currents. Concomitantly, we observed a 4-fold reduction in spontaneous miniature release events from the cdko rod terminals and an almost complete absence of evoked responses when monitoring changes in membrane incorporation after strong step depolarizations. Under control conditions, 49 and 83 vesicles were released with 0.2 and 1 s depolarizations, respectively, which is close to the maximal number of vesicles estimated to be docked at the base of the ribbon active zone, but without RIM1/2, only a few vesicles were stimulated for release after a 1 s stimulation. In conclusion, our study shows that RIM1/2 potently enhance the influx of Ca 2ϩ into rod terminals through Cav1.4 channels, which is vitally important for the release of vesicles from the rod ribbon.

Constitutive and ligand-dependent GHSR1a activity attenuates CaV2 current and hypothalamic GABA release through distinct mechanisms and signaling pathways.

The Federal Pain Research Strategy recommended development of nonopioid analgesics as a top priority in its strategic plan to address the significant public health crisis and individual burden of chronic pain faced by >100 million Americans. Motivated by this challenge, a natural product extracts library was screened and identified a plant extract that targets activity of voltage-gated calcium channels. This profile is of interest as a potential treatment for neuropathic pain. The active extract derived from the desert lavender plant native to southwestern United States, when subjected to bioassay-guided fractionation, afforded 3 compounds identified as pentacyclic triterpenoids, betulinic acid (BA), oleanolic acid, and ursolic acid. Betulinic acid inhibited depolarization-evoked calcium influx in dorsal root ganglion (DRG) neurons predominantly through targeting low-voltage-gated (Cav3 or T-type) and CaV2.2 (N-type) calcium channels. Voltage-clamp electrophysiology experiments revealed a reduction of Ca, but not Na, currents in sensory neurons after BA exposure. Betulinic acid inhibited spontaneous excitatory postsynaptic currents and depolarization-evoked release of calcitonin gene-related peptide from lumbar spinal cord slices. Notably, BA did not engage human mu, delta, or kappa opioid receptors. Intrathecal administration of BA reversed mechanical allodynia in rat models of chemotherapy-induced peripheral neuropathy and HIV-associated peripheral sensory neuropathy as well as a mouse model of partial sciatic nerve ligation without effects on locomotion. The broad-spectrum biological and medicinal properties reported, including anti-HIV and anticancer activities of BA and its derivatives, position this plant-derived small molecule natural product as a potential nonopioid therapy for management of chronic pain.

Highlights d Toll-like receptors are upregulated during CFA-induced inflammatory pain d TLR2/6 receptor activation triggers acute pain via NLRP3dependent upregulation of IL-33 d IL-33 primes pain responses via neuroimmune crosstalk d Blocking IL-33 receptors mediates analgesia during inflammatory pain states