Makoto Taketani

A new planar multielectrode array for extracellular recording: application to hippocampal acute slice.

The present paper describes a new planar multielectrode array (the MED probe) and its electronics (the MED system) which perform electrophysiological studies on acute hippocampal slices. The MED probe has 64 planar microelectrodes, is covered with a non-toxic, uniform insulation layer, and is further coated with polyethylenimine and serum. The MED probe is shown to be appropriate for both stimulation and recording. In particular, multi-channel recordings of field EPSPs obtained by stimulating with a pair of planar microelectrodes were established for rat hippocampal acute slices. The recordings were stable for 6 h. Finally a spatial distribution of long-term potentiation was studied using the MED system.

A new planar multielectrode array: recording from a rat auditory cortex

In the study of the spatiotemporal properties of the cortex, a demand often arises for recording local field evoked potentials (LFEP) and neural spikes from a quantity of points at close range from each other. In such a situation a device composed of a lot of electrodes assembled in a single bunch would be suitable. Such circumstances gave us the impetus to create the device described in this paper, namely a new planar electrode array for in vivo multisite extracellular recording. The device is made of plastic and includes platinum electrodes 50 microm in diameter. The array of 64 incorporated microelectrodes is placed on the surface of the cortex of anesthetized rats. Recordings could be made through all electrodes for more than 1 h without damage to the cortex. The inter-polar distance is approximately 100 microm so that each individual electrode can record activity from a separate population of neurons near the cortical surface. The recording system described here is highly useful for visualizing spatiotemporal structure of the cortical activities and for imaging dynamic neuronal assemblies.

Asymmetrical distribution of the Schaffer projections within the apical dendrites of hippocampal field CA1.

Continuous current source densities were calculated in two dimensions (proximo-distal vs. medio-lateral) from slices of hippocampal field CA1 placed on a 64-electrode array in the presence of GABA blockers. The synaptic sink generated by stimulation of the Schaffer-commissural fibers spread across the extent of field CA1 within the same sublamina of the stratum radiatum as the stimulation electrode. The size and shape of the current sink varied according to the proximo-distal position of the stimulation site. Sinks generated by stimulation close to the cell body layer were more compact when compared to those produced by stimulation near the top of stratum radiatum which were broad and skewed in the proximal direction. These distributions were obtained with stimulation at either the CA3 or the subicular border of CA1. Induction of LTP increased the intensity of the current field but did not notably affect its distribution. It is concluded that (1) axons remain at the same proximo-distal level as they traverse stratum radiatum of CA1 and (2) generate proximally directed collaterals. Because of this, fibers that enter CA1 stratum radiatum immediately above the pyramidal cell bodies form compact synaptic fields while those entering CA1 at the top of the lamina form much broader and asymmetrical distributed fields.

Role of conserved amino acid residues in the complementarity determining regions on hapten-antibody interaction of anti-(4-hydroxy-3-nitrophenyl)acetyl antibodies

Monoclonal antibodies (mAbs) specific to (4-hydroxy-3-nitrophenyl)acetyl (NP) were prepared at various times after immunization and the amino acid sequences of VH and V lambda 1 in these mAbs were deduced from cDNA nucleotide sequences. Replacements due to somatic mutation were not found in day 7 mAbs but were found in those of days 14, 84 and 294. The affinity of day 7 mAbs to NP-glycine(NP-Gly) was in the order of 10(4) M-1 and it increased about 8000-fold with time after immunization. The extrinsic circular dichroism (CD) spectrum of the NP-epsilon-aminocaproic acid (NP-Cap)/Ab complex was unique for each mAb, although the spectra were grouped into two types, which tended to shift from one type to another with time, suggesting a variation in the micro-environments around NP-Cap in the combining sites. All these data indicate that the structure of the combining site was altered by somatic mutation; however, the fine-specificity measured by cross-reactivity with hapten analogues did not change significantly with time. We examined the amino acid residues in CDRs responsible for recognition of NP-haptens by comparing the amino acid sequences of anti-NP mAbs. Analyses revealed the presence of several conserved amino acid residues in CDRs of VH and V lambda 1, such as Tyr-32H, and Tyr-60H, in addition to a core segment involving Arg-50H.(ABSTRACT TRUNCATED AT 250 WORDS)

Applications of Multi-Electrode Array System in Drug Discovery Using Acute and Cultured Hippocampal Slices

There are currently only limited technologies for discovering, classifying, and testing compounds that could significantly affect cognitive performance in humans. This chapter describes ways in which multi-electrode arrays can successfully be used in this context. The proposed approach emerged from collaborations between research groups at the University of California, Irvine (UCI), the University of Southern California (USC), and Tensor Biosciences. The academic groups have, for a number of years, been developing protocols and analytical software for activating and analyzing electrophysiological responses generated by complex networks in mammalian CNS. This approach represents an effort to record the nearly second-long events that are possibly the substrate of simple cognitive actions; it can also be seen as an attempt to create an experimental platform for practical applications of neural network research. Tensor Biosciences is a startup company that was founded by researchers at UCI and USC and is pursuing a multiyear contract with Matsushita Electric Industrial Co., Ltd. (Panasonic) to develop software for Panasonic’s multi-electrode array system (MED64 System) and also build drug discovery platforms by using the MED64 System. Panasonic and its subsidiary, Alpha MED Sciences, have been gradually evolving turnkey hardware and software for stimulating and recording from 64 electrodes placed beneath a brain slice. Biologically or chemically induced changes in network behavior are ultimately a reflection of effects on synaptic and extrasynaptic activity in brain networks. The latter are not easily predicted by the agent’s physiological actions at the molecular and cellular levels. Rather, networks are premier examples of complex systems in which small changes in initial conditions can have large and unexpected consequences. It seems reasonable to assume that actions of psychoactive agents at the network level are substantially larger in magnitude than their actions on individual synapses. This point has been experimentally confirmed for ampakines, a class of compounds that positively modulate AMPA-type glutamate receptors. For instance, ampakine-induced changes on the hippocampal trisynaptic loop were severalfold greater in magnitude than changes in monosynaptic responses within