摘要:

Abstract:Early studies on the physiological effects of melatonin typically reported hypnotic ‘side‐effects’. Later studies, specifically addressing this action, failed to reliably replicate hypnotic effects using standard polysomnography. This difference may be related to differences in the basic physiological action of melatonin compared with more conventional hypnotics. It is suggested that melatonin exerts a hypnotic effect through thermoregulatory mechanisms. By lowering core body temperature, melatonin reduces arousal and increases sleep‐propensity. Thus, in humans, one role of melatonin is to transduce the light‐dark cycle and define a window‐of‐opportunity in which sleep‐propensity is enhanced. As such, melatonin is likely to be an effective hypnotic agent for sleep disruption associated with elevated temperature due to low circulating melatonin levels. The combined circadian and hypnotic effects of melatonin suggest a synergistic action in the treatment of sleep disorders related to the inappropriate timing of sleep and wakefulness. Adjuvant melatonin may also improve sleep disruption caused by drugs known to alter normal melatonin production (e.g., β‐blockers and benzodiazepines). If melatonin is to be developed as a successful clinical treatment, differences between the pharmacological profile following exogenous administration and the normal endogenous rhythm should be minimized. Continued development as a useful clinical tool requires control of both the amplitude and duration of the exogenous melatonin pulse. There is a need to develop novel drug delivery systems that can reliably produce a square‐wave pulse of melatonin at physiological levels

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1993.tb00503.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Abstract:The expression of glial antigens vimentin (VIM) and glial fibrillary acidic protein (GFAP) is described in the pineal gland of cats and dogs from the first postnatal days to adulthood. VIM immunopositive cells were observed from the first postnatal days in both species. GFAP expression starts from the second postnatal week. In adults, a notable population of stellate cells immunopositive for GFAP and VIM was found dispersed throughout the gland. According to their immunocytochemical profile, these cells could be identified as astrocytes.

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1993.tb00504.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Abstract:Salivary melatonin levels were measured in 12 healthy volunteers in order to determine whether a moderate light intensity, which suppresses the nocturnal rise of melatonin, was able to shift the melatonin rhythm. The samples were collected at 1‐hr intervals under lighting of<100 lux (experiment 1) or<10 lux (experiment 2). The control melatonin profiles were determined during the first night. In the second night the subjects were exposed to light of 500 lux for 60 min during the rising phase of melatonin synthesis. The third series of samples was collected during the third night. The mean decrease of melatonin levels by the exposure to light was 56% of the prelight concentrations. The melatonin onset times were delayed significantly (about 30 min) the night after the exposure to light. The melatonin offset times tended to be delayed in experiment 2. The shifts of the melatonin offset correlated positively with the amount of the melatonin suppression. The results suggest that a relatively small and short lasting light‐induced interruption of melatonin synthesis may affect the melatonin rhythm in hum

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1993.tb00505.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Abstract:The effects of surgical pinealectomy and plane of nutrition on wool growth and plasma prolactin concentrations in young Merino wethers were investigated. In young pinealectomized wethers maintained at a low live weight under conditions of minimal stress, the decline of conditioned clean wool production on midside patches was slowed when compared to pineal‐intact controls. This difference appeared to be due in part to the observed greater secondary wool follicle density in the pinealectomized wethers; mean fiber diameter was affected to a smaller extent, while staple length growth rate was not significantly altered. Circulating prolactin profiles showed a seasonal variation (high in summer, low in winter) in both pinealectomized and control wethers. There was no difference in wool production between pinealectomized and control wethers when the diet of the same wethers was subsequently supplemented with formaldehyde‐treated cottonseed meal. While the role of melatonin in the regulation of wool growth remains to be determined, it is suggested that the hormone may have a transient effect on wool production in young wethers under conditions of limited nutrition, but not at higher nutritional levels, and that melatonin may be involved in partitioning of nutrients to the wool folli

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1993.tb00506.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Abstract:Relative activities of hydroxyindole‐O‐methyltransferase (HIOMT) of some brain and ocular structures of the rabbit and hen were analyzed using different 5‐hydroxyindoles, i.e., N‐acetylserotonin (NAS), 5‐hydroxytryptophol (HTOL), 5‐hydroxytryptophan (HTP), 5‐hydroxytryptamine (HT), and 5‐hydroxy‐3‐indoleacetic acid (HIAA), as enzyme substrates. Pineal glands of both species, as well as hen retina, are capable of producing, to varying degrees, melatonin, 5‐methoxytryptophol, and 5‐methoxytryptamine. Hen choroid and iris‐ciliary body O‐methylated NAS and HTOL, whereas rabbit choroid and, to a much lesser extent, hypothalamus and cerebral cortex all O‐methylated only NAS. No measurable HIOMT activity was found in hen brain. NAS was a preferred substrate for HIOMT in the hen tissues, whereas in the rabbit pineal gland NAS and HTOL were equally good substrates for HIOMT. Other tested 5‐hydroxyindoles, i.e., HTP, HT, and HIAA, were poor methyl acceptors. Of the tissues examined, the highest HIOMT activity was found in the hen pineal gland, followed by the rabbit pineal gland and hen retina. No significant differences between day and nighttime enzyme activities were observed in the pineal gland and retina of either species. The data suggest that in vertebrates some nervous and ocular tissues possess the potential to produce 5‐methoxyindole compounds; however, the HIOMT‐catalyzed process shows remarkable substrate, tiss

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1993.tb00507.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Abstract:The expression of somatostatin mRNA was investigated in rat pineal cells after 1 week in culture, using reverse transcription of mRNA into cDNA and the polymerase chain reaction. The positive expression in cultured pineal cells demonstrates the capacity of this gland to synthesize somatostatin in denervated cells. Thus, apart from the neural origin of pineal somatostatin, which has been described in detail in the bovine species, a parenchymal source is demonstrated.

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1993.tb00508.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Abstract:The connection between the suprachiasmatic nucleus (SCN) and the paraventricular nucleus of the hypothalamus (PVN) forms an important component of the melatonin rhythm‐generating system. However, the chemical identity of this projection is not known. To test the possible implication of the SCN peptides vasopressin (VP) and vasoactive intestinal peptide (VIP) in this projection, we performed microinfusions in the PVN during the first half of the dark period and subsequently monitored resulting plasma melatonin levels. Infusions for 7 hr of either VP or VIP, but not oxytocin, caused increased plasma melatonin levels in the middle of the dark period. These observations confirm the role of the PVN in the melatonin rhythm‐generating pathway and indicate that both VP and VIP released at the level of the PVN, and probably derived from the SCN, are able to influence peripheral plasma melatonin lev

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1993.tb00509.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Abstract:An immunohistochemical study of the bovine pineal gland was performed using rabbit polyclonal antibodies raised against neuropeptide Y (NPY) or against the C‐terminal flanking peptide of proNPY (CPON). A large number of NPY/CPON‐immunoreactive (IR) nerve fibers were demonstrated throughout bovine pineal gland. The IR‐fibers were located in the capsule of the gland, usually piercing into the gland together with blood vessels. In the gland itself, the fibers wen also located intraparenchymally between the pinealocytes. Within the rostral and caudal areas of the pineal stalk, NPY‐IR fibers were also observed, and these fibers could be followed not only into the gland bul also to the habenular and posterior commissures. The morphological localization of the NPY‐IR nerve fibers in the bovine pineal gland indicate that the majority of fibers originate from the superior cervical ganglion. However, some fibers probably originate from the bra

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1993.tb00510.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY