Opioid Inhibition of Ca²⁺ Channel Subtypes in Bovine Chromaffin Cells: Selectivity of Action and Voltage‐dependence

• Almudena Albillos

• Emilio Carbone

• Luis Gandia

• Antonio G. Garcia

• Antonella Polio

抄録

Bovine chromaffin cells possess a mixture of high‐voltage‐activated Ca 2+ channel subtypes: L‐type, dihydropyridine‐sensitive channels, and N‐, P‐ and Q‐types, ω‐conotoxin MVIIC‐sensitive channels. In these cells, we studied the reversible, naloxone‐antagonized inhibition of Ba 2+ currents by the opioid agonist met‐enkephalin (IC 50 = 272 nM). This inhibition could be resolved into a voltage‐dependent and a voltage‐independent component. The first was revealed by its slow Ba 2+ current activation kinetics at 0 mV and by the current facilitation induced by short prepulses to +90 mV. The second was estimated as the residual inhibition persisting after the facilitation protocol. The two inhibitory components varied markedly from cell to cell and each contributed to about half of the total inhibition. Replacement of internal GTP by GDP‐β‐S or cell pretreatment with pertussis toxin completely abolished the voltage‐dependent inhibition by opioids, partially preserving the voltage‐independent component. The opioid‐induced inhibition was not selective for any Ca 2+ channel subtype, being not prevented after the addition of specific Ca 2+ channel antagonists. However, when separately analyzing the contribution of each channel type to the voltage‐dependent and voltage‐independent modulation, a clear‐cut distinction could be achieved. The voltage‐independent inhibition was effective on all Ca 2+ channel subtypes but predominantly on L‐type Ca 2+ channels. The voltage‐dependent process was abolished by ω‐conotoxin‐MVIIC, but unaffected by nifedipine, and was thus sharply restricted to non‐L‐type channels (N‐, P‐ and Q‐types). Our data suggest a functionally distinct opioid receptor‐mediated modulation of L‐ and non‐L‐type channels, i.e. of the two channel classes sharing major control of catecholamine secretion from bovine chromaffin cells.

収録刊行物

• European Journal of Neuroscience

  European Journal of Neuroscience 8 (8), 1561-1570, 1996-08

  Wiley

キーワード

• General Neuroscience

詳細情報

• CRID: 1361418520536322688
• NII論文ID: 30014386232
• NII書誌ID: AA10672270
• DOI: 10.1111/j.1460-9568.1996.tb01301.x
• ISSN: 14609568
• ISSN: 0953816X
• Web Site: https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fj.1460-9568.1996.tb01301.x
• Web Site: https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1460-9568.1996.tb01301.x
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