L-type channel inhibition by CB1 cannabinoid receptors is mediated by PTX-sensitive G proteins and cAMP/PKA in GT1-7 hypothalamic neurons

Hanaa Hoddah, Andrea Marcantoni, Valentina Comunanza, Valentina Carabelli, Emilio Carbone

Research output: Contribution to journalArticle

Abstract

Using immortalized hypothalamic GT1-7 neurons, which express the CB1 cannabinoid receptor (CB1R) and three Ca2+ channel types (T, R and L), we found that the CB1R agonist WIN 55,212-2 inhibited the voltage-gated Ca2+ currents by about 35%. The inhibition by WIN 55,212-2 (10 μM) was reversible and prevented by nifedipine (3 μM), suggesting a selective action on L-type Ca2+ channels (LTCCs). WIN 55,212-2 action exhibited all the features of voltage-independent Ca2+ channel modulation: (1) no changes of the activation kinetics, (2) equal depressive action at all potentials and (3) no facilitation following strong prepulses. At variance with WIN 55,212-2, the CB1R inverse agonist AM-251 (10 μM) caused 20% increase of Ca2+ currents. The inhibition of LTCCs by WIN 55,212-2 was prevented by overnight PTX-incubation and by intracellular perfusion with GDP-β-S. The latter caused also a 20% Ca2+ current up-regulation. WIN 55,212-2 action was also prevented by application of the PKA-blocker H89 or by loading the neurons with 8-CPT-cAMP. Our results suggest that LTCCs in GT1-7 neurons are partially inhibited at rest due to a constitutive CB1R activity removed by AM-251 and GDP-β-S. Activation of CB1R via PTX-sensitive G proteins and cAMP/PKA pathway selectively depresses LTCCs that critically control the synchronized spontaneous firing and pulsatile release of gonadotropin-releasing hormone in GT1-7 neurons.

Original languageEnglish
Pages (from-to)303-312
Number of pages10
JournalCell Calcium
Volume46
Issue number5-6
DOIs
Publication statusPublished - Nov 2009

Keywords

  • cAMP/PKA signal pathway
  • Cannabinoids
  • CB1 inverse agonists
  • Immortalized GnRH neurons
  • Voltage-gated calcium channels

ASJC Scopus subject areas

  • Cell Biology
  • Molecular Biology
  • Physiology

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