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Sensory irritation due to inhalation of a series of alkylamines was estimated from the decrease in respiratory rate in normal (non-cannulated) mice (American standard method E 981–84, 1984). The irritation effects rapidly reached stable levels. The concentration-response relationships followed Michaelis-Menten equations. The maximum response decreased with increasing chain length. The concentrations depressing the respiratory rate by 50% (RD-50) were 184, 121, 97, 51, and 27 p.p.m. for n-propylamine, n-butylamine, n-pentylamine, n-hexylamine, and n-heptylamine, respectively. It is suggested that the receptor is activated partly by the amines and partly by hydroxide ions. The nose has a scrubbing effect, which partly protects the lungs against water soluble irritants. Pulmonary irritation was estimated from the decrease in respiratory rate in tracheally cannulated mice. The plateau-level of the response was reached slowly. The respective concentrations depressing the respiratory rate by 50% (tRD-50) were 416, 300, 128, 66, and 36 p.p.m. for the C3–C7 n-amines. It is suggested that the pulmonary receptor environment is lipophilic and the receptor, probably the J-receptor, is activated chemically by the amines. The sensory and pulmonary irritation data were used to estimate workplace exposure limits (TLV's) which protect against these effects.

The resting efflux of choline from perfused chicken hearts varied from 0.4 to 2.6 nmol/g min, but was constant for at least 80 min in the individual experiments. The rate of choline efflux was found to be equal to the rate of choline formation in the heart, which, from the following reasons, was essentially due to hydrolysis of choline phospholipids. Cardiac content of choline phospholipids (7,200 nmol/g) was much higher than that of acetylcholine (5.5 nmol/g). Resting release of acetylcholine was 0.016 nmol/g min and, after inhibition of cholinesterase, only about 0.1 nmol/g min. Resting efflux of choline was reduced by mepacrine, a phospholipase A2 inhibitor, by perfusion with a Ca2+-free Tyrode's solution containing EGTA and by the combination mepacrine plus Ca2+-free/EGTA solution. In all experiments the reduced choline efflux levelled off within 10 min at about 50%. Omission or elevation of Mg2+ from 1.05 to 10.5 mmol/l had no effect. Resting efflux was increased to 150% by oleic acid (as sodium salt; 2 X 10(-5) mol/l) which is known to activate phospholipase D. Likewise muscarinic agonists (carbachol and acetylcholine) caused facilitation of the efflux of endogenous choline that was blocked by 3 X 10(-7) mol/l atropine. This effect was not reduced, but even slightly enhanced, by mepacrine and by infusion of EGTA in a modified Tyrode's solution (Ca2+-free, 10.5 mmol/l Mg2+). It is concluded that the resting efflux of choline from the heart is essentially due to hydrolysis of choline phospholipids, that half of the efflux is insensitive to mepacrine and is Ca2+-independent (excluding an involvement of phospholipase A2).(ABSTRACT TRUNCATED AT 250 WORDS)

In addition to the beta-1 adrenergic receptor that mediates an increase in cardiac rate and force of contraction, myocardial alpha-1 adrenergic receptors are known to mediate a positive inotropic response with little effect on cardiac rate (Wagner and Brodde, 1978; Shibata et al., 1980). The mechanism by which cardiac alpha-1 adrenergic receptors increase force of contraction has not been established, but it appears not to be associated with accumulation of cyclic AMP or stimulation of adenylate cyclase (Brodde et al., 1978). In this respect, the alpha-1 adrenergic receptors differ from myocardial beta-adrenergic receptors. Another difference between alpha-1 and beta-1 adrenergic receptors in cardiac tissue is the slower onset and washout for alpha-1-mediated responses (Schumann et al., 1975). Electrophysiologic differences resulting from alpha-1 and beta-1 receptor activation have also been observed (Govier et al., 1966; Govier, 1967). Although beta-1 adrrenergic receptor-mediated inotropic responses occur at all rates of contraction, the effect mediated by the myocardial alpha-1 adrenergic receptor is most prominent at low heart rates (Broadley, 1982).

