Vasoactive intestinal peptide (VIP) is a 28-amino acid neuropeptide from the secretin family, which is being studied in experiments for its effects on vasodilation, smooth muscle, secretion in the digestive tract, and immune signaling.

In laboratory studies, VIP is associated with research in areas such as:

• vasodilation and relaxation of smooth muscle,
• regulation of secretion and motility in the digestive tract,
• bronchodilator and respiratory mechanisms,
• neuroprotection and circadian control in the CNS,
• immunomodulation and anti-inflammatory processes.

What is Vasoactive intestinal peptide (VIP)?

VIP is a 28-amino acid neuropeptide belonging to the secretin peptide family. It is found in neurons of the central and peripheral nervous systems, in the digestive tract, lungs and pancreas. In model systems it is associated with vasodilation, secretion modulation and anti-inflammatory signaling.

At the molecular level, VIP is being investigated for interactions with VPAC1 and VPAC2 receptors (G-protein coupled receptors), which are present in various tissues and mediate its broad physiological effects.

How VIP works

Upon binding to VPAC1/VPAC2, VIP activates adenylate cyclase via G _s , increases intracellular cAMP, and activates the PKA/CREB pathway. This promotes smooth muscle relaxation (vasodilation, bronchodilation), regulation of secretion in the digestive tract, and transcriptional programs associated with cytoprotection.

In immune models, its ability to suppress pro-inflammatory cytokines and alter the immune response profile is investigated. In the powdered form, a solution is commonly prepared before the experiment and administered according to the protocol; parenteral administration (sc or im) typically achieves high bioavailability.

Researched effects and interesting facts

• Vasodilation and smooth muscle: an increase in cAMP/PKA leads to relaxation of blood vessels and smooth muscle.
• Respiratory models: observed bronchodilation and modulation of the inflammatory response in the airways.
• Digestive tract: influencing secretion and motility, studying the effect on pancreatic and intestinal functions.
• Neuroprotection and circadian control: VIP neurons in the suprachiasmatic nucleus are associated with the regulation of circadian rhythms and with the protection of neurons from stress.
• Immunomodulation: in experimental systems, there is suppression of pro-inflammatory mediators and support of homeostasis of the immune response.

Dosage in studies

• Dose: Unspecified (titration protocols often work in low microgram ranges depending on the chosen biomarkers and target tissue).
• Form: subcutaneously or intramuscularly after preparation of solution from lyophilized powder.
• Frequency: Unspecified (defines experimental design and monitored parameters).
• Duration: Unspecified (short-term and longer follow-ups depending on the study objective).

Possible side effects (injectable form)

• local irritation, redness or tenderness at the injection site,
• transient hot flashes, facial flushing, mild drop in blood pressure, dizziness or headache,
• rarely nausea or loose stools due to intestinal secretions.

Resources

• Review papers on VIP/VPAC1/VPAC2 and cAMP/PKA signaling in smooth muscle and immune models.
• Publications mapping the role of VIP neurons in the suprachiasmatic nucleus and circadian control.
• Experimental studies on the bronchodilation, gastrointestinal secretion and anti-inflammatory effects of VIP in tissue models.