Results of phase II pharmacokinetic study of levetiracetam for prevention of post-traumatic epilepsy

Levetiracetam (LEV) has antiepileptogenic effects in animals and is a candidate for prevention of epilepsy after traumatic brain injury. Pharmacokinetics of LEV in TBI patients was unknown. We report pharmacokinetics of TBI subjects≥6years with high PTE risk treated with LEV 55mg/kg/day orally, nasogastrically or intravenously for 30days starting ≤8h after injury in a phase II safety and pharmacokinetic study. Forty-one subjects (26 adults and 15 children) were randomized to PK studies on treatment days 3 and 30. Thirty-six out of forty-one randomized subjects underwent PK study on treatment day 3, and 24/41 subjects underwent PK study on day 30. On day 3, mean T(max) was 2.2h, C(max) was 60.2μg/ml and AUC was 403.7μg/h/ml. T(max) was longer in the elderly than in children and non-elderly adults (5.96h vs. 1.5h and 1.8h; p=0.0001). AUC was non-significantly lower in children compared with adults and the elderly (317.4μg/h/ml vs. 461.4μg/h/ml and 450.2μg/h/ml; p=0.08). C(max) trended higher in i.v.- versus tablet- or n.g.-treated subjects (78.4μg/ml vs. 59μg/ml and 48.2μg/ml; p=0.07). AUC of n.g. and i.v. administrations was 79% and 88% of AUC of oral administration. There were no significant PK differences between days 3 and 30. Treatment of TBI patients with high PTE risk with 55mg/kg/day LEV, a dose with antiepileptogenic effect in animals, results in plasma LEV levels comparable to those in animal studies.     

A Comparison of Intraosseous and Intravenous Routes of Administration for Antiseizure Agents

Intravenous (i.v.) access for administration of antiepileptic drugs can be time-consuming and difficult in an infant during a seizure. This study examined the intraosseous (i.o.) route as an alternative means of vascular access for drug administration in an animal-seizure model. Domestic swine (13-20 kg) were anesthetized with ketamine (20 mg/kg i.m.) and alpha-chloralose (80 mg/kg i.v.) and given gallamine (4 mg/kg i.v.) to prevent muscle fasciculations. Tracheosotomies were performed and the animals were ventilated with a Harvard respirator. The left femoral vein was cannulated and pentylenetetrazol (PTZ) (100 mg/kg) was given to elicit epileptogenic activity. Sixty seconds after onset of epileptogenic activity, the animals received saline or diazepam (DZP) (0.1 mg/kg) or propranolol (2.5 mg/kg) i.v. or via the i.o. route (18-gauge spinal needle placed in the right proximal tibia). Both DZP and propranolol were effective in suppressing epileptogenic activity via the i.v. or i.o. routes. Thus, the i.o. route is a rapid and effective alternative route for the administration of antiepileptic drugs when an i.v. route cannot be readily established.     

Intracerebroventricular injection of interleukin-1 stimulates the release of high levels of interleukin-6 and interleukin-1 receptor antagonist into peripheral blood in the primate.

Previous studies in the rodent have shown that the cytokine IL-1 can act within the brain to influence peripheral IL-6 secretion. In order to determine if such an interaction occurs in the primate, we have compared the effects of intracerebroventricular vs. intravenous injection of IL-1beta on the release of IL-6 into the peripheral circulation of the monkey. The effects of i.c.v. IL-1beta on the release of the IL-1 receptor antagonist (IL-1ra) were studied in parallel. For comparison, we have also measured the release of both IL-6 and IL-1ra into lumbar CSF after i.c.v. IL-1beta injection. Ten ovariectomized rhesus monkeys with indwelling lateral ventricular and peripheral venous cannulae were studied. Human rIL-1beta (400 ng) was infused either i.c.v. or i.v. over 30 min and blood samples were collected for IL-6 and IL-1ra measurement by monoclonal human ELISAs. Although both i.c.v. and i.v. IL-1beta stimulated IL-6 and IL-1ra release into peripheral blood, the stimulation was much more profound after i.c.v. injection (p < 0.001). Peak IL-6 levels were 2010 +/- 590 pg/ml after i.c.v. IL-1beta compared to 243 +/- 60 pg/ml after i.v. IL-1beta. Peak IL-1ra levels were 61,310 +/- 16,190 pg/ml after i.c.v. IL-1beta compared to 18,175 +/- 4270 pg/ml after i.v. IL-1beta. There was no significant effect of an i.c.v. saline infusion on peripheral IL-6 or IL-1ra levels. In four animals, lumbar CSF was collected 7 h after i.c.v. IL-1beta injection. The mean concentration of IL-6 in CSF was 103, 570 +/- 13,780 pg/ml after i.c.v. IL-1beta vs. 224 +/- 190 pg/ml after i.c.v. saline injection; IL-1ra was 47,460 +/- 6290 pg/ml vs. 1040 +/- 550 pg/ml. As expected, both i.c.v. and i.v. IL-beta stimulated ACTH and cortisol release; the stimulation was significantly greater after i.c.v. compared to i.v. administration (p < 0.001). Thus, in the monkey, i.c.v. injection of IL-1beta stimulates the release of large amounts of IL-6 and IL-1ra into the CSF and the peripheral circulation. Both IL-6 and IL-1ra were released into the peripheral circulation to a much greater extent after i.c.v. compared to i.v. IL-1beta infusion. These studies provide further support in the primate for a mechanism by which inflammation within the brain could induce a variety of systemic responses.     

