title: Metabotropic glutamate subtype 5 receptors modulate fear-conditioning induced enhancement of prepulse inhibition in rats.
abstract: Non-startling acoustic events presented shortly before an intense startling sound can inhibit the acoustic startle reflex. This phenomenon is called prepulse inhibition (PPI), and is widely used as a model of sensorimotor gating. The present study investigated whether PPI can be modulated by fear conditioning, whose acquisition can be blocked by the specific antagonist of metabotropic glutamate receptors subtype 5 (mGluR5), 2-methyl-6-(phenylethynyl)-pyridine (MPEP). The results show that a gap embedded in otherwise continuous noise sounds, which were delivered by two spatially separated loudspeakers, could inhibit the startle reflex induced by an intense sound that was presented 50 ms after the gap. The inhibitory effect depended on the duration of the gap, and was enhanced by fear conditioning that was introduced by temporally pairing the gap with footshock. Intraperitoneal injection of MPEP (0.5 or 5mg/kg) 30 min before fear conditioning blocked the enhancing effect of fear conditioning on PPI, but did not affect either the baseline startle magnitude or PPI if no fear conditioning was introduced. These results indicate that PPI is enhanced when the prepulse signifies an aversive event after fear conditioning. Also, mGlu5Rs play a role in preserving the fear-conditioning-induced enhancement of PPI.
authors.affiliation: Department of Psychology, National Key Laboratory on Machine Perception, Speech and Hearing Research Center, Peking University, Beijing 100871, China.
authors.forename: Dan
authors.initials: D
authors.lastname: Zou
authors.forename: Juan
authors.initials: J
authors.lastname: Huang
authors.forename: Xihong
authors.initials: X
authors.lastname: Wu
authors.forename: Liang
authors.initials: L
authors.lastname: Li
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D003213:Conditioning, Psychological / Q000187:drug effects; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D005239:Fear; D007266:Inhibition, Psychological; D008297:Male; D011725:Pyridines / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D064529:Receptor, Metabotropic Glutamate 5; D018094:Receptors, Metabotropic Glutamate / Q000502:physiology*; D013216:Reflex, Startle / Q000187:drug effects / Q000502:physiology*; D013037:Spatial Behavior / Q000187:drug effects; D013997:Time Factors
chemical_list: 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