Effects of ethanol administration and withdrawal on neurotransmitter receptor systems in C57 mice

C57BL/6 mice were treated with 7% (v/v) ethanol in a Bio-Serve liquid diet for 7 days. Some animals were then allowed to withdraw from ethanol for a period of 24 hr. The severity of the ethanol withdrawal was assessed by monitoring behavioral changes and by quantitating the decrease in body temperature that occurred during the first 16 hr of withdrawal. Animals withdrawn from ethanol for 24 hr showed a decreased hypothermic response to apomorphine suggesting that changes in dopaminergic systems had occurred. This possibility was further examined in homogenates of striatum by measuring dopamine-stimulated adenylate cyclase activity and the binding of [3H]spiroperidol. However, there were no changes observed in either basal- or dopamine-stimulated adenylate cyclase activity or in the density or affinity or receptors for [3H]spiroperidol. The affinity of apomorphine for the dopamine receptor was also unchanged. In other experiments, alpha and beta adrenergic receptor-mediated increases in cyclic AMP accumulation were assessed in slices of cerebral cortex. There was no change in cyclic AMP accumulation due to either alpha or beta adrenergic receptors. There was, however, a significant decrease in the density of beta adrenergic receptors in both the ethanol-treated mice and in the withdrawn mice. This decrease was restricted to the beta-2 receptor subtype with no change being observed in the density of beta-1 adrenergic receptors. Ethanol administration was also associated with a significant increase in the density of muscarinic cholinergic receptors in the hippocampus and cerebral cortex. The effect was not observed in animals allowed to withdraw for 24 hr.     

Selective regulation of beta-2 adrenergic receptors by the chronic administration of the lipophilic beta adrenergic receptor agonist clenbuterol: an autoradiographic study

Many antidepressant drugs, when administered chronically to rats, have been shown to produce decreases in the density of beta adrenergic receptors in the central nervous system. The centrally active beta adrenergic receptor agonist clenbuterol is currently being evaluated clinically as an antidepressant. The chronic administration of this drug to rats resulted in a large decrease in the density of beta adrenergic receptors in some areas of the rat brain but not in others. Thus, autoradiographic studies revealed that the total density of beta adrenergic receptors in the molecular layer of the cerebellum, but not in layers 1 to 3 or layer 4 of the cerebral cortex, was decreased. To examine whether this regional selectivity occurred because of differences in plasticity of cerebellum and cortex or because cerebellum contains mainly beta-2 adrenergic receptors and cortex contains mainly beta-1 adrenergic receptors, separate analyses of the subtypes of beta adrenergic receptors were performed in each area. These experiments indicated that the decrease in receptor density was entirely specific for beta-2 adrenergic receptors, whereas the density of beta-1 receptors was unchanged. Thus, even in layers 1 to 3 and layer 4 of the cerebral cortex, beta-2 receptor density was decreased, with no change in beta-1 receptor density. Using the autoradiographic assay for ligand binding, it was shown that clenbuterol has equal affinity for beta-1 and beta-2 adrenergic receptors, indicating that the selective effect of this drug was not due to a selective affinity for beta-2 receptors.(ABSTRACT TRUNCATED AT 250 WORDS)     

Genetic approaches identify differential roles for alpha4beta2* nicotinic receptors in acute models of antinociception in mice

The effects of nicotine on the tail-flick and hot-plate tests were determined to identify nicotinic receptor subtypes responsible for spinally and supraspinally mediated nicotine analgesia in knockin mice expressing hypersensitive alpha(4) nicotinic receptors (L9'S), in seven inbred mouse strains (C57BL/6, DBA/2, A/2, CBA/2, BALB/cByJ, C3H/HeJ, and 129/SvEv), and in two F1 hybrids (B6CBAF1 and B6D2F1). L9'S heterozygotes were approximately 6-fold more sensitive to the antinociceptive effects of nicotine than the wild-type controls in the hot-plate test but not in the tail-flick assay. Large differences in the effects of nicotine were also observed with both tests for the seven mouse strains. A/J and 129 mice were 6- to 8-fold more sensitive than CBA and BALB mice. In addition, B6CBAF1 hybrid mice were even less sensitive than CBA mice. Nicotinic binding sites were measured in three spinal cord regions and the hindbrain of the inbred strains. Significant differences in cytisine-sensitive, high affinity [(125)I]epibatidine binding site levels (alpha(4)beta(2)(*) subtypes), but not in (125)I-alpha-bungarotoxin binding (alpha(7)(*) subtypes), were observed. Significant negative correlations between cytisine-sensitive [(125)I]epibatidine binding and nicotine ED(50) for both tests were noted. Our results indicate that alpha(4)beta(2)(*) acetylcholine nicotinic receptors (nAChR) are important in mediating nicotine analgesia in supraspinal responses, while also showing that alpha(4)beta(2)(*)-nAChR and at least one other nAChR subtype appear to modulate spinal actions.     

Thyroid status and adrenergic receptor subtypes in the rat: comparison of receptor density and responsiveness

The density and functional responsiveness of adrenergic receptor subtypes were determined in tissues from control, hyperthyroid and hypothyroid rats. There was a decrease in sensitivity to isoproterenol in spontaneously beating right atria, electrically driven left atria and field-stimulated vas deferens associated with hypothyroidism, with no change in maximum response. Hyperthyroidism increased the potency of isoproterenol in right atria, but not in left atria or vas deferens. The maximal response to isoproterenol was greatly reduced in hyperthyroid left atria. The potency of procaterol, a partial agonist at beta adrenergic receptors in right atria, was unaltered in hyper- or hypothyroidism, although the maximum stimulation by procaterol was increased in hyperthyroidism. Scatchard analysis of specific [125I]pindolol binding showed that beta adrenergic receptor density was greater in hyperthyroidism than in hypothyroidism in left atria, right atria, ventricles, vas deferens and cerebral cortex, although the proportions of beta-1 and beta-2 adrenergic receptor subtypes did not change. There was no change in the responsiveness of alpha-1 adrenergic receptors mediating contraction of caudal artery and vas deferens or mediating [3H]inositol phosphate accumulation in cerebral cortex in hyperthyroid or hypothyroid rats, although the maximal contraction of caudal artery was significantly reduced in hyperthyroidism. Scatchard analysis of specific [125I]BE 2254 binding showed that alpha-1 adrenergic receptor density was significantly decreased in the ventricles from hyperthyroid rats and increased in the ventricles of hypothyroid rats, but was unchanged in vas deferens, caudal artery and cerebral cortex. Alpha-2 adrenergic receptor density in cerebral cortex, determined by Scatchard analysis of specific [3H] rauwolscine binding, was not altered in hyperthyroid or hypothyroid rats.(ABSTRACT TRUNCATED AT 250 WORDS)     

Molecular Characterization and Functional Analysis of Murine Interleukin 4 Receptor Allotypes

The murine interleukin 4 receptor (IL-4R) exists as a transmembrane protein transducing pleiotropic IL-4 functions, or as soluble (s)IL-4–binding molecule with potent immunoregulatory effects. In this study we identified and characterized a murine IL-4R allotype. Sequence analysis of the IL-4R cDNA of BALB/c mice revealed 18 base substitutions leading to three extracellular and five cytoplasmic amino acid changes when compared with the published IL-4R sequence of C57BL/6 mice. Analyses with allotype-specific mAbs revealed that AKR/J and SJL/J mice possess the newly identified BALB/c IL-4R allotype whereas the IL-4Rs of C3H, CBA, DBA-2, and FVB/N mice are identical to that of the C57BL/6 mouse. The extracellular Thr49 to Ile substitution abrogates one N-glycosylation site in the naturally occurring BALB/c IL-4R as well as in the experimentally point mutated C57BL/6-T49I sIL-4R, and both molecules display a nearly threefold reduction in IL-4–neutralizing activity compared to the C57BL/6 sIL-4R. In line with this, a significantly enhanced dissociation rate of IL-4 was detected for the BALB/c IL-4R allotype by surface plasmon resonance and in radioligand binding studies with IL-4R–transfected cell lines. These findings suggest that the altered ligand binding behavior of the newly described IL-4R allotype may influence the IL-4 responsiveness, thus contributing to the diverse phenotypes of inbred mouse strains in IL-4–dependent diseases.     

Bacillus anthracis lethal toxin induces TNF-alpha-independent hypoxia-mediated toxicity in mice

Bacillus anthracis lethal toxin (LT) is the major virulence factor of anthrax and reproduces most of the laboratory manifestations of the disease in animals. We studied LT toxicity in BALB/cJ and C57BL/6J mice. BALB/cJ mice became terminally ill earlier and with higher frequency than C57BL/6J mice. Timed histopathological analysis identified bone marrow, spleen, and liver as major affected organs in both mouse strains. LT induced extensive hypoxia. Crisis was due to extensive liver necrosis accompanied by pleural edema. There was no evidence of disseminated intravascular coagulation or renal dysfunction. Instead, analyses revealed hepatic dysfunction, hypoalbuminemia, and vascular/oxygenation insufficiency. Of 50 cytokines analyzed, BALB/cJ mice showed rapid but transitory increases in specific factors including KC, MCP-1/JE, IL-6, MIP-2, G-CSF, GM-CSF, eotaxin, FasL, and IL-1beta. No changes in TNF-alpha occurred. The C57BL/6J mice did not mount a similar cytokine response. These factors were not induced in vitro by LT treatment of toxin-sensitive macrophages. The evidence presented shows that LT kills mice through a TNF-alpha-independent, FasL-independent, noninflammatory mechanism that involves hypoxic tissue injury but does not require macrophage sensitivity to toxin.     

Agonist-induced changes in beta adrenergic receptor density and receptor-mediated responsiveness in slices of rat cerebral cortex.

Incubation of slices of rat cerebral cortex with the beta adrenergic receptor agonist (-)-isoproterenol led to a 30 to 50% decrease in the number of binding sites for [125I]iodohydroxybenzylpindolol and to a 60 to 80% decrease in isoproterenol-stimulated cyclic AMP accumulation. The density of beta adrenergic receptors was also decreased following incubation with (-)-norepinephrine but not with (+)-isoproterenol or dopamine and the decrease in receptor density was blocked by co-incubation with the beta adrenergic receptor antagonist sotalol. The half-time for loss of receptors was approximately 3 min and recovery was observed during a 1 hr reincubation of tissue slices or following exposure to guanine nucleotides. A decrease in beta adrenergic receptor density was also observed following chronic treatment with desmethylimipramine which blocks norepinephrine reuptake and thus potentiates the effects of neurally released norepinephrine at adrenergic receptors. The loss of receptors induced in vitro could be reversed by reincubation or by exposure to guanine nucleotides. In contrast, the loss of receptors induced in vivo was not affected by these procedures.     

Presynaptic modulation of beta adrenergic receptors in rat cerebral cortex after treatment with antidepressants.

Treatment with desmethylimipramine (DMI), a tricyclic antidepressant, for 7 to 21 days resulted in a 35 to 45% decrease in the accumulation of adenosine cyclic 3':5'-monophosphate (cAMP) in response to a maximally effective concentration of (-)-isoproterenol (ISO) in rat cerebral cortical slices. The EC50 for ISO-stimulated cAMP accumulation was not affected by DMI administration. The diminution in responsiveness to catecholamines was accompanied by a 35 to 40% decrease in the density of beta adrenergic receptors as measured by the binding of [125I]iodohydroxybenzylpindolol. Decreases in ISO-sensitive cAMP accumulation and in beta adrenergic receptor density were temporally correlated, maximal decreases being observed within 5 to 7 days. Within 7 days after cessation of chronic DMI treatment ISO-stimulated cAMP accumulation and beta adrenergic receptor density returned to normal. The role of presynaptic nerve terminals in mediating these phenomena was also investigated. Treatment of newborn rats with 6--hydroxydopamine inhibited the development of noradrenergic nerve terminals in the cerebral cortex and blocked the effects of DMI on cortical cAMP accumulation and on beta adrenergic receptor density. The administration of the beta adrenergic receptor antagonist propranolol led to increases in maximal ISO-stimulated cAMP accumulations and beta adrenergic receptor density in the rat cerebral cortex. This increase was not affected by the simultaneous administration of propranolol and DMI. Thus, the effect of DMI appears to be mediated through an action of norepinephrine at beta adrenergic receptors. Chronic treatment with two other clinically effective antidepressants, pargyline and iprindole, led to effects similar to those observed with DMI administration. Pretreatment of neonates with 6-hydroxydopamine blocked the effect of iprindole on beta adrenergic receptors. Preincubation of cortical membranes with guanosinetriphosphate before determination of the density of beta adrenergic receptors had no effect on the decreased number of receptors had no effect on the decreased number of receptors seen in DMI-treated animals. These experiments suggest that antidepressants, acting presynaptically, increase the concentration of transmitter at noradrenergic synapses and induce a compensatory decrease in the density of beta adrenergic receptors.     

Coexistence of beta-1 and beta-2 adrenergic receptors in the human heart: effects of treatment with receptor antagonists or calcium entry blockers

The properties of the binding of [125I]iodopindolol ([125I]IPIN) to beta adrenergic receptors on plasma membranes prepared from right atrial tissue removed during cardiac bypass surgery were investigated. Some of the patients from whom the tissue was removed had been treated before surgery with either a beta adrenergic receptor antagonist or a calcium entry blocker or both. The specific binding of [125I]IPIN to beta adrenergic receptors was saturable, stereoselective and rapidly reversible. Studies of the inhibition of the specific binding of [125I]IPIN by drugs selective for beta-1 or beta-2 adrenergic receptors suggested that both beta-1 and beta-2 adrenergic receptors are present in the tissue, with approximately 55% of the receptors having the properties of beta-2 adrenergic receptors. The density of receptors in patients not treated with beta adrenergic receptor antagonists or calcium entry blockers was approximately 80 fmol/mg of protein, whereas the density of beta adrenergic receptors in treated patients was increased by approximately 50%. The relative proportion of beta-1 to beta-2 adrenergic receptors in subjects treated with beta adrenergic receptor antagonists and/or calcium entry blockers was not significantly different from that in untreated subjects. Studies were also carried out with a limited number of samples of human ventricular muscle obtained from untreated subjects at the time of surgery. The density of receptors was lower than that observed in studies with atrial tissue. However, as with atrial tissue, approximately half of the receptors appeared to be beta-2 adrenergic receptors.     

INHERITANCE OF ANTIBODY SPECIFICITY : I. Anti-(4-Hydroxy-3-Nitrophenyl)Acetyl of the Mouse Primary Response

Our data suggest that fine specificity of antihapten antibodies is a useful Mendelian marker of variable (V) genes. We found that some mouse strains (e.g., C57/BL6) consistently produced heteroclitic anti-(4-hydroxy-3-nitrophenyl)acetyl (NP) antibodies (relative affinity for related (4-hydroxy-5-iodo-3-nitrophenyl)acetyl and (4-hydroxy-3.5-dinitrophenyl)acetyl was always >2) while other strains (e.g., CBA) produced "conventional" anti-NP antibodies (relative affinities were consistently <1). 48 (CBA x C57BL/6)F₁ mice were studied and most of them had heteroclitic anti-NP antibodies. They were backcrossed to the recessive CBA parent, and 87 backcross animals were similarly tested. Those heterozygous for the C57BL/6 heavy (H)-chain allotype were similar to the C57BL/6 and the F₁ mice while mice homozygous for the CBA allotype were indistinguishable from the CBA. Such monogenic inheritance was observed only in the primary response. Predominance of allotype-linked genes in the control of the fine specificity characteristics was confirmed by immunizing selected homozygous mouse strains. These mice contained various mixtures of genes from C57BL, BALB/c, and other strains. Specificity of their anti-NP was exclusively determined by genes linked to the H-chain allotype, no influence could be attributed to other genes including the H-2-linked genes.     

Regulation of the anti-inulin antibody response by a nonallotype-linked gene

The antibody response to the inulin [(In), beta-(2 leads to 1) fructosan] determinant of bacterial levan [(BL), a beta-(2 leads to 6) polyfructosan that contains beta-(2 leads to 1) branch points] requires the presence of the a haplotype of the Igh gene complex. BALB/c (Igh a) mice immunized with BL produce IgG anti-In antibodies of a single spectrotype by isoelectric focusing analysis. C57BL/6 mice, which possess the b haplotype of the Igh gene complex and which fail to produce anti-In antibodies, nevertheless possess a gene, spectrotype regulation gene 1 (Sr-1), that regulates the isoelectric focusing (IEF) pattern of anti-In antibodies in mice of the a haplotype. Thus, the IEF patterns of anti-In antibodies of (BALB/c x C57BL/6)F1 mice and of B.C8 mice (C57BL/Ka . Igh-Ca) are considerably more complex than those of BALB/c. Backcross analysis indicates that Sr-1 is not linked to the Igh complex, the major histocompatibility complex, or to the genes that code for coat color. Studies of the heterogeneity of anti-In antibodies in recombinant inbred lines and their progeny from matings to BALB/c and C.B20 (BALB/c . Igh-Cb) suggest the existence of other regulatory genes.     

Changes in the density of beta adrenergic receptors in rat lymphocytes, heart and lung after chronic treatment with propranolol

Abrupt withdrawal after the chronic administration of propranolol results in clinical syndromes that suggest adrenergic hypersensitivity. Furthermore, propranolol administration has been shown to lead to an increase in the density of beta adrenergic receptors on human lymphocytes. The present studies were designed to assess the relevance of changes measured in lymphocytes to changes that may occur in solid tissues. Direct measurement of the density and properties of beta adrenergic receptors in membrane fragments was performed in vitro using the radioligand [125I]iodohydroxybenzylpindolol. Chronic infusion of propranolol by s.c. implanted osmotic minipumps generated sustained plasma concentrations of propranolol sufficient to cause chronic blockade of beta adrenergic receptors. Infusion of propranolol for 7 days resulted in significant increases in the density of beta adrenergic receptors in rat ventricles, lungs and lymphocytes. A computer-assisted graphic analysis of results obtained in studies with drugs selective for beta-1 or beta-2 receptors revealed increases in the densities of both beta-1 an beta-2 adrenergic receptors. These results are consistent with the hypothesis that change in beta adrenergic receptors on lymphocytes are qualitatively similar to alterations in beta adrenergic receptors in solid tissues not routinely accessible in humans. Increases in the densities of beta-1 and/or beta-2 adrenergic receptors in solid tissues may be related to some of the untoward effects observed in humans after abrupt discontinuation of propranolol administration.     

GENETICS OF A NEW IgVH (T15 IDIOTYPE) MARKER IN THE MOUSE REGULATING NATURAL ANTIBODY TO PHOSPHORYLCHOLINE

The idiotype present on the Fab of a phosphorylcholine-binding IgA myeloma protein TEPC 15 (T15) of BALB/c origin was found in normal serum of BALB/c mice. Molecules carrying the T15 idiotype in normal serum could be adsorbed with Sepharose phosphorylcholine beads and R36A pneumococci. The T15 idiotype is absent in germ-free BALB/c but appears when the mice are conventionalized. A survey of normal sera of inbred strains for the T15 idiotype showed it to be present in BALB/c, 129, C57L, C58, and ST and absent or in low levels in CBA, C3H, C57BL/6, C57BL/Ka, C57BL/10, SJL, B10.D2, DBA/2, RIII, A, AL, AKR, NZB, and NH inbred strains of mice. The T15 idiotype is associated with some but not all strains carrying the IgC_H allotypes found in BALB/c. Linkage of genes controlling the T15 idiotype in normal serum to the IgC_H locus of BALB/c was demonstrated in F₂ progeny of a BALB/c and C57BL cross, Bailey's recombinant inbred strains, C x BD, C x BE, C x BG, C x BH, C x BI, C x BJ, C x BK, and CB20 congenic strains. Among these strains, only those possessing the IgC_H locus of BALB/c including the F₂ progeny consisting of BALB/c homozygotes and BALB/c/C57BL heterozygotes and C x BG and C x BJ recombinants showed the T15 idiotype.     

D-2 dopamine receptors in aging mouse striatum: determination of high- and low-affinity agonist binding sites

Striatal D-2 dopamine receptors in homogenates from aged male C57BL/6J mice were examined for high and low-affinity agonist binding. High-affinity dopamine binding requires the ternary complex of the D-2 receptor and a guanine nucleotide binding regulatory protein (N). Thus, changes in the interaction of D-2 and N could contribute to previously reported changes in agonist binding in aged rodents and humans. Qualitative experiments indicated no age-change in the ability of guanine nucleotides to reduce the apparent potency of dopamine at D-2 receptors. Also, no age differences were observed in the ability of guanine nucleotides to decrease N-[3H]propylnorapomorphine binding, suggesting that the ability of guanine nucleotides to dissociate D-2 and N was similar with age. Quantitative determination of the high- (RH) and low-affinity (RL) agonist binding components of striatal D-2 dopamine receptors in the absence of guanine nucleotides indicated differences in the density of RH, and the percentage of D-2 receptors measured as RH, between the ages of 3 and 12 months. No changes in RH or percentage of RH occurred after midlife. In contrast, the total D-2 receptor population, [3H]spiperone maximum binding, declined progressively from 3 to 24 months. Age-changes were restricted to D-2 receptor density; the dissociation constants for agonist and antagonist binding were similar across age. The data suggest that age-changes in striatal D-2 dopamine receptors can occur in the density of the D-2 receptor and in the mechanism that confers the property of high-affinity agonist binding upon the D-2 receptor.     

Ability of aged rats to alter beta adrenergic receptors of brain in response to repeated administration of reserpine and desmethylimipramine.

Repeated administration of reserpine to 3-month-old rats produced dose-related increases in [3H]dihydroalprenolol (DHA) binding in pineal gland, cerebral cortex and cerebellum. Reserpine increased DHA binding by increasing the density of beta adrenergic receptors. Brain tissue from 24-month-old rats, however, had an impaired ability to increase receptor density in response to reserpine treatment, even in the pineal gland where the concentration of reserpine was nearly 7 times that found in the glands of young rats given the same dose on the basis of body weight. Repeated administration of desmethylimipramine decreased DHA binding in pineal glands by about 50% and in cerebral cortices by about 25%, but did not alter DHA binding in the cerebellum. The magnitude of these changes was similar in the 3- and 24-month-old rats, although the concentration of desmethylimipramine in the pineal glands and cerebral cortices of the aged rats was significantly higher than that of the young animals. The results indicate that the reserpine-induced decrease in noradrenergic input causes a compensatory increase in beta adrenergic receptor density in rat brain. They suggest further that although aged rats can decrease receptor density in response to increased adrenergic input, they have an impaired ability to increase beta adrenergic receptor density in response to decreased adrenergic input. This finding may explain the decreased density of beta adrenergic receptor found in aged rat brain.     

Interaction and sequence diversity among T15 VH genes in CBA/J mice

Nucleotide sequences of the four genes composing the T15 heavy chain variable region (VH) family of the CBA/J mouse have been determined. Comparison of these sequences with their published BALB/c and C57BL/10 homologues reveals that nucleotide differences found between given alleles of two strains, i.e., CBA/J and BALB/c, are observed in other family members of the same strain. We suggest that these patterns of sequence variation are most readily explained by gene interaction (conversion). Additionally, the sequence of a CBA/J hybridoma, 6G6, proposed to have been generated by gene conversion, is directly encoded by the CBA/J V11 gene indicating that the putative conversion has occurred meiotically in the germline. These results are consistent with the premise that gene correction is occurring frequently among members of this family and that such processes may contribute significantly to the evolution of Ig variable region genes even in the relatively short time frame of inbred strain derivation.     

Psychopharmacological consequences of activation of beta adrenergic receptors by SOM-1122

SOM-1122 was found to be a high-affinity, partial agonist for beta adrenergic receptors. SOM-1122 inhibited the binding of [125I]iodopindolol to membranes prepared from rat cerebral cortex and cerebellum. GTP regulated the binding of SOM-1122 by increasing the Hill coefficient in both tissues and reducing the affinity of the receptor for SOM-1122 in the cerebellum. SOM-1122 increased the concentration of cyclic AMP in slices of rat cerebral cortex in a dose-dependent manner; this effect was antagonized by propranolol. Two lines of evidence suggested that SOM-1122 was centrally active after peripheral administration. First, SOM-1122 inhibited the binding of [125I]iodopindolol in vivo in a dose-dependent manner. Second, after chronic infusion with SOM-1122 for 7 days, the density of beta adrenergic receptors in the cerebellum was reduced; receptor density also was reduced 18 hr after acute administration of SOM-1122, although to a lesser extent. SOM-1122 was found to be behaviorally active. It reduced locomotor activity and reduced response rate under a multiple fixed-interval, fixed-ratio schedule in a dose-dependent manner. SOM-1122 also reduced response rate and increased reinforcement rate under a differential-reinforcement-of-low-rate schedule. These behavioral actions of SOM-1122 appeared to be due to an interaction of the agonist with beta adrenergic receptors, as they were antagonized by propranolol. The behavioral changes produced by stimulation of beta adrenergic receptors with SOM-1122 were generally similar to those caused by other centrally acting beta adrenergic agonists and by antidepressant drugs.     

Frequencies of mitogen-reactive B cells in the mouse. I. Distribution in different lymphoid organs from different inbred strains of mice at different ages

Frequencies of mitogen-reactive B cells have been determined in vitro under culture conditions which allow every growth-inducible B cell to grow and mature into a clone of Ig-secreting PFC. The frequencies of LPS-reactive B cells in the spleen of 6- to 8-wk old mice were between 1 in 3 and 1 in 10 splenic B cells from the following inbred strains of mice: C3H/Tif; BALB/c; BALB/c ν/ν; C57BL/6J; DBA/2J; C57BL/6J x DBA/(2J)F(1); and CBA and A/J. Very similar frequencies are found for lipoprotein-reactive B cells in BALB/c, BALB/c ν/ν, C3H/Tif, and C3H/HeJ mice. No LPS-reactive cells but normal frequencies of lipoprotein-reactive cells were found in C3H/HeJ mice, genetically nonreactive to LPS. SJL mice had significantly lower frequencies of LPS- and of lipoprotein-reactive B cells (1 in approximately 30 B cells). The number of LPS- and of lipoprotein-reactive B cells in spleen was dependent upon the age of the mouse. Newborn spleen contained approximately 10 percent of the number of reactive cells found at 6- to 8-wk of age. From there the frequencies declined again to drop below 5 percent of the maximal number at ages beyond 11 mo. LPS-reactive B cells yielding IgM- and IgG-PFC responses could be found in mesenteric lymph nodes, bone marrow, thymus, thoracic duct, and peripheral blood of 6- to 8-wk old mice. Their frequencies were one in three to five lymph node cells, 1 in 50 to 100 bone marrow cells, one in 10(5) thymus cells, and 1 in 20 to 40 thoracic duct or peripheral blood cells.     

Subtype-selective regulation of beta adrenergic receptor-adenylyl cyclase coupling by phorbol esters in 3T3-L1 fibroblasts

To study the epigenetic regulation of beta adrenergic receptor subtypes, we examined the effects of phorbol esters on beta adrenergic receptor coupling to adenylyl cyclase in 3T3-L1 fibroblasts, which express both beta-1 and beta-2 adrenergic receptor subtypes. Pretreatment of intact 3T3-L1 cells with the protein kinase C activator phorbol dibutyrate caused a dose- and time-dependent decrease in subsequent cyclic AMP (cAMP) accumulation mediated by the beta adrenergic agonist isoproterenol. This effect was selective for beta-adrenergic receptor-mediated responses because there was a potentiation of cAMP accumulation caused by other activators such as prostaglandin E1, forskolin or cholera toxin. The inactive phorbol, alpha-phorbol dibutyrate was ineffective at 1 microM in attenuating isoproterenol stimulation, and 25 nM of the protein kinase C inhibitor staurosporine blocked the effects of phorbol ester on beta adrenergic agonist responses. Stimulation of cAMP accumulation by isoproterenol occurred through a greater proportion of beta-2 adrenergic receptors in phorbol dibutyrate-treated cells than in control cells. This was demonstrated using the beta-1 adrenergic selective antagonist ICI 89.406 and the beta-2 adrenergic selective antagonist ICI 118.551 to inhibit competitively isoproterenol-stimulated cAMP accumulation. Beta-2 adrenergic receptor number and subtype in these cells are regulated by glucocorticoids and butyrate. Decreasing the proportion of beta-1 adrenergic receptors and concomitantly increasing beta-2 adrenergic receptors with either glucocorticoids or butyrate decreased the ability of phorbol ester pretreatment to attenuate cAMP accumulation by isoproterenol.(ABSTRACT TRUNCATED AT 250 WORDS)