= Kainic acid
<Kainic acid> is a naturally occurring, non-proteinogenic <amino acid> with <molecular formula> $\mathrm{C_{10}H_{15}NO_4}$. Its structure is a substituted <proline> derivative containing two <carboxyl groups>. It acts as an excitatory amino-acid <agonist>, including activation of <kainate receptors>.<Kainic acid in ChEBI>[CHEBI:31746, Formula, structure and classification]{ref}<IUPAC Compendium of Chemical Terminology, fifth edition (Gold Book)>[entry 11842, kainic acid]{ref}
Its scientific usefulness comes from perturbing receptor activity with a chemically specified molecule. A <voltage clamp> experiment can measure the change in <electric current> associated with that perturbation while holding the membrane potential under a stated convention.
For a constructed example, suppose the current is $-5\,\mathrm{pA}$ before exposure and $-45\,\mathrm{pA}$ afterward. The change is $-40\,\mathrm{pA}$, not $-45\,\mathrm{pA}$: the baseline contributes to the recorded signal. A matched preparation lacking the receptor, together with suitable pharmacological comparisons, helps distinguish receptor-associated activity from background effects. These numbers illustrate analysis and are not reported experimental results.
Activation and cell injury are also different endpoints. Excessive excitatory signalling can cause <excitotoxicity>, but an observed current change alone does not measure the extent of cellular damage.<IUPAC Compendium of Chemical Terminology, fifth edition (Gold Book)>[entries 11842 and 11766, kainic acid and excitotoxicity]{ref} The molecular identity, receptor response and downstream outcome should each be established by an appropriate measurement.
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