Anticonvulsant activity of the NMDA antagonists, D(-)4-(3-phosphonopropyl) piperazine-2-carboxylic acid (D-CPP) and D(-)(E)-4-(3-phosphonoprop-2-enyl) piperazine-2-carboxylic acid (D-CPPene) in a rodent and a primate model of reflex epilepsy

D-(-)4-(3-phosphonopropyl)piperazine-2-carboxylic acid (D-CPP) and its unsaturated analogue (D(-)(E)-4-(3-phosphonoprop-2-enyl) piperazine-2-carboxylic acid (D-CPPene) have been administered to DBA/2 mice (intracerebroventricularly, i.c.v., intraperitoneally, i.p., and orally, p.o.) and to photosensitive baboons, Papio papio (intravenously, i.v., and orally), and their effects on reflexly induced epileptic responses assessed. In DBA/2 mice the clonic phase of the seizure response to sound is suppressed by D-CPP with an ED50 of 5.5 micrograms/mouse, i.c.v.; 0.69 mg (2.75 mumol)/kg i.p. and 16.6 mg (65.8 mumol)/kg p.o. compared with, for D-CPPene, 2.2 micrograms/mouse i.c.v., 0.41 mg (1.54 mumol)/kg i.p. and 10.8 mg (40.2 mumol)/kg, p.o. In Papio papio myoclonic responses to stroboscopic stimulation are suppressed 24 and 48 h after D-CPP 32 mg (127 mumol)/kg p.o. Administration of D-CPPene 8-16 mg (30-60 mumol)/kg i.v. produces protection against myoclonic responses after 1-2 h, lasting for 48 h. Oral administration of D-CPPene 32-64 mg (119-239 mumol)/kg produces protection beginning after 4 h and sustained for 48 h. Measurements of plasma D-CPPene concentration show rapid clearance after i.v. injection and a low plasma concentration 1.5-5 h after oral administration. The prolonged anticonvulsant action of D-CPP and D-CPPene following oral administration suggests that these compounds merit evaluation as antiepileptic therapy in man.     

Suppression of Pentylenetetrazol-Elicited Seizure Activity by Intraosseous Lorazepam in Pigs

Use of the intraosseous (i.o.) route as an alternative venous access for drug administration has increased. This study examined the efficacy of i.o. lorazepam (LZP) in suppressing pentylenetetrazol (PTZ)-induced seizure activity in pigs. Domestic swine (13-20 kg) were prepared for recordings of arterial blood pressure, EEG, and electrocortical activity. Seizure activity was induced by PTZ (100 mg/kg i.v.). Sixty seconds after onset of seizure activity, animals either received no drug (control) or LZP (1.0 mg/kg) administered i.v. or i.o. via an 18- or 13-gauge spinal needle inserted in the right proximal tibia. Both i.o. and i.v. LZP significantly suppressed the duration of seizure activity (DSA) (s/min interval) within 1 min following drug administration: DSA control, 46.2 +/- 3.6; i.v. LZP, 25.0 +/- 5.1; i.o. (18-gauge) LZP, 27.6 +/- 6.0; i.o. (13-gauge) LZP, 24.0 +/- 2.4. Seizure activity was essentially abolished at 1 min following LZP infusion. In addition, both i.v. and i.o. LZP did not have significant effects on the basal heart rate and mean arterial blood pressure. The data demonstrate that in swine (1) the i.o. route is an effective alternative venous access for LZP administration, and (2) the size of spinal needles does not affect the antiepileptic efficacy of i.o. infusion of LZP.     

Subcutaneous administration of nimodipine improves bioavailability in rabbits

We compared subcutaneous and oral methods of nimodipine administration to determine a method of nimodipine administration that maintained serum levels at or above the optimal therapeutic concentration (7 ng/ml). Plasma concentrations of nimodipine were measured in New Zealand White rabbits (2.6-3.9 kg). First, peak plasma concentration (C(max)), time to reach peak plasma concentration (T(max)), and area under the curve (AUC) parameters were calculated and compared between animals receiving oral or subcutaneous nimodipine (5-15 mg/kg). Next, plasma concentrations were measured 24 h after subcutaneous administration of 2.5 mg/kg of nimodipine in healthy animals and animals with experimentally induced SAH. C(max), T(max) and AUC parameters were significantly greater for subcutaneous compared to oral nimodipine administration, irrespective of dose. Mean nimodipine concentrations at 24 h were >7 ng/ml in both healthy animals (12.9 +/- 10.0 ng/ml) and in animals with SAH (11.8 +/- 4.6 ng/ml) that received 2.5 mg/kg of subcutaneous nimodipine. In this model, the subcutaneous method of nimodipine administration consistently maintains plasma levels at or above the optimal therapeutic concentration, whereas oral administration fails to do so.     

Intravenous and subcutaneous administration of desmopressin (DDAVP) to hemophiliacs: pharmacokinetics and factor VIII responses

When desmopressin (DDAVP) is given to mild and moderate hemophiliacs intravenously (i.v.) or subcutaneously (s.c.), there is a very large between-patient variability for peak levels of factor VIII coagulant activity (VIII:C). To evaluate whether or not between-patient variability is related to DDAVP levels achieved in plasma, we measured drug levels in 14 hemophilic volunteers (VIII:C 2 to 31 U/dL) who were randomly given 0.3 micrograms/Kg of i.v. or s.c. DDAVP and crossed-over to the other treatment after an interval of 15-30 days. Peak DDAVP levels (Cmax) were higher for i.v. DDAVP (p less than 0.02), times to peak levels (tmax) were shorter for i.v. DDAVP (p less than 0.001). There was no difference between the i.v. and s.c. routes for plasma DDAVP time curve (AUC) and half-life (t 1/2), but there was much larger variability for pharmacokinetic parameters with i.v. than with s.c. DDAVP. Post-DDAVP VIII:C increased 3.4 +/- 1.6 fold (i.v.) and 3.3 +/- 1.3 fold (s.c.) over baseline levels, with no significant correlation between peak VIII:C and DDAVP levels for either route of administration. These findings establish the s.c. route of DDAVP administration to be bioequivalent in effect to the i.v. route, albeit with less variability. At the DDAVP dosage used in this study and currently recommended for therapy, the VIII:C response is neither a function of the rate of absorption of the compound nor of the magnitude of its plasma concentration.     

Body weight gain after administration of antipsychotic drugs: correlation with leptin, insulin and reproductive hormones

Excessive body weight gain, hyperprolactinemia and low gonadal steroid serum levels are often observed during chronic administration of antipsychotic drugs (AP). Clinical and experimental findings suggest that leptin, the peptidic hormone involved in long-term body weight regulation, and reproductive hormones are interrelated. Therefore, we assessed circulating leptin levels in healthy, lean women (n = 12) and men (n = 7) before and after short-term administration of the AP sulpiride (SUL, 200 mg/day). In addition, we studied psychotic obese (n = 9) and lean women (n = 13) under chronic treatment with diverse AP. No significant weight changes were observed after SUL administration in healthy women--initial weight: 54.9+/-2.6 Kg; final weight: 55.04+/-2.6, NS. Leptin levels did not change either: 11.9+/-1.5 ng/ml. vs. 10.6+/-1.3, NS. By contrast, a small, but significant weight gain was found in SUL-treated men--60.6+/-1.9 Kg. vs. 61.3+/-2.1, p = 0.004. Leptin and insulin levels were significantly higher after SUL administration--leptin: 2.77+/-0.22 ng/ml. vs. 13.9+/-2.5, p=0.035; insulin: 3.59+/-0.17 mIU/ml vs. 8.81+/-0.81, p = 0.0001. In these subjects, leptin levels positively correlated with body weight change (p = 0.006), and serum prolactin change (p = 0.001). Obese psychotic women (Body Mass Index, BMI, Kg/m2 = 31.5+/-1.03) displayed higher leptin levels than non-obese psychotic women (BMI = 25.5+/-0.52): 26.8+/-4.8, vs. 12.8+/-3.4 ng/ml, p = 0.006. In these women, a significant positive correlation was found between leptin levels and BMI (p = 0.0001), and between leptin and basal insulin levels (p = 0.001). These results show that the expected circulating leptin elevation which is observed when body weight raises, is preserved in people treated with AP drugs.     

