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HERO ID
1977083
Reference Type
Journal Article
Title
Role of gonadal hormones in formalin-induced pain responses of male rats: Modulation by estradiol and naloxone administration
Author(s)
Aloisi, AM; Ceccarelli, I
Year
2000
Is Peer Reviewed?
1
Journal
Neuroscience
ISSN:
0306-4522
EISSN:
1873-7544
Volume
95
Issue
2
Page Numbers
559-566
Language
English
PMID
10658636
DOI
10.1016/S0306-4522(99)00445-5
Web of Science Id
WOS:000084303600027
URL
http://
://WOS:000084303600027
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Abstract
The aim of this study was to assess the possible mediation of endogenous opioids in the effects of gonadal hormones on the responses to formalin pain. We studied the effects of intracerebroventricular injection of estradiol and/or naloxone on the magnitude and time-course of the formalin-evoked behavioural and hormonal responses of intact and gonadectomized male rats. Animals were gonadectomized or left intact; on days 20 and 21 after surgery, they were intracerebroventricularly injected with 17beta-estradiol (1 microg/5 microl) or saline. On day 22, the animals received naloxone (2.5 microg/5 microl) or saline intracerebroventricularly and then, 15 min later, were subcutaneously injected with formalin (50 microl, 5%) or only pricked with a syringe needle in the dorsal hindpaw. The rats were then introduced to a testing apparatus where the formalin-induced licking, flexing and jerking of the injected limb and the other spontaneous behaviours were recorded for 60 min. At the end of the test, the animals were killed and blood was collected from the trunk. Gonadectomy and naloxone increased flexing duration independently of the other treatments. In gonadectomized rats, estrogen increased licking duration and decreased paw-jerk frequency during the first phase (0-15 min) of the formalin test. During the second phase (16-60 min), licking was increased by estrogen only in intact animals. Treatment with naloxone completely abolished all these modifications. The three measures of activity (rearing, inner and outer crossing) showed that while in sham-treated animals the gonadectomy-induced decrease in activity was completely counteracted by estrogen administration, in formalin-treated animals the gonadectomy-induced decrease was not affected by estrogen. In fact, estrogen appeared to further depress the motor activities in the formalin groups. Naloxone reversed these modifications only for outer crossing frequency, blocking the gonadectomy-induced decrease in sham-treated animals. Corticosterone plasma levels were increased by formalin only in estrogen-treated animals, independently of naloxone. In conclusion, these data indicate an important role of both male gonadal hormones and estrogen in formalin-pain responses, acting through opiate and non-opiate mechanisms.
Keywords
persistent pain; behaviour; gonadal hormones
Tags
IRIS
•
Formaldehyde
Nervous system effects
Found
Database search results
Snowball search
Screened
Title/abstract
Non-relevant exposure paradigm
Reproductive and Developmental Effects
Screened
Title/abstract
Methodology/therapeutics
Retroactive RIS import
Pre2013
Merged LitSearch Additions 86 Reviews SCREEN
Ref List Citations 101112
2013
HCHON tox Ref Identification 022713
2015
FA DevRepro 072115
Methodology/Therapeutics-Population Criteria
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