There are no methods available for the direct determination of the concentration of noradrenaline in the “biophase”, i.e., in the very small part of the extracellular space in the immediate neighbourhood of the receptors of adrenergically innervated organs. Hence, any discussion of the factors influencing the concentration of the amine at the receptors has to be based on indirect evidence. If the direct approach is impossible, one can gain some insight from recording responses (or changes in responses) of the effector organ to known concentrations of noradrenaline. However, any interpretation involves two crucial assumptions, namely that, in the absence of conclusive evidence to the contrary, the interaction between drug and receptor as well as the function of the link between receptor activation and eventual response remains unaffected by the change in experimental conditions which is being studied. In many experimental situations the validity of these assumptions remains questionable, since it has not been possible to obtain positive evidence.

Phosphotyrosine signaling plays a vital role in cell regulation—from receptor activation, through stimulation of signal networks and nuclear targeting, to final cellular responses. Here, we propose a new approach to monitor the spatial and temporal aspects of tyrosine phosphorylation and dephosphorylation. The method can be used to determine whether protein tyrosine phosphorylations and dephosphorylations occur in the cytosol or the nucleus and to ascertain whether such modifications are associated with nuclear traffic. Promyelocytic leukemia (HL-60) cells are used as the experimental model. Biotinylated cytosolic proteins from donor cells are used to trace nuclear transport in permeabilized recipient cells. Thereafter, 2-D gel electrophoresis is applied to fractionate the cytosolic and nuclear proteins of the recipient cells, which are subsequently blotted onto polyvinylidene difluoride membranes. The membranes are developed with streptavidin and then reprobed with anti-phosphotyrosine antibodies. The major advantages of the protocol are that it is simple to perform, and reproducible results are obtained by overlaying the patterns of biotinylated and/or tyrosine-phosphorylated proteins. Moreover, several hundred cytosolic and nuclear proteins can be analyzed in parallel. Thus, by comparing the 2-D gel electrophoresis maps of biotinylated and tyrosine-phosphorylated proteins, it is possible to determine the involvement of trafficking of the latter proteins in cell signaling.

We study the mathematical solutions to the kinetic equations arising from various simple ligand-receptor [corrected] models. Focusing on the prediction of the various models for the activity vs. concentration curve, we find that solutions to the kinetic equations arising from the so-called dimer model exhibit features observed in some experiments, most noticeably a distinct maximum in the activity curve.

A stably-transfected, Drosophila cell line (S2-DMl-1) expressing the Drosophila DMl muscarinic acetylcholine receptor (mAChR) exhibits high-affinity, saturable, specific binding of the radiolabelled muscarinic antagonist [3H]-N-methyl scopolamine ([3H]-NMS) with an equilibrium dissociation constant (Kd) of 0.67 +/- 0.02 and a Bmax of 1.53 +/- 0.3 pmol/mg protein. Displacement of [3H]-NMS by mAChR antagonists results in the pharmacological profile: 4-diphenylacetoxy-N-methylpiperidine methiodide (4-DAMP)hexahydrosiladifenidolp-fluorohexahydrosiladifenidolnitrocaramiphenpirenzepinemethoctramineAFDX-116. This antagonist profile most closely resembles that of the vertebrate M3 mAChR subtype. In this study, however, we have demonstrated that the antagonist profile of DM1 is distinct from those of vertebrate mAChR subtypes. Molecular dynamic simulations of the Drosophila muscarinic receptor are presented in the free, carbamylcholine-bound and NMS-bound forms. Theoretical, quantitative structure-activity relationship models have been developed; a good correlation is observed between the interaction energies of the minimized ligand-receptor complexes and the pharmacological affinities of the antagonists tested.

Article abstract To investigate the sensory nerve responses to selective touch stimulation, sensory nerve action potentials after brief air-puffs were recorded with a microelectrode. In patients with peripheral neuropathy, those with impairment of tactile sensations had significantly smaller responses than did those without tactile impairment, suggesting receptor activation failure as well as nerve conduction failure. Brief air-puff stimulation, when combined with microneurography, could be used for evaluating the tactile receptor properties in humans.

Vasopressin antagonists1–7 are valuable pharmacological tools for investigating physiological and behavioural functions of the nonapeptide arginine-vasopressin (AVP)8,9. The removal of glycinamide from the carboxy terminus of AVP drastically reduces its characteristic vasopressor and antidiuretic activities10. In contrast to this we show here that removal of the carboxy-terminal glycinamide or the glycine at position 9 from several vasopressin antagonists makes little difference to their ability to block vasopressor and antidiuretic responses to AVP. These data demonstrate the critical structural requirements of the carboxy-terminal position for receptor activation, in contrast to the lack of such requirements for receptor binding. They also provide an avenue to a wide variety of antagonists substituted at the carboxy terminus (for example radiolabelled derivatives and affinity ligands) and suggest clues for the development of more potent and/or selective antagonists.

The VAPB/ALS8 major sperm protein domain (vMSP) is implicated in amyotrophic lateral sclerosis and spinal muscular atrophy, yet its function in the nervous system is not well understood. In C. elegans and Drosophila, the vMSP is cleaved from its transmembrane anchor and secreted in a cell type-specific fashion. We show that vMSPs secreted by neurons act on Lar-like protein-tyrosine phosphatase and Roundabout growth cone guidance receptors expressed in striated muscle. This signaling pathway promotes Arp2/3-dependent actin remodeling and mitochondrial localization to actin-rich muscle I-bands. C. elegans VAPB mutants have mitochondrial localization, morphology, mobility, and fission/fusion defects that are suppressed by Lar-like receptor or Arp2/3 inactivation. Hence, growth cone guidance receptor pathways that remodel the actin cytoskeleton have unanticipated effects on mitochondrial dynamics. We propose that neurons secrete vMSPs to promote striated muscle energy production and metabolism, in part through the regulation of mitochondrial localization and function.

Whereas μ receptor activation reduces spinal responses to most peripheral nociceptive stimuli, κ and σ receptor activation can have differential effects between various types of nociceptive stimulus. This has led us to start a comparative study of μ (fentanyl), κ (U-50,488H) and σ (ketamine) preferring agonists on spinal nociceptive and other responses.

Glucagon-like Peptide-1 (GLP-1) is essential for normal glucose tolerance and evidence suggests that it has anti-apoptotic and cytoprotective actions. Liraglutide is a GLP-1 receptor (GLP-1r) agonist used for the treatment of Type 2 diabetes, and may also confer clinical benefits through cardiac GLP

Results: Exenatide pigs showed higher PFR (0.3 ± 0.04 vs. 0.2 ± 0.1 mL/s, p < 0.05), shorter nTPFR (9.6 ± 0.9 vs. 7.4 ± 1.9, p < 0.05) and larger irst illing volume (33.9 ± 5.1 vs. 24.31 ± 4.09mL, p < 0.05). These MRI indings were supported by our echocardiography results; Exenatidetreated animals showed greater color M-mode propagation velocities (32.9 ± 2.5 vs. 25.7 ± 6.05cm/s, p < 0.05) and improved myocardial performance index (0.53 ± 0.03 vs. 0.69 ± 0.1, p < 0.05), compared to placebo. There were no differences in LV end-diastolic pressure or pulmonary capillary wedge pressure between Exenatide treatment and placebo. There was a signiicant inverse correlation between irst illing volume and histomorphometric measures of cardiomyocyte hypertrophy (r=-0.72, p

Glutamatergic synaptic transmission mediated by the N-methyl-D-aspartate (NMDA) receptor plays a fundamental role in numerous central nervous system processes, but how the receptor becomes active is insufficiently understood. Structural studies of isolated ligand-binding domains (LBDs) revealed that agonists bind between two flexible lobes (D1 and D2) and by causing the lobes to move closer together initiate the activation reaction. In many cases, the efficacy of the agonist correlates with how narrow the cleft becomes and/or how stable the closed-cleft conformation is. In NMDA receptors, full-agonists induce cleft-closure and the formation of new stabilizing electrostatic interactions across the lobes of soluble LBDs. However, how these interactions contribute to the kinetics of NMDA receptors is not known. To evaluate the roles of putative cross-cleft interactions to the activation mechanism of intact receptors, we eliminated these salt bridges in individual subunits and quantified their effect on gating by kinetic analyses of single channel traces. We were surprised to find that: receptors containing GluN1(K483A) and GluN2A(K487A) had activities that were ∼10% higher than wild-type controls; receptors containing GluN1(K483M) had wild-type activity; and those containing GluN2(N687L) had activities that were ∼30% lower than controls. These results suggest that at these positions, residue-size as well as the ability to form cross-cleft interactions affect the gating process. They also reveal subtle distinctions between how residues in the GluN1 and GluN2A LBDs contribute to gating.