| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
Mental Retardation Research Center, Department of Psychiatry and Biobehavioral Sciences, University of California, Los Angeles, California 90024-1759
Submitted 4 April 2003; accepted in final form 19 May 2003
Circadian rhythmicity in mammals is generated by a pair of nuclei in the anterior hypothalamus known as the suprachiasmatic nuclei (SCN), whose neurons express a variety of neuropeptides that are thought to play an important role in the circadian timing system. To evaluate the influence of VIP on inhibitory synaptic transmission between SCN neurons, we used whole cell patch-clamp recording in an acute brain slice preparation of mouse SCN. Baseline spontaneous GABAergic inhibitory postsynaptic currents (IPSCs) varied significantly between regions and across phases, with a greater frequency of IPSCs observed in the dorsomedial region during the early night. Bath-applied VIP caused a significant increase in the frequency of spontaneous inhibitory postsynaptic currents (sIPSC) in a reversible and dose-dependent manner with no effect on the mean amplitude or kinetic parameters. The effect of VIP was widespread throughout the SCN and observed in both ventrolateral (VL) and dorsomedial (DM) regions. In the presence of tetrodotoxin, VIP increased the frequency of miniature IPSCs without affecting the mean magnitude or kinetic parameters. The magnitude of the enhancement by VIP was significantly larger during the day than during the night. Pretreatment with the VIP-PACAP receptor antagonist [Ac-Tyr1, D-Phe2]-GHRF 1-29 or the selective VPAC2 receptor antagonist PG 99-465 completely blocked the VIP-induced enhancement. The effect of VIP appears to be mediated by a cAMP/PKA-dependent mechanism as forskolin mimics, while the PKA antagonist H-89 blocks the observed enhancement of GABA currents. Our data suggest that VIP activates presynaptic VPAC2 receptors to regulate inhibitory synaptic transmission within the SCN and that this effect varies from day to night.
This article has been cited by other articles:
|
|
 |
|
  C. A. Christian and S. M. Moenter Vasoactive Intestinal Polypeptide Can Excite Gonadotropin-Releasing Hormone Neurons in a Manner Dependent on Estradiol and Gated by Time of Day Endocrinology, June 1, 2008; 149(6): 3130 - 3136. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 S. J. Aton, J. E. Huettner, M. Straume, and E. D. Herzog GABA and Gi/o differentially control circadian rhythms and synchrony in clock neurons PNAS, December 12, 2006; 103(50): 19188 - 19193. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 S.-H. Lee and C. L. Cox Excitatory Actions of Vasoactive Intestinal Peptide on Mouse Thalamocortical Neurons Are Mediated by VPAC2 Receptors J Neurophysiol, August 1, 2006; 96(2): 858 - 871. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
N.-L. Schneider and M. Stengl Gap Junctions Between Accessory Medulla Neurons Appear to Synchronize Circadian Clock Cells of the Cockroach Leucophaea maderae J Neurophysiol, March 1, 2006; 95(3): 1996 - 2002. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J. Itri, S. Michel, J. A. Waschek, and C. S. Colwell Circadian Rhythm in Inhibitory Synaptic Transmission in the Mouse Suprachiasmatic Nucleus J Neurophysiol, July 1, 2004; 92(1): 311 - 319. [Abstract] [Full Text] [PDF]
|
|
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
| Visit Other APS Journals Online |
