Calcium signals in olfactory neurons

Abstract

Laser scanning confocal microscopy in combination with the fluorescent calcium indicators Fluo-3 and Fura-Red was employed to estimate the intracellular concentration of free calcium ions in individual olfactory receptor neurons and to monitor temporal and spatial changes in the Ca(2+)-level upon stimulation. The chemosensory cells responded to odorants with a significant increase in the calcium concentration, preferentially in the dendritic knob. Applying various stimulation paradigma, it was found that in a population of isolated cells, subsets of receptor neurons display distinct patterns of responsiveness.

Calcium mediates the activation of the inhibitory current induced by odorants in toad olfactory receptor neurons

“…In contrast, the target for the InsP3 pathway in the rat appears to be an InsPß receptor at the ciliary membrane [13,25], but it remains unclear what the physiological effect is of this putative pathway in the olfactory neuron. Utilizing the same preparation and two odorant mixtures analogous to those of Tareilus et al [17], Restrepo et al [16] reported that both stimuli increased Ca 2+ , finding no difference between their effects. Using confocal microscopy, we have monitored increases in Ca 2+ in the apical region of toad olfactory neurons, induced by putrid odorants, in agreement with the notion that Ca 2+ is involved in the inhibitory mechanism.…”

“…Tareilus et al [17] observed that both odorants that elevate cAMP levels and odorants that induce the production of InsP3 cause an elevation of Ca 2+ preferentially in the dendritic knob of rat olfactory neurons. Although both odorant types had a similar effect on Ca 2+ levels, their pharmacological evidence is consistent with two different underlying mechanisms.…”

“…Ca 2+ enters the cell through the cyclic nucleotide-gated channel (CNG channel) and is involved in excitation [19] and adaptation [20,21]. However, in rat, Ca 2+ appears to enter the cell by a different pathway [22,17], but its physiological effect has not been defined. Since Ca 2+ ions have a central role in the inhibitory chemotransduction mechanism [9], it is important to investigate the origin of the calcium that participates in the inhibitory response to odorants.…”

“…E-mail: bacigalu@abello.dic.uchile.cl evidence for an odorant-induced Ca 2+ influx in olfactory cells [13]. An elevation of intracellular free Ca 2+ has been shown to be associated with odorant stimulation in fish [14], frog [15], rat [16,17] and human olfactory neurons [18]. Ca 2+ enters the cell through the cyclic nucleotide-gated channel (CNG channel) and is involved in excitation [19] and adaptation [20,21].…”

Calcium Entry through Cyclic Nucleotide-Gated Channels in Individual Cilia of Olfactory Receptor Cells: Spatiotemporal Dynamics

“…These studies detected elevations in [Ca 2ϩ ] i resulting from stimulation with single odor ligands or odor mixtures (Restrepo et al, 1990(Restrepo et al, , 1993aRestrepo and Boyle, 1991;Sato et al, 1991Sato et al, , 1994Nakamura et al, 1994;Tareilus et al, 1995), forskolin (Sato et al, 1991;Restrepo et al, 1993b), or dialysis of ORNs with cAMP (Nakamura et al, 1994) or IP 3 (Nakamura et al, 1994;Schild et al, 1995). Despite these abundant data, studies to date have not addressed Ca 2ϩ signals in the cilia, the site of odor transduction.…”