Optogenetic Recruitment of Dorsal Raphe Serotonergic Neurons Acutely Decreases Mechanosensory Responsivity in Behaving Mice

The inhibition of sensory responsivity is considered a core serotonin function, yet this hypothesis lacks direct support due to methodological obstacles. We adapted an optogenetic approach to induce acute, robust and specific firing of dorsal raphe serotonergic neurons. In vitro, the responsiveness of individual dorsal raphe serotonergic neurons to trains of light pulses varied with frequency and intensity as well as between cells, and the photostimulation protocol was therefore adjusted to maximize their overall output rate. In vivo, the photoactivation of dorsal raphe serotonergic neurons gave rise to a prominent light-evoked field response that displayed some sensitivity to a 5-HT1A agonist, consistent with autoreceptor inhibition of raphe neurons. In behaving mice, the photostimulation of dorsal raphe serotonergic neurons produced a rapid and reversible decrease in the animals' responses to plantar stimulation, providing a new level of evidence that serotonin gates sensory-driven responses.ERC 250334, 5-HT OptogeneticMSCA 220098info:eu-repo/semantics/publishedVersio

OLFP recovery

The .zip file contains the values for the OLFP amplitude recovery experiment (Fig. 2K; see the paper and the supporting information for a detailed description of the protocol). The files ending with "_stim_Y" contain the normalized OLFP amplitude values in the stimulation period (in blue on Fig. 2K). The files ending with "_recov_Y" contain the normalized OLFP amplitude values in the recovery period (in green on Fig. 2K). The file "Stim_X.txt" contains the time points for the stimulation period. The file "Recov_X.txt" contains the time points for the recovery period

Synchronized oscillations at alpha and theta frequencies in the lateral geniculate nucleus

In relaxed wakefulness, the EEG exhibits robust rhythms in the ? band (8–13 Hz), which decelerate to ? (2–7 Hz) frequencies during early sleep. In animal models, these rhythms occur coherently with synchronized activity in the thalamus. However, the mechanisms of this thalamic activity are unknown. Here we show that, in slices of the lateral geniculate nucleus maintained in vitro, activation of the metabotropic glutamate receptor (mGluR) mGluR1a induces synchronized oscillations at ? and ? frequencies that share similarities with thalamic ? and ? rhythms recorded in vivo. These in vitro oscillations are driven by an unusual form of burst firing that is present in a subset of thalamocortical neurons and are synchronized by gap junctions. We propose that mGluR1a-induced oscillations are a potential mechanism whereby the thalamus promotes EEG ? and ? rhythms in the intact brain

Number of spikes vs pulse duration

Experiment: assessing the number of spikes evoked in ChR2-EYFP-positive dorsal raphe neurons, for light pulses of various duration. This .csv contains the average number of spikes obtained in individual neurons in response to light pulses of different durations (0.1 to 1000 ms; n = 17 neurons). Each row corresponds to one neuron. Each column corresponds to one pulse duration (the duration is indicated in the first row). These data were used to generated Fig. 1J

Spike times at twice the photostimulation threshold

Experiment: Spiking reliability of ChR2-EYFP-positive dorsal raphe neurons in response to trains of light pulses at different frequencies, using an irradiance = twice the photostimulation threshold. This zip file contains a list of 30 .csv file. Each .csv file contains a table of spike times (time of occurrence of spikes, in seconds) measured for one neuron in response to trains of light pulses at different frequencies (1, 2, 5, 10, 20 and 50 Hz). Each column represents one frequency (the frequency is indicated in the first row). Columns are filled with NAs at the end so that they have the same length. These data were used to generate the plots in Fig. 1L, Supp. Fig. S1B and Fig. S1D1 to D3

Combined fluorescence and OLFP mapping

Experiment: combined fluorescence and OLFP (= optically-evoked field potential) mapping in vivo. This file contains the following values for 8 different animals: average fluorescence intensity in the first millimeter of tissue, maximal fluorescence intensity, position of point of maximal fluorescence, full width at half maximum of fluorescence intensity profile, maximal value of OLFP amplitude, position of point with largest OLFP and full width at half maximum of OLFP amplitude profile (see README.txt). These data were used in Fig. 2F

Fits OLFP amplitude and latency vs power

This file contains the fit parameters of the OLFP amplitude vs power and OLFP latency vs power curves for 9 mice. See README.txt for a detailed description of the fit parameters

OLFP amplitude and latency vs frequency

The .zip file contains the values of the OLFP amplitude and latency for different photostimulation frequencies in 7 mice (see the paper for a detailed description of the protocol). The files ending with "_Freq" contain the list of frequencies (in Hz). The files ending with "_Peak_vs_Freq" contain the values of the OLFP amplitude (in Volts). The files ending with "_Lat_vs_Freq" contain the values of the OLFP latency (in seconds). These data were used in Fig. 2J

Von Frey experiment

This .csv file contains the scored data for the Von Frey experiment (Fig. 3). See the paper and supporting information for a detailed description of the experiment. A description of the data contained in the .csv is available in the README.txt file

Linear pixel intensity profiles

Experiment: light propagation in the dorsal raphe nucleus. This .csv file contains normalized pixel intensity profiles for 3 brains, measured along the optical fiber axis (see paper for a detailed description of the procedure). These data are plotted in Fig. 1D