Histamine increases phospholipid methylation and H2-receptor-adenylate cyclase coupling in rat brain

Histamine stimulated the enzymatic synthesis of phosphatidylcholine from phosphatidylethanolamine in crude synaptic membranes of rat brain containing the methyl donor S-adenosyl-L-methionine (SAM). In the presence of, but not in the absence of SAM, histamine increased cyclic AMP accumulation at the concentrations that stimulate phospholipid methylation. S-Adenosyl-L-homocysteine, an inhibitor of phospholipid methyltransferases, inhibited histamine-stimulated phospholipid methylation and histamine-induced cyclic AMP accumulation in the presence of SAM in a concentration-dependent manner. Histamine-induced [3H]methyl incorporation into phospholipids exhibited a marked regional heterogeneity in rat brain in the order of cortex greater than medulla oblongata greater than hippocampus greater than striatum greater than midbrain greater than hypothalamus. The regional distribution of histamine-induced cyclic AMP accumulation exactly paralleled histamine-stimulated [3H]methyl incorporation in rat brain. Histamine-induced cyclic AMP accumulation was inhibited by the addition of cimetidine or famotidine, but not by mepyramine or diphenhydramine. The accumulation of cyclic AMP in the presence of SAM was observed by the addition of impromidine or dimaprit, but not by 2-pyridylethylamine. These results indicate that phospholipid methylation is induced by histamine and may participate in H2-receptor-mediated stimulation of adenylate cyclase in rat brain.

Solubilization and characterization of substance P binding protein from bovine brainstem

The specific binding protein for substance P (SP) was solubilized in an active form from the crude mitochondrial (P2) fraction of bovine brainstem. After incubation with 3-[(3-cholamidopropyl)dimethylammonio]-1-propane sulfonate (CHAPS) and 0.1 M NaCl at 0 degrees C for 30 min, the SP binding to the supernatant fraction (100,000 g, 60 min) was determined by the glass fiber filtration method reported by Bruns et al. (1983). The specific [3H]SP binding to the solubilized fraction was highly specific for SP and was displaced by nanomolar concentrations of SP and physalaemin, but only by micromolar concentrations of eledoisin. In addition, the binding was inhibited by GTP (approximately 40% of the specific binding decreased by 10 microM GTP) in both preparations. These results were virtually identical to those of P2 membrane preparations and suggested that this high-affinity SP binding site belongs to the SP-P type. Scatchard analyses of SP binding to the solubilized fraction revealed a single saturable component with a Bmax of 22.0 +/- 5.10 fmol/mg protein and a KD of 0.79 nM, and these values are almost the same as those obtained in the P2 fraction (Bmax = 31.3 +/- 3.56 fmol/mg protein, KD = 0.82 nM). Gel filtration analysis showed that the detergent-SP binding protein complex has two calculated molecular weights of greater than 1,000,000 and 55,000-60,000 (a corresponding Stokes radius of 35.5 nm).

Structure-activity relationship of hylambatin and its fragments as studied in the guinea-pig ileum

Hylambatin (Hyl), a dodecapeptide isolated from the skin of the African frog, Hylambates maculatus, belongs to the family of tachykinin or physalaemin-like peptides. Hylambatin and its 12 fragments were tested in the guinea-pig ileum preparation for contractile activities. All fragments except 3 had contractile activities. The C-terminal fragment as short as the octapeptide sequence was at least as active as the parent molecules. The heptapeptide fragment (Hyl6-12) and the hexapeptide fragment (Hyl7-12) were less active and the C-terminal pentapeptide fragment (Hyl8-12) and the N-terminal hexapeptide fragment (Hyl1-6) were much less active. The N-terminal pentapeptide fragment (Hyl1-5) and the N-terminal fragment from which the N-terminal Asp or Asp-Pro residues were removed (Hyl2-6, Hyl3-6), were inactive at doses used.

Effect of immobilization stress on pipecolic acid transport in mouse brain areas and peripheral tissues

Transport activity of d-pipecolic acid and of l-pipecolic acid in mouse brain and peripheral tissues were tested, and the effect of immobilization stress was described, along with the method for preparative, enantiomeric resolution and purification of d,l-pipecolic acid using high performance liquid chromatography equipped with a chiral column. It was found that l-isomer, an endogenous substance, was more rapidly transported to brain and liver than the d-isomer, non-endogenous one, which was more rapidly eliminated into the kidney. Immobilization stress caused acceleration of transport of l-pipecolic acid into the brain region, liver and heart, but not that of d-pipecolic acid. From these results it was suggested that the elevation of pipecolic acid concentration caused by stress might be exerted through its stimulatory effect on the transport of l-pipecolic acid into the tissues.

