摘要:

Experiments were designed to test the hypothesis that the pineal gland mediates the effects of changing day length and thereby synchronizes implantation within the population of spotted skunks. Intact, sham‐superior cervical ganglionectomized (SCGx), SCGx, and SCGx/bilateral orbitally enucleated (BI) pregnant skunks were subjected to a natural photoperiod, and the duration of the preimplantation period was monitored. In a second set of experiments, melatonin was administered to pregnant skunks via two methods to determine whether or not this pineal hormone would mimic the effects of short day photoperiods or B 1 on duration of the preimplantation period. Bilateral SCGx, which presumably denervated the pineal, had no effect on the average duration of the preimplantation period (232 ± 57 vs. 199 ± 6 days). However, SCGx reversed the inhibitory effect of B1 on implantation as SCGx/B1 animals had an average duration of the preimplantation period that was not significantly different from intact controls (262 ± 46 vs. 214 ± 11 days) but was significantly shortened in comparison to enucleated animals (262 ± 46 vs. 316 ± 45 days). Melatonin significantly lengthened the duration of the preimplantation period in animals receiving either daily afternoon injections of melatonin or those receiving melatonin Silastic capsule implants. These results are consistent with the hypothesis that the pineal gland synchronizes photoperiod‐induced blastocyst implantation in the western spot

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1986.tb00720.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

The usual nocturnal surge of pineal melatonin content was blocked by bilateral superior cervical ganglionectomy in male Syrian hamsters. Ganglionectomy and pinealectomy each prevented the nocturnal rise of serum melatonin concentration seen in control animals. The normal nocturnal surge of circulating inelatonin in this species appears to depend on the pineal gland and its sympathetic innervation.

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1986.tb00721.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

The nerve vesicles and synaptic ribbons were quantified in the cat pineal gland after electricl stimulation of the pineal sympathetic nerve fibers. It has been shown that the bilateral electrical stimulation of the preganglionic fibers innervating the superior cervical ganglia (SCG) markedly reduces the number of dense cores of small dark vesicles (SDV) and on the other hand modifies the number and shape of the large dark vesicles (LDV). An increase in the number of the synaptic ribbons after stimulation of the SCG supports the hypothesis that the numerical reduction of dense cores of nerve vesicles in the cat pineal gland influences the level of synaptic ribbon formation.

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1986.tb00722.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

Twelve adult Limousine rams (five pinealectomized, four sham operated, and three control) were housed under an artificial lighting regime of alternating periods of long (16L:8D) and short (8L:16D) days for 18 months, and long‐term variations in kemp follicle growth were recorded along with measurements of the plasma prolactin concentrations. In control 2nd sham‐operated rams, both parameters varied in relation to imposed lighting regime. Moult and growth of the kemp follicles occurred during each short‐day period at a time when the concentrations of prolactin were low and vice versa. Variations in the pinealectomized rams were different from those in the control or sham‐operated ones. There was no synchronous periodic kemp activity: some follicles remained active at all times, and the seasonal pattern of plasma prolactin levels disappeared. The relationship between the kemp follicle cycle and the pattern of plasma prolactin concentrations and its control by the pineal gland are di

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1986.tb00723.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

The purpose of this study was to examine the temporal effects of norepinephrine (NE) stimulation on pineal serotonin (5HT) in vitro. Rat pineal glands were individually incubated in nutrient media for 6 h. After a 2‐h preincubation, the glands were exposed to tryptophan (TRYP) or TRYP + norepinephrine (10−4M each) for 4 additional h. Media and pineals were then analyzed for 5HT and 5HIAA content. Initial exposure to TRYP increased 5HT levels in the media. Norepinephrine increased media 5HT concentrations further and also caused 5HIAA levels to rise significantly. These findings suggest that 5HT secretion and/or oxidation is an early response to stimulation of the pineal gland by NE. Following prolonged NE exposure, media 5HT declined to control values while 5HIAA remained high. Similarly, intrapineal levels of 5HT fell after prolonged stimulation with NE. Thus, pineal responses to initial and continued stimulation with NE are differentiable as early and late effects upon 5HT. Early effects may include secretion and/or oxidation of 5HT followed later by utilization of 5HT in N‐acetylation pathways such as that leading to melatonin synthesis. The finding that 5HT is secreted in response to NE suggests that the indoleamine may be a hormone of the pineal gland. Based upon its known influence on physiologic rhythms, daily secretion of 5HT from the pineal may be an important part of the gland's time‐keeping f

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1986.tb00724.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

A dose‐dependent increase in tone and reduction in amplitude of contractions was observed after serotonin (5‐HT) was administered to isolated segments of rat ileum, incubated in Locke's solution at 38°C. Melatonin (M) reduced the tone but not the amplitude or frequency of contractions. Addition of M (administered in doses 20 to 100 × higher than 5‐HT) relieved the spasm induced by 5‐HT. Furthermore, pretreatment with M significantly reduced the 5‐HT effect. N‐acetylserotonin (NAS) exhibited delayed but similar effects to M. Neither M nor NAS could prevent or relieve acetylcholine‐induced contractions or influence relief of intestinal contractions by adrenaline. This indicates that 5‐HT and M act via a different mechanism than that of adrenaline and acetycholine system. Serotonin muscle receptor blocker methysergide reduced 5‐HT effect but was not able to abolish it completely. As methysergide could not reduce the muscle tone and did not relieve spasm caused by 5‐HT, it is speculated that M is not acting as antagonist of 5‐HT‐ stimulatory receptors but rather as agonist of 5‐HT‐

