24 November 2006

Fear and anxiety's effects on pain-thresholds

Fear and anxiety: divergent effects on human pain thresholds
Rhudy, et. al.
Animal studies suggest that fear inhibits pain whereas anxiety enhances it; however it is unclear whether these effects generalize to
humans. The present study examined the effects of experimentally induced fear and anxiety on radiant heat pain thresholds. Sixty male and
female human subjects were randomly assigned to 1 of 3 emotion induction conditions: (1) fear, induced by exposure to three brief shocks;
(2) anxiety, elicited by the threat of shock; (3) neutral, with no intervention. Pain thresholds were tested before and after emotion induction.
Results suggest that ®ndings from animal studies extend to humans: fear resulted in decreased pain reactivity, while anxiety led to increased
reactivity. Pain rating data indicated that participants used consistent subjective criteria to indicate pain thresholds. Both subjective and
physiological indicators (skin conductance level, heart rate) con®rmed that the treatment conditions produced the targeted emotional states.
These results support the view that emotional states modulate human pain reactivity. q2000 International Association for the Study of Pain.
Published by Elsevier Science B.V.
Pain 84 (2000) 65-72
PII: S0304-3959(99)00183-9
Categories: , , ,

20 November 2006

Capsaicin undermines the effectiveness of vaginal self-stimulation

Following on the present theme of the analgesic effects of vaginal selt-stimulation:

Inverse relationship between intensity of vaginal self-stimulation-produced analgesia and level of chronic intake of a dietary source of capsaicin
Beverly Whipple, Margarita Martinez-Gomez, Laura Oliva-Zarate, Pablo Pacheco, and Barry R. Komisaruk
Abstract: Women who chronically ingest a diet rich in capsaicin, the pungent ingredient in hot chili peppers, showed a significantly lower magnitude of analgesia in response to vaginal self-stimulation than women with relatively low or medium levels of ingestion. Vaginal self-stimulation-produced analgesia was quantified by measuring (on the hand) pain detection thresholds, pain tolerance thresholds and tactile thresholds. Whereas vaginal self-stimulation produced a 32.6–43.8% increase in pain detection and pain tolerance thresholds in the low chili diet group, it produced only a 2.3–7.3% increase in these measures in the high chili diet group. The medium chili diet group showed an intermediate effect on the pain thresholds. Tactile thresholds were not increased by the vaginal self-stimulation. Baseline (no stimulation) pain thresholds did not differ significantly among the three groups. These findings are consistent with earlier studies in laboratory rats, in which capsaicin administered neonatally abolished vaginal stimulation-produced analgesia, but did not affect baseline pain thresholds to mechanostimulation.


Categories: , , ,

19 November 2006

Analgesia produced by copulation in rats

Momentary analgesia produced by copulation in female rats
P. Gómoraa, C. Beyera, G. González-Mariscala and B. R. Komisarukb
To assess possible changes in nociception during copulation in estrous rats, electric shocks that were 20% suprathreshold for eliciting vocalization in response to tail shock (STS), were applied to thetail before the initiation of copulation and, thereafter coincident with the onset of mounting bouts by the male (Experiment 1). Females vocalized significantly less during non-intromittive mounts (M; P 0.001), intromissions (I; P < 0.001), and ejaculation (E; P < 0.01) than before the initiation of copulation. In order to assess the importance of vaginal stimulation (VS) by penile insertion during mating, in Experiment 2 30% STS were applied 300–400 ms after the initiation of mounting to ensure that the stimulation fell within the period of penile insertion ocurring during I and E. M failed to significantly inhibit vocalizations to 30% STS. By contrast, both I and E markedly inhibited vocalizations in response to STS. This effect was transitory since subjects (Ss) vocalized to nearly all 30% STS when delivered 15 s after I or E. Copulatory analgesia (CA) was abolished by the bilateral transection of the pelvic and hypogastric nerves but not by the transection of the pudendal nerve (Experiment 3). The magnitude of CA was calibrated by determining the doses of morphine sulfate (MS) required to produce similar decrements in vocalization to STS. The analgesic effects of I and E were equivalent to more than 10 mg/kg and 15 mg/kg, respectively, of MS (Experiment 4). Pelvic-hypogastric neurectomy, but not pudendal neurectomy, also significantly reduced the effect of VS on facilitating lordosis, inducing immobilization and hind leg extension, and blocking the withdrawal reflex to foot pinch (Experiment 5). Pelvic-hypogastric neurectomy also significantly reduced sexual receptivity, as indicated by a reduction in the number of I that the females in this group received.


Categories: , , ,

18 November 2006

Vaginal stimulation and pain threshold

Elevation of pain threshold by vaginal stimulation in women.
Whipple B, Komisaruk BR.
In 2 studies with 10 women each, vaginal self-stimulation significantly increased the threshold to detect and tolerate painful finger compression, but did not significantly affect the threshold to detect innocuous tactile stimulation. The vaginal self-stimulation was applied with a specially designed pressure transducer assembly to produce a report of pressure or pleasure. In the first study, 6 of the women perceived the vaginal stimulation as producing pleasure. During that condition, the pain tolerance threshold increased significantly by 36.8% and the pain detection threshold increased significantly by 53%. A second study utilized other types of stimuli. Vaginal self-stimulation perceived as pressure significantly increased the pain tolerance threshold by 40.3% and the pain detection threshold by 47.4%. In the second study, when the vaginal stimulation was self-applied in a manner that produced orgasm, the pain tolerance threshold and pain detection threshold increased significantly by 74.6% and 106.7% respectively, while the tactile threshold remained unaffected. A variety of control conditions, including various types of distraction, did not significantly elevate pain or tactile thresholds. We conclude that in women, vaginal self-stimulation decreases pain sensitivity, but does not affect tactile sensitivity. This effect is apparently not due to painful or non-painful distraction.

Pain. 1985 Apr;21(4):357-67
Categories: , ,

09 November 2006

Breeding season affects stress-induced analgesia in mice

Sex differences in the expression and antagonism of swim stress-induced analgesia in deer mice vary with the breeding season
Kavaliers and Galea
Summary (you might want to skip to the underlined part)
Swim stress-induced analgesia (SSIA) was examined in photoperiodically induced 'breeding'
(reproductive) and 'non-breeding' (non-reproductive) adult male and female deer mice, Perornyscus maniculatus.
Nociceptive responses (50°C, hot-plate) of breeding and non-breeding deer mice were determined after either a 1-
or 3-min swim in 20°C water. The 1-min swim induced an immediate and relatively short-lasting naloxone (1.0
mg/kg) insensitive 'non-opioid'-mediated SSIA that was antagonized by the N-methyl-D-aspartate (NMDA)
antagonist, MK-801 (0.10 mg/kg) in all of the groups of mice except the breeding (reproductive) females. Breeding
females displayed a non-opioid analgesia that was insensitive to MK-801. The 3-min swim induced a relatively more
prolonged mixed opioid and 'non-opioid' SSIA of which the initial portion was sensitive to antagonism by MK-801
in all groups of the mice except the breeding females, while the latter portion (15 min after swim) was reduced by
naloxone in all of the groups of mice. Overall, the breeding males displayed greater levels of SSIA than the breeding
females, with no consistent sex differences in the non-breeding mice. Within sexes, the breeding males displayed
greater levels of opioid and non-opioid SSIA than the non-breeding males, while the non-breeding females
displayed greater levels of SSIA than the breeding females. These results show that both sex and reproductive status
affect the expression and neurochemical mediation of non-opioid SSIA. These findings also suggest that reproductive
females may have an unique or novel hormonally (estrogen) dependent mechanism associated with the
expression of SSIA

(c) 1995 Elsevier Science

Pain 65 (1995) 327-334
Categories: ,

06 November 2006

Vaginal pain during sex

Vestibular tactile and pain thresholds in pain with vulvar vestibulitis syndrome
Pukall, et al.
Vulvar vestibulitis syndrome (VVS) is a common cause of dyspareunia** in pre-menopausal women. Little is known about sensory function
in the vulvar vestibule*, despite Kinsey's assertion that it is important for sexual sensation. We examined punctate tactile and pain thresholds
to modified von Frey filaments in the genital region of women with VVS and age- and contraceptive-matched pain-free controls. Women
with VVS had lower tactile and pain thresholds around the vulvar vestibule and on the labium minus than controls, and these results were
reliable over time. Women with VVS also had lower tactile, punctate pain, and pressure-pain tolerance over the deltoid muscle on the upper
arm, suggesting that generalized systemic hypersensitivity may contribute to VVS in some women. In testing tactile thresholds, 20% of trials
were blank, and there was no group difference in the false positive rate, indicating that response bias cannot account for the lower thresholds.
Women with VVS reported significantly more catastrophizing thoughts related to intercourse pain, but there was no difference between
groups in catastrophizing for unrelated pains. Pain intensity ratings for stimuli above the pain threshold increased in a parallel fashion with
log stimulus intensity in both groups, but the ratings of distress were substantially greater in the VVS group than in controls at equivalent
levels of pain intensity. The data imply that VVS may reflect a specific pathological process in the vestibular region, superimposed on
systemic hypersensitivity to tactile and pain stimuli.
(c) 2002 International Association for the Study of Pain. Published by Elsevier Science B.V. All rights reserved

Pain 96 (2002) 163-175
PII: S0304-3959(01)00442-0

* The vulvar vestibule is located posterior to the glans clitoris between the labia minora, and contains the vaginal and urethral openings
and the ducts of the Bartholin’s glands.

**Dyspareunia: Painful sexual intercourse.


01 November 2006

Sexual headaches

My new favorite word of the day:
Coital Cephalalgia (headache during or after sex)

Of course, since sex has been shown to reduce regular headaches in normal people, pre-coital cephalalgia is not as serious a condition...

The cerebral hemodynamics of headache associated with sexual activity
Evers, et al.
Headache associated with sexual activity is an idiopathic headache disorder and regarded to be a vascular headache but no pathophysiological
studies have been performed to date to elucidate the underlying mechanisms. We investigated 12 patients with the explosive type of
sexual headache according to the criteria of the International Headache Society during a headache-free state by means of acetazolamide test
and of stress Doppler sonography. Twelve age-matched migraine patients and 14 healthy subjects served as control groups. Changes of blood
pressure, cerebral blood flow velocity (CBFV), and pulsatility index (PI) were evaluated. Patients with sexual headache showed a significantly
higher increase of blood pressure during standardized physical exercise as compared to healthy subjects and migraine patients.
Changes of CBFV by physical exercise were not different between the three examination groups. After 1 g acetazolamide, CBFV showed a
significantly higher increase in patients with sexual headache (plus 66% ^ 16%) than in healthy subjects (plus 46% ^ 18%), and PI showed a
significantly lower decrease as compared to healthy subjects and migraine patients. These data suggest that in patients with sexual headache
the metabolic rather than the myogenic component of the cerebral vasoneuronal coupling is impaired.
q 2002 International Association for the Study of Pain. Published by Elsevier Science B.V. All rights reserved

Pain 102 (2003) 73-78
Categories: ,