Some aspects of uterine motility in the mare as measured by myometrial electromyography : a thesis presented in partial fulfilment of the requirements for the degree of Master of Veterinary Science at Massey University

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(1)Copyright is owned by the Author of the thesis. Permission is given for a copy to be downloaded by an individual for the purpose of research and private study only. The thesis may not be reproduced elsewhere without the permission of the Author..

(2) SOME ASPECTS OF UTERINE M OTILITY IN THE MARE AS MEASURED BY MYOMETRIAL ELECTROMYOGRAPHY. A THESIS PRESENTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE O F MASTER OF VETERINARY SCIENCE AT MASSEY UNIVERSITY. DENISE M. JONES APRIL 1990.

(3) ii. "Difficult though it may be to record uterine activity in a unicorn the data obtained is no more reliable than similar data derived from the study of one mouse•.. Finn and Porter (1975).

(4) iii ABSTRACT. The purpose of this study was to determine how uterine motil ity as measu red by both electromyographic techniques ( emg), and to a lesser extent by intra-uterine pressure changes (IUP), is influenced by steroid hormones, uterine stimulants and relaxants, infused intra-uterine fluids, natural b reeding and the first 20 days of p regnancy. Two intact and two ovariectomised mares had uterine emg activity measured from 3-8 hours/day over a period of 1 -5 months. Simultaneous IUP recordings, using an open tipped catheter, were periodically taken. O ne intact mare during anoestrus and. both spayed mares were given exogenous courses of oestradiol. progesterone. to. simulate. oestrous cycle. activity.. Oxytocin,. and. clopro stenol,. p ropantheline bromide and clenbuterol were administered to each mare during anoestrus, transition, oestrus, and d ioestrus, where applicable.. Quantities (60-. 1 000ml) of sterile double distilled water were infused intra-uterine into each mare at various cycle stages. One intac:t mare was bred on four occasions and followed thro ugh the first 20 days of her pregnancy. Mares i n oestrus recorded synchronous short bursts (3-5 min) o f high amplitude emg activity following a crescendo-decrescendo pattern. In dioestrus burst duration i ncreased ( 15-25 min) and amplitude decreased with increasing plasma progesterone levels.. Emg results during anoestrus and transition were intermediate.. During. early pregnancy emg characteristics va ried depending on whether the conceptus was in the oviduct, migratory or fixed.. It is proposed that in oestrus emg changes. manifest as contractions, while in dioestrus as increased uteri ne tone. Oxytocin. and cloprostenol caused uterine responses at all cycle stages with the. most pronounced response during oestrus. where drug administration was followed by prolonged emg activity ( 1 0-25 min) initially and then followed by short burst activity.. The least response was seen during d ioestrus.. Propantheline bromide. decreased emg activity especially in dioestrus and is an effective uterine relaxant; clenbuterol however caused minimal measurable change..

(5) iv. Infused intra-u terine fluids resulted i n a single spike pattern o f emg activity which. was generally asynchronous between electrode sites during the first i nfusion and depressed uterine activity followi ng a subsequent second infusion. Natural service resulted in minimal emg changes similar to those seen after rectal palpation, ie a short term (5- 1 0 min) burst of densely grouped action potentials. This response is so short it seem s unlikely either endogenous oxytocin and/or prostaglandins would have any significant influence on sperm transport in the mare; it is suggested that the emg change seen at this time is more i n the nature o f a local response to vaginal stimulation by the penis of the stallion, and is similar to that seen during palpation per rect u m . Electrode site e m g variation was common, especially during dioestrus and early pregnancy. The emg activity recorded in early p regnancy is different to that found in the non pregnant dioestrus mare and probably related to the position of t he embryo; it is suggested that abnormal uterine motility could be a cause of early embryonic death in this species. During the oestrous cycle there was little correlation either statistically or visually between emg and IUP with or without drug treatment, but IUP increased with uterokinetic drugs and decreased with relaxants. IUP changes may not be a reliable method of measuring uterine activi ty in the mare . This is supported by the finding that there was no statistical difference i n IUP parameters measured between cycle stages, whereas there were important emg variations.. As the experimental mares experienced signs of intestinal discomfort. after admini stration of the uterine stimulants, and propantheline bromide is a known intestinal relaxant, the author argues that IUP results recorded after drug treatment could be influenced by t he effects o f these substances on intestinal motili ty rather than solely the consequence of a direct uterine respo nse..

