title: Blockade of NMDA or NO in the dorsal premammillary nucleus attenuates defensive behaviors.
abstract: The dorsal premammillary nucleus (PMd) is a hypothalamic structure that plays a pivotal role in the processing of predatory threats. Lesions of this nucleus virtually eliminate the expression of defensive responses to predator exposure. However, little is known about the neurotransmitters responsible for these behavioral responses. Since PMd neurons express ionotropic glutamate receptors and exposure to predators have been shown to activate nitric oxide (NO) producing cells in this region, the aim of this study was to verify the involvement of glutamate and NO-mediated neurotransmission in defensive reactions modulated by the PMd. We tested in male Wistar rats the hypothesis that intra-PMd injection of the NMDA receptor antagonist, AP7, or the NO synthase inhibitor, N-propyl-L-arginine (NP), would attenuate behavioral responses induced by cat exposure. Our results showed that both AP7 and NP significantly attenuated the behavioral responses induced by the live cat. These results suggest that the NMDA/NO pathway plays an important role in the behavioral responses mediated by the PMd.
authors.affiliation: Department of Pharmacology, School of Medicine of Ribeirão Preto, Campus USP, 14049–900, Ribeirão Preto, SP, Brazil. danieleaguiar@ufmg.br
authors.forename: Daniele Cristina
authors.initials: DC
authors.lastname: Aguiar
authors.forename: Francisco Silveira
authors.initials: FS
authors.lastname: Guimarães
mesh_terms: D015763:2-Amino-5-phosphonovalerate / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D001120:Arginine / Q000494:pharmacology; D001522:Behavior, Animal / Q000187:drug effects / Q000502:physiology; D002415:Cats; D003674:Defense Mechanisms; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D005239:Fear / Q000187:drug effects; D046352:Freezing Reaction, Cataleptic / Q000187:drug effects; D008124:Locomotion / Q000187:drug effects / Q000502:physiology; D008297:Male; D008326:Mammillary Bodies / Q000187:drug effects / Q000502:physiology*; D016202:N-Methylaspartate / Q000378:metabolism*; D009569:Nitric Oxide / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D018709:Statistics, Nonparametric
chemical_list: D018691:Excitatory Amino Acid Antagonists; D009569:Nitric Oxide; D016202:N-Methylaspartate; D015763:2-Amino-5-phosphonovalerate; D001120:Arginine; C031231:2-amino-7-phosphonoheptanoic acid