ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1990.tb08813.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Abstract:Ferritin levels were measured in postmortem brain tissue from patients dying with Parkinson's disease [treated with L‐3,4‐dihydroxyphenylalanine (L‐DOPA)] and from control patients. Ferritin levels were decreased in the substantia nigra, caudate‐putamen, globus pallidus, cerebral cortex, and cerebellum when compared with age‐matched control tissues. However, in CSF from L‐DOPA‐treated patients and in serum from L‐DOPA‐treated and untreated parkinsonian patients, ferritin levels were normal. Previous studies have suggested an increased total iron content in substantia nigra of parkinsonian brain. The failure of substantia nigra ferritin formation to be stimulated by increased iron levels suggests some defect in iron handling in this critical brain region in Parkinson's disease. The reason for decreased ferritin levels throughout the parkinsonian brain is not clear but does not seem to reflect a general system de

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1990.tb08814.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Abstract:The mechanism by which cannabinoid compounds produce their effects in the rat brain was evaluated in this investigation. Cannabinoid receptors, quantitated by [3H]CP‐55,940 binding, were found in greatest abundance in the rat cortex, cerebellum, hippocampus, and striatum, with smaller but significant binding also found in the hypothalamus, brainstem, and spinal cord. Using rat brain slice preparations, we evaluated the effect of desacetyllevonantradol on basal and forskolin‐stimulated cyclic AMP accumulation in the regions exhibiting the greatest cannabinoid receptor density. Desacetyllevonantradol (10 μM) reduced cyclic AMP levels in the hippocampus, frontal cortex, and striatum. In the cerebellum, however, the response to desacetyllevonantradol was biphasic with cyclic AMP accumulation being decreased at lower and increased at higher concentrations. Desacetyllevonantradol reduced cyclic AMP accumulation in isoproterenol‐stimulated slices in the cortex and cerebellum, but not in the hippocampus. Cells that responded to vasoactive intestinal peptide with an increase in cyclic AMP accumulation in the hippocampus and cortex also responded to desacetyllevonantradol. The modulation of cyclic AMP accumulation by desacetyllevonantradol could be attenuated following stereotaxic implantation of pertussis toxin, supporting the involvement of a G protein in the cannabinoid response in the brain. However, other actions of cannabinoid compounds may also affect the cyclic AMP levels in brain slice prepar

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1990.tb08815.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Abstract:A simple, reliable method was developed for measuring brain acetylcholine (ACh) turnover using HPLC methodology. Mice were injected intravenously with [3H]choline ([3H]Ch), and the turnover rate of ACh was calculated from the formation of [3H]ACh. Ch and ACh were separated from phosphorylcholine and from other radioactive compounds using tetraphenylboron extraction and counterion/reverse‐phase chromatography. Endogenous Ch and ACh were quantified electrochemically through hydrogen peroxide production in a postcolumn reactor containing covalently bonded ACh esterase and Ch oxidase. Labeled Ch and ACh were quantified in the same sample by collecting the chromatographic fractions for radioactive content determinations. The method is rapid, well adapted to large series, and highly reproducible, with recoveries of 72.1% for Ch and 79.3% for ACh. The turnover value in mouse cerebral hemispheres was 16.02 nmol g‐1min‐1and decreased to 9.94 nmol g‐1min‐1in mice treated with oxo

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1990.tb08816.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Abstract:The receptors responsible for the adenosine‐mediated control of acetylcholine release from immunoaffinitypurified rat striatal cholinergic nerve terminals have been characterized. The relative affinities of three analogues for the inhibitory receptor were (R)‐phenylisopropyladenosine>cyclohexyladenosine>N‐ethylcarboxamidoadenosine (NECA), with binding being dependent of the presence of Mg2+and inhibited by 5′‐guanylylimidodiphosphate [Gpp(NH)p] and adenosine receptor antagonists. Adenosine A1receptor agonists inhibited forskolin‐stimulated cholinergic adenylate cyclase activity, with an IC50of 0.5 nMfor (R)‐phenylisopropyladenosine and 500 nMfor (S)‐phenylisopropyladenosine. A1agonists inhibited acetylcholine release at concentrations approximately 10% of those required to inhibit the cholinergic adenylate cyclase. High concentrations (1 μM) of adenosine A1agonists were less effective in inhibiting both adenylate cyclase and acetylcholine release, due to the presence of a lower affinity stimulatory A2receptor. Blockade of the A1receptor with 8‐cyclopentyl‐1,3‐dipropylxanthine revealed a half‐maximal stimulation by NECA of the adenylate cyclase at 10 nM, and of acetylcholine release at approximately 100 nM. NECA‐stimulated adenylate cyclase activity copurified with choline acetyltransferase in the preparation of the cholinergic nerve terminals, suggesting that the striatal A2receptor is localized to cholinergic neurones. The possible role of feedback inhibitory and stimulatory receptors on cholinergic ne

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1990.tb08817.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Abstract:The endogenous neuropeptideN‐acetyl‐L‐aspartyl‐L‐glutamate (NAAG) fulfills several criteria required to be accepted as a neurotransmitter. NAAG inactivation may proceed through enzymatic hydrolysis intoN‐acetyl‐L‐aspartate and glutamate by anN‐acetylated‐α‐linked acidic dipeptidase (NAALADase). Therefore, some properties of NAA‐LADase activity were investigated using crude membranes from the rat forebrain. Kinetic parameters of the hydrolysis of [Glu‐3H]NAAG were determined first (Km= 0.40 ± 0.05 μM;Vmax= 155 ± 20 pmol/min/mg of protein). The enzymatic activity, i.e., NAALADase, was inhibited noncompetitively by the glutamatergic agonist quisqualate (Ki= 1.9 ± 0.3 μM), and competitively byN‐acetyl‐L‐aspartyl‐β‐linked L‐glutamate (β‐NAAG;Ki= 0.70 ± 0.05 μM). To determine whether glutamate‐containing dipeptides, such as NAAG, β‐NAAG,N‐acetyl‐L‐aspartyl‐D‐glutamate, L‐aspartyl‐L‐glutamate, L‐alanyl‐L‐glutamate, L‐glutamyl‐L‐glutamate, and L‐glutamyl‐γ‐linked L‐glutamate, were substrates of NAA‐LADase, rat brain membranes were immobilized on a C‐8 column. Thus, endogenous trapped glutamate was washed away and formation of unlabelled glutamate could be estimated using ano‐phthaldialdehyde/reverse‐phase HPLC detection procedure. β‐NAAG was shown to be a nonhydrolyzable competitive inhibitor of NAALADase. L‐Aspartyl‐L‐glutamate was hydrolyzed faster than NAAG, suggesting that the acetylated moiety is not essential for NAALADase specificity. Rat brain membranes also contained nonspecific peptidase activities (insensitive to both quisqualate

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1990.tb08818.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Abstract:The opioid modulation of histamine release was studied in rat brain slices labeled with L‐[3H]histidine. The K+‐induced [3H]histamine release from cortical slices was progressively inhibited by the preferentialk‐agonists ketocyclazocine, dynorphin A (1–13), Cambridge 20, spiradoline, U50,488H, and U69,593 in increasing concentrations. In contrast, the μ‐agonists morphine, morphiceptin, and Tyr‐D‐Ala‐Gly(NMe)Phe‐Gly‐ol (DAGO) were ineffective as were the preferential δ‐agonists [D‐Ala2,D‐Leu5]enkephalin (DADLE) and [D‐Pen2,D‐Pen5]enkephalin (DPDPE). Nor‐binaltorphimine (nor‐BNI) and MR 2266, two preferentialk‐antagonists, reversed the inhibitory effect of the variousk‐agonists more potently than did naloxone, with meanKivalues of 4 nMand 25 nM, respectively. The effects of ketocyclazocine and naloxone also were seen in slices of rat striatum, another brain region known to contain histaminergic nerve endings. We conclude thatk‐opioid receptors, presumably located on histaminergic axons, control histamine release in the brain. However, nor‐BNI and naloxone failed, when added alone, to enhance significantly [3H]histamine release from cerebral cortex or striatum, and bestatin, an aminopeptidase inhibitor, failed to decrease K+‐evoked [3H]histamine release. These two findings suggest that under basal conditions theseK‐opioid receptors are not tonically activated by endogenous dynorphin peptides. The inhibition of cerebral histamine release byK‐agonists may med

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1990.tb08819.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Abstract:The optic nerve of the bullfrog was transected and the regeneration process was investigated. We previously reported that α‐tubulin mRNA in the retina increased to a maximum 1–2 h after optic nerve transection with no specific change in actin mRNA. In the present investigation, we examined the long‐term effect of optic nerve transection. Northern blot analysis revealed that α‐tubulin mRNA increased again gradually after the rapid and transient increase and actin mRNA increased to a maximum at 7 days (more than twofold compared to the control retinas). The period during which actin mRNA reaches a maximal increase almost corresponds to the time lag between the axotomy and the initiation of axonal outgrowth. The main cytoskeletons of neuronal growth cones have been shown to consist of actin containing microfilaments. Therefore, the transient increase of actin mRNA may have a relationship to the initial out growth of axons. On the other hand, the rapid and transient increase of α‐tubulin mRNA observed in our previous studies is probably one of the initial responses of retinal ganglion cells to the axotomy, and the gradual increase in α‐tubulin mRNA observed in this study can probably be interpreted as provision of the structural materials necessary for ax

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1990.tb08820.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Abstract:Alternative splicing of the transcript encoding the β‐amyloid precursor protein (BAPP) of Alzheimer's disease produces multiple mRNA species. Translation of these mRNAs predicts protein products of 770, 751, and 695 amino acids. The difference arises from the inclusion in BAPP‐770/ 751 of a 56‐residue insert region which is homologous to Kunitz‐type protease inhibitors. We have prepared and affinity‐purified anti‐peptide antibodies that react specifically with either BAPP‐770/751 (inssert‐specific) or BAPP‐695 (junction‐specific). A detectable level of the mRNA corresponding to the BAPP‐770/751 protein was found in all cell lines tested. Immunoprecipitation of35S‐labeled proteins from these cell lines showed them to contain one or two Mr105,000 bands reactive with the insert‐specific serum, i‐291. In contrast, onlycos‐7cells and the human neuroblastoma cell line, IMR‐32, contained mRNA species that encode the BAPP 695 protein, as shown by Northern analysis with a junction spanning oligonucleotide probe. A band of Mr95,000 was immunoprecipitated specifically from these two cell lines using the junction‐specific serum, J‐284. Indirect immunofluorescence labeling of cells corroborated these findings. All cells reacted with the insert‐specific antibodies, i‐291 and i 324. Onlycos‐7and IMR‐32 cells reacted with the junction specific antibody, J‐284. These results demonstrate the use fulness of anti‐peptide antibodies for the differential det

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1990.tb08821.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Abstract:We investigated, using adult (2‐month‐old) and senescent (12‐ and 24‐month‐old) rats, the effects of aging on the relationship between the α1‐adrenergic coupling system and the membrane viscosity of the cerebral cortex. There was no age‐related difference in theKDvalues of [3H]prazosin binding on the membranes. TheBmaxvalues of [3H]prazosin binding were reduced with advanced age. Norepinephrine induced formation of3H‐labeled inositol phosphates (3H‐IPs) in the slices increased with advanced age. The EC50values for norepinephrine to stimulate the formation of3H‐IPs at advanced age were lower than that at adult age. The cholesterol content in membranes increased with advanced age. No changes in the phospholipid content in membranes were observed with advanced age. Concomitantly, an increase of the molar ratio of cholesterol to phospholipids was observed with advanced age. The membrane viscosity as measured by 1,6 diphenyl‐1,3,5‐hexatriene increased with advanced age. These results indicate that the altered cholesterol content and/or viscosity in cortical membranes of the aged rat may account for the loss of α1‐adrenergic receptor density and/or compensatory changes in the receptor‐ph

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1990.tb08822.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY