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Chronic morphine treatment decreases the Cav1.3 subunit of the L-type calcium channel

Victoria L Haller1, Marissa A Bernstein, Sandra P Welch

  • 1Department of Pharmacology and Toxicology, Virginia Commonwealth University, Richmond, Virginia 23298-0524, USA. vhaller@vcu.edu

European Journal of Pharmacology
|December 1, 2007
PubMed

Insights

Chronic morphine treatment reduced Ca(v)1.3 L-type calcium channel protein levels, suggesting a role in opioid tolerance. This finding sheds light on adaptive changes in intracellular calcium regulation during morphine use.

Area of Science:

  • Neuropharmacology
  • Molecular Biology
  • Calcium Channel Research

Background:

  • Voltage-gated calcium channels (VOCs), specifically L- and N-type, are involved in morphine's effects.
  • Opioid tolerance mechanisms, particularly concerning calcium regulation, require further elucidation.
  • VOCs are complex heteropentamers, with alpha(1) subunits forming the pore and ligand-binding sites.

Purpose of the Study:

  • To investigate the impact of chronic morphine exposure on the protein levels and phosphorylation states of specific VOC subunits.
  • To determine if alterations in VOC subunit expression contribute to the development of opioid tolerance.
  • To explore the role of Ca(v)1.2, Ca(v)1.3 (L-type), and Ca(v)2.2 (N-type) subunits in morphine-induced adaptive changes.

Main Methods:

  • Utilized Western immunoassays with subunit-specific antibodies to quantify protein levels.
  • Investigated Ca(v)1.2, Ca(v)1.3, and Ca(v)2.2 subunit expression in response to chronic morphine treatment.
  • Assessed changes in protein levels and phosphorylation states of these VOC subunits.

Main Results:

  • Chronic morphine treatment significantly decreased the protein level of the Ca(v)1.3 L-type calcium channel subunit.
  • No significant changes were observed in the protein levels or phosphorylation state of the Ca(v)1.2 L-type subunit.
  • The protein level of the Ca(v)2.2 N-type calcium channel subunit remained unchanged after chronic morphine treatment.

Conclusions:

  • The reduction in Ca(v)1.3 subunit protein is a key finding potentially contributing to opioid tolerance.
  • This downregulation may represent an adaptive mechanism to altered intracellular calcium signaling during chronic morphine exposure.
  • Further research is needed to fully understand the multifaceted adaptive changes in calcium regulation underlying opioid tolerance.

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