The influence of norepinephrine and the suckling stimulus on release of luteinizing hormone-releasing hormone from the bovine median eminence /
| Main Author: | |
|---|---|
| Other Authors: | , , |
| Format: | Thesis Book |
| Language: | English |
| Published: |
1988.
|
| Subjects: | |
| Online Access: | ProQuest, Abstract Link to OAKTrust copy |
| Abstract: | Studies were conducted to assess the influence of norepinephrine (NE), two of its agonists and the suckling stimulus upon the release of luteinizing hormone-releasing hormone (LHRH) from the bovine median eminence (ME). Utilizing an in vitro tissue culture perifusion system, ME collected from proestrous bovine females were challenged for 30 min at 130 and 220 min of perifusion with .5 (n=4) or 5 (n=11) mM concentrations of NE, methoxamine (MET, α1-agonist, n=5) or clonidine (CLO, α2-agonist, n=5). Determination of concentrations of LHRH in the culture media by radioimmunoassay (RIA) utilizing two validated antisera (AS-1 and AS-2) revealed that interpretation of the response to NE was dependent upon the AS utilized (P<.05). Release of LHRH in response to NE was suppressed (P<.05) when measured by AS-1 but not by AS-2. Challenges with MET resulted in increased (P<.05) release of LHRH as measured by AS-1 but not by AS-2. As measured by both AS, CLO stimulated (P<.01) the release of LHRH. Concentration of LHRH, during the 30-min challenge periods with both MET (P<.02) and CLO (P<.01), were consistently higher when measured by AS-1 than when measured by AS-2. These results dramatize the critical nature of AS in the evaluation of the release of LHRH in a culture system. The results are also consistent with the concept that an adrenergic mechanism is involved in the release of LHRH from the bovine ME. However, further studies are necessary to define the precise role of NE. The effect of suckling on depletion of LHRH from the ME following ovariectomy (OVX) was determined in postpartum (PP) dairy cows. Holstein cows were assigned to one of three treatment groups at calving: 1) intact, nonsuckled (INT, n=4), 2) OVX, nonsuckled (OVX, n=4) and 3) OVX, suckled by three calves (OVX-S, n=5). Plasma concentrations of luteinizing hormone (LH) in blood samples collected at 1 to 7 d prepartum, 3 to 5 d PP and 28 to 32 d post-ovx were different only at 28 to 32 d post-ovx when concentrations were higher (P<.05) in OVX cows than INT or OVX-S.. |
|---|---|
| Item Description: | Typescript (photocopy). Vita. "Major subject: Physiology of Reproduction." |
| Physical Description: | vii, 96 leaves : illustrations ; 29 cm |
| Bibliography: | Includes bibliographical references. |