Handling, genetic and housing effects on the mouse stress system, dopamine function, and behavior

Area of Science:

• Neuroscience
• Behavioral Science
• Genetics

Background:

• Early life experiences, including maternal care and handling, significantly influence adult stress regulation.
• Genetic background plays a crucial role in modulating responses to early life stress.
• Understanding these interactions is key to deciphering individual differences in stress-related disorders.

Purpose of the Study:

• To investigate the interactive effects of early handling, housing conditions, and genetic factors on adult stress regulation in mice.
• To examine how these factors influence behavioral and physiological stress responses.
• To determine if the effects of early handling are consistent across different measures and testing paradigms.

Main Methods:

• Utilized high-aggressive (NC900) and low-aggressive (NC100) mouse lines.
• Applied early postpartum handling for three weeks.
• Assessed adult stress responses using open field tests, dyadic encounters, and corticosterone (CORT) level measurements.
• Manipulated housing conditions (isolation vs. group rearing) post-handling.

Main Results:

• Handling reduced corticosterone (CORT) activation and stabilized activity in low-aggressive (NC100) mice, but not high-aggressive (NC900) mice.
• Group rearing further reduced CORT in handled NC100 mice.
• Handling increased D1 dopamine receptors in both lines, an effect amplified by group rearing in NC100 mice.
• Behavioral differences emerged: NC100 mice froze less, while NC900 mice attacked more readily in dyadic encounters.

Conclusions:

• The impact of early handling on stress regulation is significantly modulated by genetic background.
• Post-infancy experiences, such as housing, further influence the long-term effects of early stimulation.
• Handling effects vary depending on the physiological system and the social or nonsocial context of assessment.