They observed hundreds of presynaptic terminals simultaneously releasing the neurotransmitter. It turns out that all the compounds they had made covered a range of lipophilicities, and FFN511 was ...

Their data imply that glutamatergic synapses from pyramidal cells directly excite presynaptic GABAergic terminals, which then inhibit pyramidal cell somata (Fig. 1a, P 2 to terminal of I to P 3).