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Biomedical subjects

M R Hanley

Publications and source records attributed to M R Hanley.

At least 91 records · Page 5Linked to original sources
PubMed1987

The immunocytochemical localisation of 'substance-P-degrading enzyme' within the rat spinal cord.

The regional distribution of a neural endopeptidase ('substance-P-degrading enzyme', SPDE) within the rat spinal cord, as visualised by immunocytochemistry, closely paralleled the distribution of major substance P-containing nerve fibre systems. Thus, SPDE-immunoreactivity was present in laminae I and II of the dorsal horn, in large diameter neurones of the ventral horn and in the ependymal cells which line the central canal. The pattern of immunostaining, particularly in the dorsal horn, is consistent with the view that SPDE may function in the metabolism of substance P.

Animals↗
PubMed1987

Autoradiographic evidence for beta-adrenergic receptors on capsaicin-sensitive primary afferent terminals in rat spinal cord.

Specific [3H]dihydroalprenolol binding sites are enriched in the dorsal grey matter of rat spinal cord. Neonatal capsaicin treatment, known to cause a permanent loss of a population of primary afferent neurones, caused a significant loss of specific [3H]dihydroalprenolol binding sites from laminae of the dorsal horn. These results suggest that capsaicin-sensitive primary afferent terminals may bear presynaptic beta-adrenergic receptors.

Animals↗
PubMed1987

L6 skeletal muscle cells have functional V1-vasopressin receptors coupled to stimulated inositol phospholipid metabolism.

The effects of vasopressin and related peptides upon the rat skeletal muscle cell line, L6, have been examined. No effects upon cellular cyclic AMP levels were found indicating that L6 cells possess no functional V2-vasopressin receptors. Vasopressin and its analogues did, however, stimulate the rapid and dose-dependent accumulation of inositol phosphates. This effect and the rank order of potency of vasopressin analogues demonstrate the presence of functional V1-vasopressin receptors upon L6 cells. These results suggest that the L6 line may be a useful model for vasopressin effects upon skeletal muscle metabolism.

Animals↗
PubMed1987

Receptor coupled events in bradykinin action: rapid production of inositol phosphates and regulation of cytosolic free Ca2+ in a neural cell line.

The addition of bradykinin to NG115-401L cells grown on coverslips results in the generation of rapid transient increases in intracellular [Ca2+] and inositol phosphates. Changes in intracellular Ca2+, measured using the fluorescent indicator dye Fura-2, show two components; an initial rapid peak in [Ca2+]i which is essentially independent of extracellular Ca2+, and a sustained plateau dependent on the presence of extracellular Ca2+. Analysis of bradykinin stimulated production of [3H]inositol phosphates, by h.p.l.c., shows a rapid biphasic production of inositol 1,4,5-trisphosphate, inositol tetrakisphosphate and inositol bisphosphates, followed by a sustained rise in inositol 1,3,4-trisphosphate production. Quantitative measurements have indicated the presence of other, more polar, [3H]inositol-labelled metabolites which do not show major changes on bradykinin stimulation. The initial phase of inositol phosphate production parallels the rapid transient increase in intracellular [Ca2+], however, the second phase of inositol phosphate production occurs when intracellular [Ca2+] is declining and implies a complex series of regulatory events following receptor stimulation. Similar time courses of inositol 1,4,5-trisphosphate and Ca2+ signals provides supporting evidence that inositol 1,4,5-trisphosphate is the second messenger coupling bradykinin receptor stimulation to release of Ca2+ from intracellular stores.

Animals↗
PubMed1986

Autoradiographic localization of peripheral benzodiazepine, dihydroalprenolol and arginine vasopressin binding sites in the pituitaries of control, stalk transected and Brattleboro rats.

The autoradiographic distribution of [3H]arginine vasopressin, [3H]spiperone, [3H]GABA, [3H]dihydroalprenolol and the peripheral-type benzodiazepine ligand [3H]Ro5-4864 were examined in the rat pituitary before and after pituitary stalk transection. Stalk transection produced dramatic changes in the cellular architecture of the pars nervosa. Glial fibrillary acidic protein, an astrocyte marker reported in pituicytes, increased after stalk transection, whereas neurofilament, a marker for neuronal innervation, was lost. These structural changes demonstrated a successful stalk transection, permitting interpretation of changes in the densities of several [3H]-ligands over the three lobes. [3H]Ro5-4864 binding was markedly increased, suggesting that this site was located on the pituicytes. Conversely [3H]spiperone and [3H]arginine vasopressin binding density over the pars nervosa decreased. In the mutant diabetes insipidus rat (Brattleboro), which lacks pituitary vasopressin, [3H]arginine vasopressin binding was undetectable in the pars nervosa. [3H]dihydroalprenolol and [3H]GABA binding sites were unchanged by the lesion. These results are discussed in terms of the occurrence of functional acceptors on pituicytes and their possible role in neurohydrophyseal secretions.

Alprenolol↗
PubMed1985

Evidence for a kappa-opioid receptor on pituitary astrocytes: an autoradiographic study.

Specific binding of the opioid ligand [3H]etorphine was localized in cryostat sections of the rat pituitary. The binding was concentrated over the pars nervosa. Competition with partially selective unlabelled displacers indicated that the greater part of this binding was of the kappa-subtype, sensitive to inhibition by dynorphin and bremazocine. The kappa nature of the binding was confirmed using the prototype kappa ligand [3H]ethylketocyclazocine in the presence of excess unlabelled mu and delta opioid receptor ligands. Sections of the pituitary stalk caused a loss of the hypothalamic projection to the pars nervosa and a marked gliosis. Concurrent with these changes there was a significant increase in the density of kappa opioid binding. These observations suggest that the majority of opioid receptors in the pars nervosa are of the kappa subtype and are located on the pituicytes.

Animals↗
PubMed1985

Functional substance P receptors on a rat pancreatic acinar cell line.

A pancreatic acinar cell line, AR4-2J, that expresses a high density of substance P (SP)-binding sites has been identified. SP-binding sites on intact AR4-2J cells were detected with 125I-Bolton-Hunter SP (125I-BHSP). 125I-BHSP binding to AR4-2J cells has an apparent Kd of 40 pm with slow rates of association and dissociation. The number of high affinity binding sites was about 10(4)/cell. Binding of 125I-BHSP was inhibited by SP and by structurally related peptides. Physalaemin was a more potent inhibitor of binding than SP, whereas kassinin, eledoisin, and neurokinin A (substance K, neuromedin alpha, or neurokinin L) were much less potent. SP-free acid and SP (7-11) were 3 to 4 orders of magnitude less potent than SP itself. The membrane, intracellular, and secretory events elicited by exposure of AR4-2J cells to SP have also been examined. Intracellular recording from AR4-2J cells revealed resting membrane potentials of -40 to -65 mV. Pressure application of SP (100 pM to 100 nM) evoked depolarizations of 20 to 40 mV which were maintained for prolonged periods. The intracellular free calcium concentration in AR4-2J cells, measured with (2-[2-amino-5-methylphenoxy)-methyl)-6-methoxy-8-aminoquinolone tetra-acetoxy methyl ester), was between 100 and 500 nM. Addition of SP (100 pM to 10 nM) or physalaemin (1 nM) induced a transient rise in intracellular free calcium. AR4-2J cells synthesize amylase, and exposure of cells to SP resulted in a dose-dependent increase in amylase secretion.(ABSTRACT TRUNCATED AT 250 WORDS)

Amylases↗
PubMed1983

Sympathetic denervation impairs agonist-stimulated phosphatidylinositol metabolism in rat parotid glands.

Substance P, muscarinic and alpha-adrenoceptor agonists stimulated the incorporation of [3H]inositol into phosphatidylinositol in rat parotid gland slices. Surgical denervation of the sympathetic input to the rat parotid gland by superior cervical ganglionectomy produced marked reductions in these responses. The stimulated incorporation of radiolabelled precursors into phosphatidylinositol is a measure of its resynthesis after receptor-mediated breakdown of inositol phospholipids. We therefore examined the enzymic site of the lesion induced by sympathetic denervation using parotid gland slices labelled with either [3H]inositol or [32P]phosphate and stimulated with substance P. Receptor-activated phospholipase C attack upon [3H]inositol phospholipids was assayed by measuring the formation of [3H]inositol 1-phosphate in the presence of 10 mM-Li+ to inhibit further breakdown. It was not affected by denervation. Substance P elicited a rapid breakdown of phosphatidylinositol 4,5-bisphosphate and this response was reduced in the denervated gland. The second step in stimulated phosphatidylinositol turnover, phosphorylation of diacylglycerol to phosphatidate was not affected by denervation. Sympathetic denervation appears to induce a specific enzymic lesion in the parotid gland that impairs receptor-stimulated resynthesis of phosphatidylinositol from phosphatidate. This change in membrane lipid metabolism may be related to a number of the effects of sympathetic denervation, such as agonist supersensitivity, reduced gland cell proliferation and induction of new surface receptors.

Animals↗
PubMed1983

Tissue selectivity of substance P alkyl esters: suggesting multiple receptors.

Previous studies from this laboratory suggested that two subtypes of substance P receptor may exist, based on the observations that substance P and related peptides did not exhibit complete cross-desensitisation on guinea-pig ileum, and that two distinct rank orders of potency of tachykinins were observed in various test systems. The present study has added support to this hypothesis by extending the screening of tachykinins to further bioassays and by testing novel analogues. In particular, C-terminal alkyl esters of substance P were found to exhibit a high degree of selectivity to one putative receptor subtype. The synthesis of the alkyl esters by esterification of substance P free acid is described.

Animals↗
PubMed1983

A comparison of the release of substance P and some synthetic analogues from micropipettes by microiontophoresis or pressure.

The release of substance P (SP) and two analogues by iontophoresis or pressure from microelectrodes was compared. Substance P was released linearly by iontophoresis from electrodes while no release of the analogues was detected. [N-methylphenylalanine8, N-methylglycine9-] SP5-11 (DiMeC7) and [methyl-2-aminoethyl]11 SP (SP-DAE) were released from electrodes by pressure ejection with linear relationships in all cases between pressure and the amounts released. Under the tested experimental conditions, release of substance P by iontophoresis was between 2 and 3 orders of magnitude less than that by pressure over a given time. The release of substance P and the uncharged analogue DiMeC7 by pressure was very similar while release of SP-DAE was one order of magnitude less.

Electrophoresis↗
PubMed1982

Lithium amplifies agonist-dependent phosphatidylinositol responses in brain and salivary glands.

1. The effect of Li+ on the agonist-dependent metabolism of [3H]inositol has been studied in rat brain, rat parotid and the insect salivary gland. 2. When brain or parotid slices were incubated in the presence of [3H]inositol, Li+ was found to amplify the ability of agonists such as carbachol, phenylephrine, histamine, 5-hydroxytryptamine and Substance P to elevate the amount of label appearing in the inositol phosphates. 3. A different approach was used with the insect salivary gland, which was prelabelled with [3H]inositol. After washing out the label, the subsequent release of [3H]inositol induced by 5-hydroxytryptamine was greatly decreased by Li+. During Li+ treatment there was a large accumulation of [3H]inositol 1-phosphate. 4. This ability of Li+ to greatly amplify the agonist-dependent accumulation of myo-inositol 1-phosphate offers a novel technique for identifying those receptors that function by hydrolysing phosphatidylinositol. 5. The therapeutic action of Li+ may be explained by this inhibition of myo-inositol 1-phosphatase, which lowers the level of myo-inositol and could lead to a decrease in the concentration of phosphatidylinositol, especially in those neurons that are being stimulated excessively. This alteration in phosphatidylinositol metabolism may serve to reset the sensitivity of those multifunctional receptors that generate second messengers such as Ca2+, cyclic GMP and the prostaglandins.

Animals↗
PubMed1982

Substance P analog, DiMe-C7: evidence for stability in rat brain and prolonged central actions.

A metabolically protected analog of substance P, [pGlu5-MePhe8-MeGly9]SP(5-11) (DiMe-C7), was approximately equipotent with substance P in causing increased locomotor activity after microinfusion into the ventral tegmental area of rat brain, but the effects of DiMe-C7 on behavior were considerably prolonged. There was little metabolic degradation of tritiated DiMe-C7 for up to 1 hour after infusion, whereas tritiated substance P was completely degraded within 10 minutes.

Animals↗
PubMed1982

Substance P receptors in the nervous system and possible receptor subtypes.

The ability of various related peptides and substance P analogues to compete for the binding of 3H-labelled substance P to rat brain membranes corresponds with their known biological activities, providing a simple model for studies of peptide receptors in the central nervous system. In salivary gland and brain slices substance P and related peptides stimulate the rate of incorporation of phosphatidylinositol, offering an alternative biochemical model for substance P receptor studies. Two types of receptor may be responsible for the actions of substance P on peripheral tissues: the SP-P type, where all tachykinins are approximately equally active, and the SP-E type, where eledoisin and kassinin are more potent than the other tachykinins. Alkyl esters of substance P appear to act as selective SP-P agonists.

Animals↗
PubMed1982

The possible existence of multiple receptors for substance P.

1. The possible existence of multiple receptors for substance P (SP) was investigated by examining the relative pharmacological potencies of SP and related peptides in contracting guinea pig ileum, in potentiating electrically evoked contractions of rat vas deferens preparations and in competing for 3H-SP receptor binding in rat brain membranes, and by comparing the extent of cross-tachyphylaxis of various analogues with SP in the guinea pig ileum. 2. Different rank orders of potencies were observed among SP, its C-terminal fragments, analogues and related tachykinins in the different test systems, and these could not be explained by differential access to the target organ receptors. 3. In contrast to SP and physalaemin, both eledoisin and a metabolically stable SP analogue, [pGlu5, MePhe8, Sar9]-SP5-11 exhibited differential recovery from SP tachyphylaxis in the guinea pig ileum, and part of their spasmogenic action in this preparation was atropine-sensitive. 4. The results suggest the possible existence of multiple SP receptors, and the specificity of those in the brain may be different from those in the gut. The structural and pharmacological basis for subdividing tachykinins into SP-physalaemin and eledoisin-kassinin families is also discussed.

Animals↗