摘要:

In a previous work, pinealectomy was found to depress benzodiazepine (BZP) receptor binding in cerebral cortex membranes of rats killed at noon. In order to assess the effect of pineal removal on diurnal variations of BZP binding site concentration and affinity, groups of intact, pinealectomized, or sham‐ pinealectomized rats (subjected to surgery 2 wk earlier) were killed at six different time intervals during the 24‐h cycle. BZP binding was assessed by Scatchard analysis of3H‐flunitrazepam high‐affinity binding to cerebral cortex membranes. In intact and sham‐pinealectomized rats, a maximum in BZP receptor concentration was found at midnight. Pinealectomy blunted the nocturnal peak of receptor concentration and caused a significant depression of binding site number at noon. No changes in the affinity of the binding sites for the radioligand were detected as a function of time of day or following surgery. In a doseresponse experiment for melatonin ability to restore the depressed BZP receptor concentration of cerebral cortex membranes of pinealectomized rats killed at noon, a minimal effective dose of 25 μg/kg body weight was obtained. These results further support a link between pineal activity and brain BZP recepto

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1986.tb00732.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

The surface area and luminal structures of the pineal sac were studied during the prespawning, spawning, and postspawning phases of control and gonadectomized fish,Mystus vittatus, throughout the year. From the later half of prespawning to the first half of postspawning phases the values for the surface area were lower in the gonadectomized group whereas from the later half of the postspawning to the first half of prespawning phases the values were higher than in the control group. The acidophilic cell bodies were visible in the first half of prespawning and at the end of spawning phases as well as during the postspawning phase. In the control group sulfated acid mucopolysaccharides and mucoid basophils with gamma substances were faintly stained during the early months of the reproductive cycle in contrast to the experimental group; but in the later months these substances were strongly stained in both groups except in the gonadectomized group at the end of postspawning phase. The pineal lumen was narrow during the pre‐ and postspawning phases and wider in the spawning phase of the gonadectomized group in comparison to control; this may be related to the flow of cerebrospinal fluid. Thus, the morphohistochemical changes in the pineal organ of fish were evident in both groups during the prespawning, spawning, and postspawning phase

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1986.tb00733.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

The circadian plasma melatonin profile of a marsupial, the tammar, was determined at various stages of the annual reproductive cycle. At 6–14 days after each of the solstices and equinoxes, six females were exposed to a photoperiod equivalent to the natural day length at these times. Serial blood samples were taken 8 days later at 2–4‐hourly intervals, and plasma melatonin concentrations were measured by radioimmunoassay. Melatonin concentrations were elevated during the dark phase of each photoperiod, and there were significant changes between the profiles in each season. The amplitude of the nocturnal rise was significantly higher (P<0.05) during the breeding season after the summer solstice (peak 259.5 ± 26.8 pg/ml, mean ± SEM) and autumnal equinox (287 ± 53.2 pg/ml) compared to those during the nonbreeding season after the winter solstice (111.5 ± 10.5 pg/ml) and vernal equinox (154.5 ± 10.4 pg/ml). The duration of the nocturnal rise was significantly correlated (r=0.996,P<0.01) with the length of the dark phase and so was shortest after the summer solstice and longest after the winter solstice. Either of these changes in amplitude or duration might provide the photoperiodic information that regulates the annual reproductive cycle of

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1986.tb00734.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

Blood was collected over a 24‐h period from free‐living adult Weddell seals that had been exposed to natural constant daylight for some 12 weeks. The plasma melatonin concentration was low throughout the trial (range of means: 30.8–70.4 pg/ml) with the exception of a 3‐h period centered on 1700 h local time, when the plasma level rose to a mean of 131.8 pg/ml. The pineal gland of the Weddell seal is thus capable of transient bouts of activity during constant and bright daylight, a situation usually inhibitory to the function of the gland. It is suggested that circadian fluctuations in the intensity of constant light entrain variation in the pineal gland functioning of this seal during

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1986.tb00735.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

Melatonin and 5‐methoxytryptamine were administered continuously over a period of 1–3 months to adult male rats by means of subcutaneously implanted silastic capsules containing one or the other of these pineal hormones. Polygraphic recordings during several weeks following hormonal application showed an increase in the amount of time spent in both quier and rapid eye movement sleep, during the light as well as the dark period; however, diurnal sleep‐wake rhythmicity was not affected by either treatment. We conclude that pineal hormones have sleep‐promoting effects, but that their correlation with the lightdark cycle does not imply that they are causal factors in generating diurnal rhythms of sleep and wake

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1986.tb00736.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

