50 ml tubes

Pickled capers (Capparis spinosa) were sourced from Trader Joe’s (Irvine, CA, US), rinsed in deionized water to remove excess sodium chloride and homogenized with a bead mill using porcelain beads in 50 ml tubes (Omni International, Kennesaw, GA, US). We performed a methanolic extraction (80% methanol/20% water) on the caper homogenate for 48 h at room temperature on a rocking platform, with occasional inversion of the bottles to resuspend the extract. The extract was then filtered through Whatman filter paper #1 (Whatman, Maidstone, UK), and then the methanol was removed by evaporation in a fume hood for 24 h at room temperature. The caper extract was next centrifuged for 10 min at 15 °C, 4000 RCF to remove the remaining particulate matter, followed by storage at −20 °C. On the day of electrophysiological recording, we thawed the caper extract and diluted it 1:100 in bath solution (see below) immediately before use.

Plant samples comprising aerial portions (primarily leaves) were collected July 1–3, 2019 from Muir Woods National Monument under permit # MUWO-2019-SCI-0003, refrigerated for several days during the collection period and then frozen until the day of extraction. We homogenized samples using a bead mill with porcelain beads in batches in 50 ml tubes (Omni International, Kennesaw, GA, United States). We then performed methanolic extractions (80% methanol/20% water) on the homogenates for 48 h at room temperature, with occasional inversion of the bottles to resuspend the extracts. The extracts were then filtered through Whatman filter paper #1 (Whatman, Maidstone, United Kingdom), and then the methanol was removed by evaporation in a fume hood for 24–48 h at room temperature. We next centrifuged extracts for 10 min at 15°C, 4000 RCF to remove the remaining particulate matter, followed by storage at –20°C. On the day of electrophysiological recording, we thawed the extracts and diluted them 1:50 in bath solution (see below) immediately before use.