Assessing short- and long-term modifications of steady-state water infiltration rate in an extensive Mediterranean green roof

Green roof detention capacity is related to the steady-state infiltration rate, i_s, of the growing medium. With the aim to investigate short- and long-term modifications of the detention capacity of an extensive Mediterranean green roof, three mini-disk infiltrometer (MDI) measurement campaigns were conducted at construction, after one season and after five years of operation. A laboratory experiment was designed to separately measure i_s in the upper and the lower part of the substrate profile. During the first operating season, field i_s increased by a factor of 2.4 and 1.9 for near-saturated (applied pressure head, h₀ = -30 mm) and quasi-saturated conditions (h₀ = -5 mm), respectively. Similar rainfall height did not induce significant modifications in the upper layer of the laboratory columns, even if contribution of small pores to water infiltration tended to increase. Differently, i_s significantly decreased by a factor of 3.4-5.3 in the lower layer. After the simulated rainfall, the upper layer was less packed (mean bulk density, ρ_b = 1.083 kg m^-3) and the lower layer was more packed (ρ_b = 1.218 kg m^-3) as compared with the initial density (ρ_b = 1.131 kg m^-3) and the lower part enriched in small particles. Short-term modifications in the experimental plot were thus attributed to fine particles washing-off and bulk density decrease in the upper layer, yielding an overall more conductive porous medium. After five years of green roof operation, field i_s did not further increase thus showing that the washing/clogging mechanism was complete after one season or it was masked by counteracting processes, like root development and hydrophobicity.

Hydrological and hydraulic behaviour of a surface flow constructed wetland treating agricultural drainage water in northern Italy

A surface flow constructed wetland (SFCW) treating agricultural drainage water was investigated with the aim to detect modifications in hydrological and hydraulic characteristics after more than a decade of operation. Ponded infiltration tests were conducted to estimate the saturated hydraulic conductivity, K_s, of the surface soil layer at the point scale. At the global scale, infiltration rate, i, was computed from the water balance to detect leakages from the pervious wetland surface. Tracer tests were conducted to analyse the existence of preferential flow inside the system and to estimate its hydraulic retention time (HRT). Clogging phenomena occurred given a mean K_s value of 30 mm h^-1 was measured near the SFCW inlet, that was 9.61 times lower than the value at the outlet zone. The estimated infiltration losses were two orders of magnitude lower than infiltration measured at the point scale. The results also confirmed the existence of a moderate amount of preferential flow paths and dead zones in the SFCW as the actual HRT (6.7 days) was shorter than the nominal one (8.1 days). Despite this, it can be concluded that the system performance is still good after 17 years of operation.

Assessment of clogging in constructed wetlands by saturated hydraulic conductivity measurements

This study aims at defining a methodology to evaluate K_s reductions of gravel material constituting constructed wetland (CW) bed matrices. Several schemes and equations for the Lefranc's test were compared by using different gravel sizes and at multiple spatial scales. The falling-head test method was implemented by using two steel permeameters: one impervious (IMP) and one pervious (P) on one side. At laboratory scale, mean K values for a small size gravel (8-15 × 10^-2 m) measured by the IMP and the P permeameters were equal to 19,466 m/d and 30,662 m/d, respectively. Mean K_s values for a big size gravel (10-25 × 10^-2 m) measured by the IMP and the P permeameters were equal to 12,135 m/d and 20,866 m/d, respectively. Comparison of K_s values obtained by the two permeameters at laboratory scale as well as a sensitivity analysis and a calibration, lead to the modification of the standpipe equation, to evaluate also the temporal variation of the horizontal K_s. In particular, both permeameters allow the evaluation of the K_s decreasing after 4 years-operation and 1-1.5 years' operation of the plants at full scale (filled with the small size gravel) and at pilot scale (filled with the big size gravel), respectively.

Safety, Tolerability and Pharmacokinetics of BIBN 4096 BS, the First Selective Small Molecule Calcitonin Gene-Related Peptide Receptor Antagonist, Following Single Intravenous Administration in Healthy Volunteers

BIBN 4096 BS ([R-(R∗,S∗)]-N-[2-[[5-amino-1-[[4-(4-pyridinyl)-1-piperazinyl]carbonyl] pentyl]amino]-1-[(3,5-dibromo-4-hydroxyphenyl)methyl]-2-oxoethyl]-4-(1,4-dihydro-2-oxo-3(2H)-quinazolinyl)-,1-piperidinecarboxamide) is the first selective, highly potent, small molecule, nonpeptide calcitonin gene-related peptide (CGRP) receptor antagonist, which has been developed for the treatment of acute migraine. The objective of this study was to obtain information on the safety, tolerability and pharmacokinetics of BIBN 4096 BS following single intravenous administration of rising doses (0.1, 0.25, 0.5, 1, 2.5, 5 and 10 mg) in 55 healthy male and female volunteers. The study was of single-centre, double-blind (within dose levels), placebo-controlled, randomized, single rising dose design. Blood pressure, pulse rate, respiratory rate, ECG, laboratory tests and forearm blood flow did not reveal any clinically relevant, drug-induced changes. Sixteen adverse events (AEs) were reported by eight of 41 volunteers after BIBN 4096 BS compared to five AEs reported by four of 14 volunteers after placebo. Approximately two-thirds of all AEs related to active treatment occurred at the highest dose of 10 mg. At this dose level, all AEs were confined to the three BIBN 4096 BS-treated females, and consisted mainly of transient and mild paresthesias. Paresthesias were the single most frequent AE, whereas fatigue was the AE which occurred in the highest number of subjects. Only two AEs were of moderate intensity, all remaining AEs were of mild intensity. No serious AEs were reported. The local tolerability after intravenous administration was good. In summary, intravenously administered BIBN 4096 BS revealed a very favourable safety profile over the dose range tested in both genders. Generally well tolerated at all dose levels, it was of satisfactory tolerability in female subjects at the highest dose of 10 mg. The plasma concentration-time courses of BIBN 4096 BS showed multicompartmental disposition characteristics. Mean maximum concentration (Cmax) values appeared to be dose-proportional. Based on the results from the two high dose levels (5 and 10 mg) with sufficient individual subject data, BIBN 4096 BS exhibited a total plasma clearance (CL) of approximately 12 l/h and an apparent volume of distribution at steady state (Vss) of approximately 20 l, resulting in a terminal half-life (t1/2) of approximately 2.5 h. Inter-individual variability was moderate with a coefficient of variation of approximately 45% based on the area under the plasma concentration-time curve (AUC) values. The mean renal clearance (CLR) was approximately 2 l/h, suggesting that renal excretion plays only a minor role in the elimination of unchanged BIBN 4096 BS.

Difference in growth hormone response to growth hormone-releasing hormone (GHRH) testing following GHRH subacute treatment in normal aging and growth hormone-deficient adults: possible perspectives for therapeutic use of GHRH or its analogs in elderly subjects?

The somatotroph axis function shows a decline in the elderly (somatopause). In particular growth hormone (GH) response to GH-releasing hormone (GHRH) is reduced in aged man but less than that observed in GH-deficient adults (GHDAs). Plasma GH response to GHRH (1 µg/kg BW) was significantly lower in four GHDAs than in seven healthy aged men 30, 60, and 90 min after acute GHRH administration. To verify whether a priming regimen might be able to increase the reduced GH response to GHRH, both healthy aged men and GHDA patients underwent repetitive administration of GHRH (100 µg GHRH intravenously as a single morning dose, every 2 days for 12 days). After the GHRH-priming regimen, plasma GH values 30, 60, and 90 min after the acute GHRH test were significantly higher than values at the corresponding time points before priming regimen in healthy aged men but not in GHDA patients. These findings confirmed that somatotroph cells become less sensitive to GHRH with normal aging and demonstrate that repetitive administration of GHRH restores the attenuated response only in healthy aged men but not in GHDA patients. This could support the possible use of GHRH or its analogs instead of recombinant human GH in elderly patients with the advantage of preserving the endogenous pulses of GH with the secretion of the different isoforms of GH. However, concerns arise about the possible role of these molecules in tumorigenesis and tumor growth promotion.

Vasopressin release induced by hypothension is blunted in patients with diabetic autonomic neuropathy

The response of arginin-vasopressin (AVP) to baroreceptor activation (tilt testing) was investigated in patients with diabetic autonomic neuropathy (DAN). The present data show that hypothension induced by upright position showed a slight increase of AVP in patients with DAN in comparison with normal subjects and diabetic patients without DAN. These findings suggest that the blunted AVP response to hypothension may be due to lesions of afferent autonomic pathways present in DAN and plays a role in the pathogenesis of postural hypothension.

The Aurora B kinase activity is required for the maintenance of the differentiated state of murine myoblasts

Reversine is a synthetic molecule capable of inducing dedifferentiation of C2C12, a murine myoblast cell line, into multipotent progenitor cells, which can be redirected to differentiate in nonmuscle cell types under appropriate conditions. Reversine is also a potent inhibitor of Aurora B, a protein kinase required for mitotic chromosome segregation, spindle checkpoint function, cytokinesis and histone H3 phosphorylation, raising the possibility that the dedifferentiation capability of reversine is mediated through the inhibition of Aurora B. Indeed, here we show that several other well-characterized Aurora B inhibitors are capable of dedifferentiating C2C12 myoblasts. Significantly, expressing drug-resistant Aurora B mutants, which are insensitive to reversine block the dedifferentiation process, indicating that Aurora B kinase activity is required to maintain the differentiated state. We show that the inhibition of the spindle checkpoint or cytokinesis per se is not sufficient for dedifferentiation. Rather, our data support a model whereby changes in histone H3 phosphorylation result in chromatin remodeling, which in turn restores the multipotent state.

Role of the helix capping in the stability of the mouse prion (180-213) segment: investigation through molecular dynamics simulations

Molecular dynamics simulation of the 180-213 segment, forming the B and C helices in the mouse prion protein, and of three mutants, where the capping box residues or the hydrophobic staple motif residues were selectively mutated, have been carried out. The results indicate that the wild type segment is stable over all the trajectory, whilst the mutants display different degrees of destabilization. In detail mutation of Asp202 brings to a rapid unfolding of helix C likely because of the concomitant loss of a hydrogen bond and of a negative charge able to stabilize the dipole in the first turn of the helix. A lower destabilizing effect is observed upon mutation Thr199. On the other hand mutation of Phe198 and Val203, the hydrophobic staple residues, brings to an incorrect orientation of the first helix relative to the second one due to a weakening of the hydrophobic interaction. The results confirm the importance of the presence of both motifs for the structural integrity of the isolated fragment and suggest that these residues may have a main role in the structural transition observed in the inherited human prion diseases.

Molecular dynamics simulation of the antimicrobial salivary peptide histatin-5 in water and in trifluoroethanol: a microscopic description of the water destructuring effect

The results of 520 ps molecular dynamics simulation of histatin-5, a small peptide present in human saliva and possessing antimicrobial activity, dissolved in water and in 2,2,2-trifluoroethanol, are reported. The simulations indicate that histatin-5 is destabilized in water and begins to unfold after 250 ps, while in organic solvent it maintains a regular secondary structure throughout the trajectory. Analysis of the peptide-solvent hydrogen bonds indicates that 2,2,2-trifluoroethanol is a poorer proton acceptor than water. The fluorine atom of the alcohol is almost never engaged in a hydrogen bond and the organic solvent interacts mainly with the peptide through its hydroxyl group. For some residues analysis of the solvent residence time indicated longer values for 2,2,2-trifluoroethanol than for water. The most striking difference is related to the number of times the solvent enters and leaves the first coordination shell of the peptide. This value was more than one order of magnitude higher for water than for the alcohol, suggesting that this may be the main cause of alpha-helix destabilization perpetrated by water.

A model for the incorporation of metal from the copper chaperone CCS into Cu,Zn superoxide dismutase

BACKGROUND

Recent studies have identified the human copper chaperone CCS as the presumed factor responsible for copper incorporation into superoxide dismutase (SOD). A lack of knowledge of the chaperone's three-dimensional structure has prevented understanding of how the copper might be transferred.

RESULTS

The three-dimensional structure of CCS was homology modelled using the periplasmic protein from the bacterial mercury-detoxification system and the structure of one subunit of the human SOD dimeric enzyme as templates. On the basis of the three-dimensional model, a mechanism for the transfer of copper from CCS to SOD is proposed that accounts for electrostatic acceptor recognition, copper storage and copper-transfer properties.

CONCLUSIONS

The proposed model identifies a path for copper transfer based on the presence of different metal sites characterized by sulphur ligands. Such a model permits the development of strategies able to interfere with copper incorporation in SOD, providing a possible way to prevent or arrest degeneration in the fatal motor neuron disorder amyotrophic lateral sclerosis.

Glutamatergic activation of hippocampal phospholipase D: postnatal fading and receptor desensitization

Phospholipase D (PLD) activity was determined in rat hippocampal slices between postnatal days 3 and 35. After birth, basal PLD activity was low and, within 2 weeks, increased to reach a plateau that was maintained up to the adult age. Likewise the response to glutamate developed postnatally to reach a maximum at day 8, but then faded rapidly and was almost absent at day 35. Activation of PLD by 4beta-phorbol 12beta,13alpha-dibutyrate (PDB) was independent of age, whereas the effect of aluminum fluoride (AlF4-) increased to a plateau within the first week. At day 8, PLD stimulation by glutamate via metabotropic receptors involved protein kinase C activation, but was independent of Ca2+ influx; the time course of PLD activation by PDB or AlF4- was linear throughout the experiment, whereas the response to glutamate or 1-aminocyclopentane-1,3-dicarboxylic acid followed a biphasic pattern: the rapid "first phase activation" desensitized within a few minutes and disclosed a small, but maintained "second phase." Pretreatment experiments confirmed desensitization of PLD activation by glutamate, but not by AlF4- or PDB. The biphasic pattern of glutamatergic PLD activation changed during development, i.e., the first phase activation faded and the second phase remained. These results were fully confirmed by the time courses of the PLD-mediated efflux of choline evoked by glutamate. In conclusion, postnatal glutamatergic activation of hippocampal PLD is composed of a pronounced and desensitizing first phase activation and a small, but nondesensitizing second phase. The first, but not the second, phase activation fades rapidly during development. The hypothesis is discussed that the glutamatergic activation of PLD occurs along different pathways in neonate and adult tissue.

Ontogenetic and pharmacological studies on metabotropic glutamate receptors coupled to phospholipase D activation

The present study was aimed at characterizing the metabotropic receptor subtype which is involved in the activation of phospholipase D (PLD) by glutamate in rat hippocampal slices. We first observed that the ontogenetic profile of glutamate-induced hydrolysis of phosphoinositides and of phosphatidylcholine was strikingly similar. Both pathways were significantly activated by glutamate in tissue taken from 3-, 8- and 15-day old rats, but not in adult rats. PLD activation was strongest in slices taken from 8-day old rats. At this age, quisqualate had a higher potency for PLD activation (EC50: 0.6 microM) than 1S,3R-ACPD (EC50: 16 microM) and DHPG, a specific activator of group I mGluR, was a full agonist at PLD activation (EC50: 3.5 microM) indicating an involvement of a group I mGluR (mGluR1 and 5). MCPG and AIDA, two putative antagonists at mGluR1 receptors, caused a small but (in the case of MCPG) significant inhibition. DCG-IV, an activator of group II mGluR, was a weak partial agonist at PLD activation (EC50: 22 nM) while L-AP 4, an activator at group III mGluR, was totally inactive. Likewise, forskolin, a stimulant of cyclic AMP formation, was inactive either alone, or in combination with glutamatergic agonists. Pretreatment of the slices with pertussis toxin did not affect PLD activation. In summary, the glutamate-mediated activation of hippocampal PLD, which occurs transiently during postnatal development, is mediated by a group I mGluR, possibly involving mGluR5.

[Aneurysmal bone cyst: diagnostic role of computerized tomography and magnetic resonance]

Aneurysmal bone cysts (ABC) are relatively uncommon benign expansile osteolytic lesions characterized by multiple cavities with serum-blood levels and delimited by a thin periosteal external border. The differential diagnosis is difficult to make with conventional radiography, while CT and MRI are elective techniques. Ten patients with ABC (7 central and 3 eccentric lesions) were examined with CT and MRI. Four cysts were localized at the proximal femur, 2 in calcaneal, 2 in vertebral (cervical and dorsal), 1 in tibial and 1 in iliac sites. Diagnostic criteria were the presence of fluid-fluid levels and a thin hyperdense peripheral border at CT, while hyperintense cavities on T2-weighted sequences, fluid-fluid levels, pseudodiverticular features and a low-signal border were found at MRI. Intralesional levels were detected in 9 patients at CT and in 10 at MRI; the 3 peripheral cysts exhibited a hyperdense extraosseous border at CT, corresponding to the periosteal shell, considered a benignity sign. To conclude, CT and MRI, thanks to their high resolution, clearly depict the anatomopathologic features of ABC, thus allowing this type of lesion to be differentiated from other benign and malignant osteolytic lesions.

Impaired sensitivity of the hypothalamo-pituitary-thyroid axis to the suppressant effect of dexamethasone in elderly subjects

It has been shown that glucocorticoids have a suppressant effect on the thyrotropin (TSH) response to thyrotropin-releasing hormone (TRH) in young men. To assess whether this effect of corticosteroids is also present in aged individuals, six young subjects (aged 26-32 years) and six elderly men (aged 68-75 years) underwent, in random order, at 1 week intervals, three TRH stimulation tests 30 min after IV administration of placebo and 2 mg and 4 mg dexamethasone phosphate. Elderly men showed higher basal plasma levels of TSH (P less than 0.02) and lower plasma levels of FT3 (P less than 0.03) and FT4 (P less than 0.01). The TSH response to TRH was significantly lower in aged subjects than in young ones (P less than 0.009). Moreover, 2 mg dexamethasone significantly blunted the TSH response to TRH in young men (P less than 0.0001), but not in the elders. The inhibitory effect of the glucocorticoid on the TRH-induced TSH secretion, in aged subjects, was evident only after 4 mg dexamethasone administration (P less than 0.0001). These data confirm that glucocorticoids have an inhibitory role on the thyrotropic axis and show, for the first time, that normal elderly men are hyporesponsive to this suppressant effect of corticosteroids.

Alpha 2-adrenergic stimulation within the nucleus tractus solitarius attenuates vasopressin release induced by depletion of cardiovascular volume

The functional role of the nucleus tractus solitarius (NTS) in the regulation of arginine-vasopressin (AVP) release mediated by baroreceptor activation was investigated by examining the effects induced by the presynaptic alpha-adrenergic agonist clonidine. The present data show that microinjection of clonidine into NTS resulted in a significant attenuation of AVP secretion induced by hypovolemia in the rat. This effect produced by NTS injection of 8 and 10 nmol clonidine was prevented by NTS pretreatment with the alpha 2-adrenoceptor blocker, yohimbine (10 nmol), indicating alpha 2-adrenergic receptors were required for the biological response. These findings suggest that catecholaminergic projections from NTS to hypothalamic vasopressinergic neurons play a facilitatory role in controlling AVP secretion.