Comparative single- and multiple-dose pharmacokinetics of levodopa and 3-O-methyldopa following a new dual-release and a conventional slow-release formulation of levodopa and benserazide in healthy volunteers

The objective was to assess the single- and multiple-dose pharmacokinetics of levodopa and 3-O-methyldopa following administration of a new dual-release and conventional slow-release formulation of levodopa/benserazide in the dose ratio of 4:1. In an open-label, two-way cross-over study, 20 healthy volunteers were randomized to receive first either Madopar DR or Madopar HBS for 8 days. Then they crossed over to the other formulation. A first dose of 200 mg levodopa and 50 mg benserazide ('250' mg) was given on day 1, '125' mg t.i.d. on the subsequent 6 days (days 2-7), followed by '250' mg on day 8. The two treatment periods of 8 days were separated by a wash-out period of at least 7 days. Blood samples were taken at specific times over a 12-hour period (day 1) or a 36-hour period (day 8). Plasma concentrations of levodopa and 3-O-methyldopa were measured by high-performance liquid chromatography for pharmacokinetic evaluation. The pharmacokinetics of levodopa after a single-dose administration (day 1) of Madopar DR and Madopar HBS were significantly different as reflected by the respective mean values of maximum plasma concentration (C(max) 1.99 vs. 0.82 mg x l-1), time to reach maximum concentration (t(max) 0.7 vs. 2.6 h) and area under the plasma concentration-time curve (AUC(0- infinity ) 4.52 vs. 3.18 mg x h x l-1). The respective values after multiple doses (day 8) were: C(max) 1.98 vs. 0.93 mg x l-1, t(max) 0.7 vs. 2.3 h and AUC(0-infinity ) 4.84 vs. 3.96 mg x h x l-1. The relative bioavailability (Madopar DR vs. Madopar HBS) was 1.73 on day 1 and 1.32 on day 8. Bioequivalence could not be demonstrated for log-transformed data of AUC and C(max) within a predefined range of 80-125 and 70-143%, respectively. In conclusion, the observed differences in C(max), t(max) and AUC are consistent with a faster rate and higher extent of levodopa absorption after administration of Madopar DR. Statistical evaluation of these kinetic data showed that Madopar DR is not bioequivalent to Madopar HBS.     

Hypophysiotropic Role and Hypothalamic Gene Expression of Corticotropin-Releasing Factor and Vasopressin in Rats Injected with Interleukin-1β Systemically or into the Brain Ventricles

Intact adult male rats were injected intravenously (i.v., 400 ng/kg), intraperitoneally (i.p., 400 ng/kg) or intracerebroventricularly (i.c.v., 100 ng/kg) with interleukin-1β (IL-1β) or its vehicle. In comparison with vehicle-treated animals, IL-1β induced significant (P<0.01) increases in plasma ACTH levels measured 30 min later regardless of the route of cytokine administration. These changes were markedly blunted in rats administered specific antibodies directed against corticotropin-releasing factor (CRF). In contrast, vasopressin (VP) antibodies significantly blunted ACTH released by the i.c.v. injection of IL-1β, but only modestly altered the effect of the systemic injection of the cytokine. We then used semi-quantitative in situ hybridization analysis to measure changes in steady-state mRNA levels, as they might occur in response to these same doses of IL-1β. Following administration of the vehicle, measurement of gene expression in the paraventricular (PVN) portion of the hypothalamus indicated a measurable amount of hybridization signals for both CRF and VP. No detectable changes in either CRF or VP gene expression were observed in rats injected with IL-1β i.v. or i.p. 5 h earlier. In contrast, the i.c.v. administration of the cytokine significantly (P<0.01) increased both CRF and VP mRNA levels measured 5 h later. These results suggest that while endogenous CRF modulates the response of the corticotrophs to this cytokine regardless of the route of administration, the role of VP is more important in rats injected centrally than in those injected peripherally. The observation that at the dose tested and over the time-course studied, systemic injection of IL-1β failed to alter CRF or VP gene expression, supports our earlier hypothesis that blood-born IL-1β acts primarily at the level of nerve terminals in the median eminence.     

The effect of fluoxetine on the pharmacokinetics and safety of risperidone in psychotic patients

In this open, 30-day trial, the pharmacokinetics, safety and tolerability of a combination therapy of risperidone (4 or 6 mg/day)and fluoxetine (20mg/day from day 6) were evaluated in 11 psychotic inpatients. CYP2D6 genotyping revealed that 3 and 8 patients were poor metabolizers (PMs) and extensive metabolizers (EMs) of debrisoquine, respectively. The mean (+/- SD) AUC of risperidone increased from 83.1 +/- 46.8 ng.h/ml and 398.3 +/- 33.2 ng.h/ml (monotherapy) to 345.1 +/- 158.0 ng.h/ml (p < 0.05) and 514.0 +/- 144.2 ng.h/ml (p < 0.001) when coadministered with fluoxetine in EMs and PMs, respectively. The AUC of the active moiety (risperidone plus 9-hydroxy-risperidone) increased from 470.0 +/- 170.0 ng.h/ml to 663.0 +/- 243.3 ng.h/ml (p < 0.05)and from 576.3 +/- 19.6 ng.h/ml to 788.0 +/- 89.1 ng.h/ml (ns) in EMs and PMs, respectively. In EMs, the AUC of 9-hydroxy-risperidone remained similar (monotherapy vs. combination therapy: 386.8 +/- 153.0 ng.h/ml vs. 317.7 +/- 125.2 ng.h/ml, ns),whereas it increased in PMs (178.3 +/- 23.5 ng.h/ml vs. 274.0 +/- 55.1 ng.h/ml (p < 0.05)). Ten of the 11 patients showed a clinical improvement (reduction of 20% or more in total PANSS score and 70% on the mean MADRS score compared to baseline). The severity and incidence of extrapyramidal symptoms and adverse events did not significantly increase when fluoxetine was added.     

Myocardial troponin T release is associated with enhanced fibrinolysis in patients with acute coronary syndromes

Patients with acute coronary syndromes (ACS) frequently present with signs of disturbed fibrinolysis. The present study investigates the correlation of alterations in the fibrinolytic system and the amount of myocardial damage characterized by troponin release. In 85 patients with ACS markers of plasmin activation, plasminogen activator system and troponin T (TnT) were measured initially and after 48 h. Patients with TnT release (> or = 0.01 microg/l) at admission had higher TPA levels than those without release (10.2+/-0.7 ng/ml vs. 7.6+/-0.5 ng/ml; p <0.01). Additionally, patients with positive TnT had higher D-dimer levels initially (457+/-39 ng/ml vs. 316+/-22 ng/ml; p <0.01) and 48 h later (451+/-42 ng/ml vs. 275+/-37 ng/ml; p <0.01). The association of myocardial damage with a prothrombotic state and an enhanced fibrinolysis may explain the high prognostic value of troponin measurements in respect to future coronary events.     

Influence of clenbuterol, a β-adrenergic agonist, on desipramine induced growth hormone, prolactin and cortisol stimulation

We report herein the effects of the β-adrenergic agonist clenbuterol on desipramine(DMI)-induced growth hormone (GH), prolactin (PRL) and cortisol secretion in healthy male subjects. In the first study, nine subjects were treated with either clenbuterol (0.04 mg, p.o.) or placebo. In the second study, 12 subjects received either DMI (50 mg, i.v.) alone or in combination with clenbuterol (0.04 mg, p.o.) given 60 min prior to DMI administration.

Clenbuterol alone had no influence on GH, PRL, or cortisol concentrations, compared to placebo. DMI alone caused GH stimulation (mean MAXIMUM = 15.7±3.4 ng/ml), which was significantly lower after combined administration of DMI and clenbuterol (mean MAXIMUM = 7.7±1.6 ng/ml) (p≤0.01). DMI-induced PRL and cortisol stimulation was not influenced by clenbuterol pretreatment.

These results indicate the inhibiting influence of noradrenergic β-receptors on GH stimulation.     

Anticonvulsant activity of two orally active competitive N-methyl-D-aspartate antagonists, CGP 37849 and CGP 39551, against sound-induced seizures in DBA/2 mice and photically induced myoclonus in Papio papio.

