Biomedical subjects

T Glaser

Publications and source records attributed to T Glaser.

At least 55 records · Page 3Linked to original sources

PubMed1997

Calpain and calpastatin in myoblast differentiation and fusion: effects of inhibitors.

Myoblast differentiation and fusion to multinucleated muscle cells can be studied in myoblasts grown in culture. Calpain (Ca(2+)-activated thiol protease) induced proteolysis has been suggested to play a role in myoblast fusion. We previously showed that calpastatin (the endogenous inhibitor of calpain) plays a role in cell membrane fusion. Using the red cell as a model, we found that red cell fusion required calpain activation and that fusibility depended on the ratio of cell calpain to calpastatin. We found recently that calpastatin diminishes markedly in myoblasts during myoblast differentiation just prior to the start of fusion, allowing calpain activation at that stage; calpastatin reappears at a later stage (myotube formation). In the present study, the myoblast fusion inhibitors TGF-beta, EGTA and calpeptin (an inhibitor of cysteine proteases) were used to probe the relation of calpastatin to myoblast fusion. Rat L8 myoblasts were induced to differentiate and fuse in serum-poor medium containing insulin. TGF-beta and EGTA prevented the diminution of calpastatin. Calpeptin inhibited fusion without preventing diminution of calpastatin, by inhibiting calpain activity directly. Protein levels of mu-calpain and m-calpain did not change significantly in fusing myoblasts, nor in the inhibited, non-fusing myoblasts. The results indicate that calpastatin level is modulated by certain growth and differentiation factors and that its continuous presence results in the inhibition of myoblast fusion.

Animals↗

PubMed1997

A multifunctional protein: involvement of the alpha-1 serum protease inhibitor in SDS and high salt-stable DNA-protein complexes.

Occasionally new and intriguing roles arise for proteins with well established functions. The alpha-1 serum protease inhibitor (alpha-1 PI) represents another example. Sequence identities exist in the alpha-1 PI and in a nuclear 52-kDa glycoprotein which is involved in resistant DNA-polypeptide complexes. The results of Western blots support the identity of the two proteins and immunocytochemical studies indicate the nuclear location of the alpha-1 PI. Consistently, e.g. Ehrlich ascites tumor cells express the alpha-1 PI, and the fusion protein between the alpha-1 PI and the green fluorescent protein from Aequorea victoria shows intracellular accumulation and partly nuclear location.

Amino Acid Sequence↗

PubMed1997

Changes in calpain during meiosis in the rat egg.

Resumption of meiosis at fertilization is mediated by increased levels of calcium which activate several calcium-dependent enzymes. Calpain, a neutral calcium-activated thiol protease, is present in the cytoplasm of many cells. Its activation is associated with limited autolysis and relocalization in the cell. Calpain is thought to participate in the regulation of mitosis and resumption of meiosis in Xenopus oocytes. In this study we followed the activation and localization of calpain during maturation and fertilization in rat eggs using a polyclonal antibody raised against chicken muscle calpain. A band of 80 kDa was detected in GV oocytes and its level increased in unfertilized MII eggs. At the early stages of fertilization, we observed a transient decrease in the level of calpain which was regained at the pronuclear stage. Adding Ca2+ to lysate of MII eggs resulted in an additional band, representing the degraded fragment of the activated protein. In eggs activated by ionomycin, calpain level decreased, followed by an increase in a dynamic similar to that observed in fertilized eggs. Egg activation also led to changes in calpain localization. A homogenous distribution was observed in GV and in MII eggs, while in activated eggs it was localized predominantly overlying the metaphase plate. In the current study we demonstrate the presence of calpain in the rat egg. During maturation, calpain level increases; however, during egg activation, in response to [Ca2+]i changes, calpain undergoes autolysis, translocaton, and fluctuation in its level. We therefore suggest a correlation between calpain activation and fertilization.

Animals↗

PubMed1995

HMG-D is an architecture-specific protein that preferentially binds to DNA containing the dinucleotide TG.

The high mobility group (HMG) protein HMG-D from Drosophila melanogaster is a highly abundant chromosomal protein that is closely related to the vertebrate HMG domain proteins HMG1 and HMG2. In general, chromosomal HMG domain proteins lack sequence specificity. However, using both NMR spectroscopy and standard biochemical techniques we show that binding of HMG-D to a single DNA site is sequence selective. The preferred duplex DNA binding site comprises at least 5 bp and contains the deformable dinucleotide TG embedded in A/T-rich sequences. The TG motif constitutes a common core element in the binding sites of the well-characterized sequence-specific HMG domain proteins. We show that a conserved aromatic residue in helix 1 of the HMG domain may be involved in recognition of this core sequence. In common with other HMG domain proteins HMG-D binds preferentially to DNA sites that are stably bent and underwound, therefore HMG-D can be considered an architecture-specific protein. Finally, we show that HMG-D bends DNA and may confer a superhelical DNA conformation at a natural DNA binding site in the Drosophila fushi tarazu scaffold-associated region.

Animals↗

PubMed1995

Are postsynaptic 5-HT1A receptors involved in the anxiolytic effects of 5-HT1A receptor agonists and in their inhibitory effects on the firing of serotonergic neurons in the rat?

Previous studies have shown that injection of 5-hydroxytryptamine (serotonin) receptor agonists in the dorsal raphe nucleus (DRN) to stimulate somatodendritic 5-HT1A autoreceptors or in the hippocampus to stimulate postsynaptic 5-HT1A receptors, induces anxiolytic-like effects in the rat. The mechanisms triggered by the latter treatment were investigated by measuring both the electrical activity of serotonergic DRN neurons and the anxiolytic response in rats receiving injections with 8-hydroxy-2-(di-n-propylamino) tetralin (8-OH-DPAT) or ipsapirone into the dorsal hippocampus. Anxiety-related behavior was estimated by recording the time of ultrasonic vocalization (USV) due to electric foot shocks under standardized conditions. Intrahippocampal application of 8-OH-DPAT or ipsapirone produced a dose-dependent inhibition of the firing of serotonergic DRN neurons and of the shock-induced USV response. However, the range of efficient doses of 8-OH-DPAT via the intrahippocampal route (1-10 micrograms/rat) was larger than that using the i.v. route of injection (0.15-2.5 micrograms/rat). Furthermore, maximal inhibition of the firing of DRN serotonergic neurons occurred earlier when 8-OH-DPAT was injected i.v. (within 1-2 min) than when it was injected into the dorsal hippocampus (within 5 min). Interestingly, the injection of 8-OH-DPAT into the striatum, where 5-HT1A receptors are hardly detectable, or a lateral ventricle, also yielded dose-dependent reduction in both the firing rate of serotonergic DRN neurons and the USV response. Finally, local lesion with ibotenic acid to eliminate postsynaptic 5-HT1A receptors did not alter the inhibitory effects of intrahippocampal application of 8-OH-DPAT on the firing of serotonergic DRN neurons and the USV response. These data indicated that postsynaptic 5-HT1A receptors were not responsible for the inhibitory effects of 8-OH-DPAT and ipsapirone injected in forebrain areas on the electrical activity of serotonergic neurons and the USV response in rats. As shown by the autoradiographic labeling by [3H]8-OH-DPAT at distance from its injection site in the dorsal hippocampus, the diffusion of 5-HT1A receptor agonists (from injected areas in the forebrain to the DRN where they directly inhibit the electrical activity of serotonergic neurons) more likely accounted for their anxiolytic-like effects.

8-Hydroxy-2-(di-n-propylamino)tetralin↗

PubMed1994

Calpastatin in erythrocytes of young and old individuals.

To gain knowledge about the behaviour of calpastatin (the specific inhibitor of the Ca(2+)-dependent thiol protease calpain) in the intact cell, we analysed the inhibitor by specific antibodies and determined its activity in erythrocytes from individuals 20-34 years old (young) and 70-93 years old (old). Differences between old and young in the behaviour of erythrocyte calpastatin were observed. Erythrocytes of old individuals had lower amounts of calpastatin and less calpastatin activity than those of young ones. A difference between old and young was also found in the molecular-mass distribution of calpastatin subunits. Increasing the erythrocyte Ca2+ induced changes in calpastatin in young individuals, rendering it similar to calpastatin in cells of old individuals. When calpastatin (isolated from erythrocytes of a young individual) was added to erythrocyte membranes, the initial binding and subsequent association of calpastatin with the membrane were lower in old than in young individuals. We had previously found that calpain binding and activation were enhanced in erythrocyte membranes from old individuals, along with enhanced degradation of band 3 (a major erythrocyte transmembrane anion-transport protein). The overall results indicate an interaction of calpain with calpastatin in the intact cell. Enhanced activation of erythrocyte calpain and degradation of calpastatin occur under conditions of increased cellular Ca2+ and in cells of the aged.

Adult↗

PubMed1994

Two independent and interactive DNA-binding subdomains of the Pax6 paired domain are regulated by alternative splicing.

Vertebrate Pax proteins share a conserved 128-amino-acid DNA-binding motif, the paired domain. The PAX6 gene, which is mutated in the murine Small eye and human aniridia developmental defects, also encodes a second protein with a 14-amino-acid insertion in the paired domain. This protein, which arises by alternative mRNA splicing, exhibits unique DNA-binding properties. Unlike other paired domains, which bind DNA predominantly by their amino termini, the extended Pax6 paired domain interacts with DNA exclusively through its carboxyl terminus. This property can be stimulated by deletion of 30 amino-terminal residues from the Pax6 or Pax2 paired domains. Thus, the insertion acts as a molecular toggle to unmask the DNA-binding potential of the carboxyl terminus. The functional nonequivalence of the two Pax6 proteins is underscored by a T-->C mutation at position -3 of the alternative splice acceptor site that changes the ratio of the two isoforms and causes a distinct human ocular syndrome.

Alternative Splicing↗

PubMed1994

Calpain (Ca(2+)-dependent thiol protease) in erythrocytes of young and old individuals.

Limited proteolysis by calpain (Ca(2+)-activated protease; EC 3.4.22.17) is believed to regulate the function of membrane enzymes and modify the behavior of membrane structural proteins. Calpain is activated by autolysis. The degradation of band 3 protein by mu-calpain is known to be enhanced in erythrocyte membranes from human individuals > 70 years old (old) as compared with that from individuals 20-30 years old (young). In the present study, monoclonal antibody to mu-calpain was used to study the behavior of calpain in erythrocytes of young and old individuals. Less calpain was found in erythrocyte cytosol and membranes from old than in those from young. Increasing the erythrocyte Ca2+ induced translocation of calpain to the cell membrane and autolysis of the enzyme. Alkylation of erythrocyte thiols also promoted translocation of calpain to the membrane, especially in the presence of Ca2+. When calpain was added to erythrocyte membranes, initial binding was greater and subsequent autolysis faster in old than in young individuals, possibly arising from alterations in cell membranes of old individuals. The enhanced calpain autolysis was accompanied by enhanced degradation of band 3 protein in the old. The results suggest that calpain in old individuals is translocated to the cell membrane and is activated by autolysis, resulting in degradation of certain membrane proteins and loss of calpain. Enhanced calpain-induced membrane proteolysis may play a role in abnormal cell destruction (e.g., shortening the life span of erythrocytes in the aged, neuronal degeneration, etc). The erythrocyte membrane provides a convenient model for the study of age-associated alterations in cell membranes and in calpain behavior.

Adult↗

PubMed1994

Identification of a Pax paired domain recognition sequence and evidence for DNA-dependent conformational changes.

Pax genes encode a family of developmentally regulated transcription factors that have been implicated in a number of human and murine congenital disorders, as well as in tumorigenesis (Gruss, P., and Walther, C. (1992) Cell 69, 719-722; Hill, R., and van Heyningen, V. (1992) Trends Genet. 8, 119-120; Chalepakis, G., Tremblay, P., and Gruss, P. (1992) J. Cell Sci. Suppl. 16, 61-67; Maulbecker, C. C., and Gruss, P. (1993) EMBO J. 12, 2361-2367; Walther, C., Guenet, J. L., Simon, D., Deutsch, U., Jostes, B., Goulding, M. D., Plachov, D., Balling, R., and Gruss, P. (1991) Genomics 11, 424-434; Barr, R. G., Galili, N., Holick, J., Biegel, J. A., Rovera, G., and Emanuel, B. S. (1993) Nature Genet. 3, 113-117). These genes are defined by the presence of an evolutionarily conserved DNA binding domain, termed the paired domain. The structure and the DNA binding characteristics of the paired domain remain largely unknown. We have utilized repetitive rounds of a polymerase chain reaction-based selection method to identify the optimal DNA binding sequences for the Pax-2 and Pax-6 paired domains. The results suggest that the paired domain family of peptides bind similar DNA sequences. Identification of this binding site has revealed an important structural clue regarding the mechanism of paired domain binding to DNA. CD and NMR structural analyses of the purified Pax-6 paired domain reveal it to be largely structureless in solution. Upon binding the recognition sequence, the complex becomes markedly less soluble and displays CD spectroscopic evidence of significant alpha-helical structure.

Animals↗

PubMed1994

Absence of PAX6 gene mutations in Gillespie syndrome (partial aniridia, cerebellar ataxia, and mental retardation).

The PAX6 gene is expressed at high levels in the developing eye and cerebellum and is mutated in patients with autosomal dominant aniridia. We have tested the role of PAX6 mutations in three families with Gillespie syndrome, a rare autosomal recessive condition consisting of partial aniridia, cerebellar ataxia, and mental retardation. Single-strand conformational polymorphism analysis of affected individuals revealed no alteration of PAX6 sequences. In two families, the disease trait segregates independently from chromosome 11p markers flanking PAX6. We conclude that Gillespie syndrome is genetically distinct from autosomal dominant aniridia.

Alleles↗

PubMed1994

Deficient outgrowth of the ureteric bud underlies the renal agenesis phenotype in mice manifesting the limb deformity (ld) mutation.

Mice which are homozygous for the limb deformity (ld) mutation also manifest an incompletely penetrant unilateral or bilateral renal agenesis phenotype. Intercross experiments suggest that the differences in penetrance of the renal agenesis phenotype between homozygous mice with different ld alleles are due to intrinsic differences in the strength of the mutant alleles or to one or more closely linked modifying loci, and not to generalized differences in genetic background. Analysis of ld/ld embryos between embryonic days 11-13 reveals delayed outgrowth or complete absence of the ureteric bud, the inducer of metanephric mesenchyme. Since explants of ld/ld metanephric mesenchyme differentiate in culture when apposed to embryonic spinal cord, we conclude that deficient ureteric bud outgrowth is the morphologic basis for renal agenesis in ld/ld mice. However, since ld transcripts can be detected in both metanephric mesenchyme and ureteric bud, the molecular basis for the deficiency in ureteric bud outgrowth could reside in either component.

Alleles↗

PubMed1994

PAX6 gene dosage effect in a family with congenital cataracts, aniridia, anophthalmia and central nervous system defects.

The human eye malformation aniridia results from haploinsufficiency of PAX6, a paired box DNA-binding protein. To study this dosage effect, we characterized two PAX6 mutations in a family segregating aniridia and a milder syndrome consisting of congenital cataracts and late onset corneal dystrophy. The nonsense mutations, at codons 103 and 353, truncate PAX6 within the N-terminal paired and C-terminal PST domains, respectively. The wild-type PST domain activates transcription autonomously and the mutant form has partial activity. A compound heterozygote had severe craniofacial and central nervous system defects and no eyes. The pattern of malformations is similar to that in homozygous Sey mice and suggests a critical role for PAX6 in controlling the migration and differentiation of specific neuronal progenitor cells in the brain.

Abnormalities, Multiple↗

PubMed1994

1,25-Dihydroxyvitamin D3 increases the cellular content of the calcium-activated neutral protease mu-calpain in renal cell carcinoma.

mu-Calpain is a calcium-dependent neutral thiol protease activated by micromolar concentrations of calcium. mu-Calpain is implicated in various cellular functions regulated by calcium including exocytosis, cell fusion, apoptosis and control of cell proliferation. We studied the effect of 1,25-(OH)2D3 on mu-calpain levels in the human renal cell carcinoma line SK-RC-29 using monoclonal antibodies to the 80 kDa subunit of mu-calpain. Exposure of low density cultures (15000 cells/cm2) to 1,25-(OH)2D3 (100nM) for 48 hours resulted in 1.5-3 fold increase of mu-calpain cell content. The effect was not observed in higher density cultures (40000 cells/cm2). mu-Calpain content of high density cultures was higher than that of low density cultures and similar to that in low density cultures treated by 1,25-(OH)2D3. The cellular content of two other calcium binding proteins, annexin II and annexin VI was not affected by the hormone. 1,25-(OH)2D3 did not affect cell number or viability therefore its effect on mu-calpain is not secondary to changes in cell density. The effect of 1,25-(OH)2D3 was dose-dependent apparent already at 1nM and was not observed with 24,25-(OH)2D3. Increase in mu-calpain content may underlie some of the actions of 1,25-(OH)2D3 on classical and non classical target cells.

Calcitriol↗

PubMed1993

Anxiolytic effects of the 5-HT1A receptor agonist ipsapirone in the rat: neurobiological correlates.

Ipsapirone, a 5-HT1A receptor agonist, is a psychoactive compound with anxiolytic and antidepressive properties. Concerning the mechanism of action of ipsapirone, most studies point towards an interaction with the central serotonergic system. For characterization of the anxiolytic properties of ipsapirone, the ultrasonic vocalization test, a rat model based on conditioned anxiety, was used. In this test ipsapirone time and dose dependently inhibited the shock induced ultrasonic vocalization of rats after systemic application of ipsapirone, indicating its potent anxiolytic properties. To gain further insight into the mechanism underlying the anxiolytic activity of ipsapirone, the effects of this compound on the central serotonergic system of rats were characterized. Extracellular single unit recordings, measuring the firing rate of serotonergic dorsal raphe neurons in anaesthetized rats, showed that ipsapirone dose and time dependently suppressed neuronal firing. In the hippocampus, one of the projection areas of the serotonergic dorsal raphe neurons, systemic application of ipsapirone resulted in a dose- and time-dependent reduction in serotonergic neurotransmission, measured as a reduced serotonin output in microdialysis experiments with freely moving rats. The time- and dose-effect curves reflecting the anxiolytic, electrophysiological, and biochemical effects correlated well with each other for different doses of ipsapirone. It is concluded that ipsapirone exhibits its anxiolytic effects, at least partially, by stimulating presynaptic somatodendritic 5-HT1A receptors in the brain stem raphe nuclei (i.e., the dorsal raphe), resulting in attenuation of presynaptic cell firing and subsequent inhibition of serotonergic neurotransmission in the limbic system (i.e., the hippocampus).

Animals↗

PubMed1993

Subchronic treatment with anxiolytic doses of the 5-HT1A receptor agonist ipsapirone does not affect 5-HT2 receptor sensitivity in the rat.

Acute stimulation of 5-HT1A receptors has been reported to diminish some 5-HT2 receptor-mediated responses in the rat, but there is controversy as to whether repeated stimulation of 5-HT1A receptors leads to identical changes. In this study, we tested the influence of repeated treatment with the 5-HT1A receptor agonist ipsapirone (0.5 g/l in drinking water for 21 days) on some 5-HT2 receptor-mediated responses elicited by the acute injection of the 5-HT1C/5-HT2 receptor agonist 1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane (DOI). These responses included hyperglycemia, corticosterone release, and head shakes; cortical 5-HT2 receptor number and DOI-induced prolactin release (a 5-HT1C/5-HT2 receptor-mediated event) were also analyzed. In a first series of experiments, ipsapirone administration for 1, 8, 15, and 20 days reduced the duration fo shock-induced ultrasonic vocalization. Ipsapirone administration for 21 days reduced fluid intake and decreased body weight, but did not affect baseline plasma glucose, corticosterone, and prolactin levels or cortical 5-HT2 receptor number. The increases in plasma glucose levels elicited by acute injection of either DOI (0.1-1 mg/kg i.v.) or clonidine (an alpha 2-adrenoceptor agonist; 0.05 mg/kg i.v.) were reduced in ipsapirone-pretreated rats. The maximal effects of DOI and clonidine on plasma corticosterone or prolactin levels were not affected by ipsapirone pretreatment. Ipsapirone decreased the area under the corticosterone curve in both DOI- and clonidine-treated rats. Lastly, the head-shake response to DOI (0.5-2 mg/kg s.c.) was similar in vehicle- and ipsapirone-pretreated rats. These data indicate that a 3-week treatment with anxiolytic doses of the 5-HT1A receptor agonist ipsapirone does not desensitize 5-HT2 receptors.

Administration, Oral↗

PubMed1993

Ipsapirone and 8-OH-DPAT reduce ethanol preference in rats: involvement of presynaptic 5-HT1A receptors.

