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At least 19 recordsLinked to original sources
PubMed1987

Differences between muscular receptors and neural receptors for cholecystokinin-octapeptide in the guinea-pig gallbladder.

To investigate the differences between muscular and neural receptors for cholecystokinin-octapeptide (CCK-OP) in the guinea-pig gallbladder, we studied the effects of dibutyryl cyclic GMP (dbc GMP) on CCK-OP-evoked contraction and [3H]acetylcholine (ACh) release. 10(-3) M dbc GMP significantly reduced CCK-OP (10(-8) M)-evoked contractions without affecting the peptide-induced [3H]ACh release. It is suggested that there are two types of CCK-OP receptors in the guinea-pig gallbladder (dbc GMP-sensitive muscular receptors and dbc GMP-insensitive neural receptors).

Acetylcholine↗
PubMed1985

The enteric neural receptor for 5-hydroxytryptamine.

An enteric neural receptor for serotonin (5-HT) has been characterized. This receptor was assayed, using 3H-5-HT as a radioligand, by rapid filtration of isolated enteric membranes and by radioautography. In addition, intracellular recordings were made from ganglion cells of the myenteric plexus. High affinity, saturable, reversible, and specific binding of 3H-5-HT was demonstrated both to membranes of the dissected longitudinal muscle with adherent myenteric plexus and the mucosa-submucosa. Radioautographs showed these 3H-5-HT binding sites to be in myenteric ganglia and in a broad unresolved band at the mucosal-submucosal interface. Antagonists active at receptors for other neurotransmitters than 5-HT, at either of the two known types of CNS 5-HT receptor, and at 5-HT uptake sites on serotonergic neurons failed to inhibit binding of 3H-5-HT. The structural requirements of analogues for binding to the enteric 5-HT receptor matched the known pharmacology of M or neural 5-HT receptors. A novel 5-HT antagonist was found. This compound, N-acetyl-5-hydroxytryptophyl-5-hydroxytryptophan amide (5-HTP-DP), antagonized the action of 5-HT on type II/AH cells of the myenteric plexus but did not affect the release or actions of acetylcholine (nicotinic or muscarinic) or substance P. 5-HTP-DP was also an equally potent displacer of 3H-5-HT from its binding sites on enteric membranes. It is concluded that the sites responsible for specific binding of 3H-5-HT are enteric M or neural 5-HT receptors. These receptors differ from those now known to be present in the CNS.

5-Hydroxytryptophan↗
PubMed2005

Epithelial distribution of neural receptors in the guinea pig small intestine.

Neural and paracrine agents, such as dopamine, epinephrine, and histamine, affect intestinal epithelial function, but it is unclear if these agents act on receptors directly at the enterocyte level. The cellular localization and villus-crypt distribution of adrenergic, dopamine, and histamine receptors within the intestinal epithelium is obscure and needs to be identified. Single cell populations of villus or crypt epithelial cells were isolated from the jejunum of adult guinea pigs. Enterocytes were separated from intraepithelial lymphocytes by flow cytometry and specific binding was determined using fluorescent probes. Alpha1-adrenergic receptors were located on villus and crypt intraepithelial lymphocytes and enterocytes. Beta-adrenergic receptors were found on villus and crypt enterocytes. Dopamine receptors were found on all cell types examined, whereas histamine receptors were not detected (<10% for each cell population). These studies demonstrated that (1) receptors for epinephrine and dopamine exist on epithelial cells of the guinea pig jejunum, (2) beta-adrenergic receptors are found primarily on villus and crypt enterocytes and (3) intraepithelial lymphocytes contain alpha1-adrenergic, but have few beta-adrenergic, receptors. The presence of neural receptors suggests that these agents are acting, at least in part, at the enterocyte or intraepithelial lymphocyte levels to modulate intestinal and immune function.

Animals↗
PubMed1988

Serotonin neural receptors mediate motilin-induced motility in isolated, vascularly perfused canine jejunum.

