Brain-wide 3D light-field imaging of neuronal activity with speckle-enhanced resolution

A major challenge in neuroscience is to sample large-scale neuronal activity at high speed and resolution. While calcium (Ca2+) imaging allows high-resolution optical read-out of neuronal activity, it remains challenging to sample large-scale activity at high speed, as most available imaging microscopes provide a trade-off between speed and the size of the acquisition volume. One promising method that avoids the trade-off between the acquisition rate and volume size is light-field microscopy in which the full 3D profile of an object is imaged simultaneously, thereby offering high speed at the cost of reduced spatial resolution. Here we introduce speckle light-field microscopy (speckle LFM), which utilizes speckle-based structured illumination to enhance spatial resolution. Using speckle LFM we demonstrate brain-wide recording of neuronal activity in larval zebrafish at 10 Hz volume rate and at 1.4 times higher resolution compared to conventional light-field microscopy and with suppressed background fluorescence. In addition to improving resolution of spatial structure, we show that the increased resolution reduces spurious signal crosstalk between neighboring neurons. (C) 2018 Optical Society of America under the terms of the OSA Open Access Publishing Agreemen

Spinal endocannabinoids and CB1 receptors mediate C-fiber-induced heterosynaptic pain sensitization

Diminished synaptic inhibition in the spinal dorsal horn is a major contributor to chronic pain. Pathways that reduce synaptic inhibition in inflammatory and neuropathic pain states have been identified, but central hyperalgesia and diminished dorsal horn synaptic inhibition also occur in the absence of inflammation or neuropathy, solely triggered by intense nociceptive (C-fiber) input to the spinal dorsal horn. We found that endocannabinoids, produced upon strong nociceptive stimulation, activated type 1 cannabinoid (CB1) receptors on inhibitory dorsal horn neurons to reduce the synaptic release of gamma-aminobutyric acid and glycine and thus rendered nociceptive neurons excitable by nonpainful stimuli. Our results suggest that spinal endocannabinoids and CB1 receptors on inhibitory dorsal horn interneurons act as mediators of heterosynaptic pain sensitization and play an unexpected role in dorsal horn pain-controlling circuits

Pushing synaptic vesicles over the RIM

In a presynaptic nerve terminal, neurotransmitter release is largely restricted to specialized sites called active zones. Active zones consist of a complex protein network, and they organize fusion of synaptic vesicles with the presynaptic plasma membrane in response to action potentials. Rab3-interacting molecules (RIMs) are central components of active zones. In a recent series of experiments, we have systematically dissected the molecular mechanisms by which RIMs operate in synaptic vesicle release. We found that RIMs execute two critical functions of active zones by virtue of independent protein domains. They tether presyanptic Ca2+ channels to the active zone, and they activate priming of synaptic vesicles by monomerizing homodimeric, constitutively inactive Munc13. These data indicate that RIMs orchestrate synaptic vesicle release into a coherent process. In conjunction with previous studies, they suggest that RIMs form a molecular platform on which plasticity of synaptic vesicle release can operate