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Robert B Raffa

Publications and source records attributed to Robert B Raffa.

29 records · Page 2Linked to original sources
PubMed2003

Mechanism of action of analgesics used to treat osteoarthritis pain.

Acute pain is a normal, and often beneficial, physiologic process. The indiscriminant blocking of all pain can delay healing or mask serious medical problems. On the other hand, persistent pain can be nonproductive or deleterious to recovery and can negatively affect a patient's quality of life. If the treatment of pain by pharmacologic means is determined to be desirable, it is important to select an analgesic, or combination of analgesics, that have appropriate mechanisms of action (i.e., those that modulate the appropriate physiologic pathway). OA pain is an example of a complex type of pain (i.e., it often originates from multiple causes and is transmitted by multiple mediators). Therefore, the choice of the analgesics for the patient who has OA should be based upon the most appropriate mechanisms of action.

Analgesics↗
PubMed2003

Combination strategies for pain management.

At least two factors relating to pain management using oral analgesics suggest that combination strategies merit consideration: many pains arise from more than one physiological cause and current analgesics have adverse effect profiles that might be reduced by combination with another agent in smaller doses or with less frequent dosing. In addition to increased convenience, combinations sometimes also result in the unexpected benefit of synergy. But not all pains, clinical settings or combinations merit the extra expense or other potential negative features of fixed-ratio products. This review examines the multiple basic science, clinical and pharmacoeconomic issues relating to analgesic combinations and the methodologies available for assessing these issues.

Analgesics, Opioid↗
PubMed2002

Harmonic mean relationship between affinity for wild-type receptors and alanine-scan mutants.

Alanine-scanning mutagenesis involves systematic substitution of a single alanine for other amino acid constituents of a ligand or receptor protein. The sequential process generates a discrete set of "mutant" proteins, each member of which differs from the native 'wild-type' receptor (R(wt)) or ligand by the single amino acid (alpha) substitution with alanine (R(Ala)). The Ala mapsto alpha substitutions are made for amino acids suspected of being important for binding of ligand to receptor. Binding assays are then used to measure the affinity for R(wt) and mutants, quantified by the ligand-receptor equilibrium constant (K(eq)) or its reciprocal, the dissociation constant (K(d)=1/K(eq)). However, the relationship betweenR(wt)K(d) and R(Ala)K(d) values is not obvious. Neither the arithmetic mean nor the geometric mean (based on a simplified relationship between K(d) and the thermodynamic standard free energy change) of the R(Ala)K(d) values turns out to be adequate. The harmonic mean was found to be a good estimator when applied to the published data from 14 alanine-scan studies. This result is consonant with the present understanding of ligand-receptor interactions.

Alanine↗
PubMed2002

Toward RNase inhibitors: thermodynamics of 2'-CMP/RNase-A binding in multi-ion buffer.

Certain ribonucleases (RNases), such as eosinophil-derived neurotoxin, are associated with pathological conditions (e.g. asthma and inflammatory bowel disease) and can even be overtly cyto(neuro)toxic. It has been proposed that small-molecule inhibitors should have therapeutic utility. We used isothermal titration microcalorimetry to characterize reversible inhibitor cytidine 2'-monophosphate (2'-CMP) binding to RNase-A in a multi-ion buffer at 37 degrees as a representative system. The estimated parameters were: K(d)=13.9 microM; DeltaG degrees =-6.90 kcal/mol; DeltaH degrees =-15.7 kcal/mol; and DeltaS degrees =-0.028 kcal/mol-K ('enthalpy-driven' interaction). These data should assist drug design of small-molecule inhibitors of homologous RNase catalytic domains.

Animals↗
PubMed2002

Indirect modulation of dopamine D2 receptors as potential pharmacotherapy for schizophrenia: III. Retinoids.

Present antipsychotic drugs, whose clinical activity correlates with direct binding to dopamine D2 or other receptors, alleviate some of the symptoms of schizophrenia, but not all and not completely in many patients. In continuation of our overview of potential novel antipsychotic pharmacotherapy that would be based upon indirect modulation of dopamine or other neurotransmitter functioning, we focus in this article on the postulated use of retinoid analogs as novel antipsychotic agents. Several lines of evidence can be viewed as implicating retinoid dysregulation in schizophrenia, either as a causative or contributory factor. It has been proposed that using retinoid analogs to alter the downstream expression of dopamine D2 receptors might represent a novel approach to the treatment of the disease or amelioration of symptoms when used either as monotherapy or as adjunct pharmacotherapy to dopamine D2 receptor antagonists.

Antipsychotic Agents↗
PubMed2002

Toward the design of ribonuclease (RNase) inhibitors: ion effects on the thermodynamics of binding of 2'-CMP to RNase A.

Ribonucleases (RNases) possess a variety of biological activities and, under certain conditions, are deleterious. Hence, design of selective inhibitors has been suggested as a strategy for treating RNase-related disorders. In the present study, isothermal titration calorimetry was used to measure ion effects on binding thermodynamics of the RNase A competitive inhibitor 2'-CMP as a representative system. The reaction cell (37 degrees C) contained dialyzed RNase A (0.04-0.05 mM) in buffered solution (pH 5.5) of 50 mM Na(+), K(+), Ca(2+), or Mg(2+) acetate, verified spectrophotometrically. Thirty-five sequential injections (4 microl each, 3 min apart) were made of 2'-CMP (1.2 mM) in ion-matching buffer. The data were corrected for heat of dilution. There was a 1:1 interaction in each case. The estimated parameters (+/-S.D.) were: K(d) = 4.84 +/- 0.29 microM (Na(+)); 5.62 +/- 0.98 microM (K(+)); 24.44 +/- 6.96 microM (Ca(2+)); 28.74 +/- 0.43 microM (Mg(2+)); DeltaG(o) = -7.541 +/- 0.037 kcal/mol (Na(+)); -7.458 +/- 1.03 kcal/mol (K(+)); -6.574 +/- 0.173 kcal/mol (Ca(2+)); -6.442 +/- 0.009 kcal/mol (Mg(2+)); DeltaH(o) = -22.357 +/- 1.189 kcal/mol (Na(+)); -21.917 +/- 0.891 kcal/mol (K(+)); -20.223 +/- 1.503 kcal/mol (Ca(2+)); -26.570 +/- 1.579 kcal/mol (Mg(2+)); and DeltaS(o) = -0.048 +/- 0.004 kcal/mol-K (Na(+)); -0.047 +/- 0.003 kcal/mol-K (K(+)); -0.044 +/- 0.005 kcal/mol-K (Ca(2+)); -0.065 +/- 0.005 kcal/mol-K (Mg(2+)). Thus, all reactions were enthalpy-driven. Despite a 5-fold difference in K(d) between mono- and divalent ions, the ratio of ion hydration DeltaG(o) to K(d) was constant. These data should be useful for molecular modeling and suggest that inhibitor activity will be a function of cellular conditions (normal or pathological).

Animals↗
PubMed2002

LiCl attenuates M(1)AChR-mediated intrathecal pilocarpine-induced reciprocal hindlimb scratching in mice.

Pretreatment of mice with a subcutaneous (s.c.) injection of LiCl (1, 3, 10 mmol/kg) 18 h prior to testing produced dose-related attenuation of the reciprocal hindlimb scratching (RHS) response induced by intrathecal (i.t.) administration of pilocarpine. LiCl (10 mmol/kg, 424 mg/kg) pretreatment shifted the pilocarpine (2 microg)-induced RHS dose-response curve about 5-fold to the right compared to vehicle-injected controls (ED(50) = 2.97 and 0.56 microg, respectively). Coadministration of inositol-1,4,5-trisphosphate (IP(3); 5, 10, 20 microg), but not inositol hexaphosphate (0.03-3 microg), myo-inositol (10 microg) or EDTA (1.33 microg), produced dose-related reversal of the LiCl effect. IP(3) administration alone neither produced RHS nor enhanced the pilocarpine-induced RHS in animals not pretreated with LiCl. These findings provide in vivo evidence for a possible link between RHS and a LiCl-sensitive, possibly phosphoinositide-related, effector pathway.

Animals↗
PubMed1999

Synergistic antiallodynic effects of spinal morphine with ketorolac and selective COX1- and COX2-inhibitors in nerve-injured rats.

The possible role of spinal prostanoids in the tactile allodynia and thermal hyperalgesia associated with an experimental model of neuropathic pain was investigated. Neuropathic pain was induced by tight ligation of the L5 and L6 spinal nerves. Tactile allodynia was assessed 7 days after the surgery by measuring hindpaw withdrawal threshold to probing with von Frey filaments. Thermal hyperalgesia and nociception were determined by the 52 degrees C warm-water tail-flick test and by applying radiant heat to the plantar aspect of the hindpaw ipsilateral to the ligation. Minimal antiallodynic effect was produced by intrathecal (i.th.) administration of ketorolac or morphine up to the highest testable dose (100 microg) or by the (R)- or (S)-enantiomers of ketorolac (up to 6 microg) when administered alone. However, i.th. administration of a fixed ratio (1:1) of morphine plus racemic ketorolac or of morphine plus the (S)-enantiomer of ketorolac (S-ketorolac) produced a dose- and time-related antiallodynic effect: ED50 114 +/- 35.9 microg (total dose) for morphine plus ketorolac and 70.5 +/- 21.0 microg (total dose) for morphine plus S-ketorolac. The combination of i.th. morphine plus the (R)-enantiomer of ketorolac (R-ketorolac) (up to 200 microg total dose) was without effect. Similar antiallodynic activity was obtained for the co-administration of i.th. morphine and intravenous (i.v.) racemic ketorolac. In order to investigate the role of cyclooxygenase (COX) isozymes, relatively selective COX1 (piroxicam) and COX2 N-[2-cyclohexyloxy-4-nitrophenyl] metanesulfonamide (NS-398) inhibitors were administered i.th. (60 microg) alone or together with i.th. morphine. Piroxicam, NS-398, morphine and vehicle (90% DMSO) were without significant antiallodynic effect when administered alone, