BackgroundAlthough a number of clinical and preclinical studies have demonstrated analgesic effects of cannabinoid treatments, there are also instances when cannabinoids have had no effect or even exacerbated pain. The observed pro-nociceptive effects appear to be due to cannabinoid-induced disinhibition of afferent synaptic input to nociceptive circuits. To better understand how cannabinoid-mediated plasticity can have both pro- and anti-nociceptive effects, we examined the possibility that cannabinoids differentially modulate nociceptive vs. non-nociceptive synapses onto a shared postsynaptic target. These experiments were carried out in the central nervous system (CNS) of the medicinal leech, in which it is possible to intracellularly record from presynaptic nociceptive (N-cell) or pressure-sensitive (P-cell) neurons and their shared postsynaptic targets.ResultsThe endocannabinoid 2-arachidonoyl glycerol (2AG) elicited significant long-lasting depression in nociceptive (N-cell) synapses. However, non-nociceptive (P-cell) synapses were potentiated following 2AG treatment. 2AG-induced potentiation of non-nociceptive synapses was blocked by the TRPV antagonist SB366791, suggesting involvement of the same TRPV-like receptor that has already been shown to mediate endocannabinoid-dependent depression in nociceptive inputs. Treatment with the GABA receptor antagonist bicuculline also blocked 2AG-induced potentiation, consistent with the idea that increased synaptic signaling was the result of endocannabinoid-mediated disinhibition. Interestingly, while bicuculline by itself increased non-nociceptive synaptic transmission, nociceptive synapses were depressed by this GABA receptor antagonist indicating that nociceptive synapses were actually excited by GABAergic input. Consistent with these observations, GABA application depolarized the nociceptive afferent and hyperpolarized the non-nociceptive afferent.ConclusionsThese findings show that endocannabinoids can differentially modulate nociceptive vs. non-nociceptive synapses and that GABAergic regulation of these synapses plays an important role in determining whether endocannabinoids have a potentiating or depressing effect.
Induction therapy for multiple myeloma with bortezomib (Velcade), lenalidomide (Revlimid), and dexamethasone (d) (VRd) was traditionally administered as bortezomib given twice weekly on a 3 week cycle. A modified schedule of weekly bortezomib has been adopted over time to decrease treatment burden for patients and reduce treatment‐emergent neuropathy. This study evaluates the response rates and outcomes with different schedules of bortezomib in VRd administered for first‐line treatment for patients with newly diagnosed MM (NDMM). We retrospectively analyzed patients treated with upfront VRd from June 30th 2008 to December 31st 2018, for variations of bortezomib administration. Five hundred and fifty‐five (555) NDMM patients met inclusion criteria; median age 63 years and 61% men. Bortezomib was administered twice weekly every 21 days in 43%, once weekly every 21 days in 41% and once weekly every 28 days in 16%. Though peripheral sensory neuropathy was more frequent with twice weekly dosing (P = .002), this group achieved shorter time to best response (P = .01). Weekly every 21‐day treatment saw higher VGPR or better rates (P = .02). However, with median follow up time of 37 months (IQR 22–56), we found no difference in PFS or OS among the groups. While small differences in response rates were found among the varying administration schedules of bortezomib administration, there was no significant effect on PFS or OS. Given that VRd remains a first line standard of care option for newly diagnosed MM, in the absence of a large trial comparing bortezomib dosing schedule modifications, these results are helpful in supporting current practices of once weekly administration.
Response and progression-free survival according to planned treatment duration in patients with relapsed multiple myeloma treated with carfilzomib, lenalidomide, and dexamethasone (KRd) versus lenalidomide and dexamethasone (Rd) in the phase III ASPIRE study.
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