Effects of nociceptin/orphanin FQ in the acquisition of contextual and tone fear conditioning in rats.
Nociceptin, or orphanin FQ (N/OFQ), the endogenous ligand of NOP receptors, is known to regulate learning and memory processes. To verify the role of N/OFQ in the acquisition of contextual (CFC) and tone fear conditioning (TFC), Wistar male rats received intracerebroventricular injections of N/OFQ (0.1-5.0 nmol) before training, and were tested 24 and 48 hr later to access the freezing response to context and tone, respectively. The intermediate doses (1.0 and 2.5 nmol) impaired the CFC test, sparing TFC. The highest dose (5.0 nmol) reduced freezing during both tests, a result that may be due to nonspecific effects. The posttraining injection of N/OFQ (1 or 5 nmol) did not interfere with CFC and TFC, suggesting a specific effect of the peptide in acquisition processes. Moreover, the impairment observed with N/OFQ (1 nmol) in CFC cannot be attributed to a state-dependent learning because it was not reversed by its pretest administration. The data support the negative role of N/OFQ in the acquisition of aversively motivated tasks, which encompass a spatial component and depend on the hippocampus.
Fornari
Raquel V
RV
Departamento de Psicobiologia, Universidade Federal de São Paulo, Brazil.
Soares
Juliana C K
JC
Ferreira
Tatiana L
TL
Moreira
Karin M
KM
Oliveira
Maria G M
MG
D000161:Acoustic Stimulation; D000704:Analysis of Variance; D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects / Q000502:physiology; D003213:Conditioning, Psychological / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D004597:Electroshock / Q000009:adverse effects; D005239:Fear; D046352:Freezing Reaction, Cataleptic / Q000187:drug effects; D007276:Injections, Intraventricular / Q000379:methods; D008297:Male; D018847:Opioid Peptides / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D013997:Time Factors; D000097629:Nociceptin
D018847:Opioid Peptides; D000097629:Nociceptin