PhD Scientific Days 2024

Neurosciences

A thalamo-preoptic pathway inhibits aggression in rats

Text of the abstract

We have established that the posterior intralaminar thalamic nucleus (PIL) receives ascending input from the somatosensory system and that projection from the PIL to the preoptic area of the hypothalamus increases social grooming between adult female rats. It remained open if PIL neurons promote any other type of social touch between conspecifics. Therefore, in the present study, we focused on the role of PIL neurons, and the PIL-preoptic pathway in aggressive behavior. For chemogenetic manipulation of PIL neurons, we injected adeno-associated virus into the nucleus, which expressed excitatory and inhibitory DREADDs fused with mCherry. In a separate experiment, we selectively tagged socially c-Fos-activated neurons in the PIL with DREADDs. On the first day of the experiments, a vehicle was injected followed by aggressive behavioral test 1.5 hours later. On the second day, the same test was repeated starting 1.5 hours after clozapine-N-oxide (CNO) injection to activate the DREADDs. Chemogenetic stimulation decreased aggression and increased duration of positive valance contacts while inhibition of the PIL neurons resulted in an increase in aggression and a decreased duration of positive valence contacts. To establish the activity of PIL neurons and their neuronal targets during aggressive behavior, we measured the number of c-Fos-ir cells. While the PIL and its target brain regions showed elevated c-Fos activation following aggression, the inhibition of PIL neurons during aggressive behavior decreased c-Fos expression in the PIL and in one of its target brain areas, the medial preoptic area (MPOA). In turn, CNO injection into animals previously injected with an AAV encoding the stimulatory DREADD resulted in an elevated c-Fos expression in the PIL and the MPOA in the absence of social interactions. Therefore, we also investigated the PIL-MPOA pathway by injecting a stimulatory DREADD-expressing virus into the PIL and local CNO injection into the MPOA via intracerebral cannulas in order to activate the fiber terminals in the MPOA originating from the PIL. The activation of the pathway decreased aggression and increased positive valance contacts. Based on these results we suggest that PIL neurons reduce intermale aggressive behavior possibly by their projections to the medial preoptic area.
Funding:ÚNKP-23-3-II, EFPO-3.6.3 VEKOP-16-2017-00009, SE250+ fellowship