Fig. 5: Persistent optogenetic activation of DRN 5-HT neurons generates internal synchronized state and vigilance behavior in zebrafish.

a Illustration of optogenetic stimulation combined with extracellular recording of DRN 5-HT neurons using tph2:ChR2-mCherry fish to evaluate activation efficiency (left). Immunofluorescence using anti-serotonin showing DRN 5-HT neurons expressing ChR2-mCherry (right). Image represents results from six independent experiments. b Light stimulation for 120 s persistently increased discharge frequency in a DRN 5-HT neuron (left). Mean data of firing frequency of six neurons from six fish before and after optogenetic activation (right). c Illustration of optogenetic activation of DRN 5-HT neurons combined with whole-cell recording of glutamatergic neurons in Dc region using tph2:ChR2-mCherry crossed with vglut2a:DsRed fish. d Whole-cell recording from a glutamatergic neuron that displayed burst firing and a post-inhibitory rebound after optogenetic activation of DRN 5-HT neurons (left). Mean data showing burst-firing frequency of eight neurons from eight fish before and after optogenetic activation (right). e Optogenetic stimulation setup used for free-swimming zebrafish. f Timing of experimental procedures to record behavior responses to optogenetic activation of DRN 5-HT neurons (upper). Effect of 100% or 50% maximum intensity blue-light stimulation on locomotion at five minutes post stimulation in control and tph2:ChR2-mCherry fish (lower). g Mean locomotor speed for 30-min video tracking after blue-light stimulation with different duration or intensity in tph2:mCherry as control group or tph2:ChR2-mCherry fish. 100% light intensity equals 15 mW LED power. N = 10 fish in each group. h Illustration of the method used to detect the response thresholds to aversive stimuli after optogenetic activation of DRN 5-HT neurons. i Mean data shows that the response thresholds to aversive stimuli were markedly reduced in tph2:ChR2-mCherry fish 5 min after optogenetic activation of DRN 5-HT neurons. j Mean data showing that a reduction in response thresholds to aversive stimuli that endured for more than 20 min after optogenetic stimulation. All data are presented as mean ± SEM. *P < 0.05, **P < 0.01, ***P < 0.001; ns denoting no significant difference. For detailed statistics, see Supplementary Table 2. Source data are provided as a Source Data file.