Odorant response of isolated olfactory receptor cells is blocked by amiloride

Abstract

Olfactory receptor cells were isolated from the nasal mucosa of Rana esculenta and patch clamped. Best results were obtained with free-floating cells showing ciliary movement. 1) On-cell mode: Current records were obtained for up to 50 min. Under control conditions they showed only occasional action potentials. The odorants cineole, amyl acetate and isobutyl methoxypyrazine were applied in saline by prolonged superfusion. At 500 nanomolar they elicited periodic bursts of current transients arising from cellular action potentials. The response was rapidly, fully and reversibly blocked by 50 microM amiloride added to the odorant solution. With 10 microM amiloride, the response to odorants was only partially abolished. 2) Whole-cell mode: Following breakage of the patch, the odorant response was lost within 5 to 15 min. Prior to this, odorants evoked a series of slow transient depolarizations (0.1/sec, 45 mV peak to peak) which reached threshold and thus elicited the periodic discharge of action potentials. These slow depolarizing waves were reversibly blocked by amiloride, which stabilized the membrane voltage between -80 and -90 mV. We conclude that amiloride inhibits chemosensory transduction of olfactory receptor cells, probably by blocking inward current pathways which open in response to odorants.

Single-channel currents trigger action potentials insmall cultured hippocampal neurons.

“…A small number of channels is needed for randomness, to avoid the averaging effect of large populations of channels. Several reports have been presented indicating that current events originating from single ion channels may induce impulses in some secretory cell types (10-12) and in olfactory receptor cells (13)(14)(15).In this study, we present evidence suggesting that individual openings or closures of single ion channels can induce impulses in mammalian central neurons. The evidence was obtained by tight-seal recordings from a subpopulation of small cultured neurons from rat hippocampus.…”

“…A small number of channels is needed for randomness, to avoid the averaging effect of large populations of channels. Several reports have been presented indicating that current events originating from single ion channels may induce impulses in some secretory cell types (10-12) and in olfactory receptor cells (13)(14)(15).…”

Cyclic nucleotide‐activated channels in the frog olfactory receptor plasma membrane

“…Olfactory epithelium was dissociated as described in [13]; single OR cells were identified according to their characteristic morphology [14]. In this study we used: cGMP, 8BrcGMP, Hepes from Boehringer (Austria), cAMP, ATP, GTP from Reanal (Hungary) and ED-TA, EGTA from Serva (FRG); salines of the following composition (mM): 100 NaCI, 1 MgCI2, 0.…”

Inhibition of olfactory cyclic nucleotide‐activated current by calmodulin antagonists

“…Inhibition by amiloride, which is not considered a calmodulin antagonist, is shown in Figure 1 for com-parison. Amiloride has been shown to inhibit both the odour-induced receptor current (Persaud et al, 1987;Frings & Lindemann, 1988) and the cyclic AMP-gated channels (Suzuki, 1990;Frings et al, 1992).…”