The best structural data available for nicotinic superfamily channels come from ELIC, GLIC and GluCl. Of these, ELIC, a cationic channel from the prokaryote Erwinia chrisanthemi, may be the best for electrophysiological studies aimed at characterizing channel activation, as it opens to a high single channel conductance (> 80 pS) in response to a variety of small molecule agonists such as propylamine, cysteamine and GABA (Zimmermann and Dutzler, 2011). We have used the technique of rapid theta-tube application to elicit macroscopic agonist currents as an initial characterization of the channel activation process, to help us design subsequent single channel experiments. Outside-out patches were obtained from HEK293 cells expressing ELIC and held at -100 mV. Agonist concentration jumps (50 ms-1.5 s) had 20-80% exchange times faster than 500 μs (measured with diluted extracellular solution after patch rupture). We tested propylamine (10- 50 mM), cysteamine (10-50 mM) and GABA (20- 100 mM). Cysteamine was applied in the presence of 1 mM dithiotreitol. For propylamine and cysteamine, the speed with which the current on-relaxation developed reached a clear maximum at 50 mM. The rising phase of the current response was well fitted by a single exponential, with time constants of 7±1 ms (n=9 patches) and 10±1 ms (n=17) at the saturating concentration of 50 mM for cysteamine and propylamine, respectively. Agonist currents declined during sustained applications in a manner suggestive of desensitisation. This decline was well fitted by a single exponential (e.g. τ= 180±30 ms, n=9 patches, for 50 mM 400 ms cysteamine pulse). In contrast with the current onset, the off-relaxation of the macroscopic currents had a complex shape. A rebound current was observed at the end of the applications. This “off-current” does not disappear at positive potentials and therefore it is not due to the end of a voltage-dependent channel block by the agonist (a process well characterised in muscle nicotinic channels). Good fits to the decay phase of the agonist currents (from the peak of this rebound current) required two exponential components with amplitudes of opposite sign. The most striking property of agonist-evoked ELIC responses was their slow time course. This is particularly obvious if we compare them with responses obtained from vertebrate Cys-loop channels. For instance, the onset speed of currents recorded from glycine channels in response to high glycine concentrations is very fast, indeed comparable to the of the solution exchange for the patch (e.g. time constant = 0.3±0.03 ms, n=11 patches, 3 mM glycine and 40mM intracellular Cl-).