Mark A. Muhlhauser

LY392098, a novel AMPA receptor potentiator : electrophysiological studies in prefrontal cortical neurons

The present experiments investigated the ability of LY392098, a novel positive allosteric modulator of AMPA receptors, to potentiate AMPA receptor-mediated currents of neurons in the prefrontal cortex (PFC). Co-application of LY392098 (0.03-10 microM) with AMPA (5 microM) enhanced current through AMPA receptor/channels in acutely isolated PFC neurons in a concentration-dependent manner. Estimates of the potency (EC(50)) and efficacy for LY392098 yielded an EC(50) value of 1.7+/-0.5 microM and a maximal potentiation of a 31.0+/-4.1-fold increase relative to current evoked by AMPA alone. The potentiation was activity-dependent, becoming evident only in the presence of agonist, and time-dependent, continuously developing over prolonged application times. An extracellular site of action was inferred by the absence of potentiation when the compound was applied intracellularly. LY392098 also increased the potency of agonist for the receptor by approximately sevenfold. Selectivity assays showed that the effects of LY392098 were exclusive for AMPA receptors, having no activity at N-methyl-D-aspartate (NMDA) receptors in PFC neurons. Extracellular recordings from single PFC neurons in vivo showed that administration of LY392098 (0.001-10 microg/kg, i.v.) enhanced the probability of evoked action potential discharge in response to stimulation of glutamatergic afferents from the ventral subiculum of the hippocampal formation. Spontaneous activity of PFC neurons was also increased. Collectively, these results demonstrate that LY392098 is a highly potent, selective and centrally active positive modulator of native AMPA receptors.

Central muscarinic inhibition of lower urinary tract nociception.

Previous studies indicate cholinergic systems suppress somatic nociception. The present studies determined if cholinergic muscarinic systems suppress visceral nociception, specifically, chemical irritation of the lower urinary tract. Bladders of urethane-anesthetized rats were cannulated through the dome for continuous-infusion cystometrogram recordings. EMG electrodes recorded anal sphincter activity. Infusion of 0.5% acetic acid into the bladder to produce irritation increased bladder activity and anal sphincter activity (i.e. activation of a nociceptive vesicoanal reflex). Oxotremorine (a muscarinic agonist) and (-)butylthio[2.2.2] (a mixed muscarinic agonist/antagonist) dose-dependently inhibited vesicoanal reflex activity. This inhibition was antagonized by atropine (a centrally active muscarinic antagonist) but not by scopolamine methylbromide (a peripherally restricted muscarinic antagonist). Physostigmine (a centrally active cholinesterase inhibitor) also dose-dependently inhibited vesicoanal reflex activity in an atropine-sensitive manner, while neostigmine (a peripherally restricted cholinesterase inhibitor) did not. Atropine alone (i.e. administered without prior administration of muscarinic agonist or cholinesterase inhibitor) produced robust but transient (15 min) increases in vesicoanal activity and bladder activity under conditions of acetic acid infusion into the bladder. Under conditions of saline infusion into the bladder, atropine had the opposite effect on bladder activity (i.e. inhibition). These studies indicate that an endogenous cholinergic muscarinic system can be activated by lower urinary tract irritation to suppress visceral nociception through central nervous system mechanisms.

Discovery of a potent, dual serotonin and norepinephrine reuptake inhibitor.

The objective of the described research effort was to identify a novel serotonin and norepinephrine reuptake inhibitor (SNRI) with improved norepinephrine transporter activity and acceptable metabolic stability and exhibiting minimal drug-drug interaction. We describe herein the discovery of a series of 3-substituted pyrrolidines, exemplified by compound 1. Compound 1 is a selective SNRI in vitro and in vivo, has favorable ADME properties, and retains inhibitory activity in the formalin model of pain behavior. Compound 1 thus represents a potential new probe to explore utility of SNRIs in central nervous system disorders, including chronic pain conditions.

Broad spectrum efficacy with LY2969822, an oral prodrug of metabotropic glutamate 2/3 receptor agonist LY2934747, in rodent pain models

A body of evidence suggests activation of metabotropic glutamate 2/3 (mGlu2/3) receptors would be an effective analgesic in chronic pain conditions. Thus, the analgesic properties of a novel mGlu2/3 receptor agonist prodrug were investigated.

Discovery of dual positive allosteric modulators (PAMs) of the metabotropic glutamate 2 receptor and CysLT1 antagonists for treating migraine headache

Pyridylmethylsulfonamide series were the first reported example of positive allosteric modulators (PAM) of the mGlu2 receptor. The hydroxyacetophenone scaffold is a second series of mGlu2 PAMs we have identified. This series of molecules are potent mGlu2 potentiators and possess significant CysLT1 (cysteinyl leukotriene receptor 1) antagonist activity, showing in vivo efficacy in a dural plasma protein extravasation (PPE) model of migraine. In this paper, we describe the dual SAR, pharmacokinetics and preclinical in vivo efficacy data for a tetrazole containing hydroxyacetophenone scaffold.