naloxone-benzoylhydrazone and endomorphin-1

Gamma-aminobutyric acid (GABA)ergic neurons of the substantia nigra pars reticulata (SNpr) are connected to the deep layers of the superior colliculus (dlSC). The dlSC, in turn, connect with the SNpr through opioid projections. Nociceptin/orphanin FQ peptide (N/OFQ) is a natural ligand of a Gi protein-coupled nociceptin receptor (ORL1; NOP) that is also found in the SNpr. Our hypothesis is that tectonigral opioid pathways and intranigral orphanin-mediated mechanisms modulate GABAergic nigrotectal connections.. Therefore, the aim of this work was to study the role of opioid and NOP receptors in the SNpr during the modulation of defence reactions organised by the dlSC.. The SNpr was pretreated with either opioid or NOP receptor agonists and antagonists, followed by dlSC treatment with bicuculline.. Blockade of GABA. These results demonstrate that opioid pathways and orphanin-mediated mechanisms have a critical role in modulating the activity of nigrotectal GABAergic pathways during the organisation of defensive behaviours.

Topics: Aminoquinolines; Analgesics, Opioid; Animals; Benzamides; Bicuculline; Dose-Response Relationship, Drug; Fear; gamma-Aminobutyric Acid; Male; Naloxone; Nociceptin; Nociceptin Receptor; Oligopeptides; Opioid Peptides; Pars Reticulata; Rats; Rats, Wistar; Receptors, Opioid; Somatostatin; Superior Colliculi