Fig. 2. Helisoma buccal neuron B19 is inhibited by glutamate and excited by KA. (A) Diagram of the buccal ganglia showing the bilateral location of left and right (shaded in grey) B19 neuron cell bodies (adapted from Quinlan et al., 1995). (B) A right B19 neuron was injected with Lucifer Yellow. Its main projections extend ipsilaterally out through the right VBN and LBN, and contralaterally out through the left VBN. Extensive neurites leave the cell body and axonal projections; some are obscured by the bright cell body staining. Fluorescence image is a composite of 31 separate images and is layered on an HMC image of the same field (see Materials and methods). Scale bar, 100 µm. (C) Glutamate, applied for the durations indicated by horizontal bars, dose-dependently reduced AP frequency in a B19 neuron. Breaks in the trace represent 2–3 min of saline perfusion. Arrowhead indicates 0 mV. (D) Glutamate dose-dependently reduced mean (±s.e.m.) AP frequency of B19 neurons (^*P<0.05, N=9). (E) KA had no effect on mean (±s.e.m.) AP frequency at 10 µmol l^–1 (N=9), but significantly increased frequency at 30 µmol l^–1 (⁺P<0.03; N=13). (F) CNQX had no effect on mean (±s.e.m.) AP frequency in B19 neurons (N=9).