Effects of melatonin and a dopamine agonist and antagonist on seasonal changes in voluntary intake, reproductive activity and plasma concentrations of prolactin and tri-iodothyronine in red deer hinds

1990 ◽  
Vol 125 (2) ◽  
pp. 241-249 ◽  
Author(s):  
J. A. Milne ◽  
A. S. I. Loudon ◽  
A. M. Sibbald ◽  
J. D. Curlewis ◽  
A. S. McNeilly
Keyword(s):  
Dopamine Agonist ◽  
Breeding Season ◽  
Red Deer ◽  
Plasma Concentrations ◽  
Control Group ◽  
Rapid Decline ◽  
Dopamine Antagonist ◽  
Plasma Prolactin ◽  
Melatonin Treatment ◽  
The Mean

ABSTRACT Three experiments were conducted in the period between July and November with non-lactating red deer hinds to describe the effects of treatment with melatonin during this period on voluntary food intake (VFI), the onset of the breeding season, coat changes and plasma concentrations of prolactin and tri-iodothyronine (T3), and to examine whether prolactin mediated the observed effects. In experiment 1, eight animals were treated orally each day with either 10 mg melatonin at 16.00 h or 10 mg melatonin at 16.00 h plus 10 mg domperidone (a dopamine antagonist) given twice daily for 120 days from July; eight animals were maintained as controls. In experiment 2, the same numbers of animals per treatment were used to compare treatments in which 10 mg melatonin or 20 mg bromocriptine (a dopamine agonist) were given orally each day at 16.00 h for 119 days from late June and compared with an untreated control group. In experiment 3, six animals were treated daily for 105 days from mid August with 5 mg domperidone given i.m. and compared with six control animals. In experiments 1 and 2, the VFI of control animals reached a peak in late August and thereafter declined. Melatonin-treated animals showed a similar pattern but the peak in VFI was significantly (P<0·05) advanced by 2 weeks compared with controls, although the VFIs of both groups were similar in November. The mean date of onset of the breeding season of the melatonin-treated animals was advanced significantly (P < 0·05) by 23 days in both experiments and the coats of these animals had less undercoat and were pale coloured and patchy compared with the controls. The changes in VFI, coat and the onset of the breeding season were associated with the rapid decline in plasma prolactin concentration after the start of the melatonin treatment and significantly (P<0·01) lower plasma T3 concentrations than those of control animals. In experiments 1 and 3, plasma prolactin concentrations in animals treated with domperidone were higher than those of controls for periods of 2–3 weeks. These short-term increases in plasma prolactin concentration were not associated with changes in VFI, coat or onset of the breeding season compared with controls. In experiment 2, the pattern of decline in plasma prolactin concentrations was the same in bromocriptine-treated animals as in the melatonin-treated animals; plasma T3 concentrations were also similar in the two groups. The pattern of change in VFI over time in bromocriptine-treated animals was significantly (P<0·05) different from that of melatonin-treated animals and there was also a reduced amount and length of winter coat in the bromocriptine-treated animals. The mean date of onset of the breeding season in bromocriptine-treated animals was not significantly different from that of controls. It was concluded that a reduction in plasma prolactin concentration induced by bromocriptine produced different effects from that induced by melatonin treatment and that the effects of melatonin are unlikely to be induced through changes in contemporary plasma prolactin concentrations. Journal of Endocrinology (1990) 125, 241–249

EFFECT OF LOW ZINC INTAKE DURING PREGNANCY ON PLASMA PROLACTIN, PROGESTERONE, PROSTAGLANDIN, CORTISOL AND PROTEIN CONCENTRATIONS OF EWES DURING THE PERIPARTURIENT PERIOD

