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Rabbit uterine contractile activity increase following coitus
GYNECOLOGY
Rabbit uterine contractile activity increase following coitus DAVID
K.
MICHAEL,
DAVID
A.
REINKE,
East Lansing,
M.S. PH.D.
Michigan
Rabbit uterine contractile activity changes following coitus were monitored with extraluminal contractile force transducers (ECFT’s). Circular muscle contractile activity (but not that of longitudinal) initially increased following coitus. Subsequent increases in contractile force and frequency were recorded from both myometrial layers but for a longer period from longitudinal muscle than from circular muscle.
Six New Zealand White female rabbits weighing 4 to 5 kilograms were anesthetized, the ECFT’s implanted, and the contractile activity recorded as described by Michael and Reinke.s Record analysis included : (a) frequency, defined as the number of bursts of contractile activity per minute, and (b) contractile force, calculated as the average maximum contraction per burst divided by the shimstock concave surface area (units = grams per square millimeter). The results were statistically analyzed using a paired comparison (Fisher paired t analysis)6 of the differences in the frequency and contractile force for 10 minute recordings immediately preceding and following coitus.
THIZ EXTRALUMINAL contractile force transducer (ECFT) has been shown to be a reliable method for assessingunidireaional, discrete contractile activity patterns of the longitudinal and circular uterine muscle layers in the rabbit.lv3 Uterine motility patterns following coitus have been previously described for the bovine4 and the rabbit,6 but these studies do not differentiate between the contractile activity patterns of the two uterine muscle layers. The present study was concerned with obtaining discrete, unidirectional contractile activity patterns of the rabbit uterine muscle layers just prior to and following coitus.
Materials
and
methods
Uterine contractile activity patterns were monj.tored by ECFT’s described previously.2
Results From the Departments Pharmacology, Michigan University. Supported Population York.
of Physiology State
Patterns of contractiIe activity during estrus and immediately following coitus monitored by longitudinally oriented transducers are illustrated in Fig. 1 (upper tracing). Contractions of comparatively high force
and
by a grant from The Council, New York, New 453
454
Michael
and
Reinke
Amer.
June J. Obstet.
1, 1970 Gynec.
2%
A
1L-A
A AI
A
‘Fig. 1. Longitudinal (L) and circular (T) contractile activity tracings recorded from 2 rabbits 5 minutes before and 6 minutes after coitus (C). Time elapsed (for transfer and mating) at C was 8 to 12 minutes. Calibration bar height variability is due to transducer individuality.
Table I. Average
force
and frequency
following
coitus*
___ Longitudinal muscle (n = Estrus
Parameter
Contractile mm.z) Frequency “Ten-minute ~Calculated
Circular muscle (n =
3)
Postcoitus
Pt
Emus
0.49
0.90
0.63
0.67
<0.05
force (Cm./ 0.67
(bursts/minute) interval with
prior Fisher
1.07 0.53
0.31 to paired
and
coitus
following
t analysis
of
(dms
not
3)
include
time
elapsed
for
Postcoitus
transfer
and
P
mating).
differences.”
(18 to 20 g) and low frequency (< 1 per 2 minutes) appeared in rhythmic coordiduring estrus (precoitus) . nated patterns Uterine quiescence was recorded following coitus for a short (< 3 minute) period. The uterine quiescence was followed by a 20 to 40 minute period of increased uterine contractile activity, characterized by contractions ( 20 to 25 g) and frequencies (approximately 1 burst per min.) of greater magnitude than recorded during estrus. Gradual return to precoitus contractile activity patterns Ioccurred within one hour following coitus. Patterns of circular contractile activity during estrus and following coitus are illustrated in Fig. 1 (lower tracing). Contractile activity increased for only a short period of time (5 to 10 minutes) following coitus. Uterine quiescence was not recorded from the circular uterine muscle layer following coitus. Although increased contractile activity following coitus was recorded for rabbits later found to be pregnant as well as pseudopregnant, no increase in contractile activity
was recorded at the beginning of any other recording period. Data in Table I revealed the increases of contractile force and frequency recorded from both uterine muscle layers following coitus. These increases were statistically significant (p < 0.05) for the two parameters in both my-ometrial layers. Comment The uterine events following coitus in the rabbit have been described. Reynolds5 has reported a decrease in uterine motility within 5 to 8 hours and ovulation 10 to 12 hours postcoitus. Sperm were found in the uterine tubes as early as 2 hours postcoitus and within 4 hours were found in equal numbers in both the uterine lumen and Fallopian tubes.8 Fertilized ova enter progesterone influenced uteri 72 to 96 hours following coitus.” Osytocin has been shown to be released from the posterior hypophysis upon stimulation of the vagina, cervix or uterus in intact and in spinal-sectioned rabbits.lO Oxytocin administration has been reported to
Volume Number
facilitate sperm tra.nsport within the rabbit uterine lumen,* presumably by lowering myometrial cell transmembrane potentialll which would enhance estrogen dominated uterine motility. Initiating nervous reflexes due to dilation of the uterus, cervix, or vagina increase the frequency of uterine contractions, a reflex .which can be blocked by intrauterine administration of 2 per cent lidocaine.12 The influence of the sympathetic nervous system may be important in the mediation of the recorded postcoital longitudinal muscle quiescence. Although norepinephrine is the catecholamine present in the largest amounts in estrogen dominated rabbit uteri,13p I4 epinephrine has been shown to depress estrogen dominated uterine motility in the humanI rat,16 and bovine.l* The
REFERENCES
1.
2. 3. 4. 5. 6.
7. 8.
Rabbit uterine
107 3
CaXantine, M. :R., O’Brien, P. O., Windsor, B. L., and Brown, R. J.: Nature 213: 507, 1967. Dominic, J. A., and Reinke, D. A.: Fertil. St’eril. 19: 945, 1968. Michael, D. K., and Reinke, D. A.: AMER. J. OBSTET. GYHEC. 107: 188, 1970. VanDeMark, N. L., and Hays, R. L.: Amer. J. Physiol. 170: 518, 1952. Reynolds, S. R. M., and Freidman, M. H.: Amer. J. Physiol. 94: 696, 1930. Snedecor, G. W.: Statistical Methods, ed. 5, Ames, Iowa, 1.956, Iowa State University Press, Chap. 2, p. 49. Yanagimachi, R., and Chang, M. C.: J. R,eprod. Fertil. 6: 413, 1963. Mroueh, A.: Obstet. Gynec. 29: 671, 1967.
contractility
4%
period of uterine longitudinal muscle quiescence could be elicited by adrenal epinephrine release during coital excitation, causing activation of beta adrenergic receptors.16 Thus the subsequent recorded increase in contractile activity may be due to oxytocin facilitation coupled with diminishing adrenergic inhibition. Coitus causes increased bovine uterine motility within seconds.4 Our results show that increased uterine motility occurs in the rabbit following coitus. If sperm transport is occurring within the uterine lumen during the first hour following coitus, then sperm transport could be the primary function of this increased myometrial contractile activity. The excellent technical assistance of M. Taylor and K. Palmer is gratefully acknowledged.
9. Black, D. L., and Asdell, S. A.: Amer. J. Physiol. 197: 1275, 1959. 10. Ferguson, J. K. W.: Amer. J. Physiol. 126: 489, 1938. 11. Chen, T. W., MacDonald, M. A., and Hawes, R. 0.: Canad. J. Animal Sci. 46: 25, 1966. 12. Setekleiv, J.: Acta Physiol. Stand. 62: 304, 1964. 13. &man, C., and Sjoberg, N. 0.: Z. Zell14. 15. 16. 17.
forsch. 74: 182, 1966. Sjoberg, N. 0.: Acta Physiol. Stand. (Suppl.) 305: 1. 1966. Wansbiough, H., Nakanishi, H., and Wood, C.: Obstet. Gynec. 30: 779, 1967. Diamond, J., and Brody, T. M.: J. Pharmacol. EXD. Ther. 152: 202. 1966. Hays, k. L., and VanbeMark, N. L.: Amer. J. Physiol. 172: 553, 1953.