The selective serotonin(5-HT)1A receptor agonists 8-OH-DPAT and ipsapirone were tested in selectively inbred Wistar rats, with high preference [70-90%: defined as the ratio of ethanol (EtOH) to total fluid intake] for EtOH (10% v/v) over water in a two-bottle free choice situation. Rats were injected shortly before the overnight test session (8:00 P.M.-8:00 A.M.). EtOH and water consumption were determined in 20-min intervals; food consumption after the session. 8-OH-DPAT (ED50: 2.4 mg/kg, SC) and ipsapirone (ED50: 12.5 mg/kg, SC) reduced EtOH preference in a dose-dependent manner. In addition, 8-OH-DPAT increased total fluid intake, whereas ipsapirone enhanced total food intake. The EtOH preference reduction was time-dependent and reached a maximum within the second 4 h after application of 8-OH-DPAT (-73%) and ipsapirone (-72%). The preference reducing effect of ipsapirone (20 mg/kg, PO) was completely blocked by the nonselective 5-HT1A antagonist spiperone (0.05 mg/kg, SC). Local application of 8-OH-DPAT (10 micrograms, 0.5 microliters) into the dorsal raphe nucleus (DRN, a brain area rich in somatodendritic 5-HT1A autoreceptors), reduced the EtOH preference significantly as compared to the saline injection in the same animal (-12%, 8:00-12:00 P.M.). Only marginal effects on ingestion behavior were observed after microinjection into the nucleus accumbens. Reduction of brain 5-HT levels by pretreatment with the 5-HT synthesis inhibitor pCPA (2 x 150 mg/kg, IP) resulted in a short lasting, marked reduction (-54%) and a long lasting, small attenuation of the EtOH preference. Total food consumption was strongly decreased but returned soon to normal; total fluid intake was only slightly decreased. The EtOH preference reducing effect of ipsapirone (5 and 20 mg/kg, SC) was attenuated in pCPA-pretreated rats. The present data suggest that 5-HT1A receptor ligands reduce EtOH preference via stimulation of 5-HT1A receptors in the DRN. The possibility of additional mechanism(s) is discussed.

8-Hydroxy-2-(di-n-propylamino)tetralin↗

PubMed1993

Signalling via rat dopamine D2-receptors expressed in mouse fibroblasts is not influenced by compounds binding to the sigma sites of these cells.

The mouse fibroblast cell line LZR-1 is a well-established test system used to characterize the intrinsic activity of dopamine D2-receptor ligands (Neve et al., Mol. Pharmac., 1989). This cell line is transfected with a eucaryotic expression vector containing the gene of the rat dopamine D2B-receptor (short isoform of the D2-receptor) (Bunzow et al., Nature, 1988). In addition to the expression of high levels of the rat dopamine D2-receptor, these mouse cells also express sigma binding sites. Binding affinities of BMY 14,802, DTG, haloperidol, (+)-pentazocine, (+)-3-PPP, and (+)-SKF 10,047 for the sigma binding sites as well as for the D2-dopamine receptor in membranes of LZR-1 cells were determined. Using intact LZR-1 cells, it was found that the influence of sigma ligands on signalling via the dopamine D2-receptor can be explained by their affinity for the latter receptor. Specific sigma ligands did not influence dopaminergic signal transduction in LZR-1 cells. It is therefore concluded that the LZR-1 cell is a suitable test model for determination of the intrinsic activity of dopamine D2-receptor ligands even if these compounds have affinity for sigma binding sites.

Animals↗

PubMed1992

The putative 5-HT1A receptor antagonists NAN-190 and BMY 7378 are partial agonists in the rat dorsal raphe nucleus in vitro.

The present electrophysiological study examined the actions of the putative 5-HT1A receptor antagonists NAN-190 (1-(2-methoxyphenyl)-4-[4-(2-phthalimido)butyl]piperazine) and BMY 7378 (8-[2-[4-(2-methoxyphenyl)-1-piperazinyl]ethyl]-8-azaspiro[4,5]- decane-7,9-dione dihydrochloride) in the rat dorsal raphe nucleus in vitro. There was no major difference between the effects of the two drugs on any measure investigated. Both compounds reduced neuronal activity in a concentration-dependent manner, with BMY 7378 being slightly more potent than NAN-190. The threshold concentrations eliciting inhibitory effects were 1 nM for BMY 7378 and 3 nM for NAN-190. Complete inhibition occurred at concentrations close to 30 nM. The effects of the 5-HT1A receptor agonist 8-OH-DPAT (8-hydroxy-2-(di-n-propylamino)tetralin) could be antagonized when concentrations of NAN-190 or BMY 7378 were used that were too low to produce a marked inhibition. At concentrations close to threshold both compounds potentiated the inhibitory effects of 3 nM 8-OH-DPAT. The suppression of neuronal firing induced by NAN-190 and BMY 7378 could be completely antagonized with propranolol, indicating that the inhibitory actions of both drugs were not primarily due to alpha 1-adrenoceptor antagonism. By applying theorems of receptor theory the intrinsic activities for both NAN-190 and BMY 7378 were calculated to be in the range of 0.1-0.3. Thus, NAN-190 and BMY 7378 are partial agonists in the rat dorsal raphe nucleus.(ABSTRACT TRUNCATED AT 250 WORDS)

8-Hydroxy-2-(di-n-propylamino)tetralin↗