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Natural and synthetic methylxanthines inhibit insect feeding and are pesticidal at concentrations known to occur in plants. These effects are due primarily to inhibition of phosphodiesterase activity and to an increase in intracellular cyclic adenosine monophosphate. At lower concentrations, methylxanthines are potent synergists of other pesticides known to(More)
Secretion of cerebrospinal fluid by the choroid plexus can be inhibited by its cholinergic innervation. We demonstrated that carbachol inhibits the Na(+)-K(+)-ATPase in bovine choroid tissue slices and investigated the mechanism. Many of the actions of cholinergic agents are mediated by nitric oxide (NO), which plays important roles in fluid homeostasis.(More)
Although cocaine has a fascinating and complex medicinal history in man, its natural function in plants is unknown. The present studies demonstrate that cocaine exerts insecticidal effects at concentrations which occur naturally in coca leaves. Unlike its known action on dopamine reuptake in mammals, cocaine's pesticidal effects are shown to result from a(More)
The molecular mechanisms underlying regulation of fluid production by secretory epithelia such as the choroid plexus are poorly understood. Two cAMP-regulated inhibitors of protein phosphatase-1, inhibitor-1 (I1) and a dopamine- and cAMP-regulated phosphoprotein, M(r) = 32,000 (DARPP-32), are enriched in the choroid plexus. We show here that these two(More)
The physiologic mechanism that underlies the epinephrine-induced increase in facility of outflow (C) in glaucomatous human eyes and normal primate eyes is not completely understood. In this study, a recently developed in vitro human eye perfusion model was used to simultaneously monitor facility and cyclic adenosine monophosphate (AMP) changes in response(More)
Octopamine receptors in the nervous tissue of insects were investigated using a ligand-receptor assay with [3H]NC-5Z or [3H]octopamine as the radioligands. Both ligands recognized a homogeneous class of binding sites with the properties of an octopamine receptor. This receptor has been characterized pharmacologically. Both high-affinity agonists (e.g. NC 7,(More)
Atriopeptins are a recently-discovered group of polypeptides secreted from cardiac myocytes in response to fluid overload. The present studies demonstrate that atriopeptin receptors, coupled to the activation of guanylate cyclase, are present in rabbit ciliary process. Rat atrial natriuretic peptide 1-28 (rANP) activated ciliary process guanylate cyclase(More)
Previous studies utilizing relatively nonselective octopamine (OA) agonists have suggested that differences may exist between the pharmacological responses of Gs-linked OA receptors found in various insect tissues and species. The present experiments identify and characterize two structurally related phenyl(imino)imidazolidine (PII) derivatives that(More)
Octopamine, a major aminergic neurotransmitter in invertebrates, exerts many of its actions through receptors which are associated with the activation of adenylate cyclase. The present study defines and characterizes a new class of potent octopamine agonists, the substituted phenyliminoimidazolidines (PIIs). Approximately 30 of these derivatives were(More)