Rat trigeminal, olfactory and taste responses after capsaicin desensitization

Area of Science:

• Neuroscience
• Sensory Science
• Pharmacology

Background:

• The trigeminal nerve mediates responses to irritants and odorants.
• Substance P is a neuropeptide found in trigeminal nerve fibers.

Purpose of the Study:

• To investigate the role of substance P-containing trigeminal fibers in sensory perception.
• To determine if trigeminal nerve desensitization affects odor detection, discrimination, and taste.

Main Methods:

• Capsaicin injections were used to desensitize trigeminal nerve fibers.
• Behavioral tests assessed odor detection, odor aversion learning, and operant odor discrimination.
• Responsiveness to salty, sour, and bitter tastes was evaluated.

Main Results:

• Capsaicin desensitization eliminated nasal trigeminal responses to odorants.
• Desensitized animals exhibited no deficits in locating food, odor aversion learning, or odor detection/discrimination.
• Responsiveness to salty and sour tastes remained unaffected, while bitter taste rejection thresholds may have increased.

Conclusions:

• Trigeminal nerve fibers containing substance P mediate responses to odorants and irritants.
• Loss of trigeminal responsiveness does not impair the fundamental abilities of smell or taste perception.