Endogenous gonadal hormones regulate females' behavioral responses to formalin through prostaglandin E2 release.
BACKGROUND
This study aimed to determine if endogenous gonadal hormones affect the intracellular mechanisms in the spinal cord that control inflammatory pain responses.


METHODS
We analyzed behavioral responses to, and changes in, serum levels of prostaglandin E2, estradiol, progesterone, and corticosterone after administration of 5% formalin in intact and ovariectomized (OVX) female rats.


RESULTS
OVX females displayed significantly more flinching than did intact females during Phase I, and after formalin administration their corticosterone levels were significantly lower. No differences were seen across COX-1 and COX-2 protein expression in the spinal cord of either naive or formalin-treated rats. However, subsequent to formalin a main effect of gonadectomy was seen in prostaglandin E2 levels; OVX animals had significantly lower prostaglandin E2 levels than intact animals.


CONCLUSIONS
These results indicate that in female rats nociceptive responses to formalin are regulated through the levels of prostaglandin E2, an important mediator in inflammation, whereas protein levels of COX-1 and COX-2 play a more limited role.
Department of Psychology, Hunter College, City University of New York 10065, USA.
Tzipora
T
Kuba
Deirtra
D
Hunter
Luyi
L
Zhou
Shirzad
S
Jenab
Vanya
V
Quinones-Jenab
D000818:Animals; D015153:Blotting, Western; D003345:Corticosterone / Q000097:blood; D051545:Cyclooxygenase 1 / Q000097:blood; D051546:Cyclooxygenase 2 / Q000097:blood; D015232:Dinoprostone / Q000097:blood / Q000378:metabolism*; D004958:Estradiol / Q000502:physiology; D004967:Estrogens / Q000097:blood / Q000502:physiology*; D005260:Female; D005557:Formaldehyde / Q000494:pharmacology*; D007249:Inflammation / Q000503:physiopathology; D008565:Membrane Proteins / Q000097:blood; D010052:Ovariectomy; D010146:Pain / Q000503:physiopathology*; D010147:Pain Measurement; D011374:Progesterone / Q000097:blood; D051381:Rats; D017207:Rats, Sprague-Dawley; D013116:Spinal Cord / Q000737:chemistry; D013739:Testosterone / Q000502:physiology*
D004967:Estrogens; D008565:Membrane Proteins; D005557:Formaldehyde; D013739:Testosterone; D011374:Progesterone; D004958:Estradiol; D051545:Cyclooxygenase 1; D051546:Cyclooxygenase 2; C496513:Ptgs1 protein, rat; C489691:Ptgs2 protein, rat; D015232:Dinoprostone; D003345:Corticosterone