title: Periaqueductal gray μ and κ opioid receptors determine behavioral selection from maternal to predatory behavior in lactating rats.
abstract: Every mother must optimize her time between caring for her young and her subsistence. The rostro lateral portion of the periaqueductal grey (rlPAG) is a critical site that modulates the switch between maternal and predatory behavior. Opioids play multiple roles in both maternal behavior and this switching process. The present study used a pharmacological approach to evaluate the functional role of rlPAG μ and κ opioid receptors in behavioral selection. Rat dams were implanted with a guide cannula in the rlPAG and divided into three experiments in which we tested the role of opioid agonists (Experiment 1), the influence of μ and κ opioid receptor blockade in the presence of morphine (Experiment 2), and the influence of μ and κ opioid receptor blockade (Experiment 3). After behavioral test, in Experiment 4, we evaluated rlPAG μ and κ receptor activation in all Experiments 1-3. The results showed that massive opioidergic activation induced by morphine in the rlPAG inhibited maternal behavior without interfering with predatory hunting. No behavioral changes and no receptor activation were promoted by the specific agonist alone. However, κ receptor blockade increased hunting behavior and increased the level of μ receptor activation in the rlPAG. Thus, endogenous opioidergic tone might be modulated by a functional interaction between opioid receptor subtypes. Such a compensatory receptor interaction appears to be relevant for behavioral selection among motivated behaviors. These findings indicate a role for multiple opioid receptor interactions in the modulation of behavioral selection between maternal and predatory behaviors in the PAG.
authors.affiliation: Department of Pathology, School of Veterinary Medicine, University of São Paulo, Avenida Professor Doutor Orlando Marques de Paiva, 87, São Paulo, SP CEP 05508-270, Brazil; Departments of Pharmacology, Institute of Biomedical Sciences, University of São Paulo, Avenida Prof. Lineu Prestes, 1524, Biomédicas I, São Pauo, SP CEP 05508-900, Brazil.
authors.forename: Marianne Orlandini
authors.initials: MO
authors.lastname: Klein
authors.affiliation: Department of Pathology, School of Veterinary Medicine, University of São Paulo, Avenida Professor Doutor Orlando Marques de Paiva, 87, São Paulo, SP CEP 05508-270, Brazil.
authors.forename: Aline de Mello
authors.initials: Ade M
authors.lastname: Cruz
authors.affiliation: Departments of Pharmacology, Institute of Biomedical Sciences, University of São Paulo, Avenida Prof. Lineu Prestes, 1524, Biomédicas I, São Pauo, SP CEP 05508-900, Brazil; Special Laboratory of Pain and Signaling, Butantan Institute, Avenida Vital Brazil, 1500, São Paulo CEP 05503-900, Brazil.
authors.forename: Franciele Corrêa
authors.initials: FC
authors.lastname: Machado
authors.affiliation: Special Laboratory of Pain and Signaling, Butantan Institute, Avenida Vital Brazil, 1500, São Paulo CEP 05503-900, Brazil.
authors.forename: Gisele
authors.initials: G
authors.lastname: Picolo
authors.affiliation: Department of Anatomy, Institute of Biomedical Sciences, University of São Paulo, 2415, São Paulo, SP CEP 05508-900, Brazil.
authors.forename: Newton Sabino
authors.initials: NS
authors.lastname: Canteras
authors.affiliation: Department of Pathology, School of Veterinary Medicine, University of São Paulo, Avenida Professor Doutor Orlando Marques de Paiva, 87, São Paulo, SP CEP 05508-270, Brazil. Electronic address: lfelicio@usp.br.
authors.forename: Luciano Freitas
authors.initials: LF
authors.lastname: Felicio
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D005260:Female; D007774:Lactation / Q000187:drug effects / Q000502:physiology*; D008425:Maternal Behavior / Q000187:drug effects / Q000502:physiology*; D009292:Narcotic Antagonists / Q000494:pharmacology; D009294:Narcotics / Q000494:pharmacology; D010487:Periaqueductal Gray / Q000187:drug effects / Q000502:physiology*; D011235:Predatory Behavior / Q000187:drug effects / Q000502:physiology*; D011247:Pregnancy; D051381:Rats; D017208:Rats, Wistar; D017473:Receptors, Opioid, kappa / Q000378:metabolism*; D017450:Receptors, Opioid, mu / Q000378:metabolism*
chemical_list: D009292:Narcotic Antagonists; D009294:Narcotics; D017473:Receptors, Opioid, kappa; D017450:Receptors, Opioid, mu
keywords: Behavioral selection; Maternal behavior; Periaqueductal gray; Predatory hunting