Neurotensin receptors on the rat liver plasma membranes

Neurotensin (NT) is now classified as a brain-gut peptide in the central nervous system and gastrointestinal tract. In the present study, we characterized the NT receptors on the rat liver plasma membranes. The specific binding of [3H]NT was time dependent, reversible, and saturable. Scatchard analysis of the specific binding data yielded two classes of binding sites, a high affinity site and a low affinity site. The average maximum number of binding sites (Bmax) amounted to 13.3 +/- 1.1 fmol/mg protein at high affinity site and 122.3 +/- 21.5 fmol/mg protein at low affinity site, respectively. The dissociation constant (Kd) had values of 0.39 +/- 0.01 nM at high affinity site and 8.1 +/- 1.1 nM at low affinity site, respectively. The amount of specifically bound [3H]NT was significantly reduced in the presence of mono and divalent cations, EDTA, EGTA and a peptidase inhibitor bacitracin, NT1-13 competed with [3H]NT for its binding site with an IC50 of 0.19 nM at high affinity site (0.2 nM concentration of [3H]NT) and 0.7 nM at low affinity site (4.0 nM concentration of [3H]NT). Xenopsin, a NT analogue separated from the skin of Xenopus laevis, was equipotent (IC50 0.75 nM) with NT1-13 at 4.0 nM concentration of [3H]NT. C-terminal sequence of NT contains the structure necessary for interaction with NT binding sites whereas N-terminal sequence had no binding activity. Since NT has a hyperglysemic and a hypercholesterolemic effects in rats, these NT receptors on the rat liver plasma membranes may be involved in the hyperglycemia and/or hypercholesteroremia induced by NT.

Autogenous regulation of the Saccharomyces cerevisiae regulatory gene GAL80

We have suggested previously from Northern blot analysis that transcription of the negative regulatory gene GAL80 was controlled positively by another regulatory gene GAL4, and negatively by GAL80 itself, in similar way to GAL1, GAL7 and GAL10 genes encoding galactose-metabolizing enzymes in Saccharomyces cerevisiae. To study further the controlled expression of GAL80, we have exploited the gene fusion technique. We constructed gene fusions consisting of 5' fragments of GAL80 and a 5' truncated lacZ of Escherichia coli, and introduced the GAL80'-'lacZ fusions into wild-type yeast or various GAL4 or GAL80 mutants using multiple-copy or single-copy plasmid vectors. We then studied beta-galactosidase activity in the resultant transformants under uninduced, induced or glucose-repressed conditions. Expression of the GAL80'-'lacZ fusions was clearly under the control of Gal4/Gal80. Next we constructed GAL7'-'lacZ fusions, whose upstream activating sequence (UAS) from GAL7 was replaced with a GAL80 fragment containing a UAS-like sequence located in the 5' flanking region of GAL80. Synthesis of beta-galactosidase directed by the hybrid genes was inducible by galactose exactly like the original GAL7'-'lacZ fusion with a UAS from GAL7. Finally we constructed a GAL7-GAL80 hybrid gene, in which the entire 5' flanking region was derived from GAL7. When the chromosomal GAL80 gene in wild-type yeast was replaced with the hybrid gene, the uninduced level, but not the induced level, of the GAL10-encoded enzyme (uridine diphosphoglucose-4-epimerase) was significantly increased.

Histamine acting on H2 receptors stimulates phospholipid methylation in synaptic membranes of rat brain

Histamine stimulated [3H]methyl group incorporation into phospholipids in crude synaptic membranes of rat whole brain (without cerebellum) in modified Krebs-Ringer solution containing the methyl donor S-adenosyl-[methyl-3H]methionine. The transient increase of [3H]methyl incorporation into lipids peaked within 45 s after addition of histamine (5 or 10 microM) and decreased the basal level in 60 s. Histamine-stimulated [3H]methyl incorporation was increased linearly in a protein concentration-dependent manner. The stimulation was temperature and histamine concentration dependent. TLC analysis of a chloroform/methanol extract indicated that radioactive phospholipids (phosphatidylcholine, phosphatidyl-N,N-dimethylethanolamine, and phosphatidyl-N-monomethylethanolamine) accounted for 60-65% of the total radioactivity recovered. The synaptosomal fraction had the highest specific activity of all the subfractions of crude synaptic membranes (P2). Histamine-induced [3H]methyl incorporation was inhibited by addition of cimetidine (0.01-10 microM) or famotidine (0.01-1.0 microM) in a concentration-dependent manner but not by mepyramine (0.1-10 microM) or diphenhydramine (0.1-10 microM). The stimulation of [3H]methyl incorporation was also observed by addition of impromidine (0.01-10 microM) or dimaprit (1.0 microM-1.0 mM) in a concentration-dependent manner but not by 2-pyridylethylamine (1.0 microM-1.0 mM). These results indicate that phospholipid methylation is induced by histamine acting on H2 receptors in rat brain synaptosomes.

Effect of concanavalin A on 5'-nucleotidase activity of rabbit blood platelets

Ecto-5'-nucleotidase (ecto-5'-NU) of platelets was enhanced by concanavalin A (Con A). This effect of Con A was antagonized by alpha-methyl-D-mannose, a specific antagonist of Con A binding to glycoprotein. Coformycin, an adenosine deaminase inhibitor, did not change the effect of Con A on the ecto-5'-NU. Uptake of adenosine by platelets was not affected by Con A. It was suggested that the ecto-5'-NU of platelet might be a direct and primary site of action of Con A.

Pressure-volume relationships in the pulmonary "venous" system in living dogs

In this study, we examined the pressure-volume (P-V) relationships of the pulmonary "venous" (P'V') system in anesthetized living dogs, and assessed compliance by fitting the derived data of the P-V relationships to the exponential function. By definition, the P'V' system consists of the pulmonary veins and the left atrium. The pulmonary "venous" volume (P'V'V) was determined with our modified double indicator dilution method using a single injection and double sampling technique. The mean left atrial pressure (PLA) was measured directly. To observe sequential changes over a wide range of the P-V relationships, dogs were studied from the control state through the volume-loaded state with dextran. The P'V'V ranged from 3.4 to 12.2 ml X kg-1 and the PLA from 3.2 to 40.6 mmHg. We fitted the data of the P-V relationships (n = 24) to the exponential function, yielding an equation: P'V'V (ml X kg-1) = 19(1-0.833(e-0.017PLA(mmHg)). We then differentiated an above equation to estimate the slope of this curve (static compliance), giving the equation: dV/dP (ml X mmHg-1 X kg-1) = 0.269(e-0.017PLA(mmHg)). Therefore, at PLA of 10 mmHg (normal level), the compliance is 0.227 ml X mmHg-1 X kg-1. The compliance, obtained with an application of the present results in dogs to man, (disregarding expected species differences), coincides well with that in man determined with our indirect method.

Influence of pertussis toxin on the effects of guanine nucleotide on adenylate cyclase in rat striatal membranes

The influence of pertussis toxin on the effects of guanine nucleotide on adenylate cyclase activity were investigated in rat striatal membranes. GTP promoted and inhibited the activity at 1 and 100 microM, respectively. The inhibitory effects of GTP were abolished by pretreatment of the membranes with pertussis toxin. GppNHp (guanyl-5'-y1-beta,gamma-imidodiphosphate) exerted only stimulatory effects and pertussis toxin did not affect the effects of GppNHp. GDP at 10 and 100 microM caused significant inhibition which was completely suppressed by pertussis toxin. It is suggested that guanine nucleotide regulates the affinity of as in stimulatory GTP-binding regulatory protein to either beta gamma or catalytic units of adenylate cyclase in a flip-flop manner. Inhibitory GTP-binding regulatory protein seems to play a regulatory role in inhibiting alpha s activity supplying the beta gamma heterodimer.

Fluid volume balance between pulmonary intravascular space and extravascular space in dogs

We aimed to study the agreement of estimates of the pulmonary blood volume by the double indicator dilution method and the direct destructive method and the fluid volume balance between the pulmonary intravascular and extravascular spaces. We employed the double indicator dilution method using heat and indocyanine green, with a single injection (into the right atrium) and double sampling technique, that is from the pulmonary artery trunk (PAT) and the aortic root (Ao). With this method, we simultaneously determined the pulmonary extravascular water volume (PEWV), defined as the extravascular lung thermal volume estimated in Ao (LTVAo), and the pulmonary blood volume (PBV) from PAT to the left atrium (LA) (PBVPAT-LA). Dogs were divided into groups: a group without intervention (n = 16), a group loaded with dextran (n = 12) and a group loaded with alloxan (n = 7). When all groups were included, PBVPAT-LA (ml/kg) = 1.02 X PBVdirect(g/kg) + 0.96, n = 35, r = 0.83 where PBVdirect means the blood contents from the pulmonary artery bifurcation to the pulmonary vein measured by the direct destructive method. We substantiated the validity of the use of the double indicator dilution method. In studying the fluid volume balance, based on the results of the direct destructive method, the pulmonary intravascular-extravascular fluid volume ratio (intra/extra) was 1.3 +/- 0.3 (mean +/- SD) in the control state, implying that the interstitium in the lung is relatively "dry". As overt pulmonary edema developed by dextran infusion, the ratio exponentially decreased to 1.0 +/- 0.1 (p less than 0.01). The behavior of the fluid volume balance in question (intra/extra), studied with the double indicator dilution method, was essentially similar to that analyzed by the direct destructive method.

Alpha 2-adrenoceptor-GTP binding regulatory protein-adenylate cyclase system in cerebral cortical membranes of adult and senescent rats

The characterization of [3H]clonidine binding and effects of GTP, forskolin, islet-activating protein (IAP) and cholera toxin on adenylate cyclase activity were investigated in cerebral cortical membranes from 70-day-old and 2-year-old rats. Neither Kd nor Bmax values in [3H]clonidine binding were changed between day 70 and year 2. The activation of adenylate cyclase by forskolin was significantly higher in senescent than in adult animals. The inhibitory effect of adrenaline, which was completely abolished by the pretreatment with IAP/NAD on forskolin/GTP-stimulated cyclase activity, was low in senescent rats compared to that in adult ones. The stimulatory effect of cholera toxin/NAD was also low at the senescent stage compared to that at the adult stage. It is suggested that ligand binding affinity and the density in alpha 2-adrenoceptors do not change between day 70 and year 2 but that GTP binding and/or coupling activity of inhibitory as well as stimulatory GTP binding regulatory protein to catalytic units decrease in synaptic membranes of 2-year-old compared to those of 70-day-old rat brain.

