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mu-Opioid receptor activation decreases N-type Ca2+ current in magnocellular neurons of the rat basal forebrain

B L Soldo1, H C Moises

  • 1Department of Physiology, University of Michigan Medical School, Ann Arbor 48109-0622, USA. soldob@umich.edu

Brain Research
|May 30, 1997
PubMed

Insights

Mu-opioid receptors in rat basal forebrain neurons suppress calcium currents by interacting with N-type channels. This finding reveals a key mechanism for regulating neuronal activity and synaptic transmission.

Area of Science:

  • Neuroscience
  • Pharmacology
  • Molecular Biology

Background:

  • Opioid receptors modulate neuronal function, but their specific roles in basal forebrain calcium signaling are not fully understood.
  • Basal forebrain neurons are crucial for cognitive functions and are influenced by various neurotransmitter systems.

Purpose of the Study:

  • To investigate the effects of different opioid receptor subtypes on voltage-activated calcium currents in rat basal forebrain neurons.
  • To elucidate the specific calcium channel types involved in mu-opioid receptor-mediated modulation.

Main Methods:

  • Whole-cell patch-clamp recordings were used to measure calcium currents in acutely dissociated rat basal forebrain neurons.
  • Specific opioid receptor agonists (mu, delta, kappa) and antagonists were applied.
  • N-type and L-type calcium channels were selectively blocked using omega-conotoxin GVIA and nifedipine, respectively.

Main Results:

  • The mu-opioid receptor agonist DAGO significantly suppressed high-voltage activated calcium currents and slowed their activation.
  • Delta- and kappa-opioid receptor agonists had no effect on calcium currents.
  • The inhibitory effect of DAGO was abolished by omega-conotoxin GVIA, indicating involvement of N-type calcium channels.
  • Nifedipine did not affect DAGO's inhibitory action, ruling out L-type calcium channel involvement.
  • Muscarinic receptor activation also suppressed calcium currents in a subpopulation of mu-opioid sensitive neurons.

Conclusions:

  • Mu-opioid receptors are negatively coupled to N-type calcium channels in basal forebrain neurons.
  • Mu-opioid receptor activation regulates voltage-gated calcium influx in distinct neuronal subpopulations.
  • This modulation of calcium currents represents a significant mechanism for controlling neuronal excitability and synaptic transmission in the basal forebrain.

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