(6) V. ACKNOWLEDGEM ENTS. The candidate wishes to record her indebtedness to her chief supervisor Professor E.D. Fielden, Dean of the Faculty o f Veterinary Science, for his enthusiasm and guidance which made this study possible and his patient review o f this manuscript which resulted i n many positive suggestions for its preparation. She also wishes to acknowledge Dr. David Carr, Department of Physiology and Anatomy,. who. provided. electromyographic. and. the. laboratory. intra-uterine. equipment. pressure. and. recording. expertise. techniques. in and. interpretation, and also as eo-supervisor reviewed and enhanced t he quality of this thesis presentation. Special thanks are extended to Dr D irk Pfeiffer, Department of Veterinary Clinical Sciences, for his i nvaluable statistical advice and to Mrs. Fiona D ickson and Mrs. Judith McQuilkin for their aid in preparing this manuscript. Thanks are also due Dr. Keith Lapwood and Mr. John Pedley o f the Physiology and Anatomy Department. The former for providing the progesterone assay, and the latter for solving equipment difficulties. A debt is also owed to all the members of the Department of Veterinary Clinical Sciences for providing me time and space for this work, their u seful comments and occasional assistance. Finally sincere thanks to my husband Daryl for doing double d u ty as wife and mother in o rder to allow me time to prepare this manuscript and to Daryl and my daughter Piper for their great encouragement and support..

(7) TAB LE O F CONTENTS A BSTRACT ACKNOWLEDGEMENTS CHAPTER I INTRODUCTION AND LITERATURE R EVIEW. vi iii. V. 1. 1. 1. 1. INTRODUCTION. 1.2. GROSS ANATOMY OF THE UTERUS OF THE MARE. 2. 1.3. FUNCTIONAL ANATOMY OF THE UTERUS (i) Caveolae ( ii) Dense Bands ( iii) Gap Junctions or Nexuses (iv) Collagen (v) Sarcoplasmic Reticulum Mitochondria (vi) (vii) Dense Bodies (viii) Intracellular Filaments. 3 3 4 4 4 4 5 5 5. I.4. EXCITATION - CONTRACTION COUPLING. 6. 1.5. THE REPRODUCTIVE CYCLE OF THE MARE (i) Introduction (ii) Anovulatory Period (iii) Transition To The Ovulatory Phase Ovulatory Phase ( iv) (v) Early Pregnancy. 8 8 9 10 10 11. 1.6. THE STEROID HORMONES (i) Introduction (ii) Oestrogen ( i ii) . .Progesterone. 11 11 12 13. 1. 7. THE CASTRATE. 14. 1.8. THE MEASUREMENT OF UTERINE ACTIVITY (i) Introduction (ii) Electromyography (iii) I ntra-luminal Uterine Pressure. 15 15 15 16. 1.9. UTERINE MOTILITY IN THE MARE (i) Introduction (ii) Ultrasound (iii) Intra-uterine Pressure (iv) Electromyography (v) Stretch (Strain) Gauge Technique. 18 18 18 19 20 20.

(8) vii. 1. 1 0. UTERINE STIMULANTS (i) Oxytocin (ii) Prostaglandin (iii) Stretch. 21 21 25 31. 1. 1 1. UTERINE RELAXANTS (i) Clenbuterol ( ii) Propantheline Bromide. 31 31 33. CHAPTER 1 1. MATERIALS A N D M ETHODS. 34. II. 1. ANIMALS AND HOUSING. 34. II.2. ELECTROD E PREPARATION. 35. II.3. SURGERY. 35. II.4. RECORDING OF EMG. 36. II.S. INTRA-UTERINE PRESSURE RECORDINGS. 36. II.6. CYCLICAL ACTIVITY O F THE MARE. 37. II.7. DRUGS (OTHER THAN STEROID HORMONES) GIVEN. 38. II.8. OTHER MANIPULATIVE PROCEDURES. 39. II.9. ELECTROMYOGRAPHIC ANALYSIS. 40. II. 1 0. INTRA-UTERINE PRESSURE ANALYSIS. 41. II. 1 1. BLOOD SAMPLE COLLECTION AND P ROGESTERONE ASSAY. 41. STATISTICAL ANALYSIS. 42. II. 1 2. RESULTS. 46. INTACT MARES. 46. CHAPTER Ill. III. 1 III. 1 .A:. (i) (ii) (iii). Sweetie Normal Oestrous Cycle Activity (no exogenous drug influence) Pregnancy Drug Treatments Prostaglandin (a) (b) Oxytocin Clenbuterol (c) (d) Propantheline bromide. 46 46 47 48 48 49 50 50.