This study aimed to determine the extraretinal effects of melatonin upon the eyes of an avian species, the House Finch (Carpodacus mexicanus). Twelve birds (full‐grown, second‐year males) each received a Silastic tubing intraperitoneal implant, six containing melatonin (average release = 24μg/d/bird; = M birds) and six being empty (= C birds). Microscopic study of pupillary and palpebral behaviors during the final week demonstrated lesser pupillary diameters and interpalpebral distances in M birds under all test conditions. These effects could have diminished mean light levels reaching parts of the retina. Characteristics of the relative miosis and ptosis of M birds resemble signs in some CNS disorders, such as altered inhibition of the Edinger‐Westphal nucleus, and especially lesions in, or lowered activity of, higher sympathetic centers (a subtype of Horner's syndrome). Weights of eyes and their parts were the same in M and C birds, contrasting with previously reported results from male Golden Hamsters, possibly due to species differences and/or preexperimental attainment of full growth in the finches. Effects of melatonin on pupillary and palpebral behaviors, demonstrated here for the first time, foster caveats for simplistic experimental designs and interpretations with melatonin when sensory‐neural‐behavioral interactions are affected. Quantitative changes in pupillary and palpebral behaviors may, nevertheless, provide a window for monitoring central actions of melatonin in living test subjects in chron

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1986.tb00737.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

We have examined the nocturnal increase in pineal serotonin N‐acetyltransferase (SNAT) activity in the rat and the decrease in activity of this enzyme as a result of exposure of the rats to light during the nocturnal period. In females with normal ovulatory cycles and ovariectomized females, levels of the enzyme were similar during the dark (695 ± 70 pmol/min/gland vs. 590 ± 68) or after 20 min of lights on at night (107 ± 5 vs. 105 ± 8). Carbachol, a cholinergic agonist, was injected at 2400 hr (EST) into the lateral ventricle of orbitally enucleated rats. The agonist simulated the lights on effect in both intact and ovariectomized rats. Highly purified fractions of α‐bungarotoxin, a nicotinic cholinergic antagonist were injected into either the third ventricle or bilaterally adjacent to the SCN in intact females, intact males, or ovariectomized rats. These injections had no effect on either the nighttime increase or the lights on inhibition of SNAT. This study makes the following observations: 1) As was previously demonstrated [Illnerova, H. Endocrinol. Exp. 9:141–148, 1975], ovariectomy affects neither the daytime (light period) nor nighttime (dark period) activity of pineal SNAT. This study extends previous work by demonstrating that ovariectomy also has no effect on the lights on at night decrease of SNAT activity. 2) This study confirms that intraventricular infusion of carbachol decreases the nocturnal pineal SNAT activity [Zatz, M., and Brownstein, M. J. Brain Res. 213: 438–442, 1981]. 3) This study does not confirm the report that the nicotinic cholinergic antagonist α‐bungarotoxin prevents the loss of nocturnal SNAT activity induced by turning lights on at night [Zatz, M., and Brownstein, M. J. Brain Res. 213:

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1986.tb00738.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

Subcutaneous implantation of melatonin for a period of 12 weeks with reinforcement of implants every fortnight had no significant influence on photoinduced gonadal development in the pigeon. Neither the weight of the gonads or the oviduct nor the gonadal size was affected by melatonin. Pinealectomy also was found to have no significant influence on gonadal weight when examined 20 weeks after the surgery.The plasma levels of luteinizing hormone and testosterone were not significantly influenced by a 10‐week implantation of melatonin, although a trend toward an increase (statistically insignificant) in testosterone concentration was apparent in melatonin‐implanted male pigeons. Plasma concentration of estradiol was found to increase significantly in both male and female pigeons following the 10‐week melatonin implantation. A trend toward an increase in plasma corticosterone level was also apparent in these melatonin‐implanted birds, but the increase was statistically insign

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1986.tb00739.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

The effect of anticonvulsant drugs on daytime and nighttime N‐acetyltransferase (NAT) and hydroxyindole‐O‐methyltransferase (HIOMT) levels was investigated. Some of the drugs caused a significant reduction in daytime NAT and HIOMT levels, possibly owing to beta‐receptor blockade although other mechanisms cannot be excluded. Sulthiame caused an increase in daytime NAT levels, and this may represent a compensatory mechanism by the pineal gland to allow normal melatonin production. None of the drugs affected nocturnal HIOMT levels, and only phenobarbitone affected NAT levels, apparently causing a shift in the nocturnal peak later in the dar

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1986.tb00740.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

Single biweekly injections of melatonin were administered to lizards (Sceloporus occidentalis) free‐running (exhibiting their endogenous circadian activity rhythm) in constant dim illumination. The injections caused phase shifts in the activity rhythm whose magnitude and direction were a function of the time of the melatonin injections, relative to activity onsets. Plotting the direction and amount of phase shift versus the time (phase) at which the injection was given generates a phase‐response curve (PRC). The PRC shows that injections administered between midsubjective day and early subjective night (6–15 hr after activity onset) elicit phase advances in the activity rhythm, whereas injections given at other phases of the activity cycle induce phase delays. The existence of a PRC for melatonin suggests that the daily endogenous rhythm of melatonin (i. e., of pineal origin) may be involved in phasing, or entraining, the circadian system of lizards. The shape of the PRC also allows predictions as to the effects of continuous exogenous melatonin administration on the period of free‐running activity rhythms as well as on the mechanism of entrainment of activity rhythms to daily melatonin inj

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1986.tb00741.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY