Optogenetic stimulation of lateral orbitofronto-striatal pathway suppresses compulsive behaviors

Abstract

Dysfunctions in frontostriatal brain circuits have been implicated in neuropsychiatric disorders, including those characterized by the presence of repetitive behaviors. We developed an optogenetic approach to block repetitive, compulsive behavior in a mouse model in which deletion of the synaptic scaffolding gene, Sapap3, results in excessive grooming. With a delay-conditioning task, we identified in the mutants a selective deficit in behavioral response inhibition and found this to be associated with defective down-regulation of striatal projection neuron activity. Focused optogenetic stimulation of the lateral orbitofrontal cortex and its terminals in the striatum restored the behavioral response inhibition, restored the defective down-regulation, and compensated for impaired fast-spiking neuron striatal microcircuits. These findings raise promising potential for the design of targeted therapy for disorders involving excessive repetitive behavior.

Fig. 1. Sapap3 mutant mice exhibit a deficit in adaptive grooming response during conditioning task

(A) Grooming chamber. (B) Timelines. (Top) Three successive trials (two standard, one probe). (Middle) Session with 40 normal trials (white) and 10 randomly inserted probe trials (red). (Bottom) Full experiment (14). (C) Raster plots of grooming onsets (800 normal trials, 16 sessions), one mouse of each genotype. (D) Grooming onset distribution in wildtypes (WT) (n = 5) and knockout mutants (KO) (n = 5) in early, middle, and late training phases. Shading, SEM. (E) Mean grooming onset times [n = 5 mice/genotype; y axis zero, water drop; genotype effect, P < 0.05, repeated measures analysis of variance (ANOVA)]. (F) Grooming to tone, probe trials (day-genotype interaction, P < 0.01, repeated measures ANOVA). (E) and (F) Error bars show SEM.

Fig. 2. Dynamic learning-related changes in lOFC and striatal ensemble activity differ in wildtype and Sapap3 mutant mice

Average baseline firing rates of lOFC (A) and striatal (E) units. Average activity of lOFC (B to D) and striatal (F to H) units classified as task-responsive (i.e., firing preferentially between tone and water events relative to baseline activity). Mean z-scores normalized for each neuron relative to baseline activity for wildtype (WT) (n = 7) and Sapap3 mutant (KO) (n = 7) mice during training. Above, ratios of task-responsive units to total units per genotype. Shading, SEM.

Fig. 3. Optogenetic stimulation of lOFC in Sapap3 mutants enhances feed-forward inhibition in striatal circuitry

Simultaneous chronic recording and optogenetic stimulation in lOFC (A) and striatum (D) of mutants. LFP activity in lOFC (B) and striatum (C) at lOFC stimulation frequency (10 Hz, 5 mW, 5-ms pulse for 2.5 s, blue bars). (E) MSN spiking relative to FSI spikes (red line) during 2.5-s stimulation (purple) or no stimulation (black) of lOFC terminals in striatum (n = 10 FSI-MSN pairs recorded on the same tetrode, three mutants; stimulation effect P < 0.01, unpaired t test). Light stimulation (blue bars) induces synchrony of FSI population firing at stimulation frequency (F) (n = 14 units, three mutants) and long-lasting inhibition of MSNs during stimulation (G) (n = 47 units, three mutants). (H) Same stimulation protocol applied at the end of the training significantly decreased MSNs firing (purple) relative to no-stimulation condition (black). Shading, SEM.

Fig. 4. Optogenetic stimulation of lOFC alleviates compulsive grooming of Sapap3 mutant mice

Rasters of grooming onsets before, during (blue shading), and after bilateral lOFC (A) or striatal (C) stimulation (10 Hz, 5 mW, 5-ms light pulses) in a Sapap3 mutant, late in training. Grooming onsets for the Sapap3 population during session with laser stimulation (blue) in lOFC (B) (n = 4) or striatum (D) (n = 3) compared with preceding laser-off session (red). Shading, SEM. (E) Suppression of tone-evoked grooming by lOFC or striatal stimulation during probe trials (P < 0.01, unpaired t test). (F) Alleviation of compulsive grooming in Sapap3 mutants (n = 4) by lOFC or striatal stimulation (5 Hz, 5 mW, 5-ms light pulses) during 3-min free-movement periods, and control virus (n = 3) and wildtype (n = 3) comparisons (P < 0.05, unpaired t test). (G) Lack of effect of same out-of-task lOFC stimulation in mutants (n = 4) on time spent eating (top) or food consumed (bottom) during 5-min free-feeding periods. Error bars in (E to G), SEM.