Trigeminal Pain Responses in Obese ob/ob Mice Are Modality-Specific

Area of Science:

• Neuroscience
• Pain Research
• Obesity Studies

Background:

• Obesity is linked to pain disorders like migraine, but the underlying mechanisms are unclear.
• Trigeminal nociception is vital in migraine pathophysiology and is altered in diet-induced obesity.
• It remains unknown if genetic obesity models also show altered trigeminal processing.

Purpose of the Study:

• To investigate if leptin-deficient (ob/ob) mice exhibit trigeminal hyperalgesia.
• To compare trigeminal nociception in genetic (ob/ob) versus diet-induced obesity models.
• To explore the role of leptin in trigeminal pain processing.

Main Methods:

• Evaluated trigeminal thermal nociception using an operant thermal assay in ob/ob and control mice.
• Assessed capsaicin-evoked nociception and conditioned place aversion.
• Measured TRPV1 expression in trigeminal ganglia and evaluated hyperphagia's contribution.

Main Results:

• Unexpectedly, ob/ob mice displayed significant trigeminal thermal hypoalgesia, not hyperalgesia.
• Ob/ob mice showed normal responses to capsaicin-evoked nociception and aversion, unlike diet-induced obese mice.
• No significant differences in TRPV1 expression or hyperphagia's contribution to observed behaviors were found.

Conclusions:

• Leptin deficiency (ob/ob) results in trigeminal thermal hypoalgesia, contrasting with diet-induced obesity.
• Leptin's role in pain processing appears specific, influencing thermal nociception differently than capsaicin responses.
• These findings highlight distinct mechanisms by which genetic versus diet-induced obesity impact pain pathways.