encephalopathy. Therefore, we investigated adult neurogenesis in the cecal ligation and puncture (CLP) model of sepsis using a cell proliferation marker, 5-bromo-2'-deoxyuridine (BrdU). Twenty-four rats were placed into the following three groups: an un-operated control group, a sham-operated group that underwent exactly the same procedures except for CLP, and a CLP group that survived surgical procedures and developed signs of sepsis. Rats were monitored for twenty-four hours before they were euthanized and their brains were harvested. Significantly higher numbers of BrdU-immunoreactive cells were observed in the SVZ of the lateral ventricles in the CLP group as compared with both control groups, while no significant difference was found in the number of DG granule cells between the three groups. The majority of BrdU-positive cells in the SVZ co-expressed the neuronal marker doublecortin but not the astrocytic marker glial fibrillary acidic protein. Taken together, our results suggest that sepsis induced by CLP in rats increases region-specific cellular regeneration, in a possible attempt to compensate for the devastating effect of sepsis and sepsis-associated encephalopathy on the brain.

The cholinesterase inhibitors huperzine A, donepezil and rivastigmine were compared for their effects on extracellular acetylcholine concentration and acetylcholinesterase activity in the rat cortex. After i.p. injection, huperzine A (0.25-0.75 micromol/kg), donepezil (2-6 micromol/kg) and rivastigmine (0.75-1.5 micromol/kg) dose-dependently elevated the concentration of acetylcholine. The duration of huperzine A was longest. The time courses of cortical acetylcholinesterase inhibition with middle doses of these agents mirrored the increases of acetylcholine at the same doses. However, acetylcholinesterase inhibition was disproportionately greater after middle dose of rivastigmine than doses of huperzine A and donepezil that increased acetylcholine to a similar extent. Muscle fasciculation appeared only after donepezil with a dose-dependent incidence and intensity. In molar terms, huperzine A was 8- and 2-fold more potent than donepezil and rivastigmine, respectively, in increasing cortical acetylcholine levels, with a longer-lasting effect.

We examined whether huperzine A (HupA), a promising therapeutic agent for Alzheimer's disease, could alter the processing of amyloid precursor protein (APP) in rats with beta-amyloid protein-(1-40) (Abeta(1-40)) infusion into the cerebral ventricle and in human embryonic kidney 293 (HEK293sw) cells. Daily intraperitoneal administration of HupA for 12 consecutive days produced significant reversals of the Abeta(1-40)-induced down-regulation of secretory APP (APPs) and protein kinase C (PKC) in rats. In the HEK293sw cells, the level of APPs was increased significantly with HupA treatment, and there was a similar change in PKCalpha level under the same condition. However, no significant alternations in the levels of PKCdelta and PKC were found after HupA treatment. These findings suggest that HupA may affect the processing of APP by up-regulating PKC, especially PKCalpha.

The effects of huperzine A (HupA) on staurosporine-induced neuronal apoptosis and potential mechanisms were investigated in primary cultured rat cortical neurons. Pretreatment of the cells with HupA (0.1-100 microM) 2 h prior to 0.5 microM staurosporine exposure for 24 h, markedly elevated cell survival. Incubation with HupA at higher dose (1 microM) also reduced the DNA fragmentation caused by staurosporine. This dose of HupA also reduced the upregulation of the pro-apoptotic gene, bax, downregulation of the anti-apoptotic gene, bcl-2, and antagonized the decrease in immunoreactive caspase-3 proenzyme. These results demonstrated that HupA protect neurons against staurosporine-induced apoptosis via regulating the apoptotic related genes and caspase-3 proenzyme.

Recently, the potent cholinesterase inhibitor (-)-huperzine A (HupA) was demonstrated to protect neuronal and glial cells against the cytotoxicity of beta-amyloid (Abeta). Since the unnatural (+)-HupA is a much less potent inhibitor, it was of interest to examine the stereoselectivity of cellular protection by the two isomers. In the present study, effects of (+)- and (-)-HupA on Abeta(25-35)-induced injury were compared in PC12 and NG108-15 neuroblastoma cell lines. Following a 24 h exposure to 1 microM Abeta(25-35), cell survival was markedly reduced, but preincubation with (+)-HupA or (-)-HupA (0.1-10 microM) enhanced survival significantly. The potency of (-)-HupA and (+)-HupA in protecting against Abeta toxicity was similar. This result contrasted with the stereoselectivity of cholinesterase inhibition in vitro and in vivo, in which (-)-HupA is about 50-fold more potent than (+)-HupA. It is concluded that the neuroprotective properties of HupA enantiomers have no relation to anti-cholinesterase activity.

The protective effects of huperzine A on transient global ischemia in gerbils were investigated. Five min of global ischemia in gerbils results in working memory impairments shown by increased escape latency in a water maze and reduced time spent in the target quadrant. These signs of dysfunction are accompanied by delayed degeneration of pyramidal hippocampal CA1 neurons and by decrease in acetylcholinesterase activity in the hippocampus. Subchronic oral administration of huperzine A (0.1 mg/kg, twice per day for 14 days) after ischemia significantly reduced the memory impairment, reduced neuronal degeneration in the CA1 region, and partially restored hippocampal choline acetyltransferase activity. The ability of huperzine A to attenuate memory deficits and neuronal damage after ischemia might be beneficial in cerebrovascular type dementia.

By using extracellular recordings of field potential, the exact pathway by which the endogenous ACh influencing the induction of long-term potentiation (LTP) in CA1 area was analysed in slices of rat hippocampus. The results showed that: (1) the application of (-) huperzine A, an AChE inhibitor extracted from Chinese herb Qian Ceng Ta (Huperzia Serrata), could enhance the induction of LTP, while this drug showed little effect on the second components of multiple population spikes that were recorded in Mg(2+)-free medium and had proven to be N-methyl-D-aspartate (NMDA) receptor-mediated response; and (2) scopolamine, a muscarinic receptor antagonist, could significantly suppressed the induction of LTP, while most of the suppressive effect of scopolamine was blocked when slices were pretreated by bicuculline, a gamma-aminobutyric acid (GABA(A)) receptor antagonist. These results suggest that endogenous ACh potentiates the induction of LTP through the inhibition of GABAergic interneurons that modulate pyramidal neurons, but not through the activation of NMDA receptors located on pyramidal neurons.

The effects of huperzine A (HupA), a novel acetylcholinesterase inhibitor, on Abeta(25-35)-induced cell lesion, level of lipid peroxidation, antioxidant enzyme activities were investigated in the rat pheochromocytoma line PC12. Following a 48 h exposure of the cells to Abeta(25-35), a significant reduction in cell survival and activities of glutathione peroxidase (GSH-Px) and catalase (CAT), as well as increased production of malondialdehyde (MDA) and superoxide dismutase (SOD) were observed. Preincubation of the cells with HupA prior to Abeta(25-35) exposure elevated the cell survival and GSH-Px and CAT activities, and decreased the level of MDA and SOD activity. The results indicate that HupA has protective effects against Abeta-induced cell toxicity, which might be beneficial for the treatment of Alzheimer's disease.

The effects of Huperzine A (HupA), a novel acetylcholinesterase inhibitor, on hydrogen peroxide (H2O2) induced cell lesion, level of lipid peroxidation and antioxidant enzyme activities were investigated in rat pheochromocytoma line PC12. Following a 6-h exposure of the cells to H2O2 (200 microM), a marked reduction in cell survival and activities of glutathione peroxidase and catalase, as well as increased production of malondialdehyde (MDA) were observed. Pretreatment of the cells with HupA (0.1-10.0 microM) prior to H2O2 exposure significantly elevated the cell survival and antioxidant enzyme activities and decreased the level of MDA. Our results indicated that in addition to its anticholinesterase effects, HupA had protective effects against free radical-induced cell toxicity, which might be beneficial for the treatment of Alzheimer's disease.

Extracellular recordings of field potential from CA1 region of rat hippocampal slices were used to observe the effects of a shorter synthetic fragment of beta-amyloid peptide (A beta31-35) on the induction of long-term potentiation (LTP) and the action of (-)huperzine A, a potent acetylcholinesterase (AChE) inhibitor on these processes was also observed. The results showed that: (1) 0.1 microM A beta31-35 suppressed the induction of LTP in a similar mode as the longer fragment A beta25-35, did, while they did not change the amplitude of the baseline population spike (PS); (2) when PSs were recorded separately in Mg2+-free medium, which unveils the N-methyl-D-aspartate (NMDA)-mediated responses, both A beta31-35 and A beta25-35 showed little effect on the components of multiple PSs; (3) two concentrations of 0.1 microM or 1.0 microM (-)huperzine A showed no effects on the PS amplitude while the latter could enhance the LTP and (4) co-administration of (-)huperzine A with 0.1 microM concentration could block most of the suppressive action induced by A beta31-35 or A beta25-35 upon the LTP. The results suggest that the shorter fragment A beta31-35, is long enough to suppress the induction of LTP and these two fragments might suppress the induction of LTP through a NMDA receptor-independent pathway that involves cholinergic terminals in hippocampus.

