Plasticity in Intrinsic Excitability of Hypothalamic Magnocellular Neurosecretory Neurons in Late-Pregnant and Lactating Rats.

Oxytocin and vasopressin secretion from the posterior pituitary gland are required for normal pregnancy and lactation. Oxytocin secretion is relatively low and constant under basal conditions but becomes pulsatile during birth and lactation to stimulate episodic contraction of the uterus for delivery of the fetus and milk ejection during suckling. Vasopressin secretion is maintained in pregnancy and lactation despite reduced osmolality (the principal stimulus for vasopressin secretion) to increase water retention to cope with the cardiovascular demands of pregnancy and lactation. Oxytocin and vasopressin secretion are determined by the action potential (spike) firing of magnocellular neurosecretory neurons of the hypothalamic supraoptic and paraventricular nuclei. In addition to synaptic input activity, spike firing depends on intrinsic excitability conferred by the suite of channels expressed by the neurons. Therefore, we analysed oxytocin and vasopressin neuron activity in anaesthetised non-pregnant, late-pregnant, and lactating rats to test the hypothesis that intrinsic excitability of oxytocin and vasopressin neurons is increased in late pregnancy and lactation to promote oxytocin and vasopressin secretion required for successful pregnancy and lactation. Hazard analysis of spike firing revealed a higher incidence of post-spike hyperexcitability immediately following each spike in oxytocin neurons, but not in vasopressin neurons, in late pregnancy and lactation, which is expected to facilitate high frequency firing during bursts. Despite lower osmolality in late-pregnant and lactating rats, vasopressin neuron activity was not different between non-pregnant, late-pregnant, and lactating rats, and blockade of osmosensitive ΔN-TRPV1 channels inhibited vasopressin neurons to a similar extent in non-pregnant, late-pregnant, and lactating rats. Furthermore, supraoptic nucleus ΔN-TRPV1 mRNA expression was not different between non-pregnant and late-pregnant rats, suggesting that sustained activity of ΔN-TRPV1 channels might maintain vasopressin neuron activity to increase water retention during pregnancy and lactation.

Oxytocin Modulation of Maternal Behavior and Its Association With Immunological Activity in Rats With Cesarean Delivery.

Oxytocin (OT), a neuropeptide produced in the supraoptic (SON) and paraventricular (PVN) nuclei, is not only essential for lactation and maternal behavior but also for normal immunological activity. However, mechanisms underlying OT regulation of maternal behavior and its association with immunity around parturition, particularly under mental and physical stress, remain unclear. Here, we observed effects of OT on maternal behavior in association with immunological activity in rats after cesarean delivery (CD), a model of reproductive stress. CD significantly reduced maternal interests to the pups throughout postpartum day 1-8. On postpartum day 5, CD decreased plasma OT levels and thymic index but increased vasopressin, interleukin (IL)-1ß, IL-6 and IL-10 levels. CD had no significant effect on plasma adrenocorticotropic hormone and corticosterone levels. In the hypothalamus, CD decreased corticotropin-releasing hormone contents in the PVN but increased OT contents in the PVN and SON and OT release from hypothalamic implants. CD also increased c-Fos expression, particularly in the cytoplasm of OT neurons. Lastly, CD depolarized resting membrane potential and increased spike width while increasing the variability of the firing rate of OT neurons in brain slices. Thus, CD can increase hypothalamic OT contents and release but reduce pituitary release of OT into the blood, which is associated with depressive-like maternal behavior, increased inflammatory cytokine release and decreased relative weight of the thymus.

Impact of chronic variable stress on neuroendocrine hypothalamus and pituitary in male and female C57BL/6J mice.

Chronic stress exerts multiple negative effects on the physiology and health of an individual. In the present study, we examined hypothalamic, pituitary and endocrine responses to 14 days of chronic variable stress (CVS) in male and female C57BL/6J mice. In both sexes, CVS induced a significant decrease in body weight and enhanced the acute corticosterone stress response, which was accompanied by a reduction in thymus weight only in females. However, single-point blood measurements of basal prolactin, thyroid-stimulating hormone, luteinising hormone, growth hormone and corticosterone levels taken at the end of the CVS were not different from those of controls. Similarly, pituitary mRNA expression of Fshb, Lhb, Prl and Gh was unchanged by CVS, although Pomc and Tsh were significantly elevated. Within the adrenal medulla, mRNA for Th, Vip and Gal were elevated following CVS. Avp transcript levels within the paraventricular nucleus of the hypothalamus were increased by CVS; however, levels of Gnrh1, Crh, Oxt, Sst, Trh, Ghrh, Th and Kiss1 remained unchanged. Oestrous cycles were lengthened slightly by CVS and ovarian histology revealed a reduction in the number of preovulatory follicles and corpora lutea. Taken together, these observations indicate that 14 days of CVS induces an up-regulation of the neuroendocrine stress axis and creates a mild disruption of female reproductive function. However, the lack of changes in other neuroendocrine axes controlling anterior and posterior pituitary secretion suggest that most neuroendocrine axes are relatively resilient to CVS.

