Researcher adjusting an electrophysiology recording stage

Wellness · Laboratory protocol

PT-141

Melanocortin-receptor agonist (bremelanotide) with activity at MC3R and MC4R. Central-nervous-system signalling, mechanistically distinct from peripheral nitric-oxide/cGMP pathways.

For laboratory research use only. Material is supplied as a research reference standard and is not approved by Health Canada. Protocols below are compiled from published literature and supplier documentation; they are reference information, not medical advice. Anyone with a health condition or on medication should speak to a physician first.

Before you begin

• Lot-matched certificate and laboratory notebook
• Calibrated pipettes, low-binding tubes and suitable PPE
• Validated solvent, assay reagents and model-specific SOP
• Appropriate positive, negative and vehicle controls

Workflow

1Review the lot-matched COA and record identity, purity, batch number and received condition.
2Let the sealed vial equilibrate to room temperature before opening to limit condensation.
3Calculate the target stock concentration with C = mass / volume. Use only a solvent validated for the planned assay.
4Add solvent slowly down the vial wall, mix gently and avoid vortexing unless the validated method permits it.
5Prepare a log-spaced pilot concentration series; determine the usable range empirically instead of assuming a biological dose.
6Run the defined controls and technical replicates alongside every plate or experiment.
7Record preparation time, temperature, equipment, deviations and raw-data file locations.

Assay design

cAMP accumulation in cells expressing a defined melanocortin-receptor subtype, with subtype selectivity established across the panel rather than at a single receptor.

Required controls

Vehicle-only negative control
Receptor-null or antagonist condition
Validated reference material
Untreated viability control

Diluent

Sterile bacteriostatic water (0.9% benzyl alcohol) for multi-withdrawal stock, or sterile water for injection where a preservative-free stock is required by the assay.

Reconstitution concentrations

Solvent volume sets the stock concentration for this 10 mg vial. Lower volume gives a more concentrated stock and smaller working aliquots; higher volume gives a more dilute stock that is easier to measure accurately.

Stock concentration by solvent volume for a 10 mg vial
Solvent added	Stock concentration	Per 0.1 mL	Per unit (U-100)
1 mL	10 mg/mL	1 mg	100 mcg
2 mL	5 mg/mL	500 mcg	50 mcg
3 mL	3.33 mg/mL	333.33 mcg	33.33 mcg

Working range

Receptor-binding and cAMP work runs a log-spaced nanomolar series. Melanocortin-receptor subtypes differ in potency, so profile the subtypes separately.

cAMP accumulation in cells expressing a defined melanocortin-receptor subtype, with subtype selectivity established across the panel rather than at a single receptor.

Stability

Lyophilized: Stable sealed and dry at the certificate temperature.
In solution: Establish empirically for your solvent and container.

Handling notes

Profile MC1R through MC5R where selectivity is the question. A single-subtype curve is not a selectivity claim.
Protect from light during extended incubations.
Use low-binding plasticware for dilute stocks.

Documentation checklist

Record lot and COA, mass balance, solvent and concentration, preparation timestamp, storage history, plate map, replicate plan, instrument settings, exclusions and deviations. Preserve raw data and analysis code with the experiment record.