Chronoendocrinology of Vertebrates

Meier, Albert

doi:10.1007/978-1-4613-4467-4_3

Cited by 25 publications

(12 citation statements)

References 233 publications

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“…In addition, it is possible that these differences, as well as differences in liver, testis and body weight responses to prolactin, are due to the fact that the prolactin injection schedule did not adequately mimic the naturally occurring pattern of prolactin release which takes place during incubation. Differences in timing of prolactin injections or endogenous prolactin release may play an important role in determining the type and magnitude of the effects of prolactin (see Meier, 1975). Thus, daily injections of prolactin late in the day (9 h after 'lights on' in a 12 h light : 12 h darkness cycle) promote crop sac growth in pigeons to a greater degree than injections at any other time (Meier & McGregor, 1972), while injections early in the day optimally promote hepatic and abdominal fat deposition (Meier, Burns, Davis & John, 1971 ).…”

Section: Discussionmentioning

confidence: 99%

Behavioural and physiological effects of prolactin in incubating ring doves

Janik¹,

Buntin²

1985

Journal of Endocrinology

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The role of prolactin in the maintenance of incubation behaviour in ring doves was re-examined and the dose-response relationships for behavioural, target tissue and body weight changes induced by injections of prolactin were compared in doves tested during the incubation phase of the breeding cycle. Doves given injections of prolactin twice a day starting on day 4 of incubation, during a 10-day period of isolation from their mates and nests, showed a higher persistence of incubation behaviour than doves injected with saline vehicle. However, the prolactin treatment failed to maintain incubation behaviour to the same extent as that observed in non-isolated untreated breeding pairs. Liver and body weights were higher and testicular weights lower in birds treated with high doses of prolactin than in non-isolated birds which had been incubating for 14 days. Good dose-response relationships were established between body, liver, crop and testes weights and the dose of prolactin administered. However, only a weak dose-response relationship was observed between prolactin and the maintenance of incubation behaviour. Overall, females injected with prolactin displayed more quiet sitting behaviour, less body weight gain and more gonadal regression than males injected with prolactin. Males in untreated breeding pairs had higher liver weights and lower crop weights than females. It is concluded that prolactin plays a role in maintaining readiness to incubate in doves, but that other factors may also contribute to this response. Further, it appears that prolactin mediates several target tissue changes which are sex-specific during incubation.

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Section: Discussionmentioning

confidence: 99%

Behavioural and physiological effects of prolactin in incubating ring doves

Janik¹,

Buntin²

1985

Journal of Endocrinology

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“…Specific phase relations between hormones are often crucial in determining the magnitude and direction of the effect obtained [18]. The pi neal gland of hamsters responds to short days by releasing melatonin in a new phase relation to the light-dark cycle, rather than with quantitative changes in melatonin secre tion [33].…”

Section: Discussionmentioning

confidence: 99%

Photoperiodic Control of Reproduction in Olfactory-Bulbectomized Rats

Nelson¹,

Zucker²

1981

Neuroendocrinology

101

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30-day-old male rats were (1) sham-operated or subjected to (2) removal of the olfactory bulbs, (3) olfactory bulbectomy and blinding, (4) olfactory bulbectomy and pinealectomy or (5) olfactory bulbectomy, blinding and pinealectomy. Animals were exposed from 30 to 110 days of age to long-day (14 h of light per day) or short-day (8 h of light per day) photoperiods. The reproductive system of neurologically-intact rats was not affected by exposure to short days. Nor did bulbectomy affect the reproductive system of rats exposed to long days. However, bulbectomized, short-day rats had significantly lower body weights, reduced testicular and seminal vesicle weights and lower plasma testosterone levels than did bulbectomized, long-day rats. The effects of short-day exposure on bulbectomized rats were prevented by pinealectomy. Short-day exposure and blinding exerted similar effects in bulbectomized rats. The testes of rats from all groups contained elongated spermatids; blinding and short-day treatment had no effect on spermatogenesis. Neither mating behavior nor the number of young sired was influenced by photoperiod in bulbectomized or intact rats. Removal of the olfactory bulbs unmasks photoperiodic responsiveness in rats; the antigonadal effects of short-day exposure are mediated by the pineal gland in bulbectomized rats as in species traditionally designated photoperiodic. The mechanisms by which bulbectomy renders rats responsive to short days are considered.

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“…* Student's (-test, two-tailed. (Meier, 1975;Meier & Burns, 1976), little is known about the mechanisms by which these prolactin influences manifest themselves. In general the overall rates of metabolic pathways may be altered by short-term control of enzymic activity (i.e.…”

Section: Resultsmentioning

confidence: 97%

“…The responses to prolactin injections vary depending upon the time of injection relative to the daily light : darkness cycle. Prolactin injections at some times produce large increases in fat stores whereas at other times they may decrease fat stores or have no effect (review, Meier, 1975;Meier & Burns, 1976). In the Gulf killifish, Fundulus grandis, daily injections of prolactin at the onset of light cause losses in fat stores and injections 8 h after the onset of light (hours of light (L) : hours of darkness (D); 8L : 16D, 12L : 12D and 16L : 8D) stimu¬ late large increases in both liver and carcass fat (Joseph & Meier, 1971).…”

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confidence: 99%

Circadian Phase-Dependent Prolactin Mechanisms in Hepatic Lipogenesis of a Teleost

Horseman¹,

Meier²

1979

Journal of Endocrinology

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In the teleost, Fundulus grandis, injections of prolactin early in the light phase cause an immediate 50% depression in the rate of hepatic lipogenesis ([14C]acetate incorporation); 10 h later, that rate has returned to levels not different from controls. Injections of prolactin late in the light phase cause an even more dramatic immediate depression of lipogenesis (79%) followed by a gradual increase in lipogenic rate which is 2.6 times higher than the control rate after 24 h. The stimulation of lipogenesis by prolactin is blocked by simultaneous treatment with indomethacin, an inhibitor of prostaglandin synthesis. These circadian phase-dependent effects of prolactin on hepatic lipogenesis are discussed with reference to possible mechanisms of action exerted by endogenous prolactin rhythms.

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Chronoendocrinology of Vertebrates

Cited by 25 publications

References 233 publications

Behavioural and physiological effects of prolactin in incubating ring doves

Behavioural and physiological effects of prolactin in incubating ring doves

Photoperiodic Control of Reproduction in Olfactory-Bulbectomized Rats

Circadian Phase-Dependent Prolactin Mechanisms in Hepatic Lipogenesis of a Teleost

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