Hypocretin-1 dose-dependently modulates maternal behaviour in mice

Area of Science:

• Neuroscience
• Behavioral Endocrinology
• Maternal Behavior Research

Background:

• Neuronal activity of hypocretin (HCRT), a peptide regulating arousal, increases during lactation.
• HCRT is released in brain regions controlling maternal behavior, suggesting a role in supporting maternal care.
• Previous research indicates HCRT-1 receptor mRNA expression is associated with lactation.

Purpose of the Study:

• To investigate the behavioral effects of hypocretin (HCRT) on lactating mice for the first time.
• To determine the dose-dependent effects of HCRT on maternal behaviors, including nursing, pup interaction, and aggression.
• To explore the role of endogenous HCRT in maternal care using a receptor antagonist.

Main Methods:

• Intracerebroventricular (i.c.v.) administration of HCRT-1 at varying doses (0.06, 0.1, 0.3 microg) to lactating mice.
• Behavioral observation of maternal care, including licking, grooming, nursing bouts, and maternal aggression.
• Administration of the HCRT-1 receptor antagonist SB-334867 via intraperitoneal injection.
• Assessment of c-Fos immunoreactivity to identify brain regions affected by HCRT.

Main Results:

• Intermediate doses of HCRT-1 (0.06 and 0.1 microg) increased pup licking, grooming, and nursing bouts.
• High dose of HCRT-1 (0.3 microg) delayed nursing onset, reduced nursing, increased time off the nest, and decreased maternal aggression.
• Administration of HCRT-1 antagonist showed trends towards increased low-arched back nursing and decreased licking/grooming during high-arched back nursing.

Conclusions:

• Hypocretin (HCRT) modulates maternal behavior in a dose-dependent manner.
• Intermediate HCRT levels appear to support and potentially enhance specific maternal care behaviors.
• High HCRT levels can suppress maternal behavior and aggression, suggesting a critical role for endogenous HCRT in regulating maternal care expression.