Quick summary
PACAP is one of the most potent known neuroprotective agents (PACAP-38 and PACAP-27). It triggers migraine in over half of infused subjects, validating PAC1 antagonism as a drug target and showing promise as a PTSD biomarker.
Overview
PACAP (Pituitary Adenylate Cyclase-Activating Polypeptide) is a highly conserved neuropeptide belonging to the VIP/secretin/glucagon superfamily. It exists in two bioactive forms: PACAP-38 (38 AA, predominant) and PACAP-27 (27 AA, N-terminal fragment). First isolated from ovine hypothalamus in 1989 by Miyata et al., PACAP is one of the most potent known neuroprotective agents. It is expressed broadly in the nervous system, gut, testes, and adrenal glands.
Mechanism of action
PACAP acts through three GPCRs: PAC1 (PACAP-selective, high affinity), VPAC1, and VPAC2 (shared with VIP). PAC1 activation stimulates adenylate cyclase, raising cAMP, and also activates PLC through Gq coupling. This triggers PKA/PKC signaling cascades that promote neuronal survival, inhibit apoptosis, reduce neuroinflammation, and stimulate neurotrophic factor synthesis. PACAP regulates diverse functions including neurodevelopment, circadian rhythms, pain modulation, immune function, and energy metabolism.
Dosing protocols
| Purpose | Route | Dosage | Frequency | Notes |
|---|---|---|---|---|
| neuroprotection research (animal) | intravenous | 100–300 pmol/kg | per study protocol | |
| migraine research (human) | intravenous | 10–10 pmol/kg/min | 20-min infusion (research only) |
Dosing information is for educational purposes only. Consult a qualified healthcare professional before using any peptide.
Research summary
IV infusion of PACAP-38 triggers delayed migraine attacks in 55–58% of subjects, implicating it in trigeminovascular activation and validating PAC1 antagonism as a migraine target. Neuroprotective effects are demonstrated in ischemia, TBI, Parkinson's, and Alzheimer's models. PTSD-associated PACAP elevation (particularly in women) and PAC1R hypermethylation are emerging biomarkers. Short plasma half-life and metabolic instability have limited clinical translation; stable analogs are in development.[1][2][3][4][5]
Evidence grading
Each claimed benefit is graded by the strength of available evidence. Grades reflect study quality, not effect size.
Strong = multiple RCTs · Moderate = limited trials or observational · Preliminary = animal or in vitro only · Insufficient = anecdotal or no published data
Side effects
Side effects vary by individual. This is not an exhaustive list. Report unusual symptoms to a healthcare professional.
Common stacks
Peptides commonly paired with PACAP for synergistic effects.
Legal status
PACAP-38 and PACAP-27 are research peptides, not FDA-approved for human use. Available from specialty peptide suppliers for in vitro and in vivo research. Investigational PAC1 antagonists are in early clinical trials for migraine.
Sourcing & access
Research compound
PACAP is classified as a research compound. Regulatory status varies by jurisdiction. Always verify current legal status and source from vendors providing third-party certificates of analysis (COA).
Frequently asked questions
PACAP (Pituitary Adenylate Cyclase-Activating Polypeptide) is a neuropeptide belonging to the VIP/secretin/glucagon superfamily. It exists as PACAP-38 (predominant) and PACAP-27, is expressed broadly in the nervous system, gut, and adrenal glands, and is one of the most potent known neuroprotective agents.
PACAP acts through three GPCRs: PAC1 (PACAP-selective), VPAC1, and VPAC2. PAC1 activation stimulates adenylate cyclase and also activates PLC through Gq coupling, triggering PKA/PKC signaling cascades that promote neuronal survival, inhibit apoptosis, reduce neuroinflammation, and stimulate neurotrophic factor synthesis.
PACAP is a research peptide with notable side effects including flushing, vasodilation, headache and migraine induction (in 55-58% of IV-infused subjects), nausea, and transient hypotension. Its short plasma half-life of 2-10 minutes limits persistent effects.
IV infusion of PACAP-38 triggers delayed migraine attacks in 55-58% of subjects by activating the trigeminovascular system. This finding validates PAC1 receptor antagonism as a therapeutic target, and investigational PAC1 antagonists are in early clinical trials for migraine prevention.
PTSD-associated PACAP elevation, particularly in women, and PAC1R hypermethylation are emerging as potential biomarkers. However, PACAP's short plasma half-life and metabolic instability have limited clinical translation, and stable analogs are currently in development.
Research references
- Pituitary Adenylate Cyclase-Activating Polypeptide (PACAP) Protects Striatal Cells and Improves Motor Function in Huntington's Disease Models: Role of PAC1 ReceptorPubMed
- A novel small positive allosteric modulator of neuropeptide receptor PAC1-R exerts neuroprotective effects in MPTP mouse Parkinson's disease modelPubMed
- Downregulation of PACAP and the PAC1 Receptor in the Basal Ganglia, Substantia Nigra and Centrally Projecting Edinger-Westphal Nucleus in the Rotenone model of Parkinson's DiseasePubMed
- Pituitary Adenylate Cyclase-Activating Polypeptide in Learning and MemoryPubMed
- Protective effects of pituitary adenylate cyclase activating polypeptide against neurotoxic agentsReview