Evidence that cholinergic receptors of muscarinic type may modulate vasopressin release induced by metoclopramide

Studies were carried out in the rat in order to investigate whether cholinergic mechanisms may be involved in vasopressin (VP) release induced by metoclopramide (MCP). The intravenous injection of MCP induced dose-related increases in plasma VP levels in water-loaded rats. These effects were prevented by atropine sulphate, but not by pirenzepine hydrochloride indicating that activation of cholinergic receptors of M-2 type was possibly required for the biologic response.

GABA, depression and the mechanism of action of antidepressant drugs: a neuroendocrine approach

Recent evidence has suggested the involvement of the GABAergic system in depression and in the mechanism of action of somatic antidepressant treatments. In particular, GABAB receptors have been found to be increased in the rat frontal cortex following chronic antidepressant therapies. In the present study, the sensitivity of GABAB binding sites was assessed in nine healthy men and 10 depressed patients via the plasma growth hormone (GH) response to acute baclofen administration (20 mg p.o.). Depressed subjects were tested before and after 15 and 35 days of treatment with amitriptyline (100 mg/day), imipramine (100 mg/day) and fluoxetine (20 mg/day). GH response to acute GABAB receptor activation did not differ between depressed subjects and healthy controls. Moreover, chronic antidepressant treatment did not significantly modify this response, even when a clear therapeutic effect was obtained. These results do not support the idea that GABAergic mechanisms are involved in the pathophysiology of depression and in the mechanism of action of antidepressant drugs.

Repetitive growth hormone-releasing hormone administration restores the attenuated growth hormone (GH) response to GH-releasing hormone testing in normal aging

The plasma GH response to human pituitary GH (hpGH)-releasing hormone-40 (hpGHRH-40; 1 microgram/kg BW) was significantly lower in seven healthy aged men (age range, 65-78 yr) than in seven healthy young men (age range, 18-31 yr) 30, 60, and 90 min after acute hpGHRH-40 administration (P less than 0.0001, by Student's unpaired t test). To verify whether a priming regimen might be able to reverse the reduced GH response to GHRH, elderly subjects underwent repetitive administration of hpGHRH-40 and placebo in a double blind design (100 micrograms hpGHRH-40 or volume-matched saline iv as a single morning dose, every 2 days for 12 days). After the hpGHRH-40-priming regimen, plasma GH values 30, 60, and 90 min after the acute GHRH test were significantly higher than values at the corresponding time points after placebo treatment. These findings suggest that somatotroph cells become less sensitive to GHRH with normal aging and demonstrate that repetitive administration of GHRH restores the attenuated response.

Evidence for a sex difference in the basal growth hormone response to GABAergic stimulation in humans

Evidence has been provided supporting the existence of a sex-related difference in the GH secretion following different GH-releasing stimuli. Since pharmacological activation of the endogenous gammaaminobutyric acid (GABA) system results in increased basal GH release in humans, the present study was undertaken to investigate whether a sex difference is present in the GH response to GABAergic stimulation. Sixteen healthy subjects (8 women and 8 men) received orally 10 mg of baclofen, the direct GABAB agonist which freely crosses the blood-brain barrier. Blood samples were collected before (T = -30 and 0) and 30, 60, 90, 120 and 180 min after the drug administration for plasma GH measurements. Following baclofen administration, plasma GH rose in healthy males (F = 19.417, P less than 0.0001), but not in females (F = 1.67, NS). These results suggest that GABA modulation of human GH release is sex-dependent.

Pharmacological activation of the GABAergic system does not affect GH and PRL release in acromegaly

An extensive hypothalamic neurotransmitter impairment has been proposed in acromegaly. However, at the moment, the hypothalamic GABAergic system has been little investigated in this disorder. Since GABA has been shown to modulate growth hormone (GH) and prolactin (PRL) secretion in human subjects, it seemed reasonable to investigate hypothalamic GABAergic functioning through the assessment of basal GH and PRL responses to pharmacological activation of this system. 800 mg of sodium valproate (SV), a drug with GABA facilitating properties, were administered orally to 7 acromegalic patients and 9 healthy volunteers. Blood samples were collected before and after the drug administration for the measurement of plasma GH and PRL levels. SV induced a clear-cut rise in basal GH and a decrease in basal PRL in healthy subjects, but it did not induce any change in the basal levels of these hormones in acromegalics. These results suggest that the response of GH and PRL to SV in acromegaly is qualitatively different from normal controls.

Baclofen-induced growth hormone secretion is blunted in chronic schizophrenics: neuroendocrine evidence for a GABA disturbance in schizophrenia

To substantiate a previously reported disturbance of gamma-aminobutyric acid (GABA) in chronic schizophrenia, plasma growth hormone (GH) response to a direct GABA agonist (baclofen, 10 mg) was assessed in 12 unmedicated chronic schizophrenic males and 10 sex- and age-matched healthy controls. Baclofen and placebo were administered orally, in a double-blind design, and blood samples were collected before and 30, 60, 90, 120, 180, and 240 min after drug or placebo administration. Baclofen induced a clear-cut rise in plasma GH levels over baseline values, but the GH increase observed in the patients was significantly smaller than that in controls. These results support the idea that GABA mechanisms may be impaired in chronic schizophrenia.

