title: Neurotensin enhances GABAergic activity in rat hippocampus CA1 region by modulating L-type calcium channels.
abstract: Neurotensin (NT) is a tridecapeptide that interacts with three NT receptors; NTS1, NTS2, and NTS3. Although NT has been reported to modulate GABAergic activity in the brain, the underlying cellular and molecular mechanisms of NT are elusive. Here, we examined the effects of NT on GABAergic transmission and the involved cellular and signaling mechanisms of NT in the hippocampus. Application of NT dose-dependently increased the frequency of spontaneous inhibitory postsynaptic currents (sIPSCs) recorded from CA1 pyramidal neurons with no effects on the amplitude of sIPSCs. NT did not change either the frequency or the amplitude of miniature (m)IPSCs recorded in the presence of tetrodotoxin. Triple immunofluorescent staining of recorded interneurons demonstrated the expression of NTS1 on GABAergic interneurons. NT increased the action potential firing rate but decreased the afterhyperpolarization (AHP) amplitude in identified CA1 interneurons. Application of L-type calcium channel blockers (nimodipine and nifedipine) abolished NT-induced increases in action potential firing rate and sIPSC frequency and reduction in AHP amplitude, suggesting that the effects of NT are mediated by interaction with L-type Ca(2+) channels. NT-induced increase in sIPSC frequency was blocked by application of the specific NTS1 antagonist SR48692, the phospholipase C (PLC) inhibitor U73122, the IP(3) receptor antagonist 2-APB, and the protein kinase C inhibitor GF109203X, suggesting that NT increases gamma-aminobutyric acid release via a PLC pathway. Our results provide a cellular mechanism by which NT controls GABAergic neuronal activity in hippocampus.
authors.affiliation: Department of Pharmacology, Physiology and Therapeutics, University of North Dakota School of Medicine and Health Sciences, 501 N. Columbia Road, Grand Forks, ND 58202, USA.
authors.forename: Shanshan
authors.initials: S
authors.lastname: Li
authors.forename: Jonathan D
authors.initials: JD
authors.lastname: Geiger
authors.forename: Saobo
authors.initials: S
authors.lastname: Lei
mesh_terms: D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D001030:Apamin / Q000494:pharmacology; D015153:Blotting, Western; D002121:Calcium Channel Blockers / Q000494:pharmacology; D020746:Calcium Channels, L-Type / Q000187:drug effects*; D018999:Charybdotoxin / Q000494:pharmacology; D004594:Electrophysiology; D019706:Excitatory Postsynaptic Potentials / Q000187:drug effects / Q000502:physiology; D006624:Hippocampus / Q000502:physiology*; D007150:Immunohistochemistry; D066298:In Vitro Techniques; D007395:Interneurons / Q000187:drug effects / Q000502:physiology; D008297:Male; D009496:Neurotensin / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D009553:Nimodipine / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D011493:Protein Kinase C / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D018028:Receptors, Neurotensin / Q000187:drug effects; D015398:Signal Transduction / Q000187:drug effects; D010738:Type C Phospholipases / Q000502:physiology; D005680:gamma-Aminobutyric Acid / Q000502:physiology*
chemical_list: D002121:Calcium Channel Blockers; D020746:Calcium Channels, L-Type; D018028:Receptors, Neurotensin; D018999:Charybdotoxin; D001030:Apamin; D009496:Neurotensin; D005680:gamma-Aminobutyric Acid; D009553:Nimodipine; D011493:Protein Kinase C; D010738:Type C Phospholipases