Comparison of effects of tiapride and sulpiride on D-1, D-2, D-3 and D-4 subtypes of dopamine receptors in rat striatal and bovine caudate nucleus membranes

To determine the affinity of tiapride to D-1, D-2, D-3 and D-4 subtypes of dopamine (DA) receptors, inhibitory effects of tiapride on [3H]-cis-flupenthixol, [3H]spiperone and [3H]N-propylapomorphine binding were examined in the rat striatum and bovine caudate nucleus membranes and compared to those of sulpiride and haloperidol. The IC50 values of tiapride, sulpiride and haloperidol were estimated as follows: 1440, 132 and 0.295 microM for D-1; 45.8, 8.8 and 0.004 microM for D-2; greater than 100, greater than 100 and 0.64 microM for D-3; 11.7, 2.88 and 0.0044 microM for D-4, respectively. It is suggested that the affinity of tiapride is high to D-2 and D-4, but is not high to D-1 and D-3. The affinity pattern of tiapride to each DA receptor subtype is similar to but lower than those of sulpiride and haloperidol. In the D-2 receptor assay, the IC50 values of tiapride and sulpiride were 1/22.7 and 1/19.1 of those in the presence of 100 mM NaCl, respectively, suggesting that benzamide drug binds to the D-2 subtype with higher affinity in the presence of Na+ than in the control.

Long-term lithium treatment causes serotonin receptor down-regulation via serotonergic presynapses in rat brain

The effects of lithium treatment on serotonin (5-HT) receptors in rat frontal cortex and hippocampus were investigated. Long-term lithium treatment strongly blocked 5-hydroxytryptophan-induced head twitches, while acute lithium administration by itself induced head twitches in rats, and ketanserin blocked this acute lithium action. Long-term administration of lithium decreased the number of not only 5-HT2 receptors in the frontal cortex but also 5-HT1 and 5-HT2 receptors in the hippocampus in rats. Decreases in 3H-5-HT binding to hippocampal 5-HT1 receptors and 3H-spiperone binding to frontal cortical 5-HT2 receptors, caused by chronic lithium treatment, were abolished by co-administration of p-chlorophenylalanine, and were enhanced by co-administration with methiothepin. The turnover of 5-HT in either frontal cortex or hippocampus was facilitated by lithium, and co-administered methiothepin enhanced this facilitation. These results suggest that long-term lithium treatment causes the down-regulation of postsynaptic 5-HT1 and 5-HT2 receptors, in part probably through its action on presynaptic nerve terminals.

Possible involvement of inhibitory GTP binding regulatory protein in alpha 2-adrenoceptor-mediated inhibition of adenylate cyclase activity in cerebral cortical membranes of rats

Influences of alpha 2-adrenoceptor stimulation on adenylate cyclase activity were investigated in cerebral cortical membranes of rats. Pretreatment of the membranes with islet-activating protein and NAD resulted in a significant increase in basal activity as well as in GTP- or forskolin/GTP-induced elevation of adenylate cyclase activity. Strong activation of adenylate cyclase was also caused in membranes pretreated with cholera toxin together with NAD in comparison to that in control membranes, suggesting that adenylate cyclase activity is perhaps regulated by stimulatory and inhibitory GTP binding regulatory protein existing in synaptic membranes. In addition, adrenaline (with propranolol) or clonidine significantly reduced adenylate cyclase activity stimulated by pretreatment with forskolin and GTP. The inhibitory effects of adrenaline were also observed in membranes pretreated with cholera toxin and NAD. Moreover, the inhibition by adrenaline or clonidine was completely abolished by treatment with (a) yohimbine or (b) islet-activating protein and NAD. It is suggested that alpha 2-receptor stimulation causes inhibitory influences on adenylate cyclase activity mediated by the inhibitory GTP binding regulatory protein in synaptic membranes of rat cerebral cortex.

Studies on peptides. CXXVIII. Application of new heterobifunctional crosslinking reagents for the preparation of neurokinin (A and B)-BSA (bovine serum albumin) conjugates

A decapeptide corresponding to the entire amino acid sequence of neurokinin A, a porcine spinal cord peptide, was synthesized in a conventional manner using protecting groups removable by 1 M TFMSA-thioanisole in TFA. The HS-CH2CH2CO group was introduced onto the synthetic neurokinin A by reaction of 3-(S-acetyl-thiopropionyl)-thiazolidine-2-thione, followed by deacetylation with hydroxylamine. 2,4-Dinitrophenyl-p-(beta-nitrovinyl)-benzoate trapped the above HS-CH2CH2CO-neurokinin A derivative in acidic media, then BSA in basic media in nearly quantitative yield. A similar decapeptide, neurokinin B, was also synthesized and conjugated onto BSA using an alternative SH-introducing reagent, 3-(S-p-methoxybenzyl-thiopropionyl)-thiazolidine-2-thione, and the above heterobifunctional conjugating reagent.

