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TitlePostsynaptic Depolarization Enhances GABA Drive to Dorsomedial Hypothalamic Neurons through Somatodendritic Cholecystokinin Release.
Publication TypeJournal Article
Year of Publication2015
AuthorsCrosby, Karen M., Dinara V. Baimoukhametova, Jaideep S. Bains, and Quentin J. Pittman
JournalJ Neurosci
Date Published2015 Sep 23
KeywordsAnimals, Animals, Newborn, Cholecystokinin, Dorsomedial Hypothalamic Nucleus, GABA Agents, gamma-Aminobutyric Acid, Guanosine Diphosphate, In Vitro Techniques, Inhibitory Postsynaptic Potentials, Male, Neuronal Plasticity, Neurons, Patch-Clamp Techniques, Peptides, Proglumide, Quinazolinones, Rats, Rats, Sprague-Dawley, Receptor, Cholecystokinin B, Signal Transduction, Synaptosomal-Associated Protein 25, Thionucleotides

Somatodendritically released peptides alter synaptic function through a variety of mechanisms, including autocrine actions that liberate retrograde transmitters. Cholecystokinin (CCK) is a neuropeptide expressed in neurons in the dorsomedial hypothalamic nucleus (DMH), a region implicated in satiety and stress. There are clear demonstrations that exogenous CCK modulates food intake and neuropeptide expression in the DMH, but there is no information on how endogenous CCK alters synaptic properties. Here, we provide the first report of somatodendritic release of CCK in the brain in male Sprague Dawley rats. CCK is released from DMH neurons in response to repeated postsynaptic depolarizations, and acts in an autocrine fashion on CCK2 receptors to enhance postsynaptic NMDA receptor function and liberate the retrograde transmitter, nitric oxide (NO). NO subsequently acts presynaptically to enhance GABA release through a soluble guanylate cyclase-mediated pathway. These data provide the first demonstration of synaptic actions of somatodendritically released CCK in the hypothalamus and reveal a new form of retrograde plasticity, depolarization-induced potentiation of inhibition. Significance statement: Somatodendritic signaling using endocannabinoids or nitric oxide to alter the efficacy of afferent transmission is well established. Despite early convincing evidence for somatodendritic release of neurohypophysial peptides in the hypothalamus, there is only limited evidence for this mode of release for other peptides. Here, we provide the first evidence for somatodendritic release of the satiety peptide cholecystokinin (CCK) in the brain. We also reveal a new form of synaptic plasticity in which postsynaptic depolarization results in enhancement of inhibition through the somatodendritic release of CCK.

Alternate JournalJ. Neurosci.
PubMed ID26400945
Grant List / / Canadian Institutes of Health Research / Canada