Figure 6.

The majority of reticulospinal neurons required for startle responses are absent in domoic acid-exposed larvae. A, Larvae (7 dpf) were backfilled with Texas Red dextran through spinal cord transections. The figures represent the range of phenotypes observed in control and DomA-injected fish. The teal arrows mark the Mauthner cells and magenta arrows mark backfilled neurons in rhombomere 5 (r5) and rhombomere 6 (r6). B, Mauthner cells on the 2 lateral sides were scored per fish. A majority of DomA-exposed fish (identified 51 out of 60) did not have any Mauthner (M) cells. C, Other reticulospinal neurons involved in startle responses (MiD2cm, MiD3) are located in r5 and r6. The presence of any neuron backfilled in r5 and r6 on the 2 lateral sides was scored. A majority of DomA-exposed fish had one or no neurons that were backfilled in r5 and r6 (44 out of 60). Scale bar = 50 μm.