Journal: bioRxiv

Article Title: An inhibitory feedback circuit mediating sleep need and sensory gating in Drosophila

doi: 10.1101/2025.11.17.688806

Figure Lengend Snippet: A Connectomic reconstruction of a helicon cell (body-ID: 917647959) and a R3m ring neuron (body-ID: 1261768913). Black dots indicate synaptic connections from helicon to R3m. For concurrent optogenetics and voltage imaging, we expressed CsChrimson in helicon cells (24B11-LexA x LexAOP-CsChrimson) and ArcLight in R3m ring neurons (28E01-GAL4 x UAS-ArcLight). B Example electrical compound recordings of R3m neurons during optogenetic stimulation of helicon cells. Optogenetic stimulation requires the cofactor retinal. C Peak de- and hyperpolarization in R3m neurons during optogenetic stimulation of helicon cells (n = 6-8; Mann-Whitney-Test). D Example compound electrical recordings of R3m neurons during optogenetic stimulation of helicon cells before and after the application of the voltage- and Ca 2+ -gated K + channel blocker charybdotoxin (ChaT) or saline (= control). E Charybdotoxin blocks helicon-triggered hyperpolarization in R3m neurons while the depolarization is unaffected (n = 6,8; Mann-Whitney-Test).

Article Snippet: Charybdotoxin (Alomone labs) was used at a final concentration of 233 nM ( ) and Picrotoxin (Tocris) was used at 100 μM ( ).

Techniques: Optogenetics, Imaging, MANN-WHITNEY, Saline, Control

Journal: Experimental Physiology

Article Title: Calcium regulation of muscle spindle mechanosensory afferent function

doi: 10.1113/EP092558

Figure Lengend Snippet: Ca v 1.1–1.4 (L‐type) channels regulate stretch‐evoked spindle afferent firing and SLV recycling. (a). Nifedipine (L‐type blocker, n = 5) initially enhanced firing (10 µM, P = 0.001), but then totally inhibited at higher concentrations ( P < 0.001). (b). Taicatoxin (50 nM, L‐type and SK/K Ca 2.1–2.3 blocker, n = 4) enhanced firing even more than 10 µM nifedipine ( P < 0.001). (c) Compared to DMSO controls (29 spindles), nifedipine (L‐type channel blocker, 26 spindles, 3 rats) greatly increased FM1‐43 retention by sensory nerve terminals ( P < 0.001) while RN1734 (TRPV4 antagonist, 32 spindles, 3 rats) substantially decreased FM1‐43 labelling ( P = 0.032). Right column, intensity profile plots along a straight line between the two white dots. All data are from 1–3 muscles per rat.

Article Snippet: Final concentrations of VGCC blockers ω‐agatoxin‐IVA (P/Q‐type; Sigma‐Aldrich, Gillingham, UK), ω‐conotoxin‐MVIIC (N‐ and P‐type), and ω‐conotoxin‐GVIA (N‐type; Peptide Institute Inc., Osaka, Japan), K Ca blockers charybdotoxin (BK and IK), iberiotoxin (BK, Alomone Laboratories, Jerusalem, Israel) and apamin (SK1‐3, Sigma‐Aldrich), solutions were prepared with Liley's saline each day from frozen stock in the same saline.

Techniques: Muscles

Journal: Experimental Physiology

Article Title: Calcium regulation of muscle spindle mechanosensory afferent function

doi: 10.1113/EP092558

Figure Lengend Snippet: K Ca inhibition enhances firing. (a) BK (iberiotoxin and charybdotoxin), IK (TRAM 34 and charybdotoxin) and SK (apamin) inhibitors increased stretch‐evoked firing compared to their predrug control (= 100%) (iberiotoxin, n = 4, P < 0.001; charybdotoxin, n = 4, P = 0.017, TRAM 34, n = 5, P = 0.001; apamin, n = 6, P = 0.003). Conversely, BK activation (NS1619, 1 µM) entirely abolishes firing in most muscles ( n = 6, P < 0.001). (b). NS1619, even at 100 µM, had no effect on propagation or amplitude of the CAP in saphenous nerve of the same animals.

Article Snippet: Final concentrations of VGCC blockers ω‐agatoxin‐IVA (P/Q‐type; Sigma‐Aldrich, Gillingham, UK), ω‐conotoxin‐MVIIC (N‐ and P‐type), and ω‐conotoxin‐GVIA (N‐type; Peptide Institute Inc., Osaka, Japan), K Ca blockers charybdotoxin (BK and IK), iberiotoxin (BK, Alomone Laboratories, Jerusalem, Israel) and apamin (SK1‐3, Sigma‐Aldrich), solutions were prepared with Liley's saline each day from frozen stock in the same saline.

Techniques: Inhibition, Control, Activation Assay, Muscles

Journal: Experimental Physiology

Article Title: Calcium regulation of muscle spindle mechanosensory afferent function

doi: 10.1113/EP092558

Figure Lengend Snippet: Summary diagram of proposed calcium signalling, relative to other key channels currently thought to be acting in mechanosensory terminals. (a) Stretch induces a depolarising receptor potential (RP) involving the opening of one or more of the following: Piezo2 (Woo, et al., ), ASIC2 (Bornstein, et al., ), ASIC3 (Lin, et al., ) and, probably indirectly, voltage‐gated sodium channels Na v 1.1 or Na v 1.6 (Carrasco, et al., ). The present study indicates these stimuli (stretch, depolarisation) induce the following calcium signalling events. Stretch opens TRPV4, for a calcium influx to enable SLV endocytosis. The depolarisation opens L‐type (Ca v 1.1–1.4) voltage‐gated calcium channels from which calcium triggers SLV exocytosis. In addition, the calcium opens SK2 (K Ca 2.2) potassium channels. Given this sequential nature, and the calcium diffusion time, the resulting partial repolarisation of the terminal would be delayed relative to its initial peak dynamic depolarisation. The L‐type channel long open time, and the resulting prolonged calcium influx, together with substantial intracellular calcium buffering to prevent calcium‐dependent channel inactivation (Snutch, et al., ), could extend SK2 open time to maintain the repolarisation throughout a sustained stretch. This complex depolarisation wave spreads electrotonically, or perhaps even propagates as an AP (Carrasco, et al., ) (Housley, et al., ), to the preterminal axon. (b) The RP‐induced depolarisation of the preterminal axon opens voltage‐gated sodium channels (Na v 1.6 and 1.7, Carrasco, et al., ), initiating a very high frequency AP burst typical of a dynamic stretch‐onset response. The present study indicates these events then, sequentially, gate P/Q‐type (Ca v 2.1) calcium channels. The incoming calcium opens further calcium‐activated potassium channels (SK2, K Ca 2.2; IK, K Ca 3.1; BK, K Ca 1.1), repolarising the preterminal axon, reducing the afferent discharge firing rate to a sustained level until the terminal length decreases upon release. Created using Motifolio.

Article Snippet: Final concentrations of VGCC blockers ω‐agatoxin‐IVA (P/Q‐type; Sigma‐Aldrich, Gillingham, UK), ω‐conotoxin‐MVIIC (N‐ and P‐type), and ω‐conotoxin‐GVIA (N‐type; Peptide Institute Inc., Osaka, Japan), K Ca blockers charybdotoxin (BK and IK), iberiotoxin (BK, Alomone Laboratories, Jerusalem, Israel) and apamin (SK1‐3, Sigma‐Aldrich), solutions were prepared with Liley's saline each day from frozen stock in the same saline.

Techniques: Diffusion-based Assay