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Ca2+ currents in cockroach neurones: properties and modulation by neurohormone D
1Sächsische Akademie der Wissenschaften zu Leipzig, Forschungsgruppe Jena, Germany.
Neuroreport
|May 9, 1994
Summary
Neurohormone D differentially modulates calcium channel activity in cockroach neurons. It enhances low-voltage-activated (LVA) calcium currents while reducing high-voltage-activated (HVA) currents, explaining its effect on neuronal firing.
Area of Science:
- Neuroscience
- Insect Physiology
- Molecular Pharmacology
Background:
- Dorsal unpaired median (DUM) neurones in cockroaches are crucial for regulating physiological processes.
- These neurones exhibit distinct calcium (Ca2+) currents, including low-voltage-activated (LVA) and high-voltage-activated (HVA) types.
- Neurohormone D (NHD), an adipokinetic hormone (AKH) peptide, is known to modulate DUM cell activity.
Purpose of the Study:
- To investigate the specific effects of NHD on LVA and HVA Ca2+ currents in Periplaneta americana DUM neurones.
- To elucidate the underlying mechanisms of NHD-induced changes in neuronal excitability.
Main Methods:
- Electrophysiological recordings (patch-clamp) were used to isolate and characterize Ca2+ currents in DUM neurones.
- Pharmacological agents, including Cd2+, Ni2+, dihydropyridines, phenylalkylamines, omega-conotoxin GVIA, and SK&F96365, were employed to differentiate Ca2+ channel subtypes.
- The effects of NHD on identified LVA and HVA currents were quantified.
Main Results:
- Two distinct Ca2+ currents, LVA and HVA, were identified in cockroach DUM neurones.
- NHD was found to significantly increase the LVA Ca2+ current component.
- Conversely, NHD markedly decreased the HVA Ca2+ current component.
Conclusions:
- NHD differentially regulates LVA and HVA Ca2+ currents in insect DUM neurones.
- These distinct modulatory effects of NHD on Ca2+ currents provide a mechanistic explanation for its previously observed stimulatory effects on Ca2+-dependent K+ currents and neuronal spiking frequency.