Melanin concentrating hormone depresses synaptic activity of glutamate and GABA neurons from rat lateral hypothalamus

The neuropeptide melanin concentrating hormone (MCH) is synthesised only by neurons of the lateral hypothalamic (LH) area in the CNS. MCH cells project widely throughout the brain. Despite the growing interest in this peptide, in part related to its role in feeding, little has been done to character...

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Bibliographic Details
Published in:The Journal of physiology 2001-05, Vol.533 (1), p.237-252
Main Authors: Gao, Xiao‐Bing, Pol, Anthony N.
Format: Article
Language:English
Subjects:
2-Amino-5-phosphonovalerate - pharmacology
6-Cyano-7-nitroquinoxaline-2,3-dione - pharmacology
Action Potentials - drug effects
Action Potentials - physiology
Animals
Bicuculline - pharmacology
Carrier Proteins - pharmacology
Cells, Cultured
Electric Conductivity
Excitatory Amino Acid Antagonists - pharmacology
Excitatory Postsynaptic Potentials - drug effects
Excitatory Postsynaptic Potentials - physiology
Female
Fetus - cytology
GABA Antagonists - pharmacology
gamma-Aminobutyric Acid - physiology
Glutamic Acid - pharmacology
Glutamic Acid - physiology
GTP-Binding Proteins - metabolism
Hypothalamic Area, Lateral - cytology
Hypothalamic Area, Lateral - physiology
Hypothalamic Hormones - pharmacology
In Vitro Techniques
Intracellular Signaling Peptides and Proteins
Melanins - pharmacology
Neurons - drug effects
Neurons - physiology
Neuropeptides - pharmacology
Orexin Receptors
Orexins
Original
Patch-Clamp Techniques
Pituitary Hormones - pharmacology
Potassium - metabolism
Pregnancy
Rats
Rats, Sprague-Dawley
Receptors, G-Protein-Coupled
Receptors, Glutamate - physiology
Receptors, Neuropeptide
Sodium - metabolism
Synaptic Transmission - drug effects
Tetrodotoxin - pharmacology
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Summary:The neuropeptide melanin concentrating hormone (MCH) is synthesised only by neurons of the lateral hypothalamic (LH) area in the CNS. MCH cells project widely throughout the brain. Despite the growing interest in this peptide, in part related to its role in feeding, little has been done to characterise its physiological effects in neurons. Using whole-cell recording with current and voltage clamp, we examined the cellular actions in neurons from the LH. MCH induced a consistent decrease in the frequency of action potentials and reduced synaptic activity. Most fast synaptic activity in the hypothalamus is mediated by GABA or glutamate. MCH inhibited the synaptic activity of both glutamatergic and GABAergic LH neurons, each tested independently. MCH reduced the amplitude of glutamate-evoked currents and reduced the amplitude of miniature excitatory currents, indicating an inhibitory modulation of postsynaptic glutamate receptors. In the presence of tetrodotoxin to block action potentials, MCH caused a depression in the frequency of miniature glutamate-mediated postsynaptic currents, suggesting a presynaptic site of receptor expression. In voltage clamp experiments, MCH depressed the amplitude of calcium currents, suggesting that a mechanism of inhibition may involve a reduced calcium-dependent release of amino acid transmitter. Previous reports have suggested that MCH activated potassium channels in non-neuronal cells transfected with the MCH receptor gene. We found no effect of MCH on voltage-dependent potassium channels in LH neurons. Baclofen, a GABA B receptor agonist, activated G-protein gated inwardly rectifying potassium (GIRK)-type channels; in the same neurons, MCH had no effect on GIRK channels. MCH showed no modulation of sodium currents. Blockade of the G i /G o protein with pertussis toxin eliminated the actions of MCH. The inhibitory actions of MCH on both excitatory and inhibitory synaptic events, coupled with opposing excitatory actions of hypocretin, another LH peptide that projects to many of the same loci, suggest a substantial level of complexity in neuropeptide modulation of LH actions.
ISSN:0022-3751
1469-7793
DOI:10.1111/j.1469-7793.2001.0237b.x