Fig. 1.

Putative agonistic activity of cotinine at human α4β2 and α7 nAChRs. To evaluate the possible agonistic activity of R-(+)- or S-(−)-cotinine, cells expressing either the human α4β2 or α7 receptor were exposed to brief pulses of the compounds (30 seconds) at three different concentrations (indicated by the horizontal bars). Current evoked by a brief ACh test pulse (30 μM for α4β2 and 200 μM for α7, indicated by the arrows) was applied immediately after cotinine exposure to evaluate a possible antagonistic activity of this compound. Typical currents obtained in a cell expressing α4β2 are shown in the upper panel. Average results, normalized versus the ACh response recorded in control conditions, are shown by the histogram (n = 7). Results obtained at α7 nAChRs are shown in the lower panel, and average responses were obtained for n = 9.