title: The effects of morphine on the temporal structure of Wistar rat behavioral response to pain in hot-plate.
abstract: The largest amount of researches on the hot-plate test was carried out using quantitative assessments. However, the evaluation of the relationships among the different elements that compose the behavioral response to pain requires different approaches. Although previous studies have provided clear information on the behavioral structure of the response, no data are available on its temporal structure.
  
  
  
  The objective of this study was to investigate the temporal structure of the behavioral response to pain in Wistar rat tested in hot-plate and how this structure was influenced by morphine-induced analgesia.
  
  
  
  The behavior of four groups of subjects tested in hot-plate, one administered saline and three with different doses (3, 6, 12 mg/kg) of morphine IP, was analyzed by means of quantitative and t-pattern analyses. The latter is a multivariate technique able to detect the existence of statistically significant temporal relationships among the behavioral events in time.
  
  
  
  A clear-cut influence of morphine on quantitative parameters of the response to the noxious stimulation was observed. T-pattern analysis evidenced profound structural changes of behavior. Twenty-four different t-patterns were identified following saline, whereas a dose-dependent reduction was observed following morphine. Such a reduction was accompanied by a decrease of the total amount of t-patterns detected.
  
  
  
  Morphine, by reducing the effects of the noxious stimulation, orients animal behavior prevalently toward exploratory t-patterns. In addition, it is suggested that the temporal structure of the response is very quickly organized and adapted to environmental noxious cues.
authors.affiliation: Department of Experimental Biomedicine and Clinical Neurosciences, Human Physiology Section, University of Palermo, Corso Tukory 129, 90134, Palermo, Italy.
authors.forename: Maurizio
authors.initials: M
authors.lastname: Casarrubea
authors.affiliation: Department of Experimental Biomedicine and Clinical Neurosciences, Human Physiology Section, University of Palermo, Corso Tukory 129, 90134, Palermo, Italy.
authors.forename: Fabiana
authors.initials: F
authors.lastname: Faulisi
authors.affiliation: Human Behavior Laboratory, University of Iceland, Reykjavik, Iceland.
authors.forename: Magnus S
authors.initials: MS
authors.lastname: Magnusson
authors.affiliation: Department of Experimental Biomedicine and Clinical Neurosciences, Human Physiology Section, University of Palermo, Corso Tukory 129, 90134, Palermo, Italy. giuseppe.crescimanno@unipa.it.
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Crescimanno
mesh_terms: D000701:Analgesics, Opioid / Q000494:pharmacology*; D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects*; D005106:Exploratory Behavior / Q000187:drug effects*; D006358:Hot Temperature; D008297:Male; D009020:Morphine / Q000494:pharmacology*; D015999:Multivariate Analysis; D010146:Pain; D051381:Rats; D017208:Rats, Wistar; D013997:Time Factors
chemical_list: D000701:Analgesics, Opioid; D009020:Morphine
keywords: Hot-plate; Morphine; Multivariate analysis; Pain; T-pattern analysis; Wistar rat