The active principles of the branchlet and hook of Uncaria sinensis Oliv. examined with a 5-hydroxytryptamine receptor binding assay

Of the alkaloids obtained from Uncaria sinensis Oliv., geissoschizine methyl ether, corynantheine and dihydrocorynantheine decreased specific [3H]5-HT binding to membrane preparations from rat brain and from in-vitro experiments on guinea-pig ileum, these alkaloids were found to be partial agonists for 5-HT receptors. Therefore, they might be useful in the treatment of diseases resulting from disorders of 5-HT metabolism.

[Dopamine-induced up-regulation of alpha 2-adrenoceptors in crude synaptic membranes of rat brain]

After cerebral cortical membranes were incubated with 0.1-100 microM of dopamine (DA) in 50 mM Tris-HCl buffer (pH 7.7) at 37 degrees C for 30 min, [3H] clonidine binding to alpha 2-receptors was increased in a concentration-dependent manner without changing [3H] WB4101 and [3H] DHA binding to alpha 1- and beta-receptors, respectively. Scatchard analysis of [3H] clonidine binding to cortical membranes showed that DA increased the Bmax in both high- and low-affinity components. The increasing effect of DA on [3H] clonidine was dependent on incubation time and temperature, and it was antagonized by pimozide and cis-flupenthixol. The addition of GTP produced a reduction in DA-induced elevation in [3H] clonidine binding, while that of cyclic AMP did not affect the effect of DA. DA and Mn2+, though both of them increased [3H] clonidine binding, appeared to act at a different site in the membrane. Furthermore, the DA-induced increase in [3H] clonidine was found uniformly in membranes prepared from 7 other regions of the rat brain. These results suggested that DA regulates specifically alpha 2-receptor density by stimulating D1-receptors and/or via other mechanism(s).

Effects of a fluorinated pyrimidinedione anti-cancer drug, 5-fluoro-1-(tetrahydro-2-furanyl)-2,4-pyrimidinedione (FT), and related compounds on nigro-striatal dopaminergic neurons in the central nervous system

The cause of the side effects of 5-fluoro-1-(tetrahydro-2-furanyl)-2,4-pyrimidinedione (FT) on the central nervous system (CNS), and especially the extrapyramidal system were investigated by examining the effects of FT on pre- and post-synaptic functions of the dopaminergic system in comparison with the effects of 5-fluoro-2,4-pyrimidinedione (5-FU) and UFT. FT caused a significant decrease of spontaneous motor activity (SMA), significant increases in the levels of 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA), an increase in dopamine (DA) turnover induced by alpha-methyl-p-tyrosine and an inhibition of presynaptic dopamine receptors. FT also slightly inhibited [3H] spiperone binding to rat striatal membranes (10-15%) in vitro at doses of 10(-6)-5 X 10(-4) M. 5-FU slightly decreased SMA, significantly increased the levels of DOPAC and HVA, and significantly inhibited (P less than 0.05) [3H]spiperone binding (about 30% at 5 X 10(-4) M). The effects of UFT on the CNS were almost the same as those of FT, but uracil had no effect on the CNS. These results suggest that the side effects of FT on the CNS, especially its action on dopaminergic neurons, may result from blockade of pre- and post-synaptic dopamine receptors, and may be mediated by its main metabolite 5-FU in the brain.

Decrease of clonidine binding affinity to alpha 2-adrenoceptor by ADP-ribosylation of 41,000-dalton proteins in rat cerebral cortical membranes by islet-activating protein

The IC50 value for inhibition of specific [3H]yohimbine binding to rat cerebral cortical membranes by clonidine was increased, and the Hill coefficient (nH) approached unity in the presence of 150 microM GTP. Pretreatment of membranes with islet-activating protein (IAP) in the presence of NAD caused an increase in IC50 and nH values for clonidine compared with control membranes in the absence of GTP, the addition of which was without effect. Scatchard analysis showed that the Bmax value of the high-affinity component in [3H]clonidine binding was decreased by pretreatment with IAP/NAD. GTP in a concentration range of 0.1 microM-1 mM caused a significant elevation of [3H]yohimbine binding. In IAP/NAD-pretreated membranes, however, [3H]yohimbine binding was no longer affected by GTP, although IAP/NAD significantly (p less than 0.01) increased [3H]yohimbine binding compared to control. IAP ADP-ribosylated 41,000 dalton proteins of cerebral cortical membranes. From these results, it can be suggested that inhibitory guanine nucleotide regulatory protein with Mr 41,000 couples to alpha 2-adrenoceptors to regulate binding affinity of agonists and antagonists in membranes of the rat cerebral cortex.

Activation of adenylate cyclase by dopamine, GTP, NaF and forskolin in striatal membranes of neonatal, adult and senescent rats

Dopamine (DA) caused a significant activation of striatal adenylate cyclase in neonatal and adult but not in senescent rats. GTP activated cyclase at the adult stage but not at both neonatal and senescent stages. NaF and forskolin activated cyclase at every stage. The coupling mechanism between DA1 receptors and catalytic units of cyclase seems to become functional at the neonatal stage but GTP recognition and/or binding sites lack in stimulatory GTP binding protein in neonatal and senescent membranes.

Active uptake system for substance P carboxy-terminal heptapeptide (5-11) into a fraction from rabbit enriched in glial cells

In the present study, we demonstrated the existence of an active uptake system for substance P carboxy-terminal heptapeptide, (5-11)SP. When a fraction from rabbit brain enriched in glial cells was incubated with [3H] (5-11)SP, an uptake of [3H](5-11)SP was observed. The uptake system has the properties of an active transport mechanism. Kinetic analysis indicated two components of [3H](5-11)SP uptake, one representing a high and the other a low affinity transport system. After unilateral ablation of the striatum, approximately 30% of the high affinity [3H](5-11)SP uptake capacity of substantia nigra slices disappeared. The subcellular distribution of the high affinity uptake indicated that [3H] 5-hydroxytryptamine was taken up mostly into the P2B fraction (synaptosomal fraction), whereas [3H](5-11)SP was taken up into the P2A fraction (myelin fraction) to the same extent as into the P2B fraction. These results suggest that when SP is released from nerve terminals, it is hydrolysed into (5-11)SP, which is in turn accumulated into glial cells as well as nerve terminals and that this high affinity uptake mechanism may play an important role in terminating the synaptic action of SP.

The interaction between beta- and alpha 2-adrenoceptors in cerebral cortical membranes: isoproterenol-induced increase in [3H]clonidine binding in rats

The pretreatment of rat cerebral cortical membranes with 10 or 100 microM isoproterenol at 37 degrees C for 40 min caused a significant elevation of the Bmax value of [3H]clonidine binding but pretreatment at 4 degrees C did not affect the value. The isoproterenol-induced increase in the Bmax value of the binding was higher in 50 mM Tris-HCl buffer (pH 7.7) than in Krebs-Ringer solution. In 50 mM Tris-HCl buffer (pH 7.7), treatment with isoproterenol reduced the Bmax value of [3H]dihydroalprenolol binding but neither Kd nor Bmax of [3H]WB 4101 binding was affected by this treatment. Fifty microM propranolol or 100 microM GTP produced a significant reduction in isoproterenol-induced elevation of the Bmax value of [3H]clonidine binding. In contrast, 100 microM cyclic AMP did not affect the control binding and 0.1 or 1 mM theophylline did not affect the isoproterenol-induced elevation of the binding. The only Bmax value in high affinity binding of [3H]clonidine was increased by isoproterenol. It is suggested that isoproterenol increases the density of alpha 2-adrenoceptors in a temperature-dependent manner. The direct interaction between beta- and alpha 2-receptor molecules and/or their indirect interaction, mediated by GTP regulatory proteins, would exist in the cerebral cortical membranes of rats.

Developmental changes of cerebral cortical [3H]clonidine binding in rats: influences of guanine nucleotide and cations

Cerebral cortical [3H]clonidine binding and influences of GTP and cations were investigated in developing rats. The results from Scatchard plots were compatible with the presence of two populations of binding sites [high-affinity binding (KD = 0.59 nM) and low-affinity binding (KD = 7.12 nM)] in 70-day-old rats but only high-affinity binding (KD = 0.27 nM) on day 1. Low-affinity binding was detectable on day 7. KD values in high- and low-affinity binding were not significantly changed during development after 7 days. Bmax of high-affinity binding reached a peak on day 15, and the value of low-affinity binding gradually increased with age. The addition of 10 microM GTP caused a significant reduction in Bmax of high-affinity binding after day 7. Neither KD nor Bmax of low-affinity binding was affected by 10 microM GTP during development. NaCl (10 and 100 mM) diminished the binding on days 7 and 70. MnCl2 (0.1 and 1.0 mM) markedly increased the binding on days 15 and 70 but not on day 7. It is suggested that: (1) single binding sites of alpha 2-adrenoceptors with higher affinity seem to be present on day 1; (2) low-affinity binding appears on day 7; (3) the number of high-affinity binding sites reaches a peak on day 15, followed by changes in populations of high-affinity as well as low-affinity sites without changing affinity; (4) the regulatory mechanism in alpha 2-receptors by guanine nucleotide reaches functional maturity between days 1 and 7; and (5) the involvement of Na+ and Mn2+ in alpha 2-receptor binding becomes functional by days 7 and 15, respectively.

Determination of pipecolic acid in rat brain areas by high-performance liquid chromatography of dansyl derivatives with fluorimetric detection

A method for the determination of pipecolic acid in the rat brain is reported. The identification and quantification of pipecolic acid is accomplished with reverse-phase high-performance liquid chromatography including precolumn dansylation procedure by using nipecotic acid, a regio-isomer of pipecolic acid, as an internal standard. The lower limit of quantification for the method is in the picomole range. Higher concentration of pipecolic acid in the rat brain regions were found in cerebellum, medulla oblongata, hypothalamus, and midbrain than the other regions. The method establishes the usefulness of dansyl chloride for the simple and sensitive detection of pipecolic acid, and is easily adapted to routine analysis of pipecolic acid in the rat brain regions.