Huperzine A (HupA) is an alkaloid isolated from the Chinese club moss Huperzia serrata and has been used for improving memory, cognitive and behavioral function in patients with Alzheimer's disease in China. It has NMDA antagonist and anticholinesterase activity and has shown anticonvulsant and antinociceptive effects in preliminary studies when administered intraperitoneally to mice. To better characterize the antinociceptive effects of HupA at the spinal level, Holtzman rats were implanted with intrathecal catheters to measure thermal escape latency using Hargreaves thermal escape testing system and flinching behavior using the formalin test. Intrathecal (IT) administration of HupA showed a dose-dependent increase in thermal escape latency with an ED50 of 0.57 microg. Atropine reversed the increase in thermal escape latency produced by 10 microg HupA, indicating an antinociceptive mechanism through muscarinic cholinergic receptors. The formalin test showed that HupA decreased flinching behavior in a dose-dependent manner. Atropine also reversed the decrease in flinching behavior caused by 10 microg HupA. A dose-dependent increase of side effects including scratching, biting, and chewing tails was observed, although antinociceptive effects were observed in doses that did not produce any adverse effects.

The actions of huperzine A (HupA), a novel cholinesterase inhibitor, on the fast transient potassium current ( I A ) were investigated in CA1 pyramidal neurons acutely dissociated from rat hippocampus. HupA reversibly inhibited I A (IC 50 =914±1 μM). The effect was voltage-independent and insensitive to atropine. Tacrine was eight times more potent than HupA (IC 50 =115±2 μM), whereas huperzine B had little effect. HupA slowed down the decay of I A and its recovery from inactivation. HupA had no effect on the steady-state inactivation, but hyperpolarized the activation curve of I A by 6 mV. The results suggest that HupA may act as a blocker at the external mouth of the A channel. The potential relevance of the inhibitory effect of HupA on I A to the treatment of Alzheimer's disease has been discussed.

Huperzine A, a novel cholinesterase inhibitor, was found to inhibit the N -methyl- d -aspartate (NMDA) receptors in the brain. In this study, the mechanisms of the NMDA receptor inhibition were investigated using [ 3 H]dizocilpine (MK-801) binding in synaptic membrane of rat cerebral cortex. Changing the concentrations of l -glutamate and l -glycine did not alter the potency of huperzine A. Spermidine caused rightward shift of the concentration–response curve of huperzine A, and considerably increased its IC 50 value. Huperzine A did not affect the potency of unlabeled (+)-MK-801 in [ 3 H]MK-801 binding. Saturation binding studies reveal that huperzine A exerts a negative allosteric modulation on the MK-801 binding site within the NMDA receptor-channel. The results suggest that huperzine A is a non-competitive antagonist of the NMDA receptors, acting at one of the polyamine binding sites.

Huperzine A (HupA) and donepezil, two novel selective acetylcholinesterase inhibitors available for Alzheimer's disease, were tested for their ability to alleviate injury from oxygen–glucose deprivation (OGD) in the rat pheochromocytoma line PC12 cells. OGD for 30 min triggered death in more than 50% of cells, along with major changes in morphology and biochemistry including elevated levels of lipid peroxide, superoxide disamutase activity and lactate. Cells pretreated for 2 h with HupA or donepezil showed improved survival and reduced biochemical and morphologic signs of toxicity (statistically significant over the range from 10 μM down to 1.0 and 0.1 μM, respectively). Our results indicated that HupA and donepezil protected PC12 cells against OGD-induced toxicity, most likely by alleviating disturbances of oxidative and energy metabolism.

The inhibition of huperzine A, a potential therapeutic agent to treat Alzheimer's disease, on rat cortical acetylcholinesterase was found to be highly stereospecific. In the present study the effect of the enantiomers of huperzine A on [ 3 H]dizocilpine (MK-801) binding to synaptic membrane of rat cerebral cortex was compared. The natural (−)-huperzine A and the synthetic (+)-huperzine A inhibited the specific binding of [ 3 H]MK-801 with a similar potency. The IC 50 values were 65±7 and 82±12 μM ( n =5 for each enantiomer, P =0.248), respectively. The result indicates that huperzine A inhibits N -methyl- d -aspartate (NMDA) receptor in rat cerebral cortex without stereoselectivity.

Huperzine A, a selective inhibitor of acetylcholinesterase, was recently demonstrated to exert an antagonist effect on N-methyl-D-aspartate (NMDA) receptor in rat cerebral cortex. In the present study, the effects of six cholinesterase inhibitors, e.g. huperzine A, huperzine B, tacrine, donepezil (E2020), physostigmine and galanthamine on [3H]dizocilpine (MK-801) binding to synaptic membrane of rat cerebral cortex were compared. Their IC50 values (mean +/- SD) were 36.9 +/- 12.1, 316.8 +/- 93.2, 33.2 +/- 3.7, 135.0 +/- 15.1, 50.4 +/- 7.4, and 3344 +/- 295 microM, respectively. The rank order of potency is tacrine approximately huperzine Aphysostigminedonepezilhuperzine Bgalanthamine. There is no correlation between their activities to inhibit [3H]MK-801 binding and to inhibit acetylcholinesterase (r = +0.563, P = 0.245). The results suggest that most cholinesterase inhibitors available exhibit an antagonist effect on NMDA receptor in rat cerebral cortex in addition to their inhibitory effect on acetylcholinesterase.