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Updated: Aug 19, 2026

Restraint to Induce Stress in Mice and Rats
Published on: December 6, 2024
Repeated restraint stress reduces opioid receptor binding in different rat CNS structures
Giovana Dantas1, Iraci Lucena Da Silva Torres, Leonardo Machado Crema
1Departamento de Bioquímica, Instituto de Ciências Básicas da Saúde, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil. giovana.dantas@ufrgs.br
Abstract:
Different effects of exposure to acute or to repeated stress have been observed upon the nociceptive response in rats. In the present study, we repeatedly submitted Wistar rats to restraint for 40 days, a treatment known to induce an increase in the nociceptive response in the tail-flick test. Afterwards, the effect of repeated restraint stress on the density of opioid receptors in rat spinal cord, frontal cortex, and hippocampus was investigated. Results showed that repeatedly stressed rats displayed a significant decrease in opioid receptors density in all structures studied; cortex (141.3 +/- 5.7 for control and 103.3 +/- 15.9 for stressed rats), hippocampus (92.4 +/- 7.2 for control and 64.8 +/- 7.7 for stressed rats), and spinal cord (122.2 +/- 12.8 for control and 79.7 +/- 9.7 for stressed rats). These findings suggest opioid mediation of the altered responses observed in these repeatedly-stressed animals, although the participation of non-opioid mechanisms in this phenomenon cannot be ruled out.
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