The effects of morphine on the temporal structure of Wistar rat behavioral response to pain in hot-plate

Maurizio Casarrubea, Fabiana Faulisi, Magnus S. Magnusson, Giuseppe Crescimanno*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

6 Citations (Scopus)


Rationale: 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. Objectives: 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. Methods: 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. Results: 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. Conclusions: 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.

Original languageEnglish
Pages (from-to)2891-2900
Number of pages10
Issue number15-16
Publication statusPublished - 1 Aug 2016

Bibliographical note

Publisher Copyright:
© 2016, Springer-Verlag Berlin Heidelberg.

Other keywords

  • Hot-plate
  • Morphine
  • Multivariate analysis
  • Pain
  • T-pattern analysis
  • Wistar rat


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