Secretion of natriuretic peptides caused by an epileptic attack

Neuroendocrine changes in the hypothalamic-neurohypophysial system in the Wistar audiogenic rat (WAR) strain submitted to audiogenic kindling

The Wistar audiogenic rat (WAR) strain is used as an animal model of epilepsy, which when submitted to acute acoustic stimulus presents tonic-clonic seizures, mainly dependent on brainstem (mesencephalic) structures. However, when WARs are exposed to chronic acoustic stimuli (audiogenic kindling-AK), they usually present tonic-clonic seizures, followed by limbic seizures, after recruitment of forebrain structures such as the cortex, hippocampus and amygdala. Although some studies have reported that hypothalamic-hypophysis function is also altered in WAR through modulating vasopressin (AVP) and oxytocin (OXT) secretion, the role of these neuropeptides in epilepsy still is controversial. We analyzed the impact of AK and consequent activation of mesencephalic neurocircuits and the recruitment of forebrain limbic (LiR) sites on the hypothalamic-neurohypophysial system and expression of Avpr1a and Oxtr in these structures. At the end of the AK protocol, nine out of 18 WARs presented LiR. Increases in both plasma vasopressin and oxytocin levels were observed in WAR when compared to Wistar rats. These results were correlated with an increase in the expressions of heteronuclear (hn) and messenger (m) RNA for Oxt in the paraventricular nucleus (PVN) in WARs submitted to AK that presented LiR. In the paraventricular nucleus, the hnAvp and mAvp expressions increased in WARs with and without LiR, respectively. There were no significant differences in Avp and Oxt expression in supraoptic nuclei (SON). Also, there was a reduction in the Avpr1a expression in the central nucleus of the amygdala and frontal lobe in the WAR strain. In the inferior colliculus, Avpr1a expression was lower in WARs after AK, especially those without LiR. Our results indicate that both AK and LiR in WARs lead to changes in the hypothalamic-neurohypophysial system and its receptors, providing a new molecular basis to better understaind epilepsy.

Mycoplasma pneumoniae- associated encephalitis complicated by cerebral salt wasting syndrome

Cerebral salt wasting syndrome can occur in children with encephalitis. Clinicians should be aware of hyponatremia in patients who develop polyuria with the signs of dehydration and deteriorated consciousness. Furthermore, patients who present with status epilepticus or who are suspected to have high intracranial pressure may have an increased risk of cerebral salt wasting syndrome.

Cerebral salt wasting in status epilepticus: two cases and review of the literature

BACKGROUND

Cerebral salt wasting is a hypovolemic hyponatremia state, caused by natriuresis and diuresis. The most important element of treatment is to replace the volume and sodium loss and improve the current clinic.

PATIENTS

We present two children who were treated in the intensive care unit who subsequently developed cerebral salt wasting. Diagnosis was based on hyponatremia associated with high urinary sodium excretion and inappropriately high urine output in the presence of dehydration. As part of the treatment, one patient was given fluid and sodium replacement, measures that were insufficient in the other patient, who also required fludrocortisone treatment.

CONCLUSION

The status epilepticus may be involved in the etiology of cerebral salt wasting. In both patients, cerebral salt wasting was detected in the posttreatment follow-up evaluations. Cerebral salt wasting is particularly likely to occur in individuals with status epilepticus, and the electrolyte and hydration status of these patients should be monitored closely, even after the convulsions are taken under control.

Potent and direct presynaptic modulation of glycinergic transmission in rat spinal neurons by atrial natriuretic peptide

Atrial and brain natriuretic peptides (ANP and BNP) exist in the central nervous system and modulate neuronal function, although the locus of actions and physiological mechanisms are still unclear. In the present study we used rat spinal sacral dorsal commissural nucleus (SDCN) and hippocampal 'synaptic bouton' preparations, to record both spontaneous and evoked glycinergic inhibitory postsynaptic currents (sIPSCs and eIPSCs) in SDCN neurons, and the evoked excitatory postsynaptic currents (eEPSCs) in hippocampal CA3 neurons. ANP potently and significantly reduced the sIPSC frequency without affecting the amplitude. ANP also potently reduced the eIPSCs amplitude concurrently increasing the failure rate and the paired pulse ratio response. These ANP actions were blocked by anantin, a specific type A natriuretic peptide receptor (NPR-A) antagonist. The results clearly indicate that ANP acts directly on glycinergic presynaptic nerve terminals to inhibit glycine release via presynaptic NPR-A. The ANP effects were not blocked by the membrane permeable cGMP analog (8Br-cGMP) suggesting a transduction mechanisms not simply related to increasing cGMP levels in nerve terminals. BNP did not affect on glycinergic sIPSCs and eIPSCs. Moreover, both ANP and BNP had no effect on glutamatergic EPSCs in hippocampal CA3 neurons. The results indicate a potent and selective presynaptic inhibitory action of ANP on glycinergic transmission in spinal cord sensory circuits.

B-type Natriuretic Peptide: Diagnostic and Therapeutic Applications in Infants and Children

The natriuretic peptide system plays an active role in the regulation of fluid balance and systemic vascular resistance. Peptides of the natriuretic system produced through recombinant DNA technology are now available for clinical use including both atrial natriuretic peptide (ANP) and brain-type natriuretic peptide (BNP). Assays of BNP are available and may be used for both diagnostic and prognostic purposes in various clinical scenarios. The basic physiology of the natriuretic peptide system is presented, applications of BNP monitoring as a diagnostic tool are reviewed, and reports regarding the use of recombinant BNP in the pediatric population are discussed.

Interpretation and use of natriuretic peptides in non-congestive heart failure settings

Natriuretic peptides (NPs) have been found to be useful markers in differentiating acute dyspneic patients presenting to the emergency department (ED) and emerged as potent prognostic markers for patients with congestive heart failure (CHF). The best-established and widely used clinical application of BNP and NT-proBNP testing is for the emergent diagnosis of CHF in patients presenting with acute dyspnea. Nevertheless, elevated NPs levels can be found in many circumstances involving left ventricular (LV) dysfunction or hypertrophy; right ventricular (RV) dysfunction secondary to pulmonary diseases; cardiac inflammatory or infectious diseases; endocrinology diseases and high output status without decreased LV ejection fraction. Even in the absence of significant clinical evidence of volume overload or LV dysfunction, markedly elevated NP levels can be found in patients with multiple comorbidities with a certain degree of prognostic value. Potential clinical applications of NPs are expanded accompanied by emerging reports regarding screening the presence of secondary cardiac dysfunction; monitoring the therapeutic responses, risk stratifications and providing prognostic values in many settings. Clinicians need to have expanded knowledge regarding the interpretation of elevated NPs levels and potential clinical applications of NPs. Clinicians should recognize that currently the only reasonable application for routine practice is limited to differentiation of acute dyspnea, rule-out-diagnostic-tests, monitoring of therapeutic responses and prognosis of acute or decompensated CHF. The rationales as well the potential applications of NPs in these settings are discussed in this review article.

Hyponatremia and Comparison of NT-pro-BNP Concentrations in Blood Samples from Jugular Bulb and Arterial Sites after Traumatic Brain Injury in Adults: A Pilot Study

BACKGROUND

Hyponatremia after traumatic brain injury (TBI) may influence neurological function and treatment. A causal relationship between elevated serum concentrations of Type B natriuretic peptide (BNP) and hyponatremia has been implied after subarachnoid hemorrhage and other neurosurgical disorders, although the source of BNP has not been identified. We evaluated if hyponatremia and increased BNP occur after TBI and if BNP is produced/released by the brain within 24 h after injury.

RESULTS

NT-proBNP was measured in concomitant jugular venous and arterial blood samples within 24 h after TBI. NT-proBNP was elevated in both samples in six patients (24%). One patient (4%) showed an increased jugular NT-proBNP concentration above a normal arterial concentration, suggesting a brain source. In the other 24 patients the difference between jugular and arterial NT-proBNP was not statistically significant. Hyponatremia (< or =136 mEq/l) also occurred in six patients (24%), but only two (8%) had both increased arterial NT-proBNP and hyponatremia. In both the urine sodium was slightly elevated above normal, but not statistically different from other patients. The difference in serum sodium between hypo- and normo-natremic groups was significant, but mean NT-proBNP and jugular:arterial NT-proBNP differences were not.

CONCLUSIONS

In this pilot study BNP is elevated within 24 h after TBI in some patients. However, it does not originate from the brain and increased NT-proBNP concentrations are not consistently associated with hyponatremia or increased urinary sodium loss.

Brain-type Natriuretic Peptide Release and Seizure Activity during Vagal Nerve Stimulation

Vagus nerve stimulation (VNS) has emerged as an effective adjunctive therapy for medically refractory epilepsy when surgery is inadvisable. N-terminal brain-type natriuretic peptide (NT-proBNP) is a potent natriuretic, diuretic, and vasodilatative compound first discovered in the human brain but mainly synthesized in the myocardium. The monitoring of VNS effectiveness in reducing seizure frequency or the detection of possible cardiac adverse effects would be helped by a reliable biochemical marker, which has not been available thus far. We report a four-year-old boy with drug-resistant idiopathic generalized epilepsy whose NT-proBNP levels increased during VNS and seizures.

Sepsis-associated myocardial dysfunction: diagnostic and prognostic impact of cardiac troponins and natriuretic peptides

Myocardial dysfunction, which is characterized by transient biventricular impairment of intrinsic myocardial contractility, is a common complication in patients with sepsis. Left ventricular systolic dysfunction is reflected by a reduced left ventricular stroke work index or, less accurately, by an impaired left ventricular ejection fraction (LVEF). Early recognition of myocardial dysfunction is crucial for the administration of the most appropriate therapy. Cardiac troponins and natriuretic peptides are biomarkers that were previously introduced for diagnosis and risk stratification in patients with acute coronary syndrome and congestive heart failure, respectively. However, their prognostic and diagnostic impact in critically ill patients warrants definition. The elevation of cardiac troponin levels in patients with sepsis, severe sepsis, or septic shock has been shown to indicate left ventricular dysfunction and a poor prognosis. Troponin release in this population occurs in the absence of flow-limiting coronary artery disease, suggesting the presence of mechanisms other than thrombotic coronary artery occlusion, probably a transient loss in membrane integrity with subsequent troponin leakage or microvascular thrombotic injury. In contrast to the rather uniform results of studies dealing with cardiac troponins, the impact of raised B-type natriuretic peptide (BNP) levels in patients with sepsis is less clear. The relationship between BNP and both LVEF and left-sided filling pressures is weak, and data on the prognostic impact of high BNP levels in patients with sepsis are conflicting. Mechanisms other than left ventricular wall stress may contribute to BNP release, including right ventricular overload, catecholamine therapy, renal failure, diseases of the CNS, and cytokine up-regulation. Whereas cardiac troponins may be integrated into the monitoring of myocardial dysfunction in patients with severe sepsis or septic shock to identify those patients requiring early and aggressive supportive therapy, the routine use of BNP and other natriuretic peptides in this setting is discouraged at the moment.

Recurrent hyponatremia after intrathecal methotrexate not related to antidiuretic hormone: is a natriuretic peptide activated?

We report the development of recurrent hyponatremia after intrathecal methotrexate that was not associated with elevated levels of antidiuretic hormone. We speculate that a central nervous system natriuretic peptide may be involved in the pathogenesis of the naturesis following intrathecal methotrexate.

Utility of brain natriuretic peptide (BNP) measurement in cardiovascular disease

Cardiac failure is a prevalent and costly condition in Western society. The ageing of the population, together with current medical options which improve, rather than eradicate heart failure, lead to the projection that this problem will increase substantially in the foreseeable future. The availability of a simple test to assist the diagnosis and effective management of heart failure would greatly assist the clinical approach to this problem. This review examines the physiological basis for the measurement of natriuretic peptides as markers of the presence or risk of heart failure. It considers its use in the hospital and non-hospital setting and examines the cost-effectiveness of current assays. It is possible that in future natriuretic peptides may offer a form of treatment for heart failure, but this is beyond the scope of this review. Nevertheless, the review highlights the potential benefits of this group of tests in the management of heart failure.