Cortical oxytocin modulation underlying touch-related maternal care

• Applicant: Dr. Eduard Maier
• Subject Area: Cognitive, Systems and Behavioural Neurobiology ; Anatomy and Physiology ; Experimental and Theoretical Network Neuroscience ; Molecular Biology and Physiology of Neurons and Glial Cells
• Term: since 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 497591028

Maternal care is essential for survival and well-being of the infant. Similar to humans, rat mothers have a lot of tactile contact to their litter after parturition, that involves specific body parts, such as the peri-oral region during pup licking and grooming, as well as the ventral trunk with its nipples during feeding. Especially early tactile contact with these body parts is essential for the expression and maintenance of maternal behavior, which suggests that mothers acquire tactile ‘knowledge’ about their litter. Tactile experiences are processed and stored in the primary somatosensory cortex (S1). Hence, this area might play an important role in shaping behaviors related to maternal care. This is supported by previous studies that have shown an expansion, as well as a sharpening of receptive fields of the S1 ventral trunk representation in lactating, but not virgin rats. Tactile experiences, as well as maternal behavior have both been linked to oxytocin (OT). OT receptors (OTRs) are expressed in primary sensory cortices and OT transmission in the auditory cortex modulates maternal behavior. However, we still have little understanding about the neurobiological mechanisms underlying the relationship between OT, social touch and maternal behavior. In particular, no study to date addressed whether modulation of S1 neural activity by OT is related to maternal care. Therefore, I propose to study the role of OT signaling within S1 in modulation of maternal behavior by using a novel transgenic OTR Cre knock-in rat in combination with viral, anatomical, physiological and behavioral techniques. In a first set of experiments I will study whether hypothalamic OT axons and OTR-expressing cells are enriched in maternally-relevant body part representations (e.g. in S1 peri-oral and ventral trunk representations). Then I will investigate the necessity of OT in these regions for the induction of maternal behavior by employing opto- and chemogenetic techniques to inhibit axonal OT release or to silence OTR expressing cells, while monitoring maternal behavior. To find out whether OT is involved in S1 plasticity during lactation, I will complement the chemogenetic inhibition experiments by performing electrophysiological measurements of receptive fields and body part representation sizes at different postpartum days. Single-cell electrophysiological properties of opto-tagged OTR positive (+) neurons will be compared to OTR negative (-) neurons. In a final experiment, I will perform fiberphotometry-based calcium imaging to compare bulk neural activity between OTR+ and OTR- neurons in freely behaving animals and respectively analyse how responses to pup tactile stimuli change across the lactation period. My work might provide novel OT-dependent cortical mechanisms underlying maternal behaviors and thus will be important for understanding of pathophysiology and treatment development of mental health diseases in which mother-child interactions are perturbed.

• DFG Programme: WBP Position