Cocaine- and amphetamine-regulated transcript: distribution and function in rat gastrointestinal tract

Area of Science:

• Neuroscience
• Gastroenterology

Background:

• Cocaine- and amphetamine-regulated transcript (CART) peptide, initially identified in the brain, is also present in the peripheral nervous system.
• The presence and function of CART in the enteric nervous system (ENS) are not fully understood.

Purpose of the Study:

• To investigate the distribution, origin, and projections of CART-expressing enteric neurons in the rat gastrointestinal (GI) tract.
• To explore the potential motor functions of CART in the GI tract.
• To examine the role of CART in intestinal adaptation.

Main Methods:

• Immunocytochemistry and in situ hybridization were used to map CART-expressing neurons in the rat GI tract.
• In vitro studies utilized longitudinal muscle strips from the stomach, ileum, and colon to assess CART's motor effects.
• Contractile and relaxatory responses were measured in response to CART and other known signaling molecules.

Main Results:

• CART peptide was abundant in myenteric neurons across the GI tract, with scarce submucous neurons.
• CART-expressing neurons in the small and large intestines showed short descending projections.
• CART did not directly induce muscle contractions or relaxations but attenuated nitric oxide (NO)-induced relaxations in the colon.

Conclusions:

• CART peptide likely plays a modulatory role in NO transmission within the colon, rather than direct neurotransmission to longitudinal muscles.
• CART may be involved in intestinal adaptation processes.
• An additional hormonal role for CART in the GI tract is also suggested.