Linked Life Data

4020319

Source:http://linkedlifedata.com/resource/pubmed/id/4020319

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
2
pubmed:dateCreated
1985-9-19
pubmed:abstractText
The role of endogenous opiates in the regulation of photoperiodically induced testicular regression was studied in the male Syrian hamster. In reproductively active hamsters exposed to a long photoperiod (LD; 16 h light: 8 h darkness) or to short days (SD; 8 h light: 16 h darkness) for 20 weeks or to SD after pinealectomy, administration of naloxone, a competitive opiate receptor antagonist, at doses of 2.5-20 mg/kg, significantly increased serum LH concentrations. In marked contrast, these doses of naloxone did not produce any change in LH levels in reproductively quiescent hamsters exposed to SD for 8 weeks. The influence of gonadal steroids on the LH response to naloxone was studied in hamsters castrated or castrated and implanted s.c with a capsule containing testosterone. Naloxone did not induce LH release in castrated hamsters maintained in LD or in SD, but this response was restored in LD but not SD when serum testosterone concentrations were maintained at levels similar to those observed in intact reproductively active hamsters. These results show that inhibition of reproduction by the photoperiod prevents naloxone-induced LH release in the male hamster. This lack of response to naloxone is not due, however, to the lower testosterone titres present in these animals compared with reproductively active animals. Responsiveness to naloxone can be restored when the animal is rendered insensitive to the inhibitory photoperiod either by removal of the pineal gland or by induction of photorefractoriness by extended exposure to SD.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Aug
pubmed:issn
0022-0795
pubmed:author
pubmed:issnType
Print
pubmed:volume
106
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
243-8
pubmed:dateRevised
2006-11-15
pubmed:meshHeading
pubmed:year
1985
pubmed:articleTitle
Naloxone-induced secretion of LH in the male Syrian hamster: modulation by photoperiod and gonadal steroids.
pubmed:publicationType
Journal Article, Research Support, Non-U.S. Gov't