1986 ◽  
Vol 66 (3) ◽  
pp. 643-651 ◽  
Author(s):  
J. A. FITZGERALD ◽  
G. A. EVERETT ◽  
J. APGAR
Keyword(s):  
Plasma Concentrations ◽  
Normal Pregnancy ◽  
Late Gestation ◽  
Plasma Prolactin ◽  
Plasma Parameters ◽  
Zinc Intake ◽  
Periparturient Period ◽  
Prostaglandin F ◽  
The Mean ◽  
Pregnant Ewe

The effect of low dietary Zn intake upon several plasma endocrine and metabolic profiles was examined during late gestation in the ewe. Thirty adult, primiparous Finncross ewes were fed a low Zn diet with (+Zn, n = 14) or without (0Zn, n = 16) supplemental Zn in the drinking water starting day 1 of pregnancy. Although the mean prepartum progesterone and prolactin concentrations were lower (P < 0.05 and P < 0.01, respectively) in 0Zn than in +Zn ewes, the peak prolactin concentrations in 0Zn ewes at lambing were similar to +Zn ewes. Both basal and thyrotropin-releasing-hormone (TRH)-induced prolactin release were less (P < 0.01) in 0Zn ewes 2 d postpartum. Plasma concentrations of 13, 14-dihydro-15-keto prostaglandin F2α (PGFM) of ewes sampled within 45 min post-lambing were lower (P < 0.05) in 0Zn ewes. There was no difference in cortisol concentrations within 45 min after lambing between 0Zn and + Zn ewes. Plasma protein concentrations in 0Zn ewes were higher (P < 0.01) than those in +Zn ewes during pregnancy. In summary, these data show that low Zn intake in the pregnant ewe affected several endocrine and metabolic plasma parameters associated with normal pregnancy and parturition. Key words: Zinc, parturition, dystocia, feed intake, ovine

Seasonal patterns of luteal cyclicity in young red deer (Cervus elaphus) and sambar deer (Cervus unicolor)

1997 ◽  
Vol 9 (6) ◽  
pp. 587 ◽  
Author(s):  
G. W. Asher ◽  
P. D. Muir ◽  
G. Semiadi ◽  
K. T. O'Neill ◽  
I. C. Scott ◽  
...  
Keyword(s):  
Cervus Elaphus ◽  
Red Deer ◽  
Prolactin Secretion ◽  
Seasonal Patterns ◽  
Plasma Prolactin ◽  
Reproductive Seasonality ◽  
Plasma Progesterone ◽  
The Mean ◽  
Sambar Deer ◽  
Cervus Unicolor

Seasonal onset of pubertal ovulation and incidence of luteal cyclicity was assessed from plasma progesterone proles over 15 months for tame red deer (n = 7) and sambar deer (n = 7) hinds. Seasonal responses to photoperiod were determined from plasma prolactin proles. All red deer attained puberty at 17-18 months of age in May-June and expressed 3-6 luteal cycles of length 20·0 ± 10·4 days (mean ± s.e.m.) over 52-102 days. Six sambar deer attained puberty at 7-19 months of age, between August and December. Duration of luteal cyclicity was variable. While one animal remained continuously cyclic for 13 months, most entered anoestrus between November and February. The mean length of the luteal cycle was 17·2 ± 0·3 days. While red deer exhibited strongly seasonal patterns of prolactin secretion, sambar deer showed no such seasonal trends. The data collectively indicate that young sambar hinds at temperate latitudes exhibit loosely dened patterns of reproductive seasonality that are 4-6 months out of phase with those of red deer, although some individuals may be non-seasonal. Failure to express seasonal patterns of prolactin secretion indicates that sambar deer may not perceive photoperiodic cues to the same extent as do red deer.

Increased teniposide clearance with concomitant anticonvulsant therapy.

