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Properties of whole cell currents in isolated olfactory neurons from the chilean toad Caudiverbera caudiverbera
1Centro de Estudios Cientificos de Santiago, Facultad de Ciencias, Universidad de Chile.
Abstract:
Isolated olfactory neurons from the chilean toad Caudiverbera caudiverbera were found to possess a same set of currents. Outward currents, made of a delayed rectifier and a Ca(2+)-dependent component, were blocked by replacing K+ by Cs+ in the patch pipette, in the presence of millimolar concentrations of tetraethylammonium and 4-aminopyridine in the external solution. Inward currents were made of a transient and a maintained component. The transient was abolished in the absence of external Na+ and was blocked by tetrodotoxin, with an apparent dissociation constant (KDapp) of 25.4 +/- 0.3 nM. The maintained inward currents were suppressed on removing external Ca2+, could be carried also by Ba2+, and were selectively blocked by Cd2+ (KDapp = 3.2 +/- 1.3 microM). A variety of agents found to block the maintained Ca2+ inward currents, including Co2+ and Ni2+, at millimolar concentrations, and nifedipine, verapamil, amiloride, and the amiloride analogue benzamil, at micromolar concentrations, were also effective in either modifying the gating of, or in blocking, the transient inward currents.
Insights
Olfactory neurons in the Chilean toad Caudiverbera caudiverbera exhibit distinct outward and inward currents. Tetrodotoxin blocks transient inward sodium currents, while cadmium blocks maintained calcium currents.
Area of Science:
- Neuroscience
- Electrophysiology
- Amphibian Biology
Background:
- Olfactory neurons are crucial for detecting environmental cues.
- Understanding ion channel function in amphibian olfactory systems is key to comparative neurobiology.
Purpose of the Study:
- To characterize the ion currents present in isolated olfactory neurons of the Chilean toad, Caudiverbera caudiverbera.
- To identify the specific ion channels responsible for inward and outward currents in these neurons.
Main Methods:
- Patch-clamp electrophysiology was used to record ionic currents.
- Ionic substitutions (e.g., K+, Na+, Ca2+) and specific channel blockers (e.g., TEA, 4-AP, TTX, Cd2+) were employed.
Main Results:
- Outward currents comprised a delayed rectifier and a Ca(2+)-dependent component.
- Inward currents had transient (Na+-dependent, TTX-sensitive) and maintained (Ca2+-dependent, Cd2+-sensitive) components.
- Several agents blocking Ca2+ currents also affected transient inward currents.
Conclusions:
- Caudiverbera caudiverbera olfactory neurons possess a complex set of voltage-gated ion currents.
- These currents share similarities with those found in other vertebrate olfactory systems.
- The study provides insights into the molecular mechanisms of olfactory transduction in amphibians.