Assessing the role of hypothalamic microglia and blood vessel disruption in the development of angiotensin II-dependent hypertension in Cyp1a1-Ren2 rats.

Elevated plasma levels of the hormone vasopressin have been implicated in the pathogenesis of some forms of hypertension. Hypothalamic paraventricular and supraoptic nuclei neurons regulate vasopressin secretion into the circulation. Vasopressin neuron activity is elevated by day 7 in the development of angiotensin II-dependent hypertension in Cyp1a1-Ren2 rats. While microglial activation and blood-brain barrier (BBB) breakdown contribute to the maintenance of well-established hypertension, it is not known whether these mechanisms contribute to the early onset of hypertension. Hence, we aimed to determine whether microglia are activated and/or the BBB is compromised during the onset of hypertension. Here, we used the Cyp1a1-Ren2 rat model of hypertension and showed that ionised calcium-binding adapter molecule 1 staining of microglia does not change in the paraventricular and supraoptic nuclei on day 7 (early onset) and day 28 (well established) of hypertension, compared to the normotensive control. Endothelial transferrin receptor staining, which stains endothelia and reflects blood vessel density, was also unchanged at day 7, but was reduced at day 28, suggesting that breakdown of the BBB begins between day 7 and day 28 in the development of hypertension. Hence, this study does not support the idea that microglial activation or BBB disruption contribute to the onset of angiotensin II-dependent hypertension in Cyp1a1-Ren2 rats, although BBB disruption might contribute to the progression from the early onset to well-established hypertension.

Clinical Outcomes Following Primary Anterior Cruciate Ligament Reconstruction with Hamstring Autograft versus Planned Hybrid Graft.

Few studies have compared outcomes between autografts versus hybrid grafts (combination of autograft and allograft) for anterior cruciate ligament reconstruction (ACLR). The purpose of this study was to compare revision rate and patient-reported outcomes following primary ACLR with a hamstring autograft versus a preoperatively planned hybrid autograft-allograft. At a minimum 2-year follow-up, patients who had undergone primary ACLR with a double-stranded semitendinosus and gracilis hamstring autograft (A) or a planned hybrid (H) graft (single-strand semitendinosus with nonirradiated peroneus longus or tibialis posterior allograft) were contacted to fill out a survey containing the Knee Injury and Osteoarthritis Outcome Score (KOOS), Subjective International Knee Documentation Committee (IKDC) score, Single Assessment Numeric Evaluation (SANE), 12-Item Short-Form Health Survey (SF-12), and visual analog scale (VAS) for activity level prior to injury and at follow-up. From this collection of patients, a matched-pair comparison was made between groups, with patients matched by gender, age at the time of surgery, and follow-up time. Revision rate at follow-up was 8.4 and 2.4% in the A and H groups, respectively (p = 0.073). A total of 148 surveys were completed (83 A, 65 H), from which 36 matched pairs were formed. Within the matched pairs, average age at surgery did not differ significantly between groups (A: 35.7 years, H: 36.0 years, p = 0.23). Time to follow-up was 4.3 and 3.7 years in the A and H groups, respectively. Patients with a hybrid graft had significantly higher KOOS Quality of Life subscores (A 69.6, H 79.2, p = 0.028), subjective IKDC scores (A 72.6, H 79.7, p = 0.031), and SANE scores (A 83.2, H 91.4, p = 0.015) at follow-up. Otherwise, no significant differences were found in patient-reported outcome scores between groups. A preoperatively planned hybrid graft, with use of a fresh-frozen, nonirradiated allograft, should be considered as a viable alternative for primary ACLR in older patients.

Creatine supplementation prevents the accumulation of fat in the livers of rats fed a high-fat diet.