Influence of thyrotropin-releasing hormone on general behavior and striatal [3H]spiperone binding in developing rats

An intraperitoneal administration of thyrotropin-releasing hormone (TRH, 2 or 20 mg/kg) produced behavioral excitement and consequently an increase in ANIMEX counts 15 min after the injection in a dose-dependent manner in 70-day-old rats. On the other hand, TRH (2 or 20 mg/kg)-induced behavioral excitement appeared more slowly (90-150 min) and more persistently in 7-day-old animals than in 70-day-old animals. TRH (2 or 20 mg/kg) significantly reduced specific [3H]spiperone binding to striatal membranes in 7- and 70-day-old rats compared to control, when the binding was examined in the membranes obtained from animals sacrificed 15 min and 150 min following TRH injection. In vitro addition of TRH up to 0.1 mM did not affect [3H]spiperone binding on days 7 and 70. From these results, it is suggested that striatal dopamine receptors could be involved in TRH-induced behavioral excitement in developing rats.

Influences of isoproterenol pretreatment on cerebral cortical bindings of [3H]clonidine and [3H]dihydroalprenolol in infant and adult rats

Specific bindings of [3H]clonidine and [3H]dihydroalprenolol [( 3H]DHA) to crude synaptic membranes were measured after cerebral cortical slices or synaptic membranes were pre-incubated with isoproterenol, 200 microM at 37 degrees C for 40 min, in 7- and 70-day-old rats. Isoproterenol caused a significant increase of the Bmax value of [3H]clonidine binding sites at both days 7 and 70, without changing the Kd. Scatchard analysis of [3H]clonidine binding to adult synaptic membranes which was examined by using a wide range of [3H]clonidine concentration (0.05-15 nM), showed that the Bmax in only high-affinity binding sites was 4-fold increased by pretreatment of synaptic membranes with isoproterenol 200 microM. In contrast, the Bmax of [3H]DHA binding sites was significantly reduced by isoproterenol at 7 and 70 days. These results suggest that the possible interrelationship between beta- and alpha 2-adrenoceptors which exists in synaptic membranes, matures by day 7 in the cerebral cortex of rats.

Striatal [3H]GTP binding in developing rats: involvement of sulfhydryl residues, Ca2+ and Mg2+

The influence of sulfhydryl reagents and cations on specific [3H]GTP binding to striatal membranes was investigated in developing rats. Two components of non-cooperative [3H]GTP binding sites were observed in 15, 30, 70 and 360 day old rats but only a single component in 1 and 7 day old ones. The KD for low affinity binding increased with age. Bmax values for both high and low affinity binding increased with age and reached a peak at 30 days, followed by a decrease at 70 and 360 days. At 7 and 70 days, NaCl 1-100 mM did not affect [3H]GTP binding but CaCl2 and MgCl2 significantly inhibited the binding over a concentration range of 1-100 mM. TLC analysis of [3H]GTP and the metabolites in the binding medium and membranes showed that [3H]GTP in both membranes and in the medium was decreased by addition of 1 mM CaCl2 and 1 mM MgCl2 into the binding medium. On days 7 and 70, p-chloromercuriphenyl sulfonate strongly inhibited [3H]GTP binding, and dithiothreitol significantly increased binding but dopamine, apomorphine, spiperone and alpha-flupenthixol did not increase binding up to 0.1 mM. It is suggested that sulfhydryl residues, Ca2+ and Mg2+ are involved in the regulation of guanine nucleotide binding and that the regulatory mechanism becomes functional at 7 days. Ca2+ and Mg2+ seem to act by stimulating degradation of [3H]GTP. In addition, the density of GTP binding sites reaches a peak at around 30 days and the affinity decreases with age.

Interactions of divalent metal ions with bovine, human, and goat alpha-lactalbumins

Bovine, human, and goat alpha-lactalbumins prepared by the ordinary methods were found to contain 1.1-1.3 atoms of Ca per protein molecule. Removal of Ca2+ was shown to destabilize the tertiary structures in the three proteins. The three apoproteins were indicated to change in the conformation by heat from the native-like to the unfolded state. Degree of restoration of the native tertiary structure in 5 mM Tris-HCl and 0.1 mM EDTA at pH 7.2 and 25 degrees C by addition of Ca2+ was determined from change in CD ellipticity at 270 nm, and the apparent binding constant of Ca2+ was analyzed to be 2.5 X 10(8) (bovine), 3.0 X 10(8) (human), and 2.8 X 10(8) M-1 (goat). Also, value of the binding constant of Ca2+ to the native-like apoform was estimated from the apparent binding constant and equilibrium constant of the conformational change of the apoform. The binding properties of Mn2+, Mg2+, and Zn2+ to the bovine protein at neutral pH are also discussed.

