Journal article
Endogenous pain modulation: Estradiol alters on- and off-cell activity in the rostral ventromedial medulla
The journal of pain, Vol.5(3), pp.S22-S22
2004
Handle:
https://hdl.handle.net/2376/118708
Abstract
Microinjection of morphine into the periaqueductal gray or rostral ventromedial medulla (RVM) produces greater antinociception in male compared to female rats. The present study was conducted to determine whether the ovarian steroid estradiol may contribute to this sex difference by altering the activity of nociceptive modulatory neurons in the RVM. Adult female rats were ovariectomized and implanted s.c. with an estradiol-filled or placebo capsule. Sixteen to 37 days later, rats were anesthetized for single unit recording from RVM neurons. On-cells were characterized by a burst of activity, and off-cells by a pause in activity immediately preceding reflexive withdrawal of the tail from 51 and 54°C water. Although on- and off-cells were evident in both estradiol- and placebo-treated rats, the reflex-related on-cell burst and off-cell pause were dampened in estradiol-treated rats. On-cells from estradiol-treated rats had a mean activity burst of 9.1 + 2.2 Hz in the 2 s preceding the tail withdrawal reflex to 51°C water, compared to 17.9 + 4.3 Hz for on-cells in placebo controls. Off-cell activity during the 2 s preceding tail withdrawal was 4.8 + 2.2 vs. 0.1 + 0.1 Hz in estradiol vs. placebo-treated females, respectively. Similar changes in on- and off-cell activity occurred when the tail was placed in 54°C water. The present data demonstrate that estradiol constrains the magnitude of the shift in RVM on- and off-cell activity associated with nociceptive reflexes. The effect of estradiol on RVM neuronal firing may contribute to the reduced antinociceptive sensitivity to morphine previously observed in awake, ovariectomized females treated with estradiol, and in gonadally intact females compared to males. Thus, the effect of estradiol on neuronal firing in the descending inhibitory pain pathway may contribute to sex differences in opioid analgesia.
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Details
- Title
- Endogenous pain modulation: Estradiol alters on- and off-cell activity in the rostral ventromedial medulla
- Creators
- R. Craft - Washington State UniversityD. Lane - Washington State University VancouverM. Morgan - Washington State University
- Publication Details
- The journal of pain, Vol.5(3), pp.S22-S22
- Academic Unit
- Psychology, Department of
- Publisher
- Elsevier Inc
- Identifiers
- 99900907903601842
- Language
- English
- Resource Type
- Journal article