Reduction of aggressive behaviour following hypothalamic deep brain stimulation: involvement of 5-HT1A and testosterone

BackgroundAggressive behaviour (AB) may occur in patients with different neuropsychiatric disorders. Although most patients respond to conventional treatments, a small percentage continue to experience AB despite optimized pharmacological management and are considered to be treatment-refractory. For these patients, hypothalamic deep brain stimulation (pHyp-DBS) has been investigated. The hypothalamus is a key structure in the neurocircuitry of AB. An imbalance between serotonin (5-HT) and steroid hormones seems to exacerbate AB. ObjectivesTo test whether pHyp-DBS reduces aggressive behavior in mice through mechanisms involving testosterone and 5-HT. MethodsMale mice were housed with females for two weeks. These resident animals tend to become territorial and aggressive towards intruder mice placed in their cages. Residents had electrodes implanted in the pHyp. DBS was administered for 5h/day for 8 consecutive days prior to daily encounters with the intruder. After testing, blood and brain were recovered for measuring testosterone and 5-HT receptor density, respectively. In a second experiment, residents received WAY-100635 (5-HT1A antagonist) or saline injections prior to pHyp-DBS. After the first 4 encounters, the injection allocation was crossed, and animals received the alternative treatment during the next 4 days. ResultsDBS-treated mice showed reduced AB that was correlated with testosterone levels and an increase in 5-HT1A receptor density in the orbitofrontal cortex and amygdala. Pre-treatment with WAY-100635 blocked the anti-aggressive effect of pHyp-DBS. ConclusionsThis study shows that pHyp-DBS reduces AB in mice via changes in testosterone and 5-HT1A mechanisms. HIGHLIGHTS- Posterior hypothalamus DBS reduces aggressive behavior in mice - Aggressive behavior was correlated with plasma testosterone levels - DBS increased 5-HT1A receptor density in the orbitofrontal cortex and amygdala - Pre-treatment with 5-HT1A antagonist (WAY) blocked the anti-aggressive effect of DBS