Responses to 7,8-benzoquinoline (250 μM, bs) in Krebs Henseleit solution (KHS) (A) and in Hepes-buffered solution (B) are shown. The inset shows responses in four further monolayers when IBMX (100 μM, bs) was added prior to 7,8-benzoquinoline. Ac, acetazolamide (100 μM, bs); Bu, bumetanide (20 μM, bl). All monolayers were from the same batch.