Differential effects of neurokinin-1 receptor activation in subregions of the periaqueductal gray matter on conditional and unconditional fear behaviors in rats.
Central neurokinin-1 (NK-1) receptors are thought to modulate aversion, whereas the periaqueductal gray matter (PAG) is a common pathway for the integration of fear behaviors. The authors determined whether injection of an NK-1 agonist (GR73632) into subregions of the PAG would alter fear-related behaviors. Behavioral inactivity was increased by GR73632 injected into the caudodorsal PAG or the dorsal raphe. Flight behavior induced by stimulation of the dorsal PAG or by a footshock was decreased after injection of GR73632 into the dorsal PAG. Rats that had 6 pairings of a tone with a footshock after injection of GR73632 into the dorsal PAG displayed more freezing behavior than controls at the beginning of the session. However, there was no change in the shock- or the tone-induced freezing because some GR73632-treated rats, but no controls, froze during the baseline period. It is concluded that NK-1 receptors in the dorsal PAG modulate the unconditional but not the mnemonic aspects of fear behaviors.
Mongeau
R
R
Department of Physiology and Pharmacology, Medical School, Queen's Medical Centre, University of Nottingham, England. mongeau@cco.caltech.edu
De Oca
B M
BM
Fanselow
M S
MS
Marsden
C A
CA
D000161:Acoustic Stimulation; D000704:Analysis of Variance; D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects / Q000502:physiology*; D003214:Conditioning, Classical / Q000187:drug effects / Q000502:physiology*; D004597:Electroshock; D004924:Escape Reaction / Q000187:drug effects / Q000502:physiology*; D005239:Fear / Q000187:drug effects / Q000502:physiology*; D006710:Homocysteine / Q000031:analogs & derivatives / Q000494:pharmacology; D007266:Inhibition, Psychological; D008297:Male; D010147:Pain Measurement / Q000187:drug effects; D010446:Peptide Fragments / Q000037:antagonists & inhibitors; D010487:Periaqueductal Gray / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D020318:Rats, Long-Evans; D018040:Receptors, Neurokinin-1 / Q000187:drug effects / Q000502:physiology*; D013373:Substance P / Q000031:analogs & derivatives / Q000037:antagonists & inhibitors
D010446:Peptide Fragments; D018040:Receptors, Neurokinin-1; D006710:Homocysteine; C007956:homocysteic acid; C068032:GR 73632; D013373:Substance P