Effect of concanavalin A on 3H-5-hydroxytryptamine uptake in rabbit blood platelets: interaction with adenylate cyclase activity

Concanavalin A (Con A) was shown to have inhibitory effect on platelet adenylate cyclase as well as 5-hydroxytryptamine (5HT) uptake. These effects of Con A were antagonized by alpha-methyl-D-mannoside, a specific inhibitor of Con A binding to glycoprotein. The effect of Con A on adenylate cyclase was partial inhibition, and Con A had no effect on prostaglandin E1 stimulated activity, indicating the adenylate cyclase which is thought to be involved in 5HT uptake might be a minor component. The same result as Con A was demonstrated in the inhibitory effect of N-ethylmaleimide (NEM) on this activity. Impermeable sulfhydryl blocking reagents and iodoacetamide had no effect on 5HT uptake. It might be necessary for the sulfhydryl blocking reagent to pass through the cell membrane in order to exert its inhibitory effect on 5HT uptake. Furthermore, the inhibitory effect of Con A on 5HT uptake was antagonized by sulfhydryl reducing reagents and adenosine. It is postulated that a NEM sensitive, sub-membrane contractile protein system might mediate the effect of Con A, and Con A might inhibit platelet 5HT uptake by affecting the adenylate cyclase system through some possible transmembrane regulatory mechanism.

Involvement of central noradrenergic system in thyrotropin-releasing hormone-induced behavioral excitement in 6-OHDOPA-treated, infant rats

A subcutaneous (s.c.) injection of thyrotropin-releasing hormone (TRH) 20 mg/kg, produced body shake and struggle, consequently induced an increase of count in ANIMEX activity meter in 7-day-old rats pretreated with 6-hydroxydopa (6-OHDOPA), 75 mg/kg, on days 0, 2 and 4. TRH-induced behavioral excitement was markedly attenuated in the infant animals which were injected desmethylimipramine, 5 mg/kg, 30 min before 6-OHDOPA on days 0, 2 and 4. It is suggested that central catecholaminergic, in particular, noradrenergic system is involved in TRH-induced body shake and struggle in 6-OHDOPA-treated, infant rats.

Effects of acute and chronic toluene inhalation on behavior and (3H)-serotonin binding in rat

Toluene inhalation (0.7% in air) induced in rats abnormal neurological states resembling the serotonin syndrome, such as hindlimb abduction, resting tremor and head weaving. The frequency and intensity of these responses were unchanged after two weeks of exposure (0.7% in air, 15 min/day for 14 days), indicating an absence of tolerance development. An examination of specific serotonin (3H-5HT) binding to crude synaptic membranes prepared from brains of rats subjected to acute and chronic toluene exposure revealed that while no changes in either apparent Kd or apparent Bmax occurred in acutely exposed animals, in chronically treated animals specific (3H)-5HT binding decreased in hippocampus and pons + medulla oblongata. These results indicate that serotonergic mechanisms may play a role in some of the effects of toluene inhalation in rats, but cannot explain the absence of tolerance development after chronic exposure to toluene.

Ontogenetic development of the striatal [3H]spiperone binding: regulation by sodium and guanine nucleotide in rats

Ontogenetic development of specific [3H]spiperone binding to crude synaptic membranes and its regulation by Na+ and GTP was investigated in the rat striatum. (d)-Butaclamol more effectively inhibited [3H]spiperone binding than (l)-butaclamol. The ratio of inhibitory activity of (d)- and (l)-butaclamol for [3H]spiperone binding was not different between 1-, 7-, and 70-day-old animals but eight- to ninefold lower at 18 days of gestation than during the postnatal period. A Scatchard plot of specific binding indicated the presence of two types of binding: low-affinity (KD = 1.51 nM) and high-affinity (KD = 0.09 nM) binding on day 70. Only one component (KD = 0.075 nM) was observed on days 1 and 7 and both types of binding were found on day 15. Bmax gradually increased with age and reached a peak on day 30, followed by a decline on days 70 and 360. Na+, 100 mM, significantly increased specific binding on days 1, 7, 15, and 70. GTP, 50 microM, completely reversed the Na+-induced decrease in IC50 of apomorphine on both days 15 and 70, but not on day 7. It is suggested that receptors could recognize ligand stereospecificity on day 1. The density in dopamine receptors in the striatum reaches a peak on day 30, followed by a decrease on days 70 and 360. In addition, regulation by Na+ and GTP in agonist binding to dopamine receptors seems to become functional between 1 and 2 weeks after birth.

Effect of methiothepin on imipramine- or mianserin- induced subsensitivity of serotonergic receptors

Effect of methiothepin on imipramine- or mianserin- induced subsensitivity of serotonergic receptors was examined in rat brain. Treatment with either imipramine plus methiothepin or mianserin plus methiothepin for 4 days resulted in a significant decrease in [3H]5-hydroxytryptamine ([3H]5-HT) binding in synaptic membranes. The binding was not significantly decreased after treatment for this period of time with either methiothepin, imipramine or mianserin alone. It is suggested that the elevated intrasynaptic 5-HT levels could contribute to potentiation effect of methiothepin on imipramine- or mianserin-induced down regulation of serotonergic receptors.