Lipopolysaccharide injection induces rapid decrease of hypothalamic GnRH mRNA and peptide, but does not affect GnIH...

Area of Science:

• Neuroendocrinology
• Immunology
• Behavioral Biology

Background:

• Lipopolysaccharide (LPS) experimentally mimics acute infection, inducing sickness behavior and affecting stress responses.
• Sickness behavior is thought to reallocate energy from reproduction to immune function.
• The impact of LPS on brain control of reproductive behavior, particularly involving gonadotropin-inhibitory hormone (GnIH), is not well understood.

Purpose of the Study:

• To investigate the effects of LPS injection on reproductive behavior and hypothalamic neuropeptides (GnIH and GnRH) in zebra finches.
• To understand the rapid interaction between the immune system and the reproductive axis during an infection model.

Main Methods:

• Zebra finches were injected with LPS to mimic acute infection.
• Behavioral changes, including activity levels, were monitored.
• Immunoreactivity and gene expression of GnRH and GnIH in the hypothalamus were analyzed.
• Plasma levels of testosterone and corticosterone were measured.

Main Results:

• LPS injection led to decreased activity in birds.
• A significant reduction in GnRH-immunoreactive neurons and GnRH mRNA expression was observed in LPS-treated birds.
• The number of GnIH-releasing neurons and GnIH expression remained unchanged.
• Plasma testosterone and corticosterone levels showed no significant changes.

Conclusions:

• LPS injection rapidly inhibits the reproductive axis within 3 hours during an immune challenge.
• The inhibition specifically targets the GnRH system, not GnIH.
• This study enhances understanding of the immune system's interaction with the reproductive system during infection.