Pharmacology Laboratory
Graded dose–response curve (simulated isolated tissue)
Set up a simulated isolated-tissue organ bath, add an agonist at concentrations you choose, record the contractions, wash between doses, and plot the graded dose–response curve on linear and logarithmic axes to find Emax and EC50.
Objectives
- Identify the independent and dependent variables of a dose–response experiment
- Run trials with correct contact time, washout and recovery
- Plot response against concentration and against log concentration
- Estimate Emax and EC50 and explain potency and efficacy
Principle
In a graded dose–response experiment the size of a tissue's response rises with the concentration of agonist at its receptors, until every receptor that can contribute is occupied and the response reaches a maximum (Emax).
The relationship is described by the Hill equation, E = Emax·Cⁿ/(EC50ⁿ + Cⁿ). EC50 — the concentration giving half the maximum response — measures potency; Emax measures efficacy.
Plotted against concentration the curve is a rectangular hyperbola; plotted against log concentration it becomes a sigmoid, which spreads the low concentrations out and makes the central part almost linear.
This lab is a SIMULATION. The tissue, the agonist's behaviour and every response come from a teaching model (Emax 46 mm, EC50 10⁻⁷ M, Hill coefficient 1) with small deterministic variation. They are not animal or patient data, and the concentrations are organ-bath concentrations, not doses for any person or animal.
Safety
- Real isolated-tissue experiments need institutional ethical approval and training in humane handling; this simulation uses no animal.
- Agonist stock solutions are pharmacologically active: wear gloves, label every dilution and never pipette by mouth.
- Keep water and electrical equipment (circulator, transducer amplifier) apart; mop spills at once.
Apparatus and materials
- Organ bath (20 mL, water-jacketed)
- Thermostatic circulator
- Aeration line
- Tissue strip (simulated)
- Isotonic transducer on a stand
- Recorder (chart display)
- Agonist stock solutions
- Micropipette (10–200 µL)
- Physiological salt solution reservoir
- Lab notebook
Acetylcholine (simulated response) · Physiological salt solution (Tyrode-type)
Curriculum
Listed in the UoK Pharm-D practical syllabus (PHL-612 Pharmacology Lab, 4th year, 2nd semester: identifying an unknown concentration of acetylcholine from graded dose–response curves). The syllabus names no tissue; this lab is a simulation with teaching parameters. Not faculty-reviewed.
- UoK — PHL-612 Pharmacology (Lab), pcology.pdf p. 13 — “13. To identify unknown concentration of acetylcholine from graded dose-response curves.”
- HEC Pharm-D curriculum (2025) — related topic only — Acetylcholine on rabbit intestine (practical) and “Efficacy vs Potency … dose-response relationships” (theory); no graded-curve practical named.
Choose how to do it
The lab opens full screen. (for slower devices or screen readers; Learning mode — switch modes in the lab menu).
Simulated practice: results come from teaching models and illustrative data described on this page. Nothing you enter is sent anywhere unless you are signed in, in which case your completion is added to your progress.