1992 ◽  
Vol 10 (2) ◽  
pp. 311-315 ◽  
Author(s):  
D K Baker ◽  
M V Relling ◽  
C H Pui ◽  
M L Christensen ◽  
W E Evans ◽  
...  
Keyword(s):  
High Performance ◽  
Pediatric Patients ◽  
Plasma Concentrations ◽  
Substantial Reduction ◽  
Systemic Exposure ◽  
Pharmacokinetic Interaction ◽  
Lymphocytic Leukemia ◽  
Control Group ◽  
Systemic Clearance ◽  
The Mean

PURPOSE A possible pharmacokinetic interaction between teniposide and anticonvulsant medications was evaluated in pediatric patients. PATIENTS AND METHODS The systemic clearance of teniposide was determined in six pediatric patients with acute lymphocytic leukemia receiving concomitant therapy with anticonvulsants. Clearance was then compared with a control group of patients treated with the same protocol therapy and matched for age at diagnosis, sex, and race but not receiving anticonvulsants or other agents known to induce hepatic metabolism or alter protein binding of drugs. Eight blood samples were obtained during and after 4-hour infusions of teniposide, and plasma concentrations were measured by a specific high-performance liquid chromatography (HPLC) assay. A two-compartment model was fitted to each subject's data. RESULTS The mean systemic clearance (range) for the six anticonvulsant-treated patients studied during 22 courses of therapy was 32 mL/min/m2 (range, 21 to 54 mL/min/m2), significantly higher (P less than .001) than the mean value of 13 mL/min/m2 (range, 7 to 17 mL/min/m2) for the control patients studied during 26 courses of therapy. Clearance estimates for control patients were similar to previously published values for pediatric patients. CONCLUSION These data indicate that the systemic clearance of teniposide is consistently increased two- to three-fold by concomitant phenobarbital or phenytoin therapy. The consequent substantial reduction in systemic exposure may reduce teniposide's efficacy.

Effects of active immunization against LHRH and melatonin on growth and plasma hormone concentrations in red deer stags during their second year

1992 ◽  
Vol 118 (3) ◽  
pp. 371-377 ◽  
Author(s):  
A. M. Ataja ◽  
T. N. Barry ◽  
R. M. Hoskinson ◽  
P. R. Wilson
Keyword(s):  
Weight Loss ◽  
Luteinizing Hormone ◽  
Red Deer ◽  
Plasma Concentrations ◽  
Active Immunization ◽  
Plasma Prolactin ◽  
Luteinizing Hormone Releasing Hormone ◽  
Plasma Hormone ◽  
Second Year ◽  
Autumn And Winter

SUMMARYThe effects of immunization against luteinizing hormone releasing hormone (LHRH) and melatonin were studied during autumn and winter 1989 in yearling red deer stags initially aged 14 months and weighing 90–96 kg. Four out of five stags immunized against LHRH and six out of eight stags immunized against melatonin developed detectable levels of antibody titre. Immunization against LHRH reduced plasma LH concentration and both delayed and reduced weight loss associated with the rut (autumn); however, it had no effect upon carcass weight and dressing-out percentage was slightly lowered, showing that non-carcass components had been affected. Immunization against melatonin had no effect either on weight loss during the rut or on the rate of liveweight gain during winter and spring. Plasma concentrations of LH and testosterone were not affected by melatonin immunization; however, plasma prolactin concentration was consistently, but non-significantly, higher in immunized than control animals.

A note on the effect of melatonin feeding on the initiation of ovarian activity and on plasma prolactin levels in lactating and non-lactating red deer hinds

1985 ◽  
Vol 40 (3) ◽  
pp. 515-518 ◽  
Author(s):  
Rachel Nowak ◽  
R. N. Elmhirst ◽  
R. G. Rodway
Keyword(s):  
Detection Limit ◽  
Corpus Luteum ◽  
Red Deer ◽  
Inhibitory Effect ◽  
Ovarian Activity ◽  
Plasma Prolactin ◽  
Melatonin Treatment ◽  
Plasma Progesterone ◽  
Blood Samples

ABSTRACTMelatonin was fed daily at 14.00 h to eight non-lactating and six lactating hinds. Feeding was begun on 27 July 1983 (day 1) and continued until 21 September (day 57). Six non-lactating hinds were used as controls. Blood samples were taken about every 10 days from day 42 until day 73. Plasma progesterone and prolactin were determined by radioimmunoassay. Progesterone values of greater than 0·63 μg/1 were taken to indicate the presence of a corpus luteum and that the animal had ovulated. In the melatonintreated, non-lactating group seven of the eight hinds showed ovarian activity compared with two of the six controls (P < 0·01). None of the lactating hinds treated with melatonin showed evidence of ovarian activity. In both the lactating and non-lactating hinds treated with melatonin, prolactin levels were never greater than the detection limit of the assay (7·4 μg/l), while, in the control hinds mean prolactin levels were elevated on all but the last sampling day. It is, therefore, possible to induce early ovarian activity in non-lactating red deer hinds by feeding melatonin. However, although melatonin treatment similarly depressed plasma prolactin levels in both lactating and non-lactating hinds, it was unable to overcome the inhibitory effect of lactation on reproduction.

A comparison of the seasonal hormone changes and patterns of growth, voluntary food intake and reproduction in juvenile and adult red deer (Cervus elaphus) and Père David's deer (Elaphurus davidianus) hinds

1989 ◽  
Vol 122 (3) ◽  
pp. 733-745 ◽  
Author(s):  
A. S. I. Loudon ◽  
J. A. Milne ◽  
J. D. Curlewis ◽  
A. S. McNeilly
Keyword(s):  
Food Intake ◽  
Breeding Season ◽  
Seasonal Changes ◽  
Red Deer ◽  
Species Differences ◽  
Energy Utilization ◽  
Significant Advance ◽  
Plasma Prolactin ◽  
Père David’S Deer ◽  
Voluntary Food Intake

ABSTRACT Non-domesticated seasonally breeding ungulates exhibit marked seasonal changes in metabolic rate, voluntary food intake (VFI), pelage growth and moult and hormone secretion. It is not known whether these seasonal rhythms are regulated by the same central processes which control the onset and termination of the breeding season. Here we compare two closely related deer species which have significantly different mating and calving seasons. Seasonal changes in VFI, liveweight, coat growth, plasma prolactin and tri-iodothyronine (T3), and the timing of the breeding season were examined over a 15-month period in six adult post-pubertal red and Père David's deer from January to April the following year. The timing of the seasonal changes in prolactin, T3, VFI and coat growth were all significantly advanced by 56, 23, 60 and 54 days respectively in the Père David's deer. The times of onset and termination of the breeding season of Père David's deer were also significantly advanced by 90 days, but in both species, the breeding season was of similar duration (160 ± 5 (s.e.m.) days). Changes in liveweight of adult red deer could be explained by changes in VFI rather than efficiency of utilization. This was not the case in Père David's deer and may indicate seasonal changes in the efficiency of energy utilization. In order to establish whether these species differences develop with age, we undertook a second study in which seasonal changes in VFI, growth, plasma prolactin concentrations and the timing of the onset of the breeding season were recorded for ten red deer and six Père David's deer from 6 to 18 months of age. Both species exhibited a similar decline in VFI in the first autumn of life. Subsequently, the Père David's deer exhibited an advance in the timing of the seasonal peak in VFI and prolactin (21 and 66 days respectively); puberty occurred 3 months earlier than in red deer. The earlier breeding season of the Père David's deer was associated with a significant advance in a range of seasonal endocrine and physiological parameters. These species differences may develop with age. Our data indicate that seasonal patterns of metabolism and growth may be closely linked to those mechanisms which also regulate the onset and termination of the breeding season. Journal of Endocrinology (1989) 122, 733–745

A neuroendocrine model for prolactin as the key mediator of seasonal breeding in birds under long- and short-day photoperiods

2003 ◽  
Vol 81 (4) ◽  
pp. 350-358 ◽  
Author(s):  
Peter J Sharp ◽  
Dominique Blache
Keyword(s):  
Breeding Season ◽  
Plasma Concentrations ◽  
Prolactin Secretion ◽  
Gonadotropin Releasing Hormone ◽  
Critical Threshold ◽  
Plasma Prolactin ◽  
Seasonal Breeding ◽  
Releasing Hormone ◽  
Short Day ◽  
Long Day

Seasonal breeding is associated with sequential increases in plasma luteinizing hormone (LH) and prolactin in the short-day breeding emu, and in long-day breeding birds that terminate breeding by the development of reproductive photorefractoriness. A model of the avian neuroendocrine photoperiodic reproductive response is proposed, incorporating a role for prolactin, to account for neuroendocrine mechanisms controlling both long- and short-day breeding. The breeding season terminates after circulating concentrations of prolactin increase above a critical threshold to depress gonadotropin releasing hormone (GnRH) neuronal and gonadotrope (LH) activity. Subsequently, photorefractoriness develops for prolactin secretion and for LH secretion, independently of high plasma prolactin. The breeding season in the emu is advanced compared with long-day breeders, because after photorefractiness for both LH and prolactin secretion is dissipated, plasma concentrations of both hormones increase to maximum values while days are still short.Key words: seasonal breeding, prolactin, gonadotropin releasing hormone, photorefactoriness.

Effect of various anaesthetics on resting plasma concentrations of luteinizing hormone, follicle-stimulating hormone and prolactin in ovariectomized ewes

1983 ◽  
Vol 98 (1) ◽  
pp. 79-89 ◽  
Author(s):  
I. J. Clarke ◽  
B. W. Doughton
Keyword(s):  
Seasonal Variation ◽  
Luteinizing Hormone ◽  
Breeding Season ◽  
Follicle Stimulating Hormone ◽  
Plasma Concentrations ◽  
Pulse Amplitude ◽  
Experimental Series ◽  
Plasma Prolactin ◽  
Pulsatile Secretion ◽  
Induction Of Anaesthesia

Effects of various anaesthetics on plasma LH, FSH and prolactin levels were studied in ovariectomized ewes. In the first experimental series, conducted between June and November (late breeding season, early anoestrous season), the following treatments were given: saline (i.v.) (n = 7); single thiopentone injection (i.v.) (n = 4); induction of anaesthesia for 2 h with thiopentone (n = 5), ketamine/thiopentone mixture (n = 6), Alphathesin (n = 6) or induction with thiopentone and maintenance with halothane (n = 6). The major findings were: (1) halothane anaesthesia reduced mean plasma LH levels by preventing pulsatile secretion of LH; (2) Alphathesin had the least effect on tonic LH concentration; (3) a single thiopentone injection did not affect LH levels; (4) continuous thiopentone anaesthesia increased LH pulse amplitude; (5) plasma FSH concentration was not affected by any of the treatments; (6) ketamine/thiopentone-induced and Alphathesin-induced anaesthesia increased plasma prolactin levels. In a second experimental series four ovariectomized ewes were anaesthetized with thiopentone for 3 h in January. In contrast to the results obtained with thiopentone in August, treatment in January reduced plasma LH pulse amplitude and mean plasma LH levels. These latter results support the hypothesis that there may be seasonal variation in responses to barbiturate anaesthesia.

Emergence of the diurnal rhythm in plasma melatonin concentrations in newborn lambs delivered to intact or pinealectomized ewes

1990 ◽  
Vol 125 (1) ◽  
pp. 97-102 ◽  
Author(s):  
R. Nowak ◽  
I. R. Young ◽  
I. C. McMillen
Keyword(s):  
Diurnal Rhythm ◽  
Plasma Concentrations ◽  
Control Group ◽  
Dark Phase ◽  
Intact Control ◽  
Plasma Melatonin ◽  
Significant Difference ◽  
The Mean

