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PubMed1992

Chloride channels of skeletal muscle from developing, adult and aged rats are differently affected by enantiomers of 2-(p-chlorophenoxy) propionic acid.

Enantiomers of 2-(p-chlorophenoxy) propionic acid, compounds acting specifically on chloride channels of adult rat skeletal muscles, have been tested on extensor digitorum longus (EDL) muscle of developing and aged rats, in an attempt to characterize the chloride channels responsible for the low chloride conductance (GCl) found in the above physiological situations. The S-(-) enantiomer, which produces a concentration-dependent inhibition of GCl in the adult EDL, is less effective in inhibiting GCl of EDL of either 2-3 weeks or 29 months old rats, particularly at low concentrations. The R-(+) isomer, which in the adult enhances GCl at low concentrations and blocks it at concentrations higher than 10 microM, lacks inhibitory action, enhancing GCl in both developing and aged EDL. At 30-40 days of age both the enantiomers produce almost the same effects exerted in adulthood. From these data we hypothesize that the low GCl found in EDL of developing and aged rats might be due not only to a lower number of conductive channels but also to the presence of a mixed population of isoforms of chloride channels having different pharmacological properties.

2-Methyl-4-chlorophenoxyacetic Acid↗
PubMed1996

An assessment of the systemic effects of single and repeated doses of inhaled fluticasone propionate and inhaled budesonide in healthy volunteers.

The systemic effects of single and multiple doses of inhaled fluticasone propionate (FP) and budesonide were examined in 24 healthy male volunteers (age range 18-29 years). The study was of an open, placebo-controlled, randomized, three-way crossover design. On each study day, multiple blood samples were taken over a 20 h period after drug administration (after a single dose and after the last of seven doses) and area under the curve (AUC(0-20)) for plasma cortisol and white blood cell (WBC) counts was calculated. RESULTS. The present study shows that multiple dosing with FP 1.0 mg b.i.d. for 3.5 days (seven doses) resulted in a marked cortisol suppression from placebo which, at 55%, was more than double that seen with a single dose (25% suppression). Multiple dosing with budesonide 0.8 mg b.i.d. resulted in a 34% suppression in plasma cortisol compared with a suppression of 26% with a single dose. The increase in systemic activity of FP after multiple dosing is confirmed by both the number of subjects with 0800 hours plasma cortisol values below normal limits and by the changes in WBC and differential counts. CONCLUSION. The results of the present study confirm previous findings with regard to the more marked systemic effect of FP following multiple dosing as compared with a single dose. This increase in systemic effect from single dosing to multiple dosing is significantly greater for FP than for budesonide.

Administration, Inhalation↗
PubMed1977

Hypothalamic and hormonal control of photoperiodically induced vernal functions in the white-crowned sparrow, Zonotrichia leucophrys gambelii. 2. The effects of hypothalamic inplantation of testosterone propionate.

The effects of implantation of testosterone propionate (TP) in various sites in the hypothalamus on the photoperiodically induced vernal premigratory functions in the White-crowned Sparrows were investigated in order to assess the role of the hypothalamo-hypophysial-testicular axis in the induction of these responses. Implantation of glass capillary tubes containing TP in the basal infundibular nucleus (IN), in the median eminence, or in the pars distalis inhibited the photoperiodically induced increase in plasma levels of luteinizing hormone (LH), as measured by radioimmunoassay, and testicular growth. The effective inplants significantly lowered the levels of LH in birds held on nonstimulatory short days. These TP implants apparently inhibited release from the pars distalis of both LH and follicle-stimulating hormone (FSH). It is concluded that the site of sensitivity in the negative feedback by testosterone is either the basal IN or the pars distalis, or both. The implants of TP that inhibited the increase in plasma LH and testicular growth completely did not prevent the birds from fattening.

Adipose Tissue↗
PubMed1984

Lathyrus excitotoxin: mechanism of neuronal excitation by L-2-oxalylamino-3-amino- and L-3-oxalylamino-2-amino-propionic acid.

Intracellular recordings were made in cultured neurones from foetal mouse spinal cord. The effects of applications of the neurotoxin, L-3-oxalylamino-2-amino-propionic acid (a constituent of the chickling pea, Lathyrus sativus) and its 2-oxalylamino isomer on membrane potential and conductance were examined in the presence of TTX and TEA and compared to those of other excitatory amino acids. Although both compounds produced membrane depolarization and an increase in input conductance, the 3-oxalylamino isomer (beta-ODAP) was approximately equal to 10 times more potent than the 2-oxalylamino isomer (alpha-ODAP). beta-ODAP caused a voltage-independent change in conductance, as compared to an apparent voltage-dependent decrease produced in the same neurons by L-aspartic acid (L-ASP). Although reversal potentials determined for beta-ODAP resembled those for alpha-ODAP and kainic acid, they were consistently and significantly lower than the reversal level for L-ASP. Although the receptor antagonist 2-amino-5-phosphonovaleric acid (APV) and the divalent cation Cd2+ did not alter the conductance increase evoked by beta-ODAP, they markedly depressed responses to L-ASP. Such differences suggest a mechanism of excitatory action for the neurotoxin, beta-ODAP, which does not involve a Ca2+-dependent mechanism and is quite different from that for L-ASP and N-methyl-D-aspartic acid, but similar to that of kainic and quisqualic acids.(ABSTRACT TRUNCATED AT 250 WORDS)

2-Amino-5-phosphonovalerate↗
PubMed1991

Effect of age on alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA) binding sites in the rat brain studied by in vitro autoradiography.

Receptors for excitatory amino acid, L-glutamate, have been classified into three subtypes named as N-methyl-D-aspartate (NMDA), quisqualate (QA) and kainate receptors. In the present study, an effect of age on binding sites of [3H]alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (3H-AMPA), a QA agonist, was studied in the rat brain through quantitative in vitro autoradiography. 3H-AMPA binding sites were most concentrated in the hippocampus and cerebral cortex where glutamate receptors have been demonstrated to play a role in synaptic transmission. In aged rats, 3H-AMPA binding sites in the hippocampus and cerebral cortex were not significantly changed. In our previous studies, it was noticed that strychnine-insensitive glycine receptors, which functionally coupled with NMDA receptors, showed marked age-dependent decreases in telencephalic regions. It has been shown that the glutamatergic neuronal system is involved in learning and memory. Nevertheless, it is considered that AMPA binding sites are not involved in the decline of neuronal functions, especially impairment of learning and memory, accompanying with aging process.

Aging↗
PubMed1987

Characterization of quisqualate recognition sites in rat brain tissue using DL-[3H]alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA) and a filtration assay.

The binding of [3H]AMPA (DL-alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid), a ligand for the putative quisqualate excitatory amino acid receptor subtype, was evaluated using centrifugation and filtration receptor binding techniques in rat brain crude synaptosomal membrane preparations. Maximal specific binding of [3H]AMPA occurred in Triton X-100 treated membranes in the presence of the chaotropic agent potassium thiocyanate (KSCN). The effects of KSCN on binding were reversible and optimal at 100 mM. Supernatant obtained from detergent-treated membranes inhibited specific [3H]AMPA and [3H]kainic acid binding, suggesting the presence of an inhibitory agent which was tentatively identified as glutamate. Using centrifugation, saturation analysis revealed two distinct binding sites in both the absence and presence of KSCN. The chaotrope was most effective in increasing binding at the low affinity binding site, enhancing the affinity (Kd) without a concommitant change in the total number of binding sites. Using filtration, a single binding site was detected in Triton-treated membranes. Like the data obtained by centrifugation, KSCN enhanced the affinity of the receptor (Kd value = 10 nM) without altering the number of binding sites (Bmax = 1.2 pmol/mg protein). The rank order of potency of various glutamate analogs in the [3H]AMPA binding assay was quisqualate greater than AMPA greater than L-glutamate greater than kainate greater than D-glutamate, consistent with the labeling of a quisqualate-type excitatory amino acid receptor subtype. L-glutamic acid diethylester, and 2-amino-7-phosphonoheptanoic acid (AP7) were inactive. The present technique provides a rapid, reliable assay for the evaluation of quisqualate-type excitatory amino acid agonists and/or antagonists that may be used to discover more potent and selective agents.

Animals↗
PubMed1984

Postmortem increase of GABA levels in peripheral rat tissues: prevention by 3-mercapto-propionic acid.

The postmortem alteration of gamma-aminobutyric acid (GABA) levels was examined in the rat brain, kidney, ovary and oviduct up to 30 minutes after decapitation. GABA concentrations progressively increased with time in each organ. At 30 minutes, the following elevations were found in percent: brain 65, kidney 75, ovary 38 and oviduct 32. Pretreatment with 3-mercapto-propionic acid (3-MPA, 1.2 mmol/kg i.v.), 2.5 minutes prior to killing, completely prevented the postmortem increase of GABA levels in the brain, the ovary and the oviduct, but only slightly reduced the elevation of renal GABA content. In ex vivo experiments, the same treatment reduced with about 50 percent the activity of L-glutamate decarboxylase (GAD) in the brain and the oviduct, but failed to influence the enzyme activity in the kidney. In vitro, 3-MPA was far more potent in inhibiting cerebral and tubal than renal GAD. The present findings provide evidence for the ability of the 3-MPA treatment used, to prevent the postmortem increase of not only cerebral, but also oviductal and ovarian GABA levels. This procedure, however, proved to be inadequate for fixation of GABA concentration in the kidney.

3-Mercaptopropionic Acid↗
PubMed1993

Effects of high doses of testosterone propionate and testosterone enanthate on rat seminiferous tubules--a stereological and cytological study.

The effects of exogenous testosterone on various testicular variables has become of increasing significance because of its potential use in male contraception. For this reason, high doses of two testosterone esters [testosterone propionate (TP) and testosterone enanthate (TE)] were used in a study of their influence on the morphology, length and curvature of the seminiferous tubules of the rat testis, and on cytological smears of the seminiferous tubules epithelium. TP was given for 14 days (3 mg/100 g body weight, i.m.) to assess the acute effects of testosterone on the seminiferous tubules. TE was administered for 60 days (in the same manner as TP) to study possible chronic effects on the rat testis. After TP and TE treatment the seminiferous tubule epithelium showed disorganization and desquamation of spermatogenic cells. In the TP-treated testes the tubules lined with Sertoli cells only were observed. The values for the length and curvature of seminiferous tubules of the TP- and TE-treated rats were significantly reduced (p < 0.001). All these changes were observed earlier in the TP-treated than in the TE-treated animals. In cytological smears of the testis of the TP- and TE-treated rats an increase of vacuoles and residual bodies in Sertoli cell cytoplasm was noted. In addition, a reduction of spermatogenic cells, particularly sperms, was manifest in the smears after treatment. Large groups of Sertoli cells were seen in the smears from these testes.

Animals↗
PubMed1998

Effect of inhaled corticosteroids on bone mineral density in childhood asthma: comparison of fluticasone propionate with beclomethasone dipropionate.

There is a dearth of data on long-term effects of inhaled corticosteroids (ICS) on bone architecture in childhood asthma. This study was designed to assess the possible effects of two different inhaled steroids on bone mineral density (BMD) in steroid-naïve, prepubertal children. Twenty-three children were randomized to receive equipotent doses of either fluticasone propionate (100 micrograms twice daily) or beclomethasone dipropionate (200 micrograms twice daily). They were followed up over a period of 20 months with regular dual-energy X-ray absorptiometry scans for BMD. Densitometry of lumbar spine and total body showed a significant increase over time, which followed the normal patterns for growth. No difference was observed between the two subgroups. There was no change in fat distribution over time and no increase in percentage total body fat. As expected, girls had significantly higher total body fat. This absence of deleterious effects suggests that in the standard doses used neither beclomethasone nor fluticasone has any significant effect on bone density over a moderate period of time. Further studies should continue monitoring BMD through the critical years of bone mass accumulation during adolescence.

Absorptiometry, Photon↗
PubMed2000

Antinociception and (R,S)-alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid antagonism by gabapentin in the rat spinal cord in vivo.

Gabapentin, a novel anticonvulsant and analgesic with an unknown mechanism of action, was tested on spinal dorsal horn neurone activity evoked by iontophoretically applied N-methyl-D-aspartic acid (NMDA) and (R,S)-alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) and on nociceptive responses of single motor units (SMU) in anaesthetised rats. Gabapentin (10-215 mg/kg, i.v.) dose-dependently and selectively inhibited AMPA-evoked neuronal responses (ED50 106+/-24 mg/kg); no effect on NMDA-evoked activity was observed. In the same dose-range, gabapentin (10-215 mg/ kg, i.v.) dose-dependently reduced SMU responses to noxious electrical and mechanical stimulation. We conclude that gabapentin acts as an AMPA antagonist in the rat spinal cord, and that this mechanism is likely to substantially contribute to the antinociceptive effect of the drug.

Acetates↗
PubMed2004

Bioavailability of fluticasone propionate and mometasone furoate aqueous nasal sprays.

OBJECTIVES: To compare the systemic exposure for intranasal mometasone furoate (MF) and fluticasone propionate (FP) aqueous nasal sprays (ANS) in terms of serum and urinary cortisol parameters and plasma pharmacokinetics. METHODS: Twelve healthy subjects completed this three-way, cross-over study. They received FPANS (50 microg/spray), MFANS (50 microg/spray) or placebo ANS, eight sprays per nostril every 8 h for 4 days. Cortisol measurements were made at baseline and day 4. FP and MF plasma concentrations were also measured on day 4. RESULTS: MFANS produced similar mean plasma AUC (123 pmol/l h) to FPANS (112 pmol/l h). Despite the use of high doses, necessary to generate adequate pharmacokinetic data, only minor reductions in cortisol parameters were found, with no difference between FPANS and MFANS. CONCLUSIONS: FP and MF have similar and very low systemic bioavailability when administered intranasally using a high-dose regimen. It is therefore unlikely that therapeutic doses of intranasal FP or MF will produce dissimilar or significant degrees of systemic exposure or systemic effects.

Administration, Intranasal↗
PubMed1997

A dose-response study comparing suppression of plasma cortisol induced by fluticasone propionate from Diskhaler and budesonide from Turbuhaler.

OBJECTIVE: To compare the systemic potency of inhaled fluticasone propionate delivered via Diskhaler (FP-DH), and inhaled budesonide delivered via Turbuhaler (BUD-TBH) over the clinically recommended dose range using plasma cortisol suppression as a marker for systemic activity. METHODS: The systemic potency was examined in a dose-response study in 81 healthy male volunteers. The study was of an open, randomized, parallel-group (four groups) design, where two treatments were given in crossover fashion within each group. FP-DH and BUD-TBH were given b.i.d. for 7 days (14 doses): 100 and 100 micrograms (group 1); 200 and 200 micrograms (group 2); 500 and 400 micrograms (group 3); 1000 and 800 micrograms (group 4). There was a washout period of 7 days within each treatment group. All doses were administered at 08:00 and 20:00 hours. Multiple plasma cortisol samples were taken every 2 h over 24-h periods prior to randomization (baseline) and during steady state (i.e., the last two dosing intervals). Cortisol suppression was determined by comparing average plasma concentrations of cortisol before and during treatment. Dose-response curves for cortisol suppression were analyzed using multivariate non-linear regression (Hill modeling). RESULTS: Multiple dosing for 7 days with FP-DH and BUD-TBH resulted in dose-dependent cortisol suppression by both drugs, most pronounced at the two highest dose levels. FP-DH-induced suppression was 41% at 500 micrograms and 86% at 1000 micrograms b.i.d., while that induced by BUD-TBH was 19% at 400 micrograms and 47% at 800 micrograms b.i.d. Statistically significant differences were found when comparing the two steroids at these two dose levels. Doses producing 50% of maximum suppression (ED50) were estimated at 833 micrograms b.i.d. for BUD-TBH and 479 micrograms b.i.d. for FP-DH. This gave an estimated relative cortisol suppression over the dose range of 1.74:1 (FP-DH:BUD-TBH). ED50 values, estimated from cortisol concentrations at 08:00 hours (12 h after the last dose), were 1212 micrograms b.i.d. for BUD-TBH and 527 micrograms b.i.d. for FP-DH giving a relative cortisol suppression of 2.30:1 (FP-DH:BUD-TBH). Fourteen subjects on the highest FP-DH dose and 3 at the next highest dose had morning plasma cortisol levels below the lower reference limit. No subject taking budesonide, however, had morning plasma cortisol levels below the reference limit. Analysis of the time for return to pretreatment baseline levels showed that cortisol suppression, 12-24 h after the last dose, was statistically significant compared with the baseline for the highest dose of FP-DH but not for any of the BUD-TBH doses. CONCLUSIONS: The results of the present study show that FP-DH suppresses plasma cortisol more than BUD-TBH on a equivalent basis with regard to both magnitude and duration.

Administration, Inhalation↗
PubMed1998

Adrenocortical activity with repeated administration of one-daily inhaled fluticasone propionate and budesonide in asthmatic adults.

OBJECTIVE: The aim of this study was to evaluate the steady-state effects of once-daily inhaled fluticasone propionate (FP) and budesonide (BUD) on adrenocortical activity in asthmatic patients. METHODS: Ten asthmatic patients with a mean age of 31.2 years, a mean forced expiratory volume in 1 s (FEV1) of 91% predicted and a forced mid-expiratory flow (FEF25-75) of 62.3% predicted were studied in a single-blind randomised crossover design comparing placebo (PL), FP (375 microg per day and 750 microg per day) and BUD (400 microg per day and 800 microg per day) all given once daily for 4 days at each dose via a pressurised metered dose inhaler (pMDI) at 0800 hours. After 4 days of treatment, plasma cortisol was measured at 0800 hours (24 h after the last dose) and a 10-h overnight urine collection was taken, 14 h after the last dose (2200-0800 hours) for analysis of cortisol and creatinine excretion. RESULTS: Plasma cortisol levels (nmol.l(-1), as geometric mean) at 0800 hours demonstrated a significant difference between the highest doses of FP and BUD (424.1 vs 510.3 nmol.l(-1), respectively) but not between the low doses (506.8 vs 514.9 nmol.l(-1); PL 532.2 nmol.l(-1)). For the highest dose FP (750 microg) this equated to 20% suppression of 0800 hours plasma cortisol. Likewise, for overnight urinary cortisol output (nmol.10 h(-1) as geometric mean), there was a significant difference at the high doses of FP and BUD (25.5 vs 38.2 nmol.10 h(-1)), but not at the low doses 31.3 vs 34.8 nmol.10 h(-1); PL 32.0 nmol.10 h(-1). For the overnight urinary cortisol/creatinine ratio (nmol.mmol(-1), as geometric mean) there was a similar trend; 4.5 vs 6.1 nmol.mmol(-1) for high dose and 5.6 vs 6.3 nmol.mmol(-1) for low dose; PL 5.9 nmol.mmol(-1). CONCLUSION: Repeated doses of FP 750 microg once daily caused greater adrenal suppression than BUD 800 microg once daily, when comparing effects on plasma cortisol levels at 0800 hours, 24 h after the last dose, as well as effects on overnight urinary cortisol output. Neither FP 375 microg once daily nor BUD 400 microg once daily produced detectable adrenal suppression.

Adult↗
PubMed1998

Pharmacokinetic and pharmacodynamic evaluation of fluticasone propionate after inhaled administration.

OBJECTIVE: To evaluate the pharmacokinetic and systemic pharmacodynamic properties of inhaled fluticasone propionate (FP). METHODS: Single doses of 0.25, 0.5, 1.0 and 3.0 mg FP were administered to groups of six healthy subjects. Serum concentration profiles of FP were monitored over 24 h by means of high-performance liquid chromatography/mass spectrometry (HPLC/MS-MS). Systemic pharmacodynamic effects were evaluated by measuring endogenous serum cortisol and circulating white blood cells, and analyzed with previously developed integrated pharmacokinetic/pharmacodynamic (PK/PD) models. RESULTS: FP showed a dose-independent terminal half-life with a mean (SD) of 6.0 (0.7) h. Maximum serum concentrations occurred 1.0 (0.5) h after administration, ranging from 90 pg.ml(-1) for the 0.25 mg dose to 400 pg.ml(-1) for the 3.0 mg dose. This, together with an estimated mean absorption time of nearly 5 h and a known oral bioavailability of less than 1%, indicates prolonged residence at and slow absorption from the lungs. In the investigated dose range, the cumulative systemic effect was dose-dependent for both markers of pharmacodynamic activity. For doses of 0.25, 0.50, 1.0 and 3.0 mg FP, the PK/PD-based cumulative systemic-effect parameters were 159, 186, 257 and 372% .h for lymphocyte suppression, 107, 186, 202 and 348% .h for granulocyte induction and 23.6%, 33.8%, 51.0% and 73.6% for cortisol reduction, respectively. The time courses of lymphocytes, granulocytes and endogenous cortisol could be sufficiently characterized with the applied PK/PD models. The measured in vivo EC50 values, 30 pg.ml(-1) and 7.3 pg.ml(-1) for white blood cells and cortisol, respectively, were in good agreement with predictions based on the in vitro relative receptor affinity of FP. CONCLUSION: After inhalation, FP follows linear pharmacokinetics and exhibits dose-dependent systemic pharmacodynamic effects that can be described by PK/PD modeling.

Administration, Inhalation↗
PubMed2001

Relative lung delivery of fluticasone propionate via large volume spacer or nebuliser in healthy volunteers.

OBJECTIVES: High-dose nebulised fluticasone propionate (FP) has been advocated for use in patients with severe persistent asthma. As there is complete first-pass inactivation of FP for the swallowed fraction, systemic absorption is due solely to its lung bioavailability. We wished to compare the relative lung delivery of FP, using adrenal suppression as a surrogate for the respirable dose, when administered via large volume spacer (FP-spacer) or nebuliser (FP-neb) in healthy adults. METHODS: Fourteen healthy subjects, mean (SEM) age 29.4 +/- 2.6 years, were studied in a placebo-controlled, randomised study with three-way crossover design. Single nominal 2-mg doses of the following were given at 1700 hours in randomised sequence: a. FP-spacer: fluticasone pressurised metered dose inhaler (as Flixotide 250 microg ex-valve per actuation), eight puffs via a primed Volumatic 750-ml spacer. b. FP-neb: (as Flixotide Nebule 2 mg/2 ml) via Pari LC Plus nebuliser. c. Placebo nebuliser. Following each dose, measurements were made of corrected 0800-hours urinary cortisol/creatinine ratio (the primary outcome variable) and 0800-hours plasma cortisol. RESULTS: Significant (P<0.05) suppression of both endpoints occurred only with FP-spacer, FP-neb being statistically no different from placebo. Geometric mean fold differences between FP-spacer and placebo were 9.8-fold [95% confidence interval (CI) 3.4, 28.8] for urinary cortisol/creatinine and 4.1-fold (95% CI 2.2, 7.5) for plasma cortisol. Comparing FP-spacer with FP-neb, these differences were 6.8-fold (95% CI 2.3, 20.0) for urinary cortisol/creatinine and 3.3-fold (95% CI 1.8, 6.0) for plasma cortisol. CONCLUSION: For a 2-mg labelled nominal dose of fluticasone, the spacer produced about a sevenfold higher relative lung dose than the nebuliser. This suggests that a very little of the labelled nebulised dose is respirable. Other factors such as patient preference, cost and compliance will determine the inhaler device that is chosen.

Administration, Inhalation↗
PubMed1996

Reversible interruption of gap junctional communication by testosterone propionate in cultured Sertoli cells and cardiac myocytes.

A direct cell-to-cell exchange of ions and molecules occurs through specialized membrane channels built by the interaction of two half channels, termed connexons, contributed by each of the two adjacent cells. The electrical and diffusional couplings have been investigated by monitoring respectively the cell-to-cell conductance and the fluorescence recovery after photobleaching, in Sertoli and cardiac cells of young rat. In both cell types, a rapid impairment of the intercellular coupling has been observed in the presence of testosterone propionate. This interruption of the cell-to-cell communication through gap junction channels was dose-dependent, observed in the concentration range 1 to 25 microM and was progressively reversed after withdrawing the testosterone ester. Pretreatment with cyproterone acetate, an antiandrogen which blocks the nuclear testosterone receptor by binding, did not prevent the uncoupling action of the androgen ester. This observation, together with the rapid time course of the uncoupling and recoupling, and the rather high effective concentration (micromolar) of the steroid compound, suggests a nongenomic mechanism of action. The uncoupling concentrations were very similar to those of other steroid compounds known to interrupt gap junctional communication. The uncoupling could result from a direct interaction of the steroid with the proteolipidic structure of the membrane, that might alter the conformation of the gap junction channels and their functional state.

Animals↗
PubMed1996

Altered distribution of the alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate receptor subunit GluR2(4) and the N-methyl-D-aspartate receptor subunit NMDAR1 in the hippocampus of patients with temporal lobe epilepsy.

In patients with therapy-refractory temporal lobe epilepsy (TLE), alterations of glutamate receptors have been proposed as a mechanism for enhanced excitability. Using commercially available monoclonal antibodies specific for the N-methyl-D-aspartate (NMDA) receptor subunit NMDAR1 and for the alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate receptor subunit GluR2(4), we have examined the distribution of these polypeptides in human hippocampal tissue that was surgically removed from patients with intractable TLE. Surgical specimens were classified according to the presence of Ammon's horn sclerosis (AHS) or a focal lesion in the temporal lobe. Cell counts and a densitometric analysis of the immunoreactivity patterns were carried out for all hippocampal subfields. NMDAR1 and GluR2(4) levels were markedly reduced in patients with AHS, primarily in those subfields with substantial neuronal cell loss (in particular CA1, CA4 and CA3), compared to those seen in patients with focal lesions and in control specimens obtained at autopsy. In contrast, the molecular layer of the dentate gyrus (DG-ML) showed significantly higher levels of GluR2(4) immunoreactivity in AHS compared to control tissue, while NMDAR1 showed no significant up-regulation in this sublayer. When the receptor staining intensity was normalized for alterations in neuronal density, no significant alterations could be detected except for an increase in GluR2(4) in the DG-ML of patients with AHS. These changes may reflect synaptic reorganization observed in the DG-ML of specimens from patients with chronic intractable TLE.

Adolescent↗