Tissue culture tube contaminant inhibits excitatory synaptic channels.

Nicotinic acetylcholine receptors (nAChRs) were expressed in Xenopus oocytes. Large, slowly desensitizing macroscopic currents were induced by rapidly infusing an electrolyte solution containing 50 microM ACh in the presence of atropine. The N-methyl-D-aspartate (NMDA) subset of glutamate receptors was studied in CA1 hippocampal neurons. Macroscopic currents were induced by rapidly applying 30 microM NMDA and 10 microM glycine in the presence of picrotoxin, strychnine and tetrodotoxin. Exposing the electrolyte solutions to Falcon brand polypropylene tissue culture tubes (Becton Dickinson Labware) decreased the current through the nAChR channels or through the NMDA receptor channels (1). Purified water shaken in the Falcon brand tubes showed a broad absorbance peak near 200 nm. Before exposing the water to the Falcon tubes, the purified water gave no absorbance signal. The results indicate that a substance released from the Falcon tubes inhibits the currents through nAChR and NMDA receptor channels. Our experiments were with 50-ml Falcon 2098 tubes from lot numbers 72180188 and 80290188 and with 15-ml Falcon 2097 tubes from lot number 83560283. These were the only Falcon tubes we tested.