Search

Memory formation and sleep regulation are critical for brain functions in animals from invertebrates to humans. Neuropeptides play a pivotal role in regulating physiological behaviors, including memory formation and sleep. However, the detailed mechanisms by which neuropeptides regulate these physiological behaviors remains unclear. Herein, we report that neuropeptide diuretic hormone 31 (DH31) positively regulates memory formation and sleep in Drosophila melanogaster. The expression of DH31 in the dorsal and ventral fan-shaped body (dFB and vFB) neurons of the central complex and ventral lateral clock neurons (LNvs) in the brain was responsive to sleep regulation. In addition, the expression of membrane-tethered DH31 in dFB neurons rescued sleep defects in Dh31 mutants, suggesting that DH31 secreted from dFB, vFB, and LNvs acts on the DH31 receptor in the dFB to regulate sleep partly in an autoregulatory feedback loop. Moreover, the expression of DH31 in octopaminergic neurons, but not in the dFB neurons, is involved in forming intermediate-term memory. Our results suggest that DH31 regulates memory formation and sleep through distinct neural pathways., (Copyright © 2023 Elsevier Ltd and Japan Neuroscience Society. All rights reserved.)

We designed an automated device to study active avoidance learning abilities of zebrafish. Open source tools were used for the device control, statistical computing, and graphic outputs of data. Using the system, we developed active avoidance tests to examine the effects of trial spacing and aging on learning. Seven-month-old fish showed stronger avoidance behavior as measured by color preference index with discrete spaced training as compared to successive spaced training. Fifteen-month-old fish showed a similar trend, but with reduced cognitive abilities compared with 7-month-old fish. Further, in 7-month-old fish, an increase in learning ability during trials was observed with discrete, but not successive, spaced training. In contrast, 15-month-old fish did not show increase in learning ability during trials. Therefore, these data suggest that discrete spacing is more effective for learning than successive spacing, with the zebrafish active avoidance paradigm, and that the time course analysis of active avoidance using discrete spaced training is useful to detect age-related learning impairment., (Copyright © 2017 Elsevier Ireland Ltd and Japan Neuroscience Society. All rights reserved.)

Stereotyped movement of paired pectoral fins in zebrafish larvae could be considered a simple model with which to investigate the neural basis of behavior. Using a high-speed camera, we explored the repertoire of pectoral fin movements by naturally behaving larvae at 5-6 days post-fertilization. Previously, two types of fin movements were characterized in association with locomotion: 'CRAWLing,' an alternating fin movement associated with slow swimming, and 'TUCKing,' the adduction of both fins associated with fast swimming. We here describe a third mode of fin movement, which we call 'Munch's SCREAM', in which both pectoral fins were flipped anteriorly so that they reached the skin on the sides of the head, thus covering the otic vesicles. This behavior occurred spontaneously and was often associated with a slight regression or a sudden bending and change in body orientation. It could be also induced effectively in the agarose-embedded larvae by tactile stimulation on the skin around the eye and nose, some of which are associated with struggling, in which waves of bending propagate from the tail to the head. Larvae can still CRAWL and perform the SCREAM even when their forebrain and midbrain have been removed, suggesting that the neural circuits involved in the SCREAM are present in the hindbrain and/or spinal cord., (Copyright © 2014 Elsevier Ireland Ltd and the Japan Neuroscience Society. All rights reserved.)

Changes in the expression of estrogen-related substances in monkeys' brains at the menopausal transition, when estrogen deficit starts to occur, have not yet been examined thoroughly. In the present study, we immunohistochemically investigated the expression levels of estrogen receptor beta (ERβ) and aromatase (local estrogen synthesizing enzyme) in the hippocampal formation of premenopausal, menopausal, and ovariectomized premenopausal monkeys. In all monkeys tested, ERβ immunoreactivity was observed in interneurons located in the subiculum and the Ammon's horn, and most of these ERβ-immunoreactive neurons coexpressed a GABAergic neuron marker, parvalbumin. In the menopausal monkeys who exhibited a decline in estrogen concentration, hippocampal ERβ was highly upregulated, while aromatase expression was not markedly changed. By contrast, aromatase in the ovariectomized monkeys was significantly upregulated, while ERβ expression was not changed. In the brains of ovariectomized and menopausal monkeys, depletion of ovary-derived estrogen brought about different reactions which may be attributed to the senescence of brain aging., (Copyright © 2011 Elsevier Ireland Ltd and the Japan Neuroscience Society. All rights reserved.)

It is known that emotion and reward motivation promote long-term memory formation. It remains unclear, however, how and where emotion and reward are integrated during episodic memory encoding. In the present study, subjects were engaged in intentional encoding of photographs under four different conditions that were made by combining two factors (emotional valence, negative or neutral; and monetary reward value, high or low for subsequent successful recognition) during H2 15O positron emission tomography (PET) scanning. As for recognition performance, we found significant main effects of emotional valence (negative>neutral) and reward value (high value>low value), without an interaction between the two factors. Imaging data showed that the left amygdala was activated during the encoding conditions of negative pictures relative to neutral pictures, and the left orbitofrontal cortex was activated during the encoding conditions of high reward pictures relative to low reward pictures. In addition, conjunction analysis of these two main effects detected right hippocampal activation. Although we could not find correlations between recognition performance and activity of these three regions, we speculate that the right hippocampus may integrate the effects of emotion (processed in the amygdala) and monetary reward (processed in the orbitofrontal cortex) on episodic memory encoding., (2010 Elsevier Ireland Ltd and the Japan Neuroscience Society. All rights reserved.)

The recent advent of neuroimaging techniques provides an opportunity to examine brain regions related to a specific memory process such as episodic memory encoding. There is, however, a possibility that areas active during an assumed episodic memory encoding task, compared with a control task, involve not only areas directly relevant to episodic memory encoding processes but also areas associated with other cognitive processes for on-line information. We used positron emission tomography (PET) to differentiate these two kinds of regions. Normal volunteers were engaged in deep (semantic) or shallow (phonological) processing of new or repeated words during PET. Results showed that deep processing, compared with shallow processing, resulted in significantly better recognition performance and that this effect was associated with activation of various brain areas. Further analyses revealed that there were regions directly relevant to episodic memory encoding in the anterior part of the parahippocampal gyrus, inferior frontal gyrus, supramarginal gyrus, anterior cingulate gyrus, and medial frontal lobe in the left hemisphere. Our results demonstrated that several regions, including the medial temporal lobe, play a role in episodic memory encoding.

Nociceptin (orphanin FQ) may act on primary afferents and be involved in the regulation of nociceptive processing. We have shown, using reverse transcription-polymerase chain reaction (RT-PCR), that carrageenan-produced peripheral inflammation induces the expression of prepronociceptin (PPN) mRNA in the dorsal root ganglia (DRG). The present experiments were conducted to determine the localization of PPN mRNA in primary sensory neurons after peripheral inflammation, using in situ hybridization. An intraplantar injection of carrageenan induced the expression of PPN mRNA in small and medium sized neurons in the DRG; the effect peaked 0.5 h after carrageenan and subsided by 6 h. All neurons positive for PPN mRNA were positive for vanilloid receptor subtype 1 (VR1)-like immunoreactivity and some VR1-immunoreactive neurons were negative for PPN mRNA. The results suggest that peripheral inflammation induces the production of nociceptin in a sub-population of VR1-positive primary sensory neurons and support the idea that nociceptin produced there is involved in the regulation of nociceptive processing.

Pregnant rats were exposed to a single whole body X-irradiation on day 15 of gestation at a dose of 1.0 Gy. The offspring showed microcephaly at 7 weeks of age. Their body weight, brain weight, cortical thickness and the numerical density of neurons and synapses in the somatosensory and visual cortex were examined. Significant decreases in cortical thickness in both somatosensory (25%) and visual (16%) cortex were observed. However, there were no significant changes in the numerical density of neurons and synapses, nor in synapse-to-neuron ratios in both cortical regions between control and X-irradiated groups. These results suggest that prenatal X-irradiation can decrease the number of neurons, and the neurons which survive X-irradiation proliferate and elaborate connections in a normal fashion. This is in contrast to the animals exposed to ochratoxin A, in which numerical density of neurons in the somatosensory cortex is increased, with normal numerical density of synapses, resulting in low synapse-to-neuron ratios. The discrepancy in the synapse-to-neuron ratios between the X-irradiation and ochratoxin A-treatment might derive from a different effect on the developing neurons.