VIP interacts with VPAC1 and VPAC2, the two receptor types it shares with PACAP. PAC1 is different: it generally responds much more strongly to PACAP than to VIP. That is the useful starting point when a research paper mentions a “VIP receptor.” It is not a reason to treat every receptor in this family as interchangeable.
This guide explains receptor names and how to read the evidence behind them. It does not recommend a clinical use or a human-use protocol for VIP.
First separate the peptide from the receptor
VIP means vasoactive intestinal peptide. PACAP means pituitary adenylate cyclase-activating polypeptide. These are related signaling molecules, while VPAC1, VPAC2 and PAC1 are receptor names. A ligand is the molecule interacting with a receptor; it is not the receptor itself.
The IUPHAR receptor-nomenclature report explains why older literature can look inconsistent. Names such as “PACAP type I” and “PACAP type II” predate the standardized terminology. Type I corresponds to PAC1; the two shared VIP/PACAP receptors are called VPAC1 and VPAC2. Reading the publication date and original naming convention helps avoid counting the same receptor twice.
VPAC1 and VPAC2: shared recognition
Both shared receptor types recognize VIP and PACAP. The receptor number distinguishes two receptor proteins; it does not rank the peptides, identify a product strength, or describe a first and second stage of a treatment.
The IUPHAR/BPS VPAC2 entry identifies its human gene as VIPR2 and lists natural ligands, experimental assays and references separately. That organization is a useful reading model: identify the target first, then inspect the particular measurement rather than relying on a general phrase such as “VIP signaling.”
PAC1: a preference that matters
In their 1993 cloning study, Pisegna and Wank characterized a PACAP type I receptor with high affinity for PACAP and low affinity for VIP. This was a receptor-expression experiment, not a trial of a retail VIP product.
For a practical literature summary, write “PACAP-preferring” rather than “VIP and PACAP are equivalent at PAC1.” Also avoid converting that preference into “VIP can never interact with PAC1.” The receptor construct, experimental system and measured endpoint still matter. A useful summary preserves those conditions instead of turning a relative result into an absolute statement.
Binding and response are different questions
Binding experiments ask about interaction with a receptor. Functional experiments ask what response follows under specified conditions. A reported binding value and a reported signaling value should not be treated as the same measurement.
A 2006 receptor-cloning study reported ligand binding and cAMP responses as separate endpoints. Its results illustrate why an assay label belongs beside a numerical result. A change in cAMP is a laboratory readout; by itself it is not evidence of a useful outcome in a person.
A five-question reading checklist
- Which receptor is named: VPAC1, VPAC2 or PAC1?
- Which species and cell or tissue system were used?
- Does the paper identify a receptor variant or engineered construct?
- Is the result binding, signaling, gene expression or another endpoint?
- Does the conclusion stay within that experiment, or does a later summary overextend it?
For example, “VIP produced a response in a receptor-expressing cell line” leaves several unanswered questions. Adding the receptor identity, assay and model makes it a usable research note. It still does not establish that a catalog vial will reproduce the published experiment; material identity and lot documentation need their own review.
Before selecting this research material
For the VIP 5mg listing, ask for the complete sequence and terminal-group description, the lot-specific identity method, and a clear explanation of what the labeled amount represents. A mass value on a label is not a receptor-activity result. If your research depends on a particular receptor response, ask whether any relevant functional characterization exists and which system it used. Mark unavailable information as unresolved rather than borrowing it from a published experiment.
Find the relevant Dissolv research listing
Dissolv lists VIP 5mg. Use that page to identify the catalog item, then confirm the material specifications and documentation required for the intended laboratory work. PACAP appears here only to explain receptor terminology; this article does not offer a PACAP product.
Research use only. Not for human or veterinary use. Receptor recognition does not establish safety, efficacy, clinical suitability or product-specific performance.
