Cholecystokinin-2 receptors couple to cAMP-protein kinase A to depress excitatory synaptic currents in rat nucleus accumbens in vitro

• Published in: Canadian journal of physiology and pharmacology 2006-02, Vol.84 (2), p.203-211
• Main Authors: Kombian, Samuel B, Ananthalakshmi, Kethireddy V.V, Parvathy, Subramanian S, Matowe, Wandikayi C
• Format: Article
• Language: English
• Subjects: adenylyl cyclase; adénylcyclase; Amino acids; Animals; Biological and medical sciences; Cholecystokinin; cholécystokinine; Cyclic adenylic acid; Cyclic AMP-Dependent Protein Kinases - metabolism; Cyclic AMP-Dependent Protein Kinases - physiology; Excitatory Postsynaptic Potentials - drug effects; Excitatory Postsynaptic Potentials - physiology; Fundamental and applied biological sciences. Psychology; GABA; In Vitro Techniques; Male; Membranes; modulation synaptique; neuropeptides; Nucleus Accumbens - drug effects; Nucleus Accumbens - metabolism; Peptides; Protein kinases; Proteins; Rats; Rats, Sprague-Dawley; Receptor, Cholecystokinin B - agonists; Receptor, Cholecystokinin B - metabolism; Receptor, Cholecystokinin B - physiology; receptors; Rodents; récepteurs GABA; second messengers; seconds messagers; Signal Transduction - drug effects; Signal Transduction - physiology; Sincalide - analogs & derivatives; Sincalide - pharmacology; synaptic modulation; Vertebrates: anatomy and physiology, studies on body, several organs or systems
• ISSN: 0008-4212; 1205-7541
• DOI: 10.1139/y05-119

We recently reported that the activation of cholecystokinin-2 receptors depress evoked excitatory postsynaptic currents (EPSCs) in nucleus accumbens (NAc) indirectly through γ-aminobutyric acid (GABA) acting on γ-aminobutyric acid-B (GABA B ) receptors. Here, we determined the second messenger system that couples cholecystokinin-2 receptors to the observed synaptic depression. Using in vitro forebrain slices of rats and whole-cell patch recording, we tested the hypothesis that cholecystokinin-2 receptors are coupled to cAMP and protein kinase A signaling pathway. Cholecystokinin-8S induced inward currents and depressed evoked EPSCs. Forskolin, an activator of adenylyl cyclase and rolipram that is an inhibitor of phosphodiesterase type IV, independently increased EPSC amplitude and blocked the inward current and synaptic depression induced by cholecystokinin-8S. Furthermore, the membrane-permeable cAMP analog, 8-bromo-cAMP, blocked the cholecystokinin-8S effects. H89, a protein kinase A inhibitor, also blocked cholecystokinin-8S effects. However, depression of the evoked EPSC by baclofen, a GABA B receptor agonist, was not blocked by H89 or forskolin. These findings indicate that cholecystokinin-2, but not GABA B , receptors are coupled to the adenylyl cyclase - cAMP - protein kinase A signaling pathway in the NAc to induce inward currents and cause synaptic depression.