Ovary: Immunolocalization of transforming growth factor-{beta}1 and transforming growth factor-{beta}2 in the mouse ovary during gonadotrophin-induced follicular maturation

An immunohistochemical approach was utilized to evaluate thecellular distribution of transforming growth factor-₁ (TGF₁)and transforming growth factor ₂ (TGF₂) at different stagesof follicle development in the prepubertal mouse ovary underthe following conditions: (i) after pregnant mare's serum gonadotrophin(PMSG) treatment; (ii) after PMSG and human chorionic gonadotrophin(HCG) treatment; (iii) after PMSG and HCG treatment plus mating.In the immature ovary, TGFF₁ and TGF₂ immunoreactivities arelocalized in theca and granulosa cells and in oocytes. AfterPMSG treatment, TGF₁ and TGF₂ immunoreactivities are localizedin granulosa cells; in addition, TGF₂ staining is noted in thematrix surrounding antral cells. Staining for both TGF₁ andTGF₂ drops in the theca but persists in the oocyte. PMSG plusHCG treatment results in a significant increase in TGF₁ andTGF₂ immunoreactivity in the theca and in the maintenance ofTGF₁ staining in both basal granulosa cells and cumulus cellswhereas TGF₂ immunoreactivity is essentially localized in thematrix surrounding cumulus cells. Staining for TGF₁ and TGF₂persists in the oocyte. Following PMSG plus HCG treatment andmating, TGF₁ immunoreactivity is localized in the luteal cellsof corpora lutea and TGF₂ shows a similar localization pattern.This study provides evidence that TGF₁ and TGF₂ peptides areexpressed in specific cell types during induced follicular maturationin the mouse ovary.     

Transforming growth factor beta 1 inhibits gonadotropin action in cultured porcine Sertoli cells.

In the present study, we have tested the effects of transforming growth factor beta 1 (TGF beta 1) on FSH action toward aromatase activity and lactate production in cultured Sertoli cells isolated from immature porcine testes. Whereas treatment of Sertoli cells with FSH resulted in a dose-dependent increase (about 7-fold) in aromatase activity (conversion of testosterone into estradiol) (ED50 = 80 ng/ml FSH), the addition of TGF beta 1 reduced this gonadotropin action. The inhibitory effect of TGF beta 1 on FSH aromatase activity was dose dependent (ED50 = 0.1 ng/ml, 4 pM TGF beta 1) with a maximal decrease (about 40%) observed after a long term (48-h) treatment. TGF beta 1 exerted its inhibitory effect on FSH action at the level(s) of cAMP accumulation, exerting no apparent effect on the gonadotropin receptor or at a site(s) related to cAMP action. TGF beta 1 (2 ng/ml) significantly (P less than 0.002) reduced (52% decrease) FSH-stimulated cAMP levels in cultured porcine Sertoli cells. However, such an inhibitory effect of the growth factor was no longer observed when stimulation of cAMP accumulation with FSH occurred in the presence of methyl isobutyl xanthine (0.5 mM), an inhibitor of cAMP-phosphodiesterase activity. This observation suggests that TGF beta 1 decreased cAMP levels by increasing catabolism of the cyclic nucleotide through an enhancement of cAMP-phosphodiesterase activity. The inhibitory effect of TGF beta 1 was not limited to the action of FSH on aromatase activity but also extended to the gonadotropin action (mediated by cAMP) on lactate production. As for the inhibitory effect of TGF beta 1 on FSH-induced aromatase activity, the inhibitory effect of the growth factor on FSH-stimulated lactate production was dose and time dependent with a maximal decrease (about 30%) observed in the picomolar range (1 ng/ml, 40 pM) after 48 h treatment with TGF beta 1. In conclusion, the present study demonstrates that TGF beta 1 attenuates FSH action on Sertoli cell activity and that such inhibitory action is potentially exerted through a decrease in cAMP levels. Because of the local production of TGF beta 1, it is suggested that the effects of the growth factor reported here might be exerted in the context of the testicular paracrine mechanisms.     

Efficacy of an Hypericum perforatum (St. John's wort) extract in preventing and reverting a condition of escape deficit in rats.

The treatment of unselected depressed patients with an hydro-alcoholic extract of Hypericum perforatum has been reported to have an efficacy similar to that of classical antidepressants. In the present report, the effects of H. perforatum were studied on three animal models of depression: (i) an acute form of escape deficit (ED) induced by an unavoidable stress; (ii) a chronic model of ED, which can be maintained by the administration of mild stressors on alternate days; (iii) a model of anhedonia based on the finding that repeated stressors prevent the development of an appetitive behavior induced by vanilla sugar in satiated rats fed ad libitum. H. perforatum acutely protected animals from the sequelae of unavoidable stress; such an effect was partially prevented by the administration of SCH 23390 or (-)-pindolol. Moreover, H. perforatum reverted the ED maintained by repeated stressors and preserved the animal's capacity to learn to operate for earning a positive reinforcer. It was concluded that H. perforatum contains some active principle(s) endowed with antidepressant activity.     

Acetyl-L-Carnitine selectively prevents post-ischemic LTP via a possible action on mitochondrial energy metabolism

It has been hypothesized that Acetyl-L-Carnitine (ALC) contributes to mitochondrial ATP production through maintenance of key mitochondrial proteins and protects mitochondria against oxidative stress. We have investigated the role of ALC on the expression of two forms of synaptic plasticity in the striatum: (i) the physiological long-term potentiation (LTP) and (ii) the ischemic long-term potentiation (i-LTP), an aberrant form of synaptic plasticity occurring after in vitro ischemia. The application in vitro of ALC did not alter the induction or the maintenance of physiological activity-dependent LTP, while it prevented i-LTP in a dose-dependent manner. The ability of ALC to prevent i-LTP was not affected by previous application of scopolamine, a non-selective muscarinic receptors antagonist. Given the susceptibility of mitochondrial complex IV to ischemic oxidative insult, we investigated the role of this complex as possible target of ALC action. Thus, the application of a low dose of the mitochondrial toxin sodium azide, conventionally used as a model of hypoxia due to its capability to inhibit mitochondrial complex IV, induced a pathological synaptic potentiation that was fully prevented by ALC application. In the presence of a very low dose of the mitochondrial uncoupler FCCP, ALC no longer prevented i-LTP suggesting that neuroprotective effects of ALC require a compensatory activity of mitochondrial energy metabolism. Our data demonstrate that ALC exerts neuroprotective effects by preventing the expression of pathological synaptic plasticity induced by ischemia. These effects crucially depend on the ability on ALC to affect mitochondrial processes.     

Intermittent theta‐burst stimulation rescues dopamine‐dependent corticostriatal synaptic plasticity and motor behavior in experimental parkinsonism: Possible role of glial activity

Background : Recent studies support the therapeutic utility of repetitive transcranial magnetic stimulation in Parkinson's disease (PD), whose progression is correlated with loss of corticostriatal long‐term potentiation and long‐term depression. Glial cell activation is also a feature of PD that is gaining increasing attention in the field because astrocytes play a role in chronic neuroinflammatory responses but are also able to manage dopamine (DA) levels. Methods : Intermittent theta‐burst stimulation protocol was applied to study the effect of therapeutic neuromodulation on striatal DA levels measured by means of in vivo microdialysis in 6‐hydroxydopamine‐hemilesioned rats. Effects on corticostriatal synaptic plasticity were studied through in vitro intracellular and whole‐cell patch clamp recordings while stepping test and CatWalk were used to test motor behavior. Immunohistochemical analyses were performed to analyze morphological changes in neurons and glial cells. Results : Acute theta‐burst stimulation induced an increase in striatal DA levels in hemiparkinsonian rats, 80 minutes post‐treatment, correlated with full recovery of plasticity and amelioration of motor performances. With the same timing, immediate early gene activation was restricted to striatal spiny neurons. Intense astrocytic and microglial responses were also significantly reduced 80 minutes following theta‐burst stimulation. Conclusion : Taken together, these results provide a first glimpse on physiological adaptations that occur in the parkinsonian striatum following intermittent theta‐burst stimulation and may help to disclose the real potential of this technique in treating PD and preventing DA replacement therapy‐associated disturbances. © 2017 International Parkinson and Movement Disorder Society     

TrkB/BDNF-Dependent Striatal Plasticity and Behavior in a Genetic Model of Epilepsy: Modulation by Valproic Acid

In mice lacking the central domain of the presynaptic scaffold Bassoon the occurrence of repeated cortical seizures induces cell-type-specific plasticity changes resulting in a general enhancement of the feedforward inhibition within the striatal microcircuit. Early antiepileptic treatment with valproic acid (VPA) reduces epileptic attacks, inhibits the emergence of pathological form of plasticity in fast-spiking (FS) interneurons and restores physiological striatal synaptic plasticity in medium spiny (MS) neurons. Brain-derived neurotrophic factor (BDNF) is a key factor for the induction and maintenance of synaptic plasticity and it is also implicated in the mechanisms underlying epilepsy-induced adaptive changes. In this study, we explore the possibility that the TrkB/BDNF system is involved in the striatal modifications associated with the Bassoon gene (Bsn) mutation. In epileptic mice abnormal striatum-dependent learning was paralleled by higher TrkB levels and an altered distribution of BDNF. Accordingly, subchronic intrastriatal administration of k252a, an inhibitor of TrkB receptor tyrosine kinase activity, reversed behavioral alterations in Bsn mutant mice. In addition, in vitro manipulations of the TrkB/BDNF complex by k252a, prevented the emergence of pathological plasticity in FS interneurons. Chronic treatment with VPA, by reducing seizures, was able to rebalance TrkB to control levels favoring a physiological redistribution of BDNF between MS neurons and FS interneurons with a concomitant recovery of striatal plasticity. Our results provide the first indication that BDNF is involved in determining the striatal alterations occurring in the early-onset epileptic syndrome associated with the absence of presynaptic protein Bassoon.     

l-DOPA dosage is critically involved in dyskinesia via loss of synaptic depotentiation

The emergence of levodopa (l-DOPA)-induced dyskinesia and motor fluctuations represents a major clinical problem in Parkinson's disease (PD). While it has been suggested that the daily dose of l-DOPA can play a critical role, the mechanisms linking l-DOPA dosage to the occurrence of motor complications have not yet been explored. Using an experimental model of PD we have recently demonstrated that long-term l-DOPA treatment leading to the induction of abnormal involuntary movements (AIMs) alters corticostriatal bidirectional synaptic plasticity. Dyskinetic animals, in fact, lack the ability to reverse previously induced long-term potentiation (LTP). This lack of depotentiation has been associated to a defect in erasing unessential motor information. Here chronic l-DOPA treatment was administered at two different doses to hemiparkinsonian rats, and electrophysiological recordings were subsequently performed from striatal spiny neurons. Both low and high doses of l-DOPA restored normal LTP, which was disrupted following dopamine (DA) denervation. By the end of the chronic treatment, however, while the low l-DOPA dose induced AIMs only in half of the rats, the high dose caused motor complications in all the treated animals. Interestingly, the dose-related expression of motor complications was associated with a lack of synaptic depotentiation. Our study provides further experimental evidence to support a direct correlation between the daily dosage of l-DOPA and the induction of motor complications and establishes a critical pathophysiological link between the lack of synaptic depotentiation and the expression of AIMs.     

Neuronal networks and synaptic plasticity in Parkinson's disease: beyond motor deficits

The excitatory corticostriatal pathway, which plays a critical role in the building up and storage of adaptive motor behaviours, can undergo long-lasting, activity-dependent changes in the efficacy of synaptic transmission, named long-term potentiation (LTP) and long- term depression (LTD). Both forms of plasticity are thought to underlie motor learning and depend upon the concomitant activation of glutamatergic corticostriatal and dopaminergic nigrostriatal pathways. Accordingly, corticostriatal LTP and LTD are altered in Parkinson's Disease (PD) models. The dopamine (DA)/acetylcholine(Ach) synaptic unbalance could be responsible of some of the cognitive deficits described in PD patients. The impairment of DA/ACh-dependent cellular learning could lead to the storage of unessential memory traces, as it has been postulated for the induction of L-DOPA-induced dyskinesias. Other non-motor symptoms involve not only the central dopaminergic system, but also in the noradrenergic, serotoninergic and cholinergic transmitter systems.