The aim of the present study was to examine the effects of creatine supplementation on liver fat accumulation induced by a high-fat diet in rats. Rats were fed 1 of 3 different diets for 3 wk: a control liquid diet (C), a high-fat liquid diet (HF), or a high-fat liquid diet supplemented with creatine (HFC). The C and HF diets contained, respectively, 35 and 71% of energy derived from fat. Creatine supplementation involved the addition of 1% (wt:v) of creatine monohydrate to the liquid diet. The HF diet increased total liver fat concentration, liver TG, and liver TBARS and decreased the hepatic S-adenosylmethionine (SAM) concentration. Creatine supplementation normalized all of these perturbations. Creatine supplementation significantly decreased the renal activity of l-arginine:glycine amidinotransferase and plasma guanidinoacetate and prevented the decrease in hepatic SAM concentration in rats fed the HF diet. However, there was no change in either the phosphatidylcholine:phosphatidylethanolamine (PE) ratio or PE N-methyltransferase activity. The HF diet decreased mRNA for PPARα as well as 2 of its targets, carnitine palmitoyltransferase and long-chain acylCoA dehydrogenase. Creatine supplementation normalized these mRNA levels. In conclusion, creatine supplementation prevented the fatty liver induced by feeding rats a HF diet, probably by normalization of the expression of key genes of ß-oxidation.

Acute morphine administration and withdrawal from chronic morphine increase afterdepolarization amplitude in rat supraoptic nucleus neurons in hypothalamic explants.

Supraoptic nucleus (SON) neurons secrete either oxytocin or vasopressin into the bloodstream from their axon terminals in the posterior pituitary gland. SON neurons are powerfully inhibited by the classical µ-opioid receptor agonist, morphine. Oxytocin neurons develop morphine dependence when chronically exposed to this opiate, and undergo robust withdrawal excitation when morphine is subsequently acutely antagonized by naloxone. Morphine withdrawal excitation is evident as an increased firing rate and is associated with an increased post-spike excitability that is consistent with the expression of an enhanced post-spike afterdepolarization (ADP) during withdrawal. Here, we used sharp electrode recording from SON neurons in hypothalamic explants from morphine naïve and morphine treated rats to determine the effects of morphine on the ADP, and to test the hypothesis that morphine withdrawal increases ADP amplitude in SON neurons. Acute morphine administration (0.05-5.0 µM) caused a dose-dependent hyperpolarization of SON neurons that was reversed by concomitant administration of 10 µM naloxone, or by washout of morphine; counter-intuitively, acute exposure to 5 µM morphine increased ADP amplitude by 78 ± 11% (mean ± SEM). Naloxone-precipitated morphine withdrawal did not alter baseline membrane potential in SON neurons from morphine treated rats, but increased ADP amplitude by 48 ± 11%; this represents a hyper-activation of ADPs because the basal amplitude of the ADP was similar in SON neurons recorded from explants prepared from morphine naïve and morphine treated rats. Hence, an enhanced ADP might contribute to morphine withdrawal excitation of oxytocin neurons.

The cascaded nature of lexical selection and integration in auditory sentence processing.

An event-related brain potential experiment was carried out to investigate the temporal relationship between lexical selection and the semantic integration in auditory sentence processing. Participants were presented with spoken sentences that ended with a word that was either semantically congruent or anomalous. Information about the moment in which a sentence-final word could uniquely be identified, its isolation point (IP), was compared with the onset of the elicited N400 congruity effect, reflecting semantic integration processing. The results revealed that the onset of the N400 effect occurred prior to the IP of the sentence-final words. Moreover, the factor early or late IP did not affect the onset of the N400. These findings indicate that lexical selection and semantic integration are cascading processes, in that semantic integration processing can start before the acoustic information allows the selection of a unique candidate and seems to be attempted in parallel for multiple candidates that are still compatible with the bottom-up acoustic input.

Mechanisms of rhythmogenesis: insights from hypothalamic vasopressin neurons.

Many neurons in the CNS, including hypothalamic vasopressin-expressing cells, display rhythmic activity patterning. These vasopressin neurons receive random synaptic input but fire action potentials in alternating periods of activity and silence that each lasts tens of seconds. Recent work demonstrates that vasopressin cell rhythmicity depends on feedback modulation of intrinsic membrane properties and synaptic inputs by peptides released from the dendrites of these neurons. Many other neurons across the CNS release neurotransmitters from their dendrites; therefore, vasopressin cells provide an insight into the potential mechanisms that support neuronal activity patterning across the CNS.

Morphine withdrawal increases intrinsic excitability of oxytocin neurons in morphine-dependent rats.

To determine whether intrinsic mechanisms drive supraoptic nucleus oxytocin neuron excitation during morphine withdrawal, we calculated the probability of action potential (spike) firing with time after each spike for oxytocin neurons in morphine-naive and morphine-dependent rats in vivo and measured changes in intrinsic membrane properties in vitro. The opioid receptor antagonist, naloxone, increased oxytocin neuron post-spike excitability in morphine-dependent rats; this increase was greater for short interspike intervals (<0.1 s). Naloxone had similar, but smaller (P=0.04), effects in oxytocin neurons in morphine-naive rats. The increased post-spike excitability for short interspike intervals was specific to naloxone, because osmotic stimulation increased excitability without potentiating excitability at short interspike intervals. By contrast to oxytocin neurons, neither morphine dependence nor morphine withdrawal increased post-spike excitability in neighbouring vasopressin neurons. To determine whether increased post-spike excitability in oxytocin neurons during morphine withdrawal reflected altered intrinsic membrane properties, we measured the in vitro effects of naloxone on transient outward rectification (TOR) and after-hyperpolarization (AHP), properties mediated by K+ channels and that affect supraoptic nucleus neuron post-spike excitability. Naloxone reduced the TOR and AHP (by 20% and 60%, respectively) in supraoptic nucleus neurons from morphine-dependent, but not morphine-naive, rats. In vivo, spike frequency adaptation (caused by activity-dependent AHP activation) was reduced by naloxone (from 27% to 3%) in vasopressin neurons in morphine-dependent, but not morphine-naive, rats. Thus, multiple K+ channel inhibition increases post-spike excitability for short interspike intervals, contributing to the increased firing of oxytocin neurons during morphine withdrawal.

Cellular mechanisms underlying neuronal excitability during morphine withdrawal in physical dependence: lessons from the magnocellular oxytocin system.

Opiates are used clinically as analgesics, but their euphoric actions can lead to continued use and to dependence and addiction. While there are many factors involved in drug abuse, avoidance of stressful withdrawal symptoms is a key feature of addiction and its treatment. Fundamental to this is the need to understand the cellular processes that induce dependence and lead to the withdrawal syndrome. Many neurones in the brain express opioid receptors but only a few types of neurone develop dependence during chronic morphine exposure. The physiology of opiate-dependent cells is altered such that they require the continued presence of the drug to function normally and this is revealed, in cells that are inhibited by initial acute exposure to opiate, by a rebound hyperexcitation upon opiate withdrawal. Hypothalamic oxytocin neurones robustly develop morphine dependence and provide an exceptional opportunity to probe the cellular mechanisms underlying morphine dependence and withdrawal excitation. Although expression of morphine withdrawal excitation by oxytocin cells requires afferent inputs, the underlying mechanisms appear to reside within the oxytocin neurones themselves and probably involve changes in the intrinsic membrane properties of these neurones.

Therapeutic approach of patients with IgA nephropathy.

Immunoglobulin A nephropathy (IgAN) is the most commonly encountered primary glomerulonephritis and it usually follows an indolent clinical course. However, hypertensive patients with proteinuria and renal insufficiency at presentation and patients with severe histological involvement are at high risk to develop end stage renal failure. There is no consensus for the treatment of patients with IgA nephropathy. In general, patients with normal renal function, mild proteinuria (3 g/24 h) and in progressive disease despite treatment with ACE inhibitors. Fish oil might be an alternative to corticosteroids in cases with renal insufficiency and chronic histological lesions. Combinations of corticosteroids and cytotoxic drugs are saved for patients with IgA nephropathy and a rapidly progressive course.

ERP effects of subject-verb agreement violations in patients with Broca's aphasia.

This article presents electrophysiological data on on-line syntactic processing during auditory sentence comprehension in patients with Broca's aphasia. Event-related brain potentials (ERPs) were recorded from the scalp while subjects listened to sentences that were either syntactically correct or contained violations of subject-verb agreement. Three groups of subjects were tested: Broca patients (n = 10), nonaphasic patients with a right-hemisphere (RH) lesion (n = 5), and healthy aged-matched controls (n = 12). The healthy, control subjects showed a P600/SPS effect as response to the agreement violations. The nonaphasic patients with an RH lesion showed essentially the same pattern. The overall group of Broca patients did not show this sensitivity. However, the sensitivity was modulated by the severity of the syntactic comprehension impairment. The largest deviation from the standard P600/SPS effect was found in the patients with the relatively more severe syntactic comprehension impairment. In addition, ERPs to tones in a classical tone oddball paradigm were also recorded. Similar to the normal control subjects and RH patients, the group of Broca patients showed a P300 effect in the tone oddball condition. This indicates that aphasia in itself does not lead to a general reduction in all cognitive ERP effects. It was concluded that deviations from the standard P600/SPS effect in the Broca patients reflected difficulties with on-line maintaining of number information across clausal boundaries for establishing subject-verb agreement.