We report a site selective Cu-NMR study on underdoped Hg-based five-layered high-Tc cuprate HgBa2Ca4CU5O(12+delta) with a Tc = 72 K. Antiferromagnetism (AFM) has been found to take place at T(N) = 290 K, exhibiting a large antiferromagnetic moment of 0.67-0.69 microB at three inner planes (IP). This value is comparable to the values reported for nondoped cuprates, suggesting that the IP may be in a nearly nondoped regime. Most surprisingly, the AFM order is also detected with M(AFM)(OP) = 0.1 microB even at two outer planes (OP) that are responsible for the onset of superconductivity (SC). The high-Tc SC at Tc = 72 K can uniformly coexist on a microscopic level with the AFM at OP's. This is the first microscopic evidence for the uniform mixed phase of AFM and SC on a single CuO2 plane in a simple environment without any vortex lattice and/or stripe order.

We report unusual magnetic and superconducting ͑SC͒ characteristics in multilayered CuO 2 planes in Hgand Cu-based high-T c cuprates through the 63 Cu-NMR measurements. These compounds, in which the number of CuO 2 planes ͑n͒ ranges from 3 to 5 in a unit cell, include crystallographically inequivalent outer ͑OP͒ and inner ͑IP͒ CuO 2 plane that are surrounded by pyramidal and square oxygen, respectively. The Knight shift ( 63 K) at the OP and IP exhibits respective characteristic temperature dependence, consistent with its own doping level. Using an experimental relation between the spin part in 63 K at room temperature and the doping level in a CuO 2 layer N h , we show that N h (OP) at the OP is larger than N h (IP) at the IP for all the systems and its difference ⌬N h ϭN h (OP)ϪN h (IP) increases as either a total carrier content ␦ or n increases. At ⌬N h 's exceeding a critical value, the pseudogap behavior in the normal state is seen alone at the IP, and a bulk SC transition does not set in simultaneously at the IP and OP. A SC nature at the OP becomes consistent with a mean-field behavior only below T c2 that is significantly lower than T c . Reduction in T c with increasing n is associated with an increase in ⌬N h . It is a rather remarkable aspect that a T c is not always reduced even though these multilayered high-T c compounds are heavily overdoped. This arises, we show, because the IP remains underdoped and keeps a high value of T c , while the OP is predominantly overdoped. This may be a microscopic origin for the lowest anisotropic SC characteristics reported to date in Cu-based multilayered high-T c compounds.

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Domoic acid (0.6 mg/kg) was injected intravenously through the caudal vein in pregnant female mice on the 13th day of gestation and EEG was monitored in the developing progeny during postnatal days 10-30. No clinical seizure activity was observed during this period. However, these mice demonstrated generalized electrocortical inhibition associated with diffuse spike and wave activity in their basal EEG records. Intrauterine domoic acid-exposed (IUD) mice had significantly reduced seizure thresholds to an additional dose of domoic acid, given postnatally. At the light microscopic level, hippocampus of IUD mice exhibited age related developmental neurotoxicity. No cellular damage was observed on postnatal day 1. On day 14, severe neuronal damage was observed in the hippocampal CA3 and dentate gyrus regions. On day 30, in addition to CA3 and dentate gyrus, CA4 was also involved. Brain regional GABA levels were significantly reduced and glutamate levels increased in IUD mice. Kainate receptor binding to hippocampal synaptosomal membranes from IUD mice at 30 d of age was significantly increased. There was also an enhanced 45Ca influx into cortical and hippocampal slices of these mice. These findings suggest that intrauterine exposure to domoic acid can induce hippocampal excitotoxicity by increasing the neuronal calcium influx through kainate receptor activation. Histological changes suggest progressive hippocampal damage in IUD mice, but without overt clinical seizures.

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