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1986.tb00725.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

The effects of arginine vasotocin and the pineal indoles melatonin, serotonin, Nacetylserotonin, hydroxytryptophol, methoxytryptophol, hydroxyindoleacetic acid, methoxyindoleacetic acid, and methoxytryptamine on lipolysis and lipogenesis in isolated adipocytes were studied. Basal lipolysis was inhibited by all the indoles tested at a dose of I μmole except hydroxytryptophol. Methoxytryptamine and serotonin inhibited hormone‐induced lipolysis in a dosedependent manner and exhibited the highest antilipolytic activity in isolated rat, rabbit, and hamster adipocytes. However, their antilipolytic activity could not be overcome by increasing the dose of the lipolytic hormone. Dibutyryl cyclic AMP‐induced lipolysis was also inhibited. All the pineal indoles tested were capable of suppressing basal and insulin‐stimulated lipogenesis in the dose range 0.33–3 nmole. At lower doses there was no effect. Arginine vasotocin at a dose of 25 nmole significantly augmented basal lip

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1986.tb00726.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

Removal of the pineal gland produces stereotyped tonic convulsions in parathyroidectomized rats. Inasmuch as central levels of norepinephrine (NE) are decreased in these animals, the purpose of this study was to investigate the effects of alterations in central catecholamine function on convulsions produced by pinealectomy in parathyroidectomized rats. The treatment of rats with α‐methyl‐p‐tyrosine or FLA‐63 produced large reductions in forebrain levels of both NE and dopamine or NE alone, respectively, which were not associated with facilitation of convulsions. However, the incidence of convulsions was increased by FLA‐63 in rats pretreated with the catecholamine precursor L‐dihydroxyphenylalanine. Reserpine, a monoamine depleter, had no effect on either the incidence or severity of convulsions. An acute injection of desipramine, an inhibitor of the reuptake of NE, however, significantly lowered the incidence of convulsions. Timolol, a β‐adrenergic receptor antagonist, reduced, in a dose‐dependent manner, the average latency to onset of convulsions and increased the average number of convulsions each rat experienced. Clonidine, an α2‐adrenergic agonist, did not significantly alter convulsions. Thus presynaptic mechanisms such as synthesis and storage of both NE and DA appear to have little, if any, effect on pinealectomy‐induced convulsions, whereas enhancing synaptic levels of NE by blocking its reuptake into adrenergic axons had an anticonvulsant effect. Further evidence suggesting a role for NE in modulating these convulsions is provided by the proconvulsant effect of blocking central

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1986.tb00727.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

The effects of timed melatonin infusion on prolactin secretion were examined in the pineal denervated goat. Ovariectomized Shiba goats (n = 5) were subjected to bilateral superior cervical ganglionectomy (SCGX); this procedure resulted in complete abolition of endogenous melatonin release during the dark phase. SCGX goats failed to coordinate their prolactin secretion with the prevailing photoperiod. Melatonin was infused (20 μg/h, s. c.) daily into these goats either for 8 h (the long‐day‐type infusion) or for 16 h (the short‐day‐type infusion) to mimic the nocturnal profile of plasma melatonin under long days or short days, respectively. The long‐day‐type melatonin infusion for 9 days, in comparison with control saline infusion, accelerated prolactin secretion, inducing a nocturnal rise in plasma prolactin; this was comparable to that seen in the pineal intact goats under long photoperiods. On the other hand, the short‐day‐type melatonin infusion suppressed prolactin secretion throughout the day as the short‐day treatment did in intact goats. The prevailing photoperiod appeared to have no distinct effect on these prolactin responses to exogenous melatonin, which were indistinguishable under 16L8D and 8L16D conditions. The results indicate that the information about external light‐dark cycles is converted by the pineal gland into the endocrine signal as a daily pattern of melatonin secretion, which eventually regulates prolactin secretion from the pituita

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1986.tb00728.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

In order to elucidate further the role of sympathetic innervation for pineal function, the influence of sympathectomy on the spontaneous electrical activity of single cells in the pineal gland of adult male rats was investigated. Extracellular single‐unit recordings were made during nighttime in the pineal gland of urethane‐anesthetized, blinded adult male rats that had been treated neonatally with 6‐hydroxydopamine, or that were ganglionectomized either during, or 12–16 h or 36–40 h, prior to the recording experiment. These experiments revealed that the excitatory influence of the sympathetic system on pineal nocturnal electrical activity can be abolished by either chemical sympathectomy of neonatal rats or surgical superior cervical ganglionectomy in adul

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1986.tb00729.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY