Single-step genomic BLUP enables joint analysis of disconnected breeding programs: an example with Eucalyptus globulus Labill.

Single-step GBLUP (HBLUP) efficiently combines genomic, pedigree, and phenotypic information for holistic genetic analyses of disjunct breeding populations. We combined data from two independent multigenerational Eucalyptus globulus breeding populations to provide direct comparisons across the programs and indirect predictions in environments where pedigreed families had not been evaluated. Despite few known pedigree connections between the programs, genomic relationships provided the connectivity required to create a unified relationship matrix, H, which was used to compare pedigree-based and HBLUP models. Stem volume data from 48 sites spread across three regions of southern Australia and wood quality data across 20 sites provided comparisons of model accuracy. Genotyping proved valuable for correcting pedigree errors and HBLUP more precisely defines relationships within and among populations, with relationships among the genotyped individuals used to connect the pedigrees of the two programs. Cryptic relationships among the native range populations provided evidence of population structure and evidence of the origin of landrace populations. HBLUP across programs improved the prediction accuracy of parents and genotyped individuals and enabled breeding value predictions to be directly compared and inferred in regions where little to no testing has been undertaken. The impact of incorporating genetic groups in the estimation of H will further align traditional genetic evaluation pipelines with approaches that incorporate marker-derived relationships into prediction models.

Photoperiodic effects on seasonal physiology, reproductive status and hypothalamic gene expression in young male F344 rats.

Seasonal or photoperiodically sensitive animals respond to altered day length with changes in physiology (growth, food intake and reproductive status) and behaviour to adapt to predictable yearly changes in the climate. Typically, different species of hamsters, voles and sheep are the most studied animal models of photoperiodism. Although laboratory rats are generally considered nonphotoperiodic, one rat strain, the inbred Fischer 344 (F344) rat, has been shown to be sensitive to the length of daylight exposure by changing its physiological phenotype and reproductive status according to the season. The present study aimed to better understand the nature of the photoperiodic response in the F344 rat. We examined the effects of five different photoperiods on the physiological and neuroendocrine responses. Young male F344 rats were held under light schedules ranging from 8 h of light/day to 16 h of light/day, and then body weight, including fat and lean mass, food intake, testes weights and hypothalamic gene expression were compared. We found that rats held under photoperiods of ≥ 12 h of light/day showed increased growth and food intake relative to rats held under photoperiods of ≤ 10 h of light/day. Magnetic resonance imaging analysis confirmed that these changes were mainly the result of a change in lean body mass. The same pattern was evident for reproductive status, with higher paired testes weight in photoperiods of ≥ 12 h of light/day. Accompanying the changes in physiological status were major changes in hypothalamic thyroid hormone (Dio2 and Dio3), retinoic acid (Crabp1 and Stra6) and Wnt/ß-Catenin signalling genes (sFrp2 and Mfrp). Our data demonstrate that a photoperiod schedule of 12 h of light/day is interpreted as a stimulatory photoperiod by the neuroendocrine system of young male F344 rats.

Neuromedin U partly mimics thyroid-stimulating hormone and triggers Wnt/ß-catenin signalling in the photoperiodic response of F344 rats.

In seasonal animals, photoperiod exerts profound effects on physiology, such as growth, energy balance and reproduction, via changes in the neuroendocrine axes. A key element of the photoperiodic response is the thyroid hormone level in the hypothalamus, which is controlled via retrograde transport of thyroid-stimulating hormone (TSH) from the pars tuberalis of the pituitary. TSH regulates type II deiodinase (Dio2) expression, which transforms inactive thyroid hormone to its active form, via TSH receptors expressed in the ependymal cells of the hypothalamus. In the present study, we hypothesised that a second peptide hormone, neuromedin U (NMU), may play a role in the photoperiodic response alongside TSH because the gene for NMU is also expressed in a strongly photoperiod-dependent manner in the pars tuberalis and its receptor NMU2 is expressed in the ependymal layer of the third ventricle in photoperiod-sensitive F344 rats. Consistent with other studies conducted in nonseasonal mammals, we found that acute i.c.v. injections of NMU into the hypothalamus negatively regulated food intake and body weight and increased core body temperature in F344 rats. At the same time, NMU increased Dio2 mRNA expression in the ependymal region of the hypothalamus similar to the effects of TSH. These data suggest that NMU may affect acute and photoperiodically controlled energy balance through distinct pathways. We also showed that TSH inhibits the expression of type III deiodinase (Dio3) in F344 rats, a response not mimicked by NMU. Furthermore, NMU also increased the expression of genes from the Wnt/ß-catenin pathway within the ependymal layer of the third ventricle. This effect was not influenced by TSH. These data indicate that, although NMU acts with some similarities to TSH, it also has completely distinct signalling functions that do not overlap. In summary, the present study of NMU signalling reveals the potential for a new player in the control of seasonal biology.

Divergent regulation of hypothalamic neuropeptide Y and agouti-related protein by photoperiod in F344 rats with differential food intake and growth.

Hypothalamic genes involved in food intake and growth regulation were studied in F344 rats in response to photoperiod. Two sub-strains were identified: F344/NHsd (F344/N) and F344/NCrHsd (F344/NCr); sensitive and relatively insensitive to photoperiod respectively. In F344/N rats, marked, but opposite, changes in the genes for neuropeptide Y (NPY) (+97.5%) and agouti-related protein (AgRP) (-39.3%) expression in the arcuate nucleus were observed in response to short (8 : 16 h light/dark cycle, SD) relative to long (16 : 8 h light/dark cycle, LD) day photoperiods. Changes were associated with both reduced food intake and growth. Expression of the genes for cocaine and amphetamine-regulated transcript (CART) and pro-opiomelanocortin (POMC) in the arcuate nucleus was unchanged by photoperiod. POMC in the ependymal layer around the third ventricle was markedly inhibited by SD. Parallel decreases in the genes for growth hormone-releasing hormone (GHRH) and somatostatin (Somatostatin) mRNA in the arcuate nucleus and Somatostatin in the periventricular nucleus were observed in SD. Serum levels of insulin-like growth factor (IGF)-1 and insulin were lower in F344/N rats in SD, whereas neither leptin nor corticosterone levels were affected. By contrast, F344/NCr rats that show only minor food intake and growth rate changes showed minimal responses in these genes and hormones. Thus, NPY/AgRP neurones may be pivotal to the photoperiodic regulation of food intake and growth. Potentially, the SD increase in NPY expression may inhibit growth by decreasing GHRH and Somatostatin expression, whereas the decrease in AgRP expression probably leads to reduced food intake. The present study reveals an atypical and divergent regulation of NPY and AgRP, which may relate to their separate roles with respect to growth and food intake, respectively.

Photoperiod regulates genes encoding melanocortin 3 and serotonin receptors and secretogranins in the dorsomedial posterior arcuate of the Siberian hamster.

The mechanism(s) involved in the regulation of the seasonal-appropriate body weight of the Siberian hamster are currently unknown. We have identified photoperiodically regulated genes including VGF in a sub-region of the arcuate nucleus termed the dorsomedial posterior arcuate (dmpARC). Gene expression changes in this nucleus so far account for a significant number of those reported as photoperiodically regulated and are therefore likely to contribute to seasonal physiological responses of the hamsters. The present study aimed to identify additional genes expressed in the dmpARC regulated by photoperiod that could be involved in regulating the activity of this nucleus with respect to seasonal physiology of the Siberian hamster. Using laser capture microdissection coupled with a microarray analysis and a candidate gene approach, we have identified several photoperiodically regulated genes in the dmpARC that are known to have roles in secretory and intracellular signalling pathways. These include secretogranin (sg) III and SgVI (secretory pathway), melanocortin 3 receptor (MC3-R) and serotonin (5-HT) receptors 2A and 7 (signalling pathway), all of which increase in expression under a short photoperiod. The spatial relationship between receptor signalling and potential secretory pathways was investigated by dual in situ hybridisation, which revealed that 5-HT2A and 5-HT7 receptors are expressed in neurones expressing VGF mRNA and that a sub-population (approximately 40%) of these neurones express MC3-R. These gene expression changes in dmpARC neurones may reflect the functional requirement of these neurones for seasonal physiological responses of the hamster.

Altered expression of SOCS3 in the hypothalamic arcuate nucleus during seasonal body mass changes in the field vole, Microtus agrestis.

We have previously shown that cold-acclimated (8 degrees C) male field voles (Microtus agrestis) transferred from short day (SD, 8 h light) to long day (LD, 16 h light) photoperiod exhibit an increase in body mass lasting 4 weeks, after which they stabilise at a new plateau approximately 7.5 g (24.8%) higher than animals maintained in SD. By infusing voles with exogenous leptin, we have also demonstrated that SD voles respond to the hormone by reducing body mass and food intake, whereas LD animals increasing body mass are resistant to leptin treatment. In the present study, we investigated whether seasonal changes in body mass could be linked to modulation of the leptin signal by suppressor of cytokine signalling-3 (SOCS3). We used in situ hybridisation to examine hypothalamic arcuate nucleus (ARC) expression of SOCS3, neuropeptide Y (NPY), agouti-related peptide (AgRP), pro-opiomelanocortin (POMC) and cocaine- and amphetamine-regulated transcript (CART) genes in 90 voles exposed to either SD or LD for up to 11 weeks. LD voles increasing body mass had significantly higher levels of SOCS3 mRNA than SD or LD voles with a stable body mass. There were no associated changes in expression of NPY, AgRP, POMC and CART genes. These results suggest that voles that regulate body mass at either the lower (SD) or upper (LD) plateau remain sensitive to leptin action, whereas SOCS3-mediated leptin resistance is a short-term mechanism that enables animals to move between the stable body mass plateaus. Our data provide evidence that expression of SOCS3 in the ARC is involved in the modulation of the strength of the leptin signal to facilitate seasonal cycles in body mass and adiposity.

The suppressor of cytokine signalling 3, SOCS3, may be one critical modulator of seasonal body weight changes in the Siberian hamster, Phodopus sungorus.

The Siberian hamster, Phodopus sungorus, exhibits a remarkable cycle of body weight, reproduction and leptin sensitivity in response to a seasonal change in photoperiod. In the present study, we investigated the hypothesis that the suppressor of cytokine signalling 3 (SOCS3) plays a critical role in the regulation of the seasonal body weight cycle. We analysed arcuate nucleus SOCS3 gene expression in short day length (SD; 8 : 16 h light/dark) acclimated Siberian hamsters that were transferred back to long day length (LD; 16 : 8 h light/dark) and in hamsters that spontaneously became photorefractory to SD induced by prolonged exposure. SD acclimated hamsters that were transferred back to LD for 1, 2, 3, 4 or 6 weeks, increased arcuate nucleus SOCS3 gene expression to the LD level within 2 weeks, and maintained this higher level thereafter. The early increase of SOCS3 gene expression preceded the LD-induced rise in body weight by approximately 3 weeks. Hamsters kept in SD for an extended period (25 weeks), began to become refractory to SD and to increase body weight. By this time, there was no difference in level of SOCS3 gene expression between LD and SD photoperiods, although body weight was still suppressed in SD hamsters. Finally, we addressed whether SOCS3 gene expression is related to SD-induced gonadal regression or to body weight decrease by comparing Siberian hamsters with Syrian hamsters. The latter exhibited substantial SD-induced gonadal regression but only limited seasonal changes in body weight. Acclimation to either LD or SD for 14 weeks had no effect on SOCS3 gene expression. This implies that arcuate nucleus SOCS3 gene expression is unlikely to be related to seasonal cycles in reproductive activity. Taken together, the findings further strengthen our hypothesis that SOCS3 may be one molecular trigger of seasonal cycles in body weight.

Photoperiodic programming of body weight through the neuroendocrine hypothalamus.

The photoperiodic mammal undergoes quite remarkable changes in physiology as part of its natural adaptations to seasonal fluctuations in the environment. Changes in energy balance and body weight are among these adaptations. In some seasonal mammals, such as the Siberian hamster (Phodopus sungorus), these changes in body weight have been explored in detail, and there is evidence for tightly controlled systems of energy balance that are coordinated by photoperiod acting via the temporal pattern of melatonin secretion from the pineal gland. The pathways and systems involved appear to be quite distinct from the hypothalamic pathways identified to regulate energy balance in studies of both mice and rats thus far. Instead it appears that in the Siberian hamster a tightly regulated system under the control of photoperiod is able to reset the tone of the systems involved in energy balance regulation. Understanding how photoperiod and melatonin act within the hypothalamus to regulate energy balance offers potentially fundamental and important new insights into the control of energy balance. This review describes the current state of our knowledge.

Peripartum management of a patient with dopamine beta-hydroxylase deficiency, a rare congenital cause of dysautonomia.