(9) (iv). III. l . B: (i) (ii). (iii). 111.2. Observations Breeding Changes during natural luteolysis Induced Abortion. Fling Normal Oestrous Cycle Activity (no exogenous drug influence) Artificial Oestrus and Dioestrus Induced by Steroid Hormones Oestrogen (a) Progesterone (b) Drug Treatment Prostaglandin (a) Oxytocin (b) Clenbuterol (c) (d) Propantheline Bromide. OVARIECTOMISED MARES. 111.2.A: (i) (ii). 111.2.B: (i) (ii). 111.3. Other (a) (b) (c). v iii. 51 51 51 52. 76 76 76 76 77 77 77 78 79 80 88. Jo Simulated Cycle Stages Drug Treatment (non steroid hormones) Prostaglandin (a) Oxytocin (b) Clenbuterol (c) Propantheline Bromide (d). 88 88 89 89 90 90 91. Snowy Simulated Cycle Stages Drug Treatment ( non steroid hormones) Prostaglandin (a) Oxytocin (b) Clenb uterol (c) Propantheline Bromide (d). 107 107 107 107 108 108 108. RESP.ONSES TO MISCELLANEOUS DISTURBANCES, RECTAL EXAMINATION AND UTERINE STRETCH USING DISTILLED WATER INFUSIONS:ALL MARES Extraneous I n fluences (i) (ii) Rectal Examination (iii) Uterine Stretch. 1 17 1 17 1 17 1 17. 111.4. . SUMMARY Of EMG RESULTS. 123. 111.5. INTRA-UTERINE PRESSURE. 125. 111.5.A. INTRODUCTION. 125. III.5.B. CORRELATION OF IUP INDICES TO EMG A/HR AND AMPLITUDE. 125.

(10) ix. III.5 . C COMPARISON OF CYCLE STAGES Individual Mare Comparisons (i) (ii) All Mares Combined III.5.D: (i) (ii). C HAPTER IV. 125 125 126. DRUG TREATMENT INFLUENCED ACTIVITY (NON STEROID HORMONE) Correlation Between IUP Indices, Emg A/h r, And Amplitude Effect Of Individual Drugs On IUP indices (mares combined) (a) Prostaglandin Oxytocin (b) (c) Propantheline Bromide Clenbuterol (d). 126 126 127 127 128. DISCUSSION AND C ONCLUSIONS. 144. 126 126. IV.1. GENERAL DISCUSSION. 144. IV.2. VARIATION BETWEEN ELECTRODE SITES. 148. IV.3. EARLY PREGNANCY. 148. IV.4. EXTRANEOUS INFLUENCES. 149. IV.5. UTERINE DISTENTION. 150. IV.6. BREEDING. 15 1. IV. 7. UTERINE STIMULANTS. 153. IV.8. UTERINE RELAXANTS. 155. IV.9. INTRA-UTERINE PRESSURE. 156. IV.10 CRITIQUE OF EXPERIMENTAL DESIGN .. .. 158. IV. 1 1. FUTURE STUDIES. 159. IV. 12. CONCLUSIONS. 161. REFERENCES. 163. APPEND I X A. 1 82. APPEND I X B. 203. APPEND I X C. 205.

(11) X. LIST O F TAB LES. Table I,II. 53. Table Ill. 54. Table IV. 55. Table V. 56. Table VI. 57. Table VII. 58. Table VIII. 59. Table IX, X. 81. Table XI, XII. 82. Table XIII. 83. Table XIV. 84. Table XV. 85. Table XVI. 86. Table XVII, XVIII. 92. Table IX. 93. Table XX. 94. Table XXI. 95. Table XXII. 96. Table XXIII, XXIV. 1 10. Table XXV. 111. Table XXVI. 1 12. Table XXVII. 1 13. Table XXVIII. 1 14. Table XXIXa. 129. Table XXIXb. 130. Table XXX. 131. Table XXXI, XXXII. 132. Table XXXIII, XXXIV. 133. Table XXXV, XXXVI. 134. Table XXXVII, XXXVIII. 135.

(12) LIST O F FIGURES. xi. Figure 1. 44. Figure 2. 45. Figure 3. 60. Figure 4a. 61. Figure 4b. 62. Figure 5. 63. Figure 6. 64. Figure 7. 65. Figure 8. 66. Figure 9a. 67. Figure 9b. 68. Figure l Oa. 69. Figure l Ob. 70. Figure 1 1. 71. Figure 1 2. 72. Figure 1 3. 73. Figure 1 4a. 74. Figure 1 4b. 75. Figure 1 5. 87. Figure 1 6. 97. Figure 1 7. 98. Figure 1 8. 99. Figure 1 9. 1 00. Figure 20. 101. Figure 2 1. 1 02. Figure 22. 1 03. Figure 23. 1 04. Figure 24. 1 05. Figure 25. 1 06. Figure 26. 1 15. Figure 27. 1 16. Figure 28a,28b. 1 20. Figure 29a. 121.

(13) xii. Figure 29b. 122. Figure 30a. 136. Figure 30b. 131. Figure 3 0c. 138. Figure 3 1 a. 139. Figure 3 1b. 140. Figure 3 1c. 141. Figure 32a. 1 42. Figure 32b. 143.

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