PhD Scientific Days 2023

KDP Poster session

Control of Social Grooming by a Thalamo-Preoptic Neuronal Pathway

Text of the abstract

Social touch is an essential component of communication. Little is known about the underlying pathways and mechanisms. The hypothalamus is a major regulatory center of rodent social behavior. It is also likely to be involved in the control of instinctive behaviors in humans. It is conceivable that ascending sensory pathways carrying information on social touch might project directly to the hypothalamus. Here, we discovered a novel neuronal pathway from the posterior intralaminar thalamic nucleus (PIL) to the medial preoptic area (MPOA) is involved in control of social grooming.
First, we determined the effect of chemogenetic stimulation of PIL neurons on social interactions between familiar adult female rats. Activity-dependent tagging of PIL neurons was performed in rats experiencing physical social contacts. The selective chemogenetic stimulation of the preoptic area-projecting PIL neurons was performed using double viral injections and also by CNO administration directly into the preoptic area.
We found that neurons in the PIL and MPOA were naturally activated by physical contact between female rats and also by chemogenetic stimulation of PIL neurons. Chemogenetic activation of these neurons increased social grooming between familiar rats as did selective activation of the PIL-MPOA pathway. Neurons projecting from the PIL to the MPOA express the neuropeptide parathyroid hormone 2 (PTH2) and central infusion of its receptor antagonist diminished social grooming. We showed its increased expression in the PIL in response to social interaction. Finally, we showed similarity in the anatomical organization of the PIL-MPOA circuit in the rat and human brain.
We propose that the discovered PIL-MPOA neuronal pathway facilitates physical contacts in both rodents and human. Therefore, the pathway as well as the PTH2 neuropeptide and its receptor should be investigated in the future in disorders where deficits in direct social interactions are found, such as autism spectrum disorder.
Support: New National Excellence Program and Doctoral Student Scholarship Program of the Co-operative Doctoral Program of the National Research, Development and Innovation Office, Excellence Program of the Semmelweis University, EFOP-3.6.3-VEKOP-16-2017-00009, the National Brain Program of the Hungarian Academy of Sciences 2022 (NAP3) and OTKA K134221.