Rabbit uterine contractile activity increase following coitus DAVID
K.
MICHAEL,
DAVID
A.
REINKE,
East Lansing,
M.S. PH.D.
Michigan
Rabbit uterine contractile activity changes following coitus were monitored with extraluminal contractile force transducers (ECFT’s). Circular muscle contractile activity (but not that of longitudinal) initially increased following coitus. Subsequent increases in contractile force and frequency were recorded from both myometrial layers but for a longer period from longitudinal muscle than from circular muscle.
Six New Zealand White female rabbits weighing 4 to 5 kilograms were anesthetized, the ECFT’s implanted, and the contractile activity recorded as described by Michael and Reinke.s Record analysis included : (a) frequency, defined as the number of bursts of contractile activity per minute, and (b) contractile force, calculated as the average maximum contraction per burst divided by the shimstock concave surface area (units = grams per square millimeter). The results were statistically analyzed using a paired comparison (Fisher paired t analysis)6 of the differences in the frequency and contractile force for 10 minute recordings immediately preceding and following coitus.
THIZ EXTRALUMINAL contractile force transducer (ECFT) has been shown to be a reliable method for assessingunidireaional, discrete contractile activity patterns of the longitudinal and circular uterine muscle layers in the rabbit.lv3 Uterine motility patterns following coitus have been previously described for the bovine4 and the rabbit,6 but these studies do not differentiate between the contractile activity patterns of the two uterine muscle layers. The present study was concerned with obtaining discrete, unidirectional contractile activity patterns of the rabbit uterine muscle layers just prior to and following coitus.
Materials
and
methods
Uterine contractile activity patterns were monj.tored by ECFT’s described previously.2
Results From the Departments Pharmacology, Michigan University. Supported Population York.
of Physiology State
Patterns of contractiIe activity during estrus and immediately following coitus monitored by longitudinally oriented transducers are illustrated in Fig. 1 (upper tracing). Contractions of comparatively high force
and
by a grant from The Council, New York, New 453
454
Michael
and
Reinke
Amer.
June J. Obstet.
1, 1970 Gynec.
2%
A
1L-A
A AI
A
‘Fig. 1. Longitudinal (L) and circular (T) contractile activity tracings recorded from 2 rabbits 5 minutes before and 6 minutes after coitus (C). Time elapsed (for transfer and mating) at C was 8 to 12 minutes. Calibration bar height variability is due to transducer individuality.
Table I. Average
force
and frequency
following
coitus*
___ Longitudinal muscle (n = Estrus
Parameter
Contractile mm.z) Frequency “Ten-minute ~Calculated
Circular muscle (n =
3)
Postcoitus
Pt
Emus
0.49
0.90
0.63
0.67
<0.05
force (Cm./ 0.67
(bursts/minute) interval with
prior Fisher
1.07 0.53
0.31 to paired
and
coitus
following
t analysis
of
(dms
not
3)
include
time
elapsed
for
Postcoitus
transfer
and
P
mating).
differences.”
(18 to 20 g) and low frequency (< 1 per 2 minutes) appeared in rhythmic coordiduring estrus (precoitus) . nated patterns Uterine quiescence was recorded following coitus for a short (< 3 minute) period. The uterine quiescence was followed by a 20 to 40 minute period of increased uterine contractile activity, characterized by contractions ( 20 to 25 g) and frequencies (approximately 1 burst per min.) of greater magnitude than recorded during estrus. Gradual return to precoitus contractile activity patterns Ioccurred within one hour following coitus. Patterns of circular contractile activity during estrus and following coitus are illustrated in Fig. 1 (lower tracing). Contractile activity increased for only a short period of time (5 to 10 minutes) following coitus. Uterine quiescence was not recorded from the circular uterine muscle layer following coitus. Although increased contractile activity following coitus was recorded for rabbits later found to be pregnant as well as pseudopregnant, no increase in contractile activity
was recorded at the beginning of any other recording period. Data in Table I revealed the increases of contractile force and frequency recorded from both uterine muscle layers following coitus. These increases were statistically significant (p < 0.05) for the two parameters in both my-ometrial layers. Comment The uterine events following coitus in the rabbit have been described. Reynolds5 has reported a decrease in uterine motility within 5 to 8 hours and ovulation 10 to 12 hours postcoitus. Sperm were found in the uterine tubes as early as 2 hours postcoitus and within 4 hours were found in equal numbers in both the uterine lumen and Fallopian tubes.8 Fertilized ova enter progesterone influenced uteri 72 to 96 hours following coitus.” Osytocin has been shown to be released from the posterior hypophysis upon stimulation of the vagina, cervix or uterus in intact and in spinal-sectioned rabbits.lO Oxytocin administration has been reported to
Volume Number
facilitate sperm tra.nsport within the rabbit uterine lumen,* presumably by lowering myometrial cell transmembrane potentialll which would enhance estrogen dominated uterine motility. Initiating nervous reflexes due to dilation of the uterus, cervix, or vagina increase the frequency of uterine contractions, a reflex .which can be blocked by intrauterine administration of 2 per cent lidocaine.12 The influence of the sympathetic nervous system may be important in the mediation of the recorded postcoital longitudinal muscle quiescence. Although norepinephrine is the catecholamine present in the largest amounts in estrogen dominated rabbit uteri,13p I4 epinephrine has been shown to depress estrogen dominated uterine motility in the humanI rat,16 and bovine.l* The
REFERENCES
1.
2. 3. 4. 5. 6.
7. 8.
Rabbit uterine
107 3
CaXantine, M. :R., O’Brien, P. O., Windsor, B. L., and Brown, R. J.: Nature 213: 507, 1967. Dominic, J. A., and Reinke, D. A.: Fertil. St’eril. 19: 945, 1968. Michael, D. K., and Reinke, D. A.: AMER. J. OBSTET. GYHEC. 107: 188, 1970. VanDeMark, N. L., and Hays, R. L.: Amer. J. Physiol. 170: 518, 1952. Reynolds, S. R. M., and Freidman, M. H.: Amer. J. Physiol. 94: 696, 1930. Snedecor, G. W.: Statistical Methods, ed. 5, Ames, Iowa, 1.956, Iowa State University Press, Chap. 2, p. 49. Yanagimachi, R., and Chang, M. C.: J. R,eprod. Fertil. 6: 413, 1963. Mroueh, A.: Obstet. Gynec. 29: 671, 1967.
contractility
4%
period of uterine longitudinal muscle quiescence could be elicited by adrenal epinephrine release during coital excitation, causing activation of beta adrenergic receptors.16 Thus the subsequent recorded increase in contractile activity may be due to oxytocin facilitation coupled with diminishing adrenergic inhibition. Coitus causes increased bovine uterine motility within seconds.4 Our results show that increased uterine motility occurs in the rabbit following coitus. If sperm transport is occurring within the uterine lumen during the first hour following coitus, then sperm transport could be the primary function of this increased myometrial contractile activity. The excellent technical assistance of M. Taylor and K. Palmer is gratefully acknowledged.
9. Black, D. L., and Asdell, S. A.: Amer. J. Physiol. 197: 1275, 1959. 10. Ferguson, J. K. W.: Amer. J. Physiol. 126: 489, 1938. 11. Chen, T. W., MacDonald, M. A., and Hawes, R. 0.: Canad. J. Animal Sci. 46: 25, 1966. 12. Setekleiv, J.: Acta Physiol. Stand. 62: 304, 1964. 13. &man, C., and Sjoberg, N. 0.: Z. Zell14. 15. 16. 17.
forsch. 74: 182, 1966. Sjoberg, N. 0.: Acta Physiol. Stand. (Suppl.) 305: 1. 1966. Wansbiough, H., Nakanishi, H., and Wood, C.: Obstet. Gynec. 30: 779, 1967. Diamond, J., and Brody, T. M.: J. Pharmacol. EXD. Ther. 152: 202. 1966. Hays, k. L., and VanbeMark, N. L.: Amer. J. Physiol. 172: 553, 1953.