Patch-clamp study of neurones in rat olfactory cortex slices: properties of a slow post-stimulus afterdepolarizing...

Whole-cell recordings were made from neurones in slices of rat olfactory cortex (10-19 days old), using potassium methylsulphate-filled pipettes. Positive commands applied from -60 mV in the presence of oxotremorine-M (10-20 microgramM, 20 of 30 cells) or trans-ACPD (10-50 microgramM, 4 of 9 cells) evoked a slow inward tail current similar to the K+ -mediated tail current (I K,ADP) recorded with sharp electrodes. I ADP was reduced by hyperpolarization, showed a 27% decrease in input conductance at its peak and was depressed by Cd(2+), 4AP or high K+ but unaffected by Cs+, Ba(2+) or TEA (5 mM). IADP was significantly larger in cells between postnatal days 13 and 15 than in younger neurones (10-12 days). These data show that stable whole-cell recordings of I ADP can be made from olfactory neurones in cortical slices, and support our hypothesis that IADP is a slowly reactivating, Ca(2+) -sensitive K+ conductance.