Repeated stress effects on nociception and on ectonucleotidase activities in spinal cord synaptosomes of female rats.
It has been reported that animals submitted to repeated restraint stress present various adaptation responses which are dependent on the sex. These adaptations include changes in nociception and adenine nucleotide hydrolysis. In this study, we report the effect of chronic administration of a gonadal steroid (17beta-estradiol) on ATP, ADP and AMP hydrolysis in spinal cord synaptosomes of adult ovariectomized (OVX) Wistar rats submitted to repeated restraint stress over 40 days. We also measured nociceptive threshold in these animals using the tail-flick test. The results show that tail-flick latencies were decreased in both stressed groups, OVX and OVX rats receiving estradiol replacement therapy, indicating reduced nociceptive threshold after exposure to repeated stress. Repeated restraint stress caused no effect on ATPase or ADPase activities. On the other hand, AMP hydrolysis in spinal cord synaptosomes from repeatedly stressed rats was decreased in OVX rats compared to non-stressed OVX ones, indicating reduced extracellular adenosine production; this effect was reversed by hormonal replacement. These observations suggest that nociceptive sensitivity to noxious stimuli is affected by repeated stress and that modulation of neurotransmission by adenine nucleotides in spinal cord may be altered by the interaction of sexual hormones and psychological factors, such as exposure to stress.
Fontella
Fernanda Urruth
FU
Instituto de Ciências Básicas da Saúde, UFRGS, Ramiro Barcelos, 2600, anexo-90035-003, Porto Alegre, RS, Brazil. furruth@terra.com.br
Bruno
Alessandra N
AN
Balk
Rodrigo S
RS
Rücker
Bárbara
B
Crema
Leonardo M
LM
Corrêa
Martha D
MD
Battastini
Ana M O
AM
Sarkis
João J F
JJ
Alexandre Netto
Carlos
C
Dalmaz
Carla
C
D000244:Adenosine Diphosphate / Q000378:metabolism; D000249:Adenosine Monophosphate / Q000378:metabolism; D000251:Adenosine Triphosphatases / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000378:metabolism; D000704:Analysis of Variance; D000818:Animals; D004958:Estradiol / Q000008:administration & dosage*; D005260:Female; D006868:Hydrolysis / Q000187:drug effects; D009619:Nociceptors / Q000503:physiopathology*; D010052:Ovariectomy / Q000379:methods; D010147:Pain Measurement / Q000379:methods; D051381:Rats; D017208:Rats, Wistar; D011930:Reaction Time / Q000187:drug effects; D012149:Restraint, Physical / Q000379:methods; D013116:Spinal Cord / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism; D013312:Stress, Physiological / Q000201:enzymology*; D013574:Synaptosomes / Q000187:drug effects* / Q000201:enzymology
D000249:Adenosine Monophosphate; D004958:Estradiol; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D000251:Adenosine Triphosphatases; C027201:ectoATPase