We present the first reported case involving the peripartum anaesthetic management of dopamine beta-hydroxylase deficiency in a 22-year-old primigravida with high-grade placenta praevia. Elective caesarean section was performed at 36 weeks gestation with a combined spinal-epidural regional anaesthetic technique. Extensive preparation was undertaken to manage the consequences of obstetric haemorrhage and consideration given to potential pharmacological sensitivities suspected to exist in patients with this rare disorder affecting sympathetic nervous system function. An uncomplicated caesarean section was performed from which the patient recovered well to be discharged home with a healthy baby.

Photoperiod regulates growth, puberty and hypothalamic neuropeptide and receptor gene expression in female Siberian hamsters.

In seasonal mammals, both the growth and reproductive axes are regulated by photoperiod. Female Siberian hamsters were kept, for up to 12 weeks, in long-day (LD) or short-day (SD) photoperiod, from weaning at 3 weeks of age (Exp 1). LD hamsters had characteristically faster growth and higher asymptotic body weight, adiposity, and leptin gene expression in adipose tissue. Only LD females attained puberty. Gene expression in the hypothalamic arcuate nucleus for leptin receptor (OB-Rb), POMC, and melanocortin 3-receptor (MC3-R) was higher in LD but did not change from weaning levels in SD. In contrast, gene expression in the arcuate nucleus for cocaine and amphetamine-regulated transcript (CART) was higher in SD than LD, a difference that was apparent at 2 weeks post weaning. Transfer of SD females to LD at 15 weeks post weaning (Exp 2) increased body weight, leptin signal, and gene expression for POMC but failed to induce normal puberty onset or to increase gene expression for OB-Rb and MC3-R. Therefore, photoperiodic regulation of puberty may be modulated by age, by photoperiodic history, and by changes in leptin signaling and the activity of the leptin-sensitive hypothalamic melanocortin system (POMC, MC3-R). A role for CART in photoperiodic regulation of growth is suggested, because the changes in CART gene expression preceded significant divergence of growth trajectories in the opposite photoperiods.

Neuroimaging contrast agents in ophthalmology.

Magnetic resonance (MR) imaging and computed tomography (CT) are routinely performed with the use of contrast materials in the diagnosis of neuro-ophthalmologic disease. Iodinated agents are commonly used in CT scanning and femoral contrast arteriography, and gadolinium is used in MR imaging. While contrast materials contribute greatly to diagnostic accuracy, they may also be responsible for adverse effects, ranging in severity from mild discomfort to death. The most frequent and severe side effects are associated with ionic iodinated contrast agents, while the rate of adverse reactions is less with use of nonionic iodinated contrast agents. Side effects and adverse reactions to gadolinium are uncommon, but they do occur. In neuro-ophthalmologic diagnosis, MR imaging is generally preferred over CT scanning, partly because of its greater ability to delineate soft tissue intracranial structures, but also because of the relative safety of gadolinium as a contrast agent. Properties of contrast agents are discussed in the context of specific imaging techniques and tissues investigated. Types and severity of adverse effects as well as risk factors for incurring such effects are summarized.

Photoperiod regulates arcuate nucleus POMC, AGRP, and leptin receptor mRNA in Siberian hamster hypothalamus.

Siberian hamsters decreased body weight by 30% during 18 wk in short day (SD) vs. long day (LD) controls. Subsequent imposed food deprivation (FD; 24 h) caused a further 10% decrease. In the hypothalamic arcuate nucleus (ARC), SDs reduced proopiomelanocortin (POMC) gene expression and agouti-related protein (AGRP) mRNA was elevated, changes that summate to reduced catabolic drive through the melanocortin receptors. There was no effect of photoperiod on neuropeptide Y (NPY), melanin concentrating hormone, orexin, or corticotropin-releasing factor mRNAs. Superimposed FD increased AGRP gene expression and caused a localized elevation of NPY mRNA in the ARC. Both adipose tissue leptin and ARC leptin receptor (OB-Rb) mRNAs were downregulated in SDs, whereas FD increased OB-Rb gene expression. Thus OB-Rb mRNA is differentially regulated by acute and chronic changes in plasma leptin in this species. In a separate experiment in LDs, AGRP gene expression was increased by 24 or 48 h FD, whereas POMC mRNA was downregulated in the caudal ARC. AGRP and NPY mRNAs were extensively coexpressed in the ARC, and their differential regulation by photoperiod and FD is suggestive of transcript-specific regulation at the level of individual neurons.

Decoding photoperiodic time through Per1 and ICER gene amplitude.

