Single channel properties of neuronal nicotinic ACh receptors in stratum radiatum interneurons of rat hippocampal slices

Abstract

The single channel properties of neuronal nicotinic ACh receptors (nAChRs) were investigated in outside-out patches from CA1 stratum radiatum interneurons from thin slices of rat hippocampus. The application of ACh (10 microM to 1 mM) induced the opening of observable single channel currents with two distinct current levels, which corresponded to conductance levels of 38 +/- 3 and 62 +/- 2 pS. The 38 pS channel was observed in 10 % (n = 260) of patches, whereas the 62 pS channel was observed in 4 % of patches; these two channel types were most often observed independently. The alpha7-selective nAChR antagonist methyllycaconitine (MLA; 50 nM) reduced the open probability of the 38 pS channel by 73 %. In contrast, the 62 pS channel was unaffected by MLA, but instead was blocked by dihydro-beta-erythroidine (DHbetaE; 10 microM), a broad spectrum nAChR antagonist. These data suggest that rat hippocampal CA1 stratum radiatum interneurons in the slice possess at least two different types of functional nAChRs, an alpha7-containing subtype with a single channel conductance of 38 pS, and a non-alpha7 subtype with a single channel conductance of 62 pS.