The heat and capsaicin receptor, TRPV1, is required for the detection of painful heat by primary afferent pain fibers (nociceptors), but the extent to which functional TRPV1 channels are expressed in the central nervous system (CNS) is debated. As previous evidence is based largely on indirect physiological responses to capsaicin, here we genetically modified the TrpV1 locus to reveal, with excellent sensitivity and specificity, the distribution of TRPV1 in all neuronal and non-neuronal tissues. In contrast to reports of widespread and robust expression in the CNS, we find that neuronal TRPV1 is largely restricted to nociceptors in primary sensory ganglia, with minimal expression in a few discrete brain regions, most notably in a contiguous band of cells within and adjacent to the caudal hypothalamus. We confirm hypothalamic expression in the mouse using several complementary approaches, including in situ hybridization, calcium imaging, and electrophysiological recordings. Additional in situ hybridization experiments in rat, monkey and human brain demonstrate that the restricted expression of TRPV1 in the CNS is conserved across species. Outside of the CNS, we find TRPV1 expression in a subset of arteriolar smooth muscle cells within thermoregulatory tissues. Here, capsaicin increases calcium uptake and induces vasoconstriction, an effect that likely counteracts the vasodilation produced by activation of neuronal TRPV1.

Super-resolution microscopy has overcome a long-held resolution barrier-the diffraction limit-in light microscopy and enabled visualization of previously invisible molecular details in biological systems. Since their conception, super-resolution imaging methods have continually evolved and can now be used to image cellular structures in three dimensions, multiple colors, and living systems with nanometer-scale resolution. These methods have been applied to answer questions involving the organization, interaction, stoichiometry, and dynamics of individual molecular building blocks and their integration into functional machineries in cells and tissues. In this Review, we provide an overview of super-resolution methods, their state-of-the-art capabilities, and their constantly expanding applications to biology, with a focus on the latter. We will also describe the current technical challenges and future advances anticipated in super-resolution imaging.

In traditional folk medicine, Xanthoxylum plants are referred to as 'toothache trees' because their anesthetic or counter-irritant properties render them useful in the treatment of pain. Psychophysical studies have identified hydroxy-α-sanshool as the compound most responsible for the unique tingling and buzzing sensations produced by Szechuan peppercorns or other Xanthoxylum preparations. Although it is generally agreed that sanshool elicits its effects by activating somatosensory neurons, the underlying cellular and molecular mechanisms remain a matter of debate. Here we show that hydroxy-α-sanshool excites two types of sensory neurons, including small-diameter unmyelinated cells that respond to capsaicin (but not mustard oil) as well as large-diameter myelinated neurons that express the neurotrophin receptor TrkC. We found that hydroxy-α-sanshool excites neurons through a unique mechanism involving inhibition of pH-and anesthetic-sensitive two-pore potassium channels (KCNK3, KCNK9 and KCNK18), providing a framework for understanding the unique and complex psychophysical sensations associated with the Szechuan pepper experience.Somatosensation, or the sense of touch, is the process whereby we detect changes in ambient temperature or pressure. This sensory modality is mediated by subsets of primary afferent neurons that detect chemical, thermal or mechanical stimuli over a range of stimulus intensities. Generally speaking, pain-producing (noxious) stimuli are detected by neurons (referred to as nociceptors) that have small-to medium-diameter somata that correspond to unmyelinated C and lightly myelinated Aδ nerve fibers. In contrast, innocuous stimuli, such as light touch, are detected by large-diameter neurons corresponding to more heavily Reprints and permissions information is available online at

Background Stochastic optical reconstruction microscopy (STORM) and related methods achieves sub-diffraction-limit image resolution through sequential activation and localization of individual fluorophores. The analysis of image data from these methods has typically been confined to the sparse activation regime where the density of activated fluorophores is sufficiently low such that there is minimal overlap between the images of adjacent emitters. Recently several methods have been reported for analyzing higher density data, allowing partial overlap between adjacent emitters. However, these methods have so far been limited to two-dimensional imaging, in which the point spread function (PSF) of each emitter is assumed to be identical. Methods In this work, we present a method to analyze high-density super-resolution data in three dimensions, where the images of individual fluorophores not only overlap, but also have varying PSFs that depend on the z positions of the fluorophores. Results and Conclusion This approach can accurately analyze data sets with an emitter density five times higher than previously possible with sparse emitter analysis algorithms. We applied this algorithm to the analysis of data sets taken from membrane-labeled retina and brain tissues which contain a high-density of labels, and obtained substantially improved super-resolution image quality.