Selective damage of neuron perikarya in the medial septum of the rat forebrain: effects on food and water intake, urine output and body weight

The intraseptal administration of the neurotoxin kainic acid (KA) induced a significant depletion of the neuronal population and glial proliferation in medial septal areas. The behavioral effects induced by this selective destruction of the neurons indigenous to the medial septal areas were investigated. KA produced a marked increase in urine output and a transient reduction in body weight, but failed to affect water and food intake.

Neuroanatomical and biochemical evidence for the involvement of the area postrema in the regulation of vasopressin release in rats

Studies were carried out in the rat to determine if the area postrema (AP), a medullary circumventricular organ, might be involved in the control of vasopressin (VP) release. The data from this study demonstrate the existence of direct neural connections between the AP and the hypothalamic VPergic neurons of the supraoptic nucleus (SON) as showed by the retrograde tracer horseradish peroxidase (HRP). Labeled neurons were observed in the AP following HRP injections into the SON. In addition, rats with AP lesions showed an impaired ability to conserve water and concentrate their urine in response to an hypertonic NaCl load. They, also, failed to maintain sodium retention and showed an attenuation of VP release during intracellular dehydration. These findings indicate that AP plays an important role in the regulation of VP release during changes in osmotic environment and suggest that this medullary circumventricular organ is a part of central circuitry subserving salt-water balance.

Combined alpha-adrenergic stimulation results in biphasic response of growth hormone release in man

Oral clonidine administration or insulin-induced hypoglycemia may enhance GH secretion through alpha 2-adrenergic stimulation in man. To further characterize the role of adrenergic transmission in the regulation of GH release, the effects of combined administration of clonidine and insulin were investigated in 16 normal men randomly assigned to 2 groups. The first group received 0.1 U/kg regular insulin, iv, followed by placebo or clonidine (0.150 mg), orally, on 2 different days, 2 weeks apart. The second group received oral clonidine (0.150 mg), followed by iv placebo or insulin (0.1 U/kg) on 2 different days, 2 weeks apart. Insulin induced a clear-cut increase in plasma GH (F = 79.88; P less than 0.001) that was not affected by placebo, whereas it was significantly inhibited by oral clonidine (P less than 0.001 at 60, 90, and 120 min). Similarly, oral clonidine administration resulted in a clear-cut rise in plasma GH levels (F = 16.44; P less than 0.001) that was significantly reduced by insulin (P less than 0.001, P less than 0.02, and P less than 0.05 at 60, 90, and 120 min, respectively). These results suggest that while moderate activation of the alpha 2-adrenergic system stimulates GH release, further stimulation of the same system may result in inhibition, rather than further activation, of GH secretion.

Prolactin response to sodium valproate in schizophrenics with and without tardive dyskinesia

Sodium valproate, a GABAergic agent (800 mg), and placebo were administered orally, as a single dose, to nine chronic schizophrenics with tardive dyskinesia (TD), seven chronic schizophrenics without TD and ten healthy controls, according to a double blind design. Blood samples were collected before and after drug administration, to determine plasma prolactin concentrations. Sodium valproate decreased plasma prolactin levels in healthy subjects (P less than 0.001) and in schizophrenic patients with TD (P less than 0.001), but not in chronic schizophrenics without TD. Moreover, in dyskinetic subjects, the maximum per cent decrease of plasma prolactin from basal value was positively correlated to the score of the abnormal involuntary movement scale (r = 0.724, P less than 0.02). Although the neural or biochemical substrate underlying the different responses of plasma prolactin to sodium valproate in schizophrenics with and without TD remains unclear, these results provide the first neuroendocrine evidence able to differentiate dyskinetic subjects from those without TD within a schizophrenic population.

Is the dexamethasone suppression test predictive of response to specific antidepressant treatment in major depression?

The authors attempt to correlate the response to dexamethasone suppression test (DST) with a clinical response to antidepressant drugs in 68 patients with major depression. Antidepressants that influence noradrenergic or serotonergic transmission with relative different potencies were selected and used in standard doses for 6 weeks. The response was evaluated weekly by raters blind to DST results and to antidepressant medications prescribed. The retrospective analysis failed to correlate DST response with outcome of treatment. Therefore the present results suggest that this laboratory test does not help to identify subgroups of depressed patients responding preferentially to various antidepressant drugs.

Gonadal steroids do not affect basal growth hormone response to naloxone in humans

Evidence has accumulated that endogenous hypothalamic opioid activity fluctuates through the menstrual cycle depending upon the ovarian steroid milieu. In fact, naloxone, the specific opiate antagonist, is more effective in producing neuroendocrine changes in the late follicular and midluteal phases of the menstrual cycle, when the functional activity of hypothalamic opiate system is high. In order to investigate a possible regulatory function of endogenous opioids on basal growth hormone (GH) secretion in humans, we studied the basal GH response to naloxone (2 mg iv as a bolus) in different phases of the menstrual cycle in ten regularly menstruating women and in eight hypogonadal (postmenopausal) females before and after estrogen treatment. This protocol was carried out to test the hypothesis that estrogens could sensitize basal GH response to opiate receptor blockade. The results do not support this view and suggest that, under basal conditions, hypothalamic opiates have minimal influence on GH secretion in humans.

Impaired growth hormone response to sodium valproate in normal aging

Evidence has been provided for impaired neurotransmitter functioning in the brain of elderly subjects. In order to assess central GABAergic transmission, the activity of the hypothalamic GABA system may be investigated by basal growth hormone (GH) response to the GABAergic drug sodium valproate (SV). For this purpose 15 healthy men (aged 19-81 years) received orally 800 mg SV or placebo tablets on two different occasions, 1 week apart. Blood samples were collected before and after drug administration for determining GH and SV plasma levels. A clear-cut increase in plasma GH was observed following SV (P less than 0.001 in young persons, P less than 0.005 in old subjects), but in the aged subjects this rise was statistically lower than in the young men (P less than 0.001 at t = 90 min). No difference was observed in basal GH levels and in SV plasma concentrations between elderly and young subjects. delta GH (= maximum post-SV GH level minus baseline GH value) was significantly inversely related to age (r = -0.90, P less than 0.001). These results may suggest an impaired hypothalamic-pituitary responsiveness to a pharmacological challenge enhancing endogenous GABA tone in the elderly.

Pharmacological evidence for a dual GABAergic regulation of growth hormone release in humans

Effects of sodium valproate, which is believed to act via a gamma-aminobutyric acid mechanism, on basal and exercise-induced rise of growth hormone release have been tested in eighteen healthy volunteers. The exercise test consisted of using a stationary bicycle ergometer at 450 kg/min for 20 min. 600 mg per os of the drug resulted in a significant enhancement in plasma hormonal concentrations, whereas no effects were induced by placebo (p less than 0.005). Conversely, the growth hormone rise stimulated by exercise was markedly inhibited by sodium valproate (p less than 0.001 and p less than 0.01 at time 20, 40 and 60 min respectively). The results of this study are consistent with the hypothesis that a dual GABAergic control of growth hormone secretion is present in man.

Vasopressin release after enhanced serotonergic transmission is not due to activation of the peripheral renin-angiotensin system

Pharmacological enhancement of 5-hydroxytryptamine (5-HT) transmission increases plasma vasopressin in rats. To investigate whether this effect is mediated through activation of the peripheral renin-angiotensin system, plasma vasopressin concentrations were measured after 5-HT activation in rats with lesions of the subfornical organ or pretreated with saralasin. The results show that the 5-HT-induced elevation of vasopressin is not due to activation of the peripheral renin-angiotensin system.

Growth hormone response to sodium valproate in chronic schizophrenia

The hypothesis of a gamma-aminobutyric acid (GABA) involvement in the pathophysiology of schizophrenia has been recently proposed but not confirmed. As GABA has been shown to affect basal growth hormone (GH) secretion in humans, the assessment of plasma GH response to a GABAergic drug, such as sodium valproate (SV), in schizophrenic subjects might be a tool with which to investigate central GABA activity in this illness. For this purpose, we administered orally 800 mg of SV or placebo to 13 chronic schizophrenics and to 10 normal controls, and measured plasma GH levels before and after the drug administration. SV enhanced basal GH secretion in healthy male volunteers, but not in chronic schizophrenics. These results suggest a defect of the endogenous GABA system in chronic schizophrenia. Whether the reduced responsiveness observed represents a primary defect or a secondary alteration of the GABA system in schizophrenia is as yet unknown.

Effect of substances influencing brain serotonergic transmission on plasma vasopressin levels in the rat

Studies were carried out in the rat to investigate whether serotonin (5-HT) is involved in the regulation of vasopressin (ADH) release. For this purpose plasma ADH levels were measured in rats treated with drugs enhancing 5-HT transmission, such as d-fenfluramine and quipazine and with 5-HT depleting drugs, p-chlorophenylalanine (PCPA) and 5,7-dihydroxytryptamine (5,7-DHT). Forebrain 5HT, noradrenaline (NA) and dopamine (DA) were also measured. d-Fenfluramine and quipazine induced dose-related increases in plasma ADH levels in normohydrated rats. The effects of quipazine and d-fenfluramine were prevented by PCPA, indicating that 5-HT transmission was required for the biologic response. 5,7-DHT and PCPA pretreatment decreased forebrain 5-HT content and prevented ADH increases involved by water deprivation, suggesting that 5HT is necessary for the hormonal response to osmotic stimuli. The results summarized imply that serotonin may have a role in the physiological release of ADH from neurohypophysis.

