Dopaminergic modulation of endocannabinoid-mediated plasticity at GABAergic synapses in the prefrontal cortex

• Published in: The Journal of neuroscience 2010-05, Vol.30 (21), p.7236-7248
• Main Authors: Chiu, Chiayu Q, Puente, Nagore, Grandes, Pedro, Castillo, Pablo E
• Format: Article
• Language: English
• Subjects: Animals; Animals, Newborn; Benzoxazines - pharmacology; Cannabinoid Receptor Modulators; Chelating Agents - pharmacology; Dopamine - metabolism; Dopamine Agents - pharmacology; Egtazic Acid - analogs & derivatives; Egtazic Acid - pharmacology; Endocannabinoids; Female; gamma-Aminobutyric Acid - metabolism; In Vitro Techniques; Inhibitory Postsynaptic Potentials - drug effects; Inhibitory Postsynaptic Potentials - genetics; Isoquinolines - pharmacology; Membrane Potentials - drug effects; Mice; Mice, Inbred C57BL; Mice, Knockout; Microscopy, Electron, Transmission - methods; Morpholines - pharmacology; Naphthalenes - pharmacology; Neuronal Plasticity - genetics; Neuronal Plasticity - physiology; Patch-Clamp Techniques; Piperidines - pharmacology; Prefrontal Cortex - cytology; Prefrontal Cortex - ultrastructure; Protein Kinase Inhibitors - pharmacology; Pyrazoles - pharmacology; Rats; Rats, Wistar; Receptor, Cannabinoid, CB1 - agonists; Receptor, Cannabinoid, CB1 - deficiency; Receptor, Cannabinoid, CB1 - metabolism; Receptors, Dopamine D2 - metabolism; Silver Staining - methods; Sulfonamides - pharmacology; Synapses - drug effects; Synapses - physiology; Synapses - ultrastructure
• ISSN: 0270-6474; 1529-2401
• DOI: 10.1523/jneurosci.0736-10.2010

Similar to dopamine (DA), cannabinoids strongly influence prefrontal cortical functions, such as working memory, emotional learning, and sensory perception. Although endogenous cannabinoid receptors (CB(1)Rs) are abundantly expressed in the prefrontal cortex (PFC), very little is known about endocannabinoid (eCB) signaling in this brain region. Recent behavioral and electrophysiological evidence has suggested a functional interplay between the dopamine and cannabinoid receptor systems, although the cellular mechanisms underlying this interaction remain to be elucidated. We examined this issue by combining neuroanatomical and electrophysiological techniques in PFC of rats and mice (both genders). Using immunoelectron microscopy, we show that CB(1)Rs and dopamine type 2 receptors (D(2)Rs) colocalize at terminals of symmetrical, presumably GABAergic, synapses in the PFC. Indeed, activation of either receptor can suppress GABA release onto layer 5 pyramidal cells. Furthermore, coactivation of both receptors via repetitive afferent stimulation triggers eCB-mediated long-term depression of inhibitory transmission (I-LTD). This I-LTD is heterosynaptic in nature, requiring glutamate release to activate group I metabotropic glutamate receptors. D(2)Rs most likely facilitate eCB signaling at the presynaptic site as disrupting postsynaptic D(2)R signaling does not diminish I-LTD. Facilitation of eCB-LTD may be one mechanism by which DA modulates neuronal activity in the PFC and regulates PFC-mediated behavior in vivo.