Metabotropic glutamate receptors subtype 5 are necessary for the enhancement of auditory evoked potentials in the lateral nucleus of the amygdala by tetanic stimulation of the auditory thalamus.
The lateral nucleus of the amygdala (LA) receives axonal projections from the auditory thalamus, the medial geniculate nucleus (MGN), and mediates auditory fear conditioning. Tetanic electrical stimulation of the MGN can induce long-term potentiation of acoustically-evoked responses (AEPs) recorded in the LA of anesthetized rats. The present study investigated the temporal development of tetanus-induced AEP potentiation recorded in the LA of anesthetized rats during the recording time up to 120 min after tetanization. In addition, the present study investigated whether the artificially-induced AEP potentiation is mediated by the metabotropic glutamate receptors subtype 5 (mGluR5). The results show that AEPs recorded in the LA to a broadband-noise burst were significantly enhanced immediately after tetanic but not low-frequency stimulation of the MGN. The AEP potentiation was well retained up to 120 min after tetanization. High-dose (1.5 microg/4 microl) microinjection of the selective antagonist of mGluR5, 2-methyl-6-(phenylethynyl)-pyridine (MPEP), into the ipsilateral lateral ventricle 30 min before tetanization completely blocked the AEP potentiation without affecting the baseline AEP. Low-dose (0.5 microg/4 microl) microinjection partially suppressed the AEP potentiation. When the high-dose MPEP was injected 40 min after tetanization, the AEP potentiation was not affected. These results indicate that in anesthetized rats mGluR5 receptors are necessary for the induction or early maintenance (40 min) of AEP potentiation in the LA by tetanic stimulation of the MGN.
Department of Psychology, Speech and Hearing Research Center, State Key Laboratory on Machine Perception, Peking University, 5 Yiheyuan Road, Beijing, China 100871.
J
J
Zheng
X
X
Wu
L
L
Li
D000161:Acoustic Stimulation; D000679:Amygdala / Q000187:drug effects / Q000502:physiology*; D000818:Animals; D001306:Auditory Pathways / Q000187:drug effects / Q000502:physiology; D005072:Evoked Potentials, Auditory / Q000187:drug effects / Q000502:physiology*; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D005829:Geniculate Bodies / Q000187:drug effects / Q000502:physiology*; D017774:Long-Term Potentiation / Q000187:drug effects / Q000502:physiology*; D008297:Male; D011725:Pyridines / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D064529:Receptor, Metabotropic Glutamate 5; D018094:Receptors, Metabotropic Glutamate / Q000187:drug effects / Q000378:metabolism*; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology
D018691:Excitatory Amino Acid Antagonists; C578937:Grm5 protein, rat; D011725:Pyridines; D064529:Receptor, Metabotropic Glutamate 5; D018094:Receptors, Metabotropic Glutamate; C121465:6-methyl-2-(phenylethynyl)pyridine