We previously reported that motilin induced both motility and endoluminal release of serotonin (5-HT) in canine jejunum. The motility response was blocked by nonspecific tachyphylaxis of 5-HT receptors. In this study, we investigated the effect of a selective neural serotonin receptor (5-HT3) antagonist, ICS 205-930, given into either the artery or the lumen, on motilin-induced motility. Segments of canine jejunum were arterially perfused with Kreb's HCO3 solution containing 15% RBCs in an organ preservation system. Following a 15-min basal period (Basal-1), 500 fM motilin was infused into the artery over 15 min (Motilin-1). After a 30-min rest, the cycle was repeated (Basal-2 and Motilin-2) in the presence and absence (control) of ICS 205-930, which was given as a continuous infusion either into the artery or into the lumen (0.1 to 1.0 microM). From continuous intraluminal pressure tracings, a motility index (MI) was calculated for 5- or 15-min periods from the product of the frequency and the mean amplitude of phasic waves for that period. In control segments, motilin reproducibly induced significant (P less than 0.05) increases in MI over basal levels during both Motilin-1 and Motilin-2. Arterial 0.1 microM ICS 205-930 abolished the motor response to rechallenge with motilin: 145 +/- 28 to 288 +/- 10 mm Hg (Motilin-1) versus 168 +/- 27 to 168 +/- 13 mm Hg (Motilin-2). An infusion of 1 microM ICS 205-930 into the lumen was required to inhibit the response. Thus, motilin-induced motility is mediated by neural 5-HT receptors. Since both arterial and luminal antagonist was effective, it is likely that 5-HT3 receptors on both myenteric plexus neurons and neurons in proximity to mucosal enterochromaffin cells mediate the motor response to motilin.

Animals↗
PubMed2002

Odorant-induced olfactory receptor neural oscillations and their modulation of olfactory bulbar responses in the channel catfish.

Peripheral waves (PWs) in the channel catfish are odorant-induced neural oscillations of synchronized populations of olfactory receptor neurons (ORNs) that appear after the initial approximately 500 msec of the response. The mean dominant frequency during the initial 2 sec of PW activity is approximately 28 Hz, declining to approximately 20 Hz in the last sec of a 5 sec stimulus. Recordings of PWs from different regions of a single olfactory lamella and simultaneously from widely separated lamellae within the olfactory organ suggest that PWs are initiated in the sensory epithelium within each olfactory lamella. Simultaneous recordings in vivo from the olfactory organ [electro-olfactogram (EOG) or integrated neural activity], local field potentials (LFPs) from the olfactory bulb (OB), and single and few-unit activity from OB neurons were performed. Cross-correlation analysis of simultaneously recorded odor-induced OB LFPs and either EOG or ORN neural activity showed that oscillations occurring within the OB were lower (<20 Hz) than those of PWs; however, during PW activity, OB LFPs increased both their magnitude and dominant frequencies and became correlated with the PWs. Also during odorant-induced PW activity, the responses of different OB neurons with similar odorant specificity became phase locked to each other and to both the PWs and OB LFPs. PWs are hypothesized to function to strengthen the synaptic transfer of olfactory information at specific glomeruli within the OB.

Adaptation, Physiological↗
PubMed1987

Development of neural receptors for serotonin in the murine bowel.

During the ontogeny of the enteric nervous system, the varicosities of mature neurons contact dividing neural precursors, which persist in the developing murine gut for several weeks postnatally. This phenomenon has led to the hypothesis that the release of transmitter from mature neurons may influence the subsequent development of uncommitted neuroblasts. In order to test this hypothesis, it is necessary to know the timing of the expression of postsynaptic receptors for enteric neurotransmitters. Since serotoninergic neurons are among the earliest of enteric neurons to develop (appearing on day E12 of development in the mouse), the ontogeny of enteric neural serotonin receptors (5-HTR) was studied. These receptors have previously been characterized in adult guinea pigs and rabbits. In the current experiments, 5-HTR were identified in the adult murine bowel; their properties were compared with the 5-HTR of guinea pig and rabbits; their ontogeny was followed throughout the length of the developing mouse gut; and the properties of 5-HTR in the developing murine bowel were compared with those of the mature gut. The 5-HTR were assayed by measuring the binding of 3H-serotonin (3H-5-HT) to isolated enteric membranes by rapid filtration, and to frozen sections of bowel by radioautography. A single saturable, high affinity 3H-5-HT binding site was found in membranes from the adult mouse gut (KD = 3.9 +/- 0.5 nM; Bmax = 1.6 +/- 0.3 pmoles/mg protein). Binding of 3H-5-HT at this site was not antagonized by compounds known to be antagonists at receptors for other neurotransmitters or at the 5-HT1 or 5-HT2 class of CNS 5-HTR. Hydroxylation of the indole ring of analogues of serotonin was required for affinity at the enteric 3H-5-HT binding site. Binding of 3H-5-HT was inhibited by N-acetyl-5-hydroxytryptophyl-5-hydroxytryptophan dipeptide, a compound that has been demonstrated to antagonize those responses of myenteric neurons to serotonin that resemble slow excitatory postsynaptic potentials, but not by ICS 205-930 (Sandoz), a serotonin antagonist that does not block these responses. All of these properties of adult murine 3H-5-HT binding sites are virtually identical of those of guinea pigs and rabbits, which have previously been shown to be 5-HTR; therefore, murine enteric 3H-5-HT binding sites are probably 5-HTR as well.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1999

Antisecretory effect of peptide YY through neural receptors in the rat jejunum in vitro.

Basal short circuit current (Isc) was measured in stripped rat jejunum after addition of neural antagonists and of peptide YY (PYY). Basal Isc was slightly (by 10-21%) but significantly inhibited by tetrodotoxin, hexamethonium, idazoxan, and the sigma antagonist BMY 14,802. PYY (10(-7) M) reduced basal Isc by approximately 54%. This inhibition was unchanged by hexamethonium but reduced by 44-68% in the presence of tetrodotoxin, idazoxan, haloperidol, BMY 14,802, and atropine. The Y2 agonist pYY(3-36) was more potent than the Y1 agonist (Leu31,Pro34)PYY. In conclusion, PYY reduces basal Isc in rat jejunum in part through a neural mechanism involving muscarinic receptors, alpha2 adrenoceptors, and sigma receptors and, in part, through a direct effect on enterocytes. The PYY effect seems mainly carried out through Y2-receptor activation.

Animals↗
PubMedDate not supplied

Excitatory amino acid receptors, neural membrane phospholipid metabolism and neurological disorders.

Excitatory amino acids and their receptors play an important role in membrane phospholipid metabolism. Persistent stimulation of excitatory amino acid receptors by glutamate may be involved in neurodegenerative diseases and brain and spinal cord trauma. The molecular mechanism of neurodegeneration induced by excitatory amino acids is, however, not known. Excitotoxin induced calcium entry causes the stimulation of phospholipases and lipases. These enzymes act on neural membrane phospholipids and their stimulation results in accumulation of free fatty acids, diacylglycerols, eicosanoids and lipid peroxides in neurodegenerative diseases and brain and spinal cord trauma. Other enzymes such as protein kinase C and calcium-dependent proteases may also contribute to the neuronal injury. Excitotoxin-induced alteration in membrane phospholipid metabolism in neurodegenerative diseases and neural trauma can be studied in animal and cell culture models. The models can be used to study the molecular mechanisms of the neurodegenerative processes and to screen the efficacy of therapeutic drugs for neurodegenerative disease and brain and spinal cord trauma.

Animals↗
PubMed1997

ALK, the chromosome 2 gene locus altered by the t(2;5) in non-Hodgkin's lymphoma, encodes a novel neural receptor tyrosine kinase that is highly related to leukocyte tyrosine kinase (LTK)

Anaplastic Lymphoma Kinase (ALK) was originally identified as a member of the insulin receptor subfamily of receptor tyrosine kinases that acquires transforming capability when truncated and fused to nucleophosmin (NPM) in the t(2;5) chromosomal rearrangement associated with non-Hodgkin's lymphoma, but further insights into its normal structure and function are lacking. Here, we characterize a full-length normal human ALK cDNA and its product, and determine the pattern of expression of its murine homologue in embryonic and adult tissues as a first step toward the functional assessment of the receptor. Analysis of the 6226 bp ALK cDNA identified an open reading frame encoding a 1620-amino acid (aa) protein of predicted mass approximately 177 kDa that is most closely related to leukocyte tyrosine kinase (LTK), the two exhibiting 57% aa identity and 71% similarity over their region of overlap. Biochemical analysis demonstrated that the approximately 177 kDa ALK polypeptide core undergoes co-translational N-linked glycosylation, emerging in its mature form as a 200 kDa single chain receptor. Surface labeling studies indicated that the 200 kDa glycoprotein is exposed at the cell membrane, consistent with the prediction that ALK serves as the receptor for an unidentified ligand(s). In situ hybridization studies revealed Alk expression beginning on embryonic day 11 and persisting into the neonatal and adult periods of development. Alk transcripts were confined to the nervous system and included several thalamic and hypothalamic nuclei; the trigeminal, facial, and acoustic cranial ganglia; the anterior horns of the spinal cord in the region of the developing motor neurons; the sympathetic chain; and the ganglion cells of the gut. Thus, ALK is a novel orphan receptor tyrosine kinase that appears to play an important role in the normal development and function of the nervous system.

Amino Acid Sequence↗
PubMed1991

Galactosyl ceramide or a derivative is an essential component of the neural receptor for human immunodeficiency virus type 1 envelope glycoprotein gp120.

This report demonstrates that galactosyl ceramide (GalCer) or a molecule derived from it may serve as an alternative receptor for human immunodeficiency virus in the nervous system. Recombinant gp120, an envelope glycoprotein of human immunodeficiency virus type 1, specifically binds to GalCer and its derivatives. This specificity was studied by inhibiting binding of radioiodinated gp120 to GalCer with antibodies to GalCer, antibodies to gp120, and an excess of unlabeled gp120. Binding activity was also removed by absorbing gp120 with liposomes containing GalCer. In addition, studies using natural and semisynthetic lipids indicate that the linkage between galactose and ceramide is essential for binding. The significance of an alternative receptor for human immunodeficiency virus in the nervous system is discussed.

Binding Sites↗
PubMed2003

The neural receptor protein tyrosine phosphatase DPTP69D is required during periods of axon outgrowth in Drosophila.

We have isolated and characterized a series of 18 chemically induced alleles of Ptp69D ranging in strength from viable to worse than null, which represent unique tools for probing the structure, function, and signaling pathway of DPTP69D. Three alleles are strongly temperature sensitive and were used to define the developmental periods requiring DPTP69D function; adult health requires DPTP69D during the mid- to late-pupal stage, eclosion requires DPTP69D during the early to mid-larval stage, and larval survival requires DPTP69D during embryogenesis. Mutations predicted to abolish the phosphatase activity of the membrane proximal D1 domain severely reduce but do not abolish DPTP69D function. Six alleles appear null; only 20% of null homozygotes pupate and <5% eclose, only to fall into the food and drown. One allele, Ptp69D(7), confers axon and viability defects more severe than those of the null phenotype. Sequence analysis predicts that Ptp69D(7) encodes a mutant protein that may bind but not release substrate. Like mutations in the protein tyrosine phosphatase gene Dlar, strong Ptp69D alleles cause the ISNb nerve to bypass its muscle targets. Genetic analysis reveals that the bypass defect in Dlar and Ptp69D mutants is dependent upon DPTP99A function, consistent with the hypothesis that DPTP69D and DLAR both counteract DPTP99A, allowing ISNb axons to enter their target muscle field.

Alleles↗
PubMed1991

trkB, a neural receptor protein-tyrosine kinase: evidence for a full-length and two truncated receptors.

We have screened an adult rat cerebellar cDNA library in search of novel protein tyrosine-kinase (PTK) cDNAs. A cDNA for a putative PTK, trkB, was cloned, and its sequence indicates that it is likely to be derived from a gene for a ligand-regulated receptor closely related to the human trk oncogene. Northern (RNA) analysis showed that the trkB gene is expressed predominantly in the brain and that trkB expresses multiple mRNAs, ranging from 0.7 to 9 kb. Hybridization of cerebral mRNAs with a variety of probes indicates that there are mRNAs encoding truncated trkB receptors. Two additional types of cDNA were isolated, and their sequences are predicted to encode two distinct C-terminally truncated receptors which have the complete extracellular region and transmembrane domain, but which differ in their short cytoplasmic tails.

Amino Acid Sequence↗
PubMedDate not supplied

Neural receptors and asthma.

Neurotransmitters released from sensory, parasympathetic, and sympathetic nerves regulate epithelial, vascular, glandular, and contractile processes in the human respiratory tract. The actions of these neurotransmitters are dependent upon the distribution and subtypes of their specific receptors expressed on the resident cells in the respiratory tract. The distributions of these receptors, and their potential activities in asthma, will be investigated with the hope of discriminating between the pharmacological and physiological actions of mediators and neurotransmitters in normal and asthmatic airways.

Asthma↗