Two novel N-methyl-D-aspartate (NMDA) antagonists, DL-(E)-2-amino-4-methyl-5-phosphono-3-pentenoic acid CPG 37849 and the corresponding 1-ethyl ester CGP 39551, were tested as anticonvulsants in DBA/2 mice and photosensitive Senegalese baboons, Papio papio. In DBA/2 mice, CGP 37849 is more potent than CGP 39551 when administered intracerebroventricularly (i.c.v.) or intraperitoneally (i.p.) (ED50 for suppression of clonic seizures at 60 min: i.c.v. 0.038 and 0.21 nmol; i.p. 3.40 and 19.1 mumol/kg, respectively). When administered orally in mice, the two compounds are approximately equipotent (ED50 CGP 37849, 35.2 mumol/kg; ED50 CGP 39551, 28.1 mumol/kg). The time course of action of CGP 39551 is exceptionally prolonged: 42 mumol/kg i.p. protects against clonic seizures for 48 h. Protection provided by other NMDA antagonists in mice is of much shorter duration: 2-amino-5-phosphono-pentanoic acid (AP5) 1 h, 2-amino-7-phosphono-heptanoic acid (AP7) 4 h, 2-amino-7-phosphono-heptanoic acid 1-ethyl ester 3 h, 4-(3-phosphonopropyl)-2-piperazine carboxylic acid (CPP) 2 h, cis-4-(phosphonomethyl)-2-piperidine-carboxylic acid (CGS 19755) 4 h, and CGP 37849 4 h. After oral administration of the drugs, the therapeutic index (TI = ratio of the ED50 values for rotorod performance and anticonvulsant protection) remains relatively constant at 5.9-7.2 for 3 h (CGP 37849) and 4.0-6.1 for 24 h (CGP 39551). After i.p. administration, the TI values are CGP 37849 at 1 h 2.4, and at 3 h 20.0, CGP 39551 at 1 h 2.3, at 3 h 7.1, and at 24 h 3.6. In baboons, acute administration of CGP 37849 at doses of 48-191 mumol/kg intravenously (i.v.) suppresses photically induced myoclonus for at least 285 min, with severe side effects at the highest dose tested. CGP 39551 at doses of 169-675 mumol/kg i.v. shows weak anticonvulsant activity only at the highest dose tested (accompanied by severe side effects). CGP 37849 at 48-96 mumol/kg orally (p.o.) fails to protect against photically induced myoclonus up to 4 h after administration, but 191 mumol/kg (40 mg/kg) p.o. produces complete suppression of seizures after 24 h. On the other hand, CGP 39551 at 169 mumol/kg (40 mg/kg) p.o. produces total suppression of seizure activity at 4 h with a longer duration of anticonvulsant action (2-3 days).(ABSTRACT TRUNCATED AT 400 WORDS)     

Intravenous antidepressants: a review

Antidepressant medications have an onset of action of several weeks and have moderate efficacy. Their mode of administration is oral (p.o.). Some clinicians wondered whether intravenous (i.v.) administration would speed onset of action and increase efficacy. In this article we review controlled studies on i.v. administration of antidepressants. These include clomipramine, citalopram, and other antidepressants. Overall these studies do not support increased efficacy of i.v. over p.o.administration but there are suggestions of a faster onset of action. In one study i.v. citalopram showed superior response rates over p.o. citalopram (79% vs. 63%) in severely depressed patients at 8 weeks.     

Effects of Growth Hormone-Releasing Peptide-6 on the Nocturnal Secretion of GH, ACTH and Cortisol and on the Sleep EEG in Man: Role of Routes of Administration

After repeated intravenous (i.v.) boluses of growth hormone-releasing peptide-6 (GHRP-6) we found recently increases of growth hormone (GH), corticotropin (ACTH) and cortisol levels and of the amount of stage 2 sleep. In clinical use, oral (p.o.), intranasal (i.n.) and sublingual (s.l.) routes of administration have advantages over i.v. administration. We compared the sleep-endocrine effects of 300 microg/kg of body weight (b.w.) GHRP-6 in enteric-coated capsules given p.o. at 21.00 h and of 30 microg/kg GHRP-6 i.n. or 30 microg/kg GHRP-6 sl. given at 22.45 h in normal young male controls with placebo conditions. After GHRP-6 p.o. secretion of GH, ACTH and cortisol remained unchanged. The only effect of GHRP-6 s.l. was a trend toward an increase in GH in the first half of the night. GHRP-6 i.n. prompted a significant increase in GH concentration during the total night and a trend toward an increase in ACTH secretion during the first half of the night, whereas cortisol secretion remained unchanged. Furthermore, after GHRP-6 i.n., sleep stage 2 increased in the second half of the night by trend, and spectral analysis of total night non-rapid eye movement (REM) sleep revealed a decrease of delta power by trend. In contrast sleep stage 2 decreased during the second half of the night after GHRP-6 p.o. Our data demonstrate that GHRP-6 is capable of modulating GH and ACTH secretion as well as sleep. However, the effects depend upon dosage, duration and route of administration.     

Oral Mg(2+) supplementation reverses age-related neuroendocrine and sleep EEG changes in humans

The process of normal aging is accompanied by changes in sleep-related endocrine activity. During aging, an increase in cortisol at its nadir and a decrease in renin and aldosterone concentration occur. In aged subjects, more time is spent awake and slow-wave sleep is reduced: there is a loss of sleep spindles and accordingly a loss of power in the sigma frequency range. Previous studies could show a close association between sleep architecture, especially slow-wave sleep, and activity in the glutamatergic and GABAergic system. Furthermore, recent studies could show that the natural N-methyl-D-aspartate (NMDA) antagonist and GABA(A) agonist Mg(2+) seems to play a key role in the regulation of sleep and endocrine systems such as the HPA system and renin-angiotensin-aldosterone system (RAAS). Therefore, we examined the effect of Mg(2+) in 12 elderly subjects (age range 60-80 years) on the sleep electroencephalogram (EEG) and nocturnal hormone secretion. A placebo-controlled, randomised cross-over design with two treatment intervals of 20 days duration separated by 2 weeks washout was used. Mg(2+) was administered as effervescent tablets in a creeping dose of 10 mmol and 20 mmol each for 3 days followed by 30 mmol for 14 days. At the end of each interval, a sleep EEG was recorded from 11 p.m. to 7 a.m. after one accommodation night. Blood samples were taken every 30 min between 8 p.m. and 10 p.m. and every 20 min between 10 p.m. and 7 a.m. to estimate ACTH, cortisol, renin and aldosterone plasma concentrations, and every hour for arginine-vasopressin (AVP) and angiotensin 11 (ATII) plasma concentrations. Mg(2+) led to a significant increase in slow wave sleep (16.5 +/- 20.4 min vs. 10.1 +/- 15.4 min, < or =0.05), delta power (47128.7 microV(2) +21417.7 microV(2) vs. 37862.1 microV(2) +/- 23241.7 microV(2), p < or =0.05) and sigma power (1923.0 microV(2) + 1111.3 microV(2) vs. 1541.0 microV(2) + 1134.5 microV(2), p< or =0.05 ). Renin increased (3.7 +/- 2.3 ng/ml x min vs. 2.3 +/- 1.0 ng/ml x min, p < 0.05) during the total night and aldosterone (3.6 +/- 4.7 ng/ml x min vs. 1.1 +/- 0.9 ng/ml x min, p < 0.05) in the second half of the night, whereas cortisol (8.3 +/- 2.4 pg/ml x min vs. 11.8 +/- 3.8 pg/ml x min, p < 0.01) decreased significantly and AVP by trend in the first part of the night. ACTH and ATII were not altered. Our results suggest that Mg(2+) partially reverses sleep EEG and nocturnal neuroendocrine changes occurring during aging. The similarities of the effect of Mg(2+) and that of the related electrolyte Li+ furthermore supports the possible efficacy of Mg(2+) as a mood stabilizer.     

Leukotrienes in brain: natural occurrence and induced changes

Peptidoleukotrienes (SP-LTs) (both total product and individual LTC4 and LTE4 and LTB4 were measured by radioimmunoassay in cerebrospinal fluid (CSF) collected from the third ventricle of conscious cats. Total SP-LT was expressed as LTE4 after treating samples with crude gamma-glutamyltranspeptidase. Prostaglandin (PG) E2 and thromboxane (TX) B2, the stable metabolite of TXA2, were also assayed in part of the experiments. Under basal conditions, SP-LT and LTC4 were consistently measurable (respectively, 327 +/- 14 and 244 +/- 41 pg/ml), while native LTE4 was below the threshold of the assay (60-280 pg/ml) in most cases. LTB4 was barely detectable (30 +/- 2 pg/ml) or not detectable at all. PGE2 was normally less abundant than TXB2 (31 +/- 4 vs 281 +/- 47 pg/ml). Intracerebroventricular (i.c.v.) administration of arachidonic acid (40 microgram) caused a 4-fold increase in SP-LT levels which was relatively small and transient compared to PGE2 (76-fold) and TXB2 (23-fold), while there was no change in either native LTE4 or LTB4. A similar response was obtained with platelet-activating factor (PAF, 1 microgram i.c.v.), though SP-LT elevation (4-fold) was more persistent. A further rise in SP-LT (9-fold) was noted when PAF administration was preceded by indomethacin (500 microgram i.c.v.), whereas PAF effect was reversed by pretreatment with either the PAF antagonist, BN52021 (1 microgram i.c.v.), or the 5-lipoxygenase inhibitors, U-60,257 (75 micrograms i.c.v.) and L-651,392 (10 mg/kg p.o.). PAF was also effective in causing a 3-fold rise in LTC4. Unlike PAF, pyrogens (endotoxin i.c.v. or i.v.; interleukin-1 i.v.) at doses above threshold for fever had no effect on LT levels in CSF, both in the absence and presence of indomethacin pretreatment. We conclude that SP-LTs are a normal constituent of CSF, LTC4, being the major species. The response to PAF accords with a pathogenetic role of the compounds in inflammatory processes and the reactive changes to injury. No evidence was obtained for the involvement of SP-LTs in the central mechanism of fever.     

Levels of DHEA and DHEAS and responses to CRH stimulation and hydrocortisone treatment in chronic fatigue syndrome

Background: An association between chronic fatigue syndrome (CFS) and abnormalities of the hypothalamo-pituitary-adrenal axis has been described, and other adrenal steroid abnormalities have been suggested. Dehydroepiandrostenedione (DHEA) and its sulphate (DHEA-S), apart from being a precursor of sex steroids, have other functions associated with memory, depression and sleep. It has been suggested that CFS may be associated with a state of relative DHEA(-S) deficiency. Therefore we investigated basal levels of DHEA(-S), the cortisol/DHEA molar ratio and the responsiveness of DHEA to stimulation by corticotrophin-releasing hormone (CRH). Recent studies have also suggested that low dose hydrocortisone may be effective at reducing fatigue in CFS. We therefore also assessed these parameters prior to and following treatment with low dose oral hydrocortisone. Methods: Basal levels of serum DHEA, DHEAS and cortisol were measured in 16 patients with CFS without depression and in 16 controls matched for age, gender, weight, body mass index and menstrual history. CRH tests (1 g/kg i.v.) were carried out on all subjects and DHEA measured at 0, +30 and +90 min. In the patient group, CRH tests were repeated on two further occasions following treatment with hydrocortisone (5 or 10 mg, p.o.) or placebo for 1 month each in a double-blind cross over study protocol. Results: Basal levels of DHEA were higher in the patient, compared to the control, group (14.1+/-2.2 vs. 9.0+/-0.90 ng/ml, P=0.04), while levels of DHEAS in patients (288.7+/-35.4 microg/dl) were not different from controls (293.7+/-53.8, P=NS). Higher DHEA levels were correlated with higher disability scores. Basal cortisol levels were higher in patients, and consequently the cortisol/DHEA molar ratio did not differ between patients and controls. Levels of DHEA (8.9+/-0.97 ng/ml, P=0.015) and DHEAS (233.4+/-41.6 microg/dl, P=0.03) were lower in patients following treatment with hydrocortisone. There was a rise in DHEA responsiveness to CRH in the patients after treatment but this did not attain significance (AUCc: 2.5+/-1.7 ng/ml h pre-treatment vs. 6.4+/-1.2 ng/ml h post-hydrocortisone, P=0.053). However, those patients who responded fully to hydrocortisone in terms of reduced fatigue scores did show a significantly increased DHEA responsiveness to CRH (AUCc: -1.4+/-2.5 ng/ml h at baseline, 5.0+/-1.2 ng/ml h after active treatment, P=0.029). Conclusions: DHEA levels are raised in CFS and correlate with the degree of self-reported disability. Hydrocortisone therapy leads to a reduction in these levels towards normal, and an increased DHEA response to CRH, most marked in those who show a clinical response to this therapy.     

Central administration of orexin A suppresses basal and domperidone stimulated plasma prolactin

Orexin immunoreactive fibres are abundant in the hypothalamus suggesting a neuroendocrine regulatory role. Intracerebroventricular (ICV) administration of orexin A suppressed plasma prolactin in male rats by 71% at 20 min post-injection and 83% at 90 min post-injection (P < 0.005 vs saline at both time points). To investigate whether this effect was through the tuberoinfundibular dopaminergic (TIDA) system, a supra-maximal dose of domperidone, a dopamine receptor antagonist, was injected intraperitoneally (i.p.) prior to ICV injection of orexin A. ICV orexin A significantly suppressed domperidone (9 mg/kg)-stimulated plasma prolactin levels, by up to 40% (i.p. domperidone + ICV orexin A 3 nmol 34.5 +/- 7.4 ng/ml and i.p. domperidone + ICV orexin A 20 nmol 43.5 +/- 4.3 ng/ml, both P < 0.005 vs i.p. domperidone + ICV saline 57.9 +/- 2.7 ng/ml). Orexin A, 100 nM, significantly stimulated release of neurotensin, vasoactive intestinal polypeptide, somatostatin, corticotropin releasing factor and luteinizing hormone releasing hormone, but had no effect on release of dopamine, thyrotropin releasing hormone (TRH), vasopressin or melanin-concentrating hormone from hypothalamic explants in vitro. Orexin A did not alter basal or TRH stimulated prolactin release in dispersed pituitary cells harvested from male rats. The data suggest that ICV administration of orexin A suppresses plasma prolactin in part through a pathway independent of the dopaminergic system.