Reversal-input superposing technique for all-optical neural networks.

The proposed technique for optical neural networks can perform all the neural operations in a positive range. Bipolar weights of the neurons are represented by unipolar weights with a positive constant. By superposing the reversal inputs to the weighted sums, we can perform subtraction in a neuron by the nonlinear output function with a negative offset constant. This means that the number of processing elements needed in the proposed system is the same as that of neurons in the original neural network model. An experimental neural system is demonstrated for verification of this technique. The Hopfield model is adapted as an example of the neural networks implemented in the experimental neural system.

Selective reduction of serotonin immunoreactivity in some forebrain regions of rats induced by acute methamphetamine treatment; quantitative morphometric analysis by serotonin immunocytochemistry.

The influence of acute methamphetamine treatment on serotonin-like immunoreactive axons was studied in the rat forebrain. Animals, sacrificed 90 min after i.p. injection of methamphetamine (16 mg/kg) or saline, were processed for immunocytochemistry using serotonin antiserum. The numerical density of immunoreactive boutons of terminals and varicosities was quantitatively analyzed by a computer-assisted image analyzer. Compared with the control, administration of methamphetamine caused varying degrees of reduction in the numerical density in several forebrain regions. A high decrement (over -90%) was found in deep layers of the cerebral cortex, striatum and thalamic paraventricular nucleus, while a less prominent reduction (about -50%) was seen in such regions as the suprachiasmatic nucleus and basolateral amygdaloid nucleus. Moreover, superficial layers of the cerebral cortex contained uncommon features of immunopositive axons which were characterized by intensely stained fibers with large varicosities. The results suggest that the rat forebrain contains at least two types of serotonin nerves, one very sensitive to methamphetamine and another relatively insensitive or resistant to it.

Quantitative morphometric analysis of two types of serotonin-immunoreactive nerve fibres differentially responding to p-chlorophenylalanine treatment in the rat brain.

Two types of serotonin neurons differentially responding to treatment with p-chlorophenylalanine, a potent inhibitor of serotonin synthesis, have been demonstrated in the rat brain by immunohistochemistry using a serotonin monoclonal antibody in combination with a quantitative morphometric analysis. In control rats, the numerical density of serotonin-immunoreactive varicosities and terminals varied considerably from region to region. In p-chlorophenylalanine-treated rats, the numerical density was reduced in every region, but the degree of reduction in each region differed markedly. No correlation was seen in values of the numerical density between the control and p-chlorophenylalanine-treated rats, indicating that serotonin-positive axons in p-chlorophenylalanine-treated rats were present independent of the degrees of the axon density seen in the controls. It is postulated, therefore, that there are at least two types of positive axons; one highly sensitive to p-chlorophenylalanine treatment and another relatively resistant to it. Since the numerical density in any region was always smaller in p-chlorophenylalanine-treated rats than in the controls, p-chlorophenylalanine-sensitive axons appeared to be more or less distributed in every region where positive axons were detectable under normal conditions. However, a number of regions were innervated purely by p-chlorophenylalanine-sensitive axons. By contrast, p-chlorophenylalanine-insensitive axons were observed in several definite regions. These regions appeared to be related to the limbic system, or cranial motor and parasympathetic nuclei. In the latter nuclei, p-chlorophenylalanine-insensitive axons seemed to possess such common morphological features as having relatively large varicosities and being situated adjacent to neural somata, suggesting their inhibitory roles in neurotransmission. The present result indicates that the two types of serotonin axons may play important roles in the behavioural events observed in rats following p-chlorophenylalanine treatment.

Reversible serotoninergic neurotoxicity of N-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) in mouse striatum studied by neurochemical and immunohistochemical approaches.

Effects of N-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) on serotonin (5-HT) were studied in mouse striatum. The 5-HT level was significantly reduced at 1 week after MPTP, though returned at 4 weeks. The level of 5-hydroxyindoleacetic acid (5-HIAA) increased at both 1 and 4 weeks. The ratio of increase in 5-HT induced by pargyline administration was larger in MPTP-pretreated mice than in vehicle-pretreated controls at 1 week, although it was identical in both groups at 4 weeks. The 5-HT immunohistochemical study confirmed the biochemical change of 5-HT. These results suggest that MPTP functionally affects the 5-HT metabolism in mouse striatum.

Qualitative abnormalities of choline acetyltransferase in Alzheimer type dementia.

The maximum activity of choline acetyltransferase (ChAT), the affinity for choline or acetyl-CoA and the isozyme pattern in the cerebral cortex of 5 cases of Alzheimer type dementia (ATD) and 6 age-matched control subjects were examined post-mortem. Maximum activities of ChAT were estimated in 5 cerebral cortical areas of Brodmann: 4, 7, 10, 17 and 22. A significant reduction in maximum activities of ChAT was found in all cortical areas for the cases of ATD. The affinity for choline or acetyl-CoA was measured in the frontal cortex (Brodmann's areas 4 and 6) and in the temporal cortex (Brodmann's areas 21 and 22). The affinity was significantly decreased in both cortices of demented patients. A significant correlation was observed between maximum activity of ChAT and the affinity for choline or acetyl-CoA. The isozyme pattern obtained by column chromatography on Sephadex G-200 was similar to that obtained by centrifugation on a sucrose density gradient. The isozyme pattern of ATD was different from that of the control subjects. These results suggest qualitative as well as quantitative abnormalities in the ChAT in autopsied brains of ATD.