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A myograph is a laboratory instrument that measures the contraction and relaxation of an isolated muscle or blood-vessel preparation. In vascular work, two designs dominate: the wire myograph, which records isometric force from a vessel segment mounted on two wires, and the pressure myograph, which cannulates the vessel and records its internal diameter under isobaric (constant-pressure) conditions.
This page is general equipment information for lab staff and people specifying instruments. It is not a protocol and does not replace the manufacturer’s manual or your institution’s animal-use and safety approvals.
Definition and scope
The word “myograph” covers instruments that record muscle activity, but in laboratory pharmacology and physiology it most often means a vessel myograph for small arteries, veins and airways. REPROCELL describes the wire myograph as measuring “changes in contractile force of luminal tissue segments under isometric conditions” and lists arteries, veins and airways smaller than about 2 mm as typical preparations (REPROCELL, read 2026-11-08). Do not confuse it with surface electromyography, which records electrical activity from a person’s muscles; see EMG electrodes for that device class.
How a myograph is used in practice
In a wire myograph, the tissue segment is held on two wires passed through its lumen, with one wire attached to a force transducer. Multi-myograph systems give each preparation its own bath, so several segments can be tested side by side (REPROCELL). DMT, a manufacturer, states that its wire myographs “measure isometric force in isolated blood vessel rings” and that they measure force, not diameter (DMT, read 2026-11-08).
Typical readouts named by these sources:
- Isometric force, with sensitivity quoted by REPROCELL at the micro-Newton level.
- Contraction and relaxation responses to drugs, summarised as concentration-response curves and EC50 values.
- Viability and endothelial integrity checks, which REPROCELL illustrates with KPSS and acetylcholine.
Uses listed by DMT include vascular reactivity, endothelial function, receptor pharmacology, disease models and ion-channel signalling. REPROCELL adds cardiovascular safety studies that support ICH S7A safety pharmacology and calls wire myography, together with perfusion myography, “considered the gold standard for measuring vasoactivity in small blood vessels.” Follow your own approved SOP for protocol details; see standard operating procedure (SOP).
Wire myograph vs pressure myograph
A comparison study of rat mesenteric small arteries, indexed in PubMed Central as PMC1910357, mounted vessels either on two steel wires for isometric force measurement or cannulated for measurement of internal diameter under isobaric conditions. Its authors called the isobaric condition “the more physiologically appropriate” one (read 2026-11-08, abstract).
| Feature | Wire myograph | Pressure myograph |
|---|---|---|
| Primary measurement | Isometric force | Internal diameter |
| Loading condition | Isometric (fixed length) | Isobaric (set pressure) |
| Mounting | Two steel wires through the lumen | Vessel cannulated |
| Handling noted in the comparison study | Passive data converted using the Laplace relation (wall tension against internal circumference) | Vessels stretched longitudinally to avoid buckling |
Source for all rows: PMC1910357 abstract and the DMT and REPROCELL pages above. Wire data and pressure data are not interchangeable without conversion.
What the comparison study found
- Passive pressure-diameter relations were similar on both systems in rat mesenteric small arteries.
- For noradrenaline and phenylephrine, the threshold concentration was 8 to 10 times lower and the EC50 4 to 5 times lower on the pressure myograph than on the wire myograph.
- For potassium, EC50 and slope did not differ between systems; vasopressin EC50 was also similar.
The practical point for readers of the literature: agonist potency from a wire myograph and from a pressure myograph can differ for the same vessel type and drug, so compare EC50 values across papers only when the myograph design matches.
Checklist: questions to settle when specifying a system
These questions follow the options DMT lists on its wire myograph page; they are not recommendations or price guidance.
- How many preparations at once? DMT lists the 320A for one vessel, the 420A for two preparations with a divider, and the 620M and 630MA with four chambers.
- Manual or automated normalization? The 620M uses manual normalization; the 630MA is automated. DMT also offers MyoNORM normalization software.
- Do you need imaging? The DMT 360CW combines force measurement with confocal or fluorescence imaging. Related background: light sheet microscopy.
- Which acquisition software? DMT lists MyoDAQ for data acquisition.
- Is force enough, or do you need diameter? A wire myograph measures force, not diameter.
- Do your preparation size and expected force fit the system? DMT advises confirming both with the manufacturer before selecting a system.
Record the instrument model, software version and calibration approach in your lab records so results can be reproduced; see ALCOA+ data integrity.
Where it matters for labs and procurement
Because the measured quantity differs by design (force or diameter), the design decision is a scientific one made before a purchasing one. Vessels come from animal or human tissue, so animal-use oversight applies where relevant; see OLAW. Safety pharmacology use, as REPROCELL notes, links to ICH S7A.
Common misunderstandings
- “A myograph measures diameter.” A wire myograph measures isometric force; diameter is the pressure myograph readout.
- “The two designs give the same potency.” In the cited rat study, EC50 values for noradrenaline and phenylephrine differed 4 to 5 times.
- “Myograph means EMG.” Electromyography is a different technique that records electrical signals from muscle, not force from an isolated bath preparation.
Frequently asked questions
What does a myograph measure?
Wire myographs measure isometric force of isolated vessel segments; pressure myographs measure internal diameter at a set pressure.
What is the difference between a wire and a pressure myograph?
The wire type mounts a segment on two wires and records force at fixed length. The pressure type cannulates the vessel and records diameter under constant pressure, which the cited study’s authors called more physiologically appropriate.
What size of vessel is used?
REPROCELL describes small arteries, veins and airways smaller than about 2 mm for wire myography. Confirm limits for a specific instrument with its manufacturer.
Sources
- PubMed Central, PMC1910357, comparison of wire and pressure myograph on rat mesenteric small arteries: pmc.ncbi.nlm.nih.gov/articles/PMC1910357 (read 2026-11-08).
- REPROCELL, myograph overview: reprocell.com/blog/biopta/myograph (read 2026-11-08).
- DMT, wire myograph systems: dmt.dk/wire.html (read 2026-11-08).