The mammalian Per1 gene is expressed in the suprachiasmatic nucleus of the hypothalamus, where it is thought to play a critical role in the generation of circadian rhythms. Per1 mRNA also is expressed in other tissues. Its expression in the pars tuberalis (PT) of the pituitary is noteworthy because, like the suprachiasmatic nucleus, it is a known site of action of melatonin. The duration of the nocturnal melatonin signal encodes photoperiodic time, and many species use this to coordinate physiological adaptations with the yearly climatic cycle. This study reveals how the duration of photoperiodic time, conveyed through melatonin, is decoded as amplitude of Per1 and ICER (inducible cAMP early repressor) gene expression in the PT. Syrian hamsters display a robust and transient peak of Per1 and ICER gene expression 3 h after lights-on (Zeitgeber time 3) in the PT, under both long (16 h light/8 h dark) and short (8 h light/16 h dark) photoperiods. However, the amplitude of these peaks is greatly attenuated under a short photoperiod. The data show how amplitude of these genes may be important to the long-term measurement of photoperiodic time intervals.

Oestrogen and progesterone receptor immunoreactivity and c-fos expression in the ovine cervix.

Immunocytochemistry was used to detect the presence of oestrogen and progesterone receptors in the cervices of prepubertal lambs, seasonally anoestrous ewes, cyclic ewes, and pregnant ewes of known gestational stages, to define the roles of gonadal steroids in cervical function. The presence of the immediate early gene product, c-Fos, a marker for cellular activation, was also investigated using immunocytochemistry and in situ hybridization. Oestrogen receptor immunoreactivity was restricted to the endometrium on days 0-3 of the oestrous cycle (day 0 = oestrus). In immature animals, very few scattered nuclei in the endometrium were immunoreactive. Oestrogen receptor immunoreactivity was not apparent in the endometrium during the remainder of the oestrous cycle or in this region in anoestrous animals. In pregnant ewes, oestrogen receptor immunostaining appeared as relatively few isolated nuclei in the connective tissue stroma. Progesterone receptor immunoreactivity was found in the endometrium at days 0-3 of the oestrous cycle and also in the luminal epithelium, the myometrium and the blood vessels. Progesterone receptor immunoreactivity was also found in these regions, with the exception of the endometrium, at all other stages examined. Immunostaining for c-Fos was present in the endometrium at days 0-3 of the oestrous cycle, and some scattered immunopositive nuclei were present in prepubertal animals. c-Fos immunoreactivity was also found in the myometrium and in blood vessels at all other stages examined. Visualization of c-fos gene expression by in situ hybridization showed that it occurred in the luminal epithelium and blood vessels at oestrus, but was restricted to the blood vessels in all other samples examined.

oPer1 is an early response gene under photoperiodic regulation in the ovine pars tuberalis.

Mammalian Per1 (or RIGUI) is a recently described putative clock gene that is expressed in the suprachiasmatic nucleus. It is also expressed in the pars tuberalis (PT) of the pituitary, where melatonin appears to drive its expression. This study examines the regulation of Per1 expression. In ovine PT cells, oPer1 is an early response gene transiently expressed after stimulation with forskolin, but melatonin has no independent effect on its expression. In sheep, PT tissue photoperiodic background influences the magnitude or timing of expression of oPer1 2 h after lights-on. These data demonstrate that oPer1 mRNA is elevated in the PT following the decline in night-time melatonin, and that the amplitude or timing of this elevation is dependent upon the duration of the nocturnal melatonin signal.

A novel interaction between inhibitory melatonin receptors and protein kinase C-dependent signal transduction in ovine pars tuberalis cells.

This study revealed an important and unexpected finding: namely, that inhibitory melatonin receptors can inhibit a phorbol 12,13 myristate acetate (PMA)-induced, protein kinase C (PKC)-dependent increase in c-fos messenger RNA expression in ovine pars tuberalis (PT) cells. PMA induces dose-dependent stimulation of c-fos expression that is attenuated by melatonin in a dose-dependent and pertussis toxin-sensitive manner. The effect of 100 nM PMA is blocked by Ro31-8220 (1 microM), yet is not mimicked by 4alpha-PMA (100 nM). PMA (100 nM) induces PKC activity in PT cells (P < 0.05) within 5 min, but melatonin has no effect on this response. PMA (100 nM) stimulates both phospholipase D and mitogen-activated protein kinase (MAPK) (p42/44) activities in PT cells, but melatonin has no effect on these responses. The results indicate that neither of these second-messenger activities contribute to the melatonin-sensitive pathway of c-fos activation. The MEK (MAPK kinase) inhibitor, PD98059 (50 microM), does not block the induction of c-fos by PMA, although at the same dose it inhibits PMA-mediated activation of p42/44 MAPK by 50-70%, and activation by forskolin or insulin-like growth factor-I by 100%. These data suggest that p42/44 MAPK may not be the primary mediator of PKC-dependent c-fos induction. In contrast to the effect of melatonin on PMA-mediated c-fos induction in PT cells, in L cells stably transfected with the sheep Mel1 alphabeta receptor, melatonin potentiates the c-fos response in a pertussis toxin-sensitive manner. These data indicate the tissue-specific nature of melatonin receptor signaling, and reveal that a pertussis toxin-sensitive pathway can block PKC-mediated c-fos induction in PT cells.

Mel 1a melatonin receptor expression is regulated by protein kinase C and an additional pathway addressed by the protein kinase C inhibitor Ro 31-8220 in ovine pars tuberalis cells.

The expression of the melatonin receptor is positively regulated by cAMP and negatively regulated by melatonin in the ovine pars tuberalis (PT). Furthermore, when PT cells are dispersed in primary culture, both messenger RNA (mRNA) and protein levels spontaneously increase through a process that can be blocked by melatonin, but does not involve cAMP. This suggests that other second messengers may be regulated by melatonin, which, in turn, regulates melatonin receptor mRNA and protein levels. In this study using ribonuclease protection assays, ligand binding, protein kinase C (PKC), and cAMP analysis, we demonstrate that the levels of Mel 1a mRNA and protein expression in ovine PT are reduced by phorbol 12-myristate 13-acetate in a cAMP-independent process. This is indicative of an inhibitory role for PKC in receptor regulation. Melatonin, however, does not act through PKC activation to reduce Mel 1a mRNA or protein levels. Basal PKC activity in PT cells can be inhibited by the PKC inhibitor Ro 31-8220, and this suggests that basal PKC activity may suppress Mel 1a receptor expression. Paradoxically, however, Ro 31-8220 also inhibits melatonin receptor mRNA and protein levels in PT cells by a cAMP-independent mechanism. This suggests that other undefined pathways must play an important role in the physiological self-regulation of Mel 1a receptor expression by melatonin.

The use of DNA fingerprinting to assess monozygotic twinning in Meishan and Landrace x large white pigs.

The extent of embryo mortality is usually estimated by the difference between the numbers of corpora lutea and embryos in the same animal, which assumes that each corpora lutea represents one potential embryo. Recent observations from the authors' laboratory reveal situations in which the number of embryos exceeds the number of corpora lutea, implicating the presence of identical twins. The objective of the present study was to establish DNA fingerprinting techniques to investigate the prevalence of monozygotic twinning in two breeds of pig. DNA fingerprints of every fetus carried by 6 Meishan (MS) and 6 Landrace x Large White (LxLW) gilts on Day 29 +/- 2 of pregnancy were obtained. Five LxLW and 3 MS litters carried no identical fetuses. The remaining gilts carried a pair of fetuses with indistinguishable DNA profiles. No pairs of fetuses were monochorionic. These results suggest that monozygotic twinning in the pig occurs during embryo cleavage or blastocyst development and may be more prevalent in MS compared with indigenous breeds.

Melatonin suppresses the induction of AP-1 transcription factor components in the pars tuberalis of the pituitary.

In ovine pars tuberalis cells which express high affinity Mel 1a melatonin receptors, the ability of melatonin to directly stimulate or inhibit AP-1 transcription factor gene expression was studied. Effects of melatonin upon mRNA expression by forskolin, serum and IGF-1 were also investigated. Northern analysis showed melatonin had no direct stimulatory nor inhibitory effect upon transcription or translation. Melatonin was able to significantly inhibit forskolin-stimulated induction of c-fos and jun B mRNA whilst forskolin had no effect upon c-jun or jun D. Induction of c-Fos translation by forskolin was also inhibited by melatonin. Serum induced c-fos and c-jun, but melatonin was unable to affect these changes. Similarly IGF-1 stimulated c-fos and melatonin had no effect upon this induction. From these results it can be concluded that melatonin has no independent effects on expression of the AP-1 genes, rather its primary function is to inhibit cell activities through cyclic AMP-dependent routes of gene activation.