Thirst and vasopressin secretion following central administration of angiotensin II in rats with lesions of the septal area and subfornical organ

Various dipsogenic stimuli, including peripheral and central administration of angiotensin II, have been shown to be capable of releasing vasopressin from the neurohypophyseal system. Studies were carried out in the rat to investigate whether the septal area, which contains a high concentration of angiotensin-sensitive cells and has neural connections with hypothalamic vasopressin-secreting neurons, mediated the stimulatory effect produced by angiotensin II on vasopressin release. Rats with electrolytic lesions in the region of the septal area had increased daily water consumption and urine output when these lesions included the medioventral or lateral nuclei of the septal forebrain, but not when the lesion involved the subfornical organ. No difference was observed in drinking responses following water deprivation or intracerebroventricular injection of angiotensin II in all experimental groups. In addition, the impaired ability to maintain water homeostasis (polyuro-polydipsic syndrome) of septal-lesioned rats was associated septal-lesioned rats was associated with decreased levels of circulating radioimmunoassayable vasopressin. Furthermore, the vasopressin release which occurred in response to intracerebroventricular angiotensin II in normal controls, sham-lesioned and subfornical organ-lesioned rats was significantly attenuated in rats with electrolytic lesion of the medioventral or lateral septal area. Since cells in the lateral septal area are excited by iontophoretic application of angiotensin II, the present data might be consistent with the hypothesis that the stimulatory effect produced by central administration of angiotensin II on vasopressin release rests upon the integrity of the lateral septal area.

Effect of nicotine on drinking and diuresis in septal lesioned rats

Lesions of septal nuclei in rats enhance water intake and urine outflow. The effects of nicotine tartrate (2.5 mg/kg) on drinking and diuresis were investigated in normal, sham and septal lesioned rats. Nicotine administration resulted in a surprising hyperdipsia and polyuria in lesioned animals, the mean output rose from 38 +/- 1.3 ml (before treatment) to 101.6 +/- 6.1 (during treatment) and water intake increased from 74.2 +/- 1.8 ml to 129.8 +/- 6.4 ml.

Evidence for a GABAergic control of the exercise-induced rise in GH in man

The effect of the GABAergic drug sodium valproate (SV) on the exercise-induced release of growth hormone (GH) was investigated in 10 healthy males. The exercise test consisted of using a stationary bicycle ergometer at 450 kg/min for 20 min. SV 600 mg blunted the increase in GH induced by the exercise, suggesting GABAergic regulation of GH secretion in man, at least under certain physiological conditions.

Vasopressin release to central and peripheral angiotensin II in rats with lesions of the subfornical organ

Angiotensin II (Ang II), peripherally or centrally administered, increases plasma vasopressin concentrations in the rat. Peripherally injected Ang II was unable to effect the release of vasopressin in rats with subfornical organ (SFO) lesions. In contrast, a normal increase of plasma vasopressin levels was induced by centrally injected Ang II. These results suggest that peripherally administered Ang II elicits antidiuretic hormone (ADH) release by stimulating receptors in the SFO, whereas centrally administered Ang II acts at receptors outside the SFO.

Inhibition of septal hyperreactivity by testosterone and its reversion by an estrogen antagonist in weanling female rats

Neonatal administration of testosterone inhibits emotional hyperreactivity to capture and tactile stimulation in female rats following septal lesions at 25 days of age. Testosterone, an aromatizable androgen, after metabolization to estrogen interacts with estrogen receptors in neonatal rat brain. In order to investigate whether the testosterone inhibited septal hyperreactivity via estrogen receptors rats were tested after pretreatment with the estrogen receptor antagonist tamoxifen. Weanling female rats pretreated with tamoxifen showed emotional hyperreactivity, while androgenized females showed no change. In addition, estradiol benzoate, neonatally administered, was able to inhibit emotional reactivity displayed after septal lesions. These results suggest that the action of testosterone on septal hyperreactivity might be mediated by estrogen receptors.

Muscimol inhibits ADH release induced by hypertonic sodium chloride in rats

The effect of the GABA-agonist muscimol on ADH release induced in rats by administration of hypertonic sodium chloride solutions was studied by means of intracerebroventricular and intraperitoneal injections of the drug. Injected by the intracerebroventricular route, muscimol produced a significant reduction of plasma ADH concentration not only in animals treated with hypertonic sodium chloride, but also in unstimulated animals. Following intraperitoneal administration larger doses were required to produce such an effect, thus suggesting a central site of action for the effect of muscimol on ADH release. Bicuculline, given intraperitoneally before muscimol injection, completely blocked ADH inhibition induced by muscimol, thus suggesting a specific involvement of GABAergic receptors. These findings indicate that GABAergic mechanisms may be involved in the regulation of body fluids in the rat by affecting ADH release.