Loss of AP-3 function affects spontaneous and evoked release at hippocampal mossy fiber synapses

Synaptic vesicle (SV) exocytosis mediating neurotransmitter release occurs spontaneously at low intraterminal calcium concentrations and is stimulated by a rise in intracellular calcium. Exocytosis is compensated for by the reformation of vesicles at plasma membrane and endosomes. Although the adaptor complex AP-3 was proposed to be involved in the formation of SVs from endosomes, whether its function has an indirect effect on exocytosis remains unknown. Using mocha mice, which are deficient in functional AP-3, we identify an AP-3-dependent tetanus neurotoxin-resistant asynchronous release that can be evoked at hippocampal mossy fiber (MF) synapses. Presynaptic targeting of the tetanus neurotoxin-resistant vesicle soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) tetanus neurotoxin-insensitive vesicle-associated membrane protein (TI-VAMP) is lost in mocha hippocampal MF terminals, whereas the localization of synaptobrevin 2 is unaffected. In addition, quantal release in mocha cultures is more frequent and more sensitive to sucrose. We conclude that lack of AP-3 results in more constitutive secretion and loss of an asynchronous evoked release component, suggesting an important function of AP-3 in regulating SV exocytosis at MF terminals

Calmodulin mediates rapid recruitment of fast-releasing synaptic vesicles at a calyx-type synapse.

In many synapses, depletion and recruitment of releasable synaptic vesicles contribute to use-dependent synaptic depression and recovery. Recently it has been shown that high- frequency presynaptic stimulation enhances recovery from depression, which may be mediated by Ca2+. We addressed this issue by measuring quantal release rates at the calyx of Held synapse and found that transmission is mediated by a heterogeneous population of vesicles, with one subset releasing rapidly and recovering slowly and another one releasing reluctantly and recovering rapidly. Ca2+ promotes refilling of the rapidly releasing synaptic vesicle pool and calmodulin inhibitors block this effect. We propose that calmodulin- dependent refilling supports recovery from synaptic depression during high-frequency trains in concert with rapid recovery of the slowly releasing vesicles

Mottainai as a Japanese Cultural Keyword： A Key Semantic Difference to the English Word Waste

認知・機能言語学研究(7

Multivesicular release differentiates the reliability of synaptic transmission between the visual cortex and the somatosensory cortex.

Neurons in layer 4 (L4) of the cortex play an important role in transferring signals from thalamus to other layers of the cortex. Understanding the fundamental properties of synaptic transmission between L4 neurons helps us gain a clear picture of how the neuronal network in L4 cooperates to process sensory information. In the present study, we have determined the underlying parameters that govern synaptic strength, such as quantal size, size of readily releasable vesicle pool, and release probability (Pr) of excitatory synaptic connections within L4 of the visual cortex (V1) and the somatosensory cortex (S1) in mice. Although only a single vesicle is released per release site under physiological conditions at V1 synapses, multivesicular release (MVR) is observed at S1 synapses. In addition, we observed a saturation of postsynaptic receptors at S1 synapses. Other synaptic properties are similar in both cortices. Dynamic clamp experiments suggest that higher Pr and MVR at S1 synapses lower the requirement of the number of synaptic inputs to generate postsynaptic action potentials. In addition, the slower decay of synaptic current and the intrinsic membrane properties of the postsynaptic neuron also contribute to the reliable transmission between S1 neurons.</jats:p

Mechanistic insights into cAMP-mediated presynaptic potentiation at hippocampal mossy fiber synapses

Presynaptic plasticity is an activity-dependent change in the neurotransmitter release and plays a key role in dynamic modulation of synaptic strength. Particularly, presynaptic potentiation mediated by cyclic adenosine monophosphate (cAMP) is widely seen across the animals and thought to contribute to learning and memory. Hippocampal mossy fiber-CA3 pyramidal cell synapses have been used as a model because of robust presynaptic potentiation in short- and long-term forms. Moreover, direct presynaptic recordings from large mossy fiber terminals allow one to dissect the potentiation mechanisms. Recently, super-resolution microscopy and flash-and-freeze electron microscopy have revealed the localizations of release site molecules and synaptic vesicles during the potentiation at a nanoscale, identifying the molecular mechanisms of the potentiation. Incorporating these growing knowledges, we try to present plausible mechanisms underlying the cAMP-mediated presynaptic potentiation

Individual and Technological Factors Affecting Undergraduates' Use of Mobile Technology in University of Ilorin, Nigeria

The proliferation and utilization of handheld mobile technology among undergraduates for mobile learning cannot be underestimated. This study was geared towards investigating individual and technological factors affecting the perceived usefulness of mobile technology by undergraduates in university of Ilorin. The study was a descriptive research of the survey type. Samples were randomly drawn from all students in the 15 faculties. A total of 100 undergraduates were sampled. Two research questions, and one hypothesis was tested. Mean was used to answer the research questions; while Pearson Product Moment Correlation (PPMC) was used to test the relationship between the technological and individual factors. Findings from the study revealed that the technological and individual factors positively affected the perceived usefulness of mobile technology among undergraduates. More so, there was a positive relationship between technological and individual factors that affected perceived usefulness of mobile technology. Based on the findings, it was concluded that both the individual and technological factors affected the perceived usefulness of mobile technology positively. It was recommended that students should be encouraged in the use of Mobile technology devices for learning

Integrating traditional knowledge with modern breeding techniques: A case study of cattle production in Nigeria's southern guinea and derived savanna agroecological zones

Nomadic pastoralists and agropastoralists are the primary custodians of cattle production in Nigeria, they operate a low external input production system which is proving difficult to modernize especially in the areas of breeding and reproduction for genetic improvement. This study was carried out to gather historical, phenotypic, and perceived genetic information associated with cattle breeding and reproduction practices of the nomadic pastoralists and agropastoralists in the Nigeria Southern Guinea Savanna and Derived Savanna agroecological zones through interviewer-led focus group meetings. The study revealed that the respondents operate similar breeding practices which are native knowledge and practices preserved and transmitted over many generations. The practices are communal in nature and consider climate conditions as well as being comparably similar with the modern scientific standards, hence it was concluded that the respondents have the potential to easily adopt the modern approach of animal breeding and reproduction. These findings suggest a pathway for integrating traditional knowledge with contemporary breeding techniques to enhance cattle production. Future research should explore specific strategies to facilitate this integration and evaluate its impact on productivity and sustainability in the agro-ecological zone

The meaning of setsunai : A Japanese emotion term to express the “mixed” feelings

認知・機能言語学研究 (9