ABSTRACT We have monitored the 24-h profiles of plasma melatonin concentrations between birth and 10 weeks of age, in lambs which were delivered to, and suckled, either pineal-intact (control group) or pinealectomized (pinealectomized group) ewes. Between 0 and 2 weeks of age, plasma concentrations of melatonin in lambs suckling either intact or pinealectomized ewes were highest at 01.00 h. At this age, however, there was no significant difference in the mean plasma concentrations of melatonin between the entire dark and light phases in lambs in either the control group (dark, 39·7 ± 6·0 (s.e.m.) pmol/l; light, 39·5 ± 8·1 pmol/l) or the pinealectomized group (dark, 79·8 ± 43·3 pmol/l; light, 60·9 ±8·7 pmol/l). Between 3 and 4 weeks of age, however, a diurnal rhythm in plasma melatonin concentrations was clearly present in the lambs in both the control and pinealectomized groups (control group: dark, 164·1 ± 5·6 pmol/l; light 26·2 ± 2·5 pmol/l; pinealectomized group: dark, 52·7± 8·0 pmol/l; light, 19·1 ± 5·3 pmol/l; P<0·001). Between 3 and 10 weeks of age, plasma concentrations of melatonin in the dark phase were significantly (P<0·05) lower in the lambs suckling pinealectomized ewes than in the control group. In both the control lambs and lambs suckling pinealectomized ewes, the mean plasma concentrations of melatonin in the dark and light phases increased significantly (P<0·05) between 3 and 6 weeks after birth. In conclusion, we have demonstrated that a clear diurnal plasma rhythm in melatonin concentrations does not emerge until 3–4 weeks of age in lambs suckling either pinealectomized or intact ewes. We have also measured lower melatonin concentrations during the dark phase in lambs suckling pinealectomized ewes when compared with lambs suckling pineal-intact ewes between 3 and 10 weeks of age. Journal of Endocrinology (1990) 125, 97–102

Evidence of altered dopaminergic modulation of Prl, LH and TSH secretion in patients with normoprolactinaemic amenorrhoea

1984 ◽  
Vol 106 (1) ◽  
pp. 8-14 ◽  
Author(s):  
Claus Hagen ◽  
Karsten Petersen ◽  
Henning Djursing ◽  
Anders Nyboe Andersen
Keyword(s):  
Plasma Concentrations ◽  
Ideal Body Weight ◽  
Control Group ◽  
Hormonal Changes ◽  
Tsh Secretion ◽  
Basal Plasma ◽  
Hormone Responses ◽  
The Mean ◽  
Normal Women ◽  
Plasma Prl

Abstract. Basal plasma concentrations of Prl, LH, FSH, GH, TSH, T3, T4, resin T3 uptake (RT3U), and oestradiol as well as hormone responses to iv metoclopramide (MTC) were investigated in 16 consecutive patients with normoprolactinaemic, normogonadotrophic amenorrhoea. The control group consisted of 17 normal menstruating women between day 3 and 6 of the menstrual cycle. The mean age of the amenorrhoeic patients was 24.0 years (range 19 to 34) and the mean duration of amenorrhoea was 31 months (range 12 to 60). Amenorrhoeic patients had significantly (P < 0.05) lower basal levels of LH, oestradiol and RT3U, whereas other hormone levels were similar in the two groups. Plasma Prl and TSH concentrations rose significantly (P < 0.05) after the administration of MTC in the two groups. A significant positive correlation (r = 0.69 P < 0.01) was found between the TSH response to MTC and basal TSH levels in controls, but not in amenorrhoeic patients. Plasma LH levels increased significantly (P < 0.05) in amenorrhoeic patients, but not in controls. The Prl and TSH responses to MTC were significantly (P < 0.001) lower in amenorrhoeic patients than in normal women. In amenorrhoeic patients none of the hormonal parameters correlated significantly (P > 0.05) with the percentage of ideal body weight. It is concluded that the hormonal changes in amenorrhoeic patients may in part be caused by a raised dopaminergic acvitity leading to a depression of central ovulatory mechanisms.

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