Enterin in the radula mechanoafferent sensory neurons of the buccal ganglion. A, A buccal ganglion from a juvenile Aplysia (10 gm) double labeled with rat antibody to enterin (A1, rhodamine red) and rabbit antibody to SCP (A2, fluorescein). B, A buccal hemiganglion from an adult Aplysia (200 gm). Enterin immunostaining (rhodamine red) is shown in B1, and SCP immunostaining (fluorescein) is shown in B2. C, A buccal hemiganglion from an adult animal immunostained with enterin (C1) in which B21 (arrows) was electrophysiologically identified and injected with carboxyfluorescein (C2). Scale bar (shown in C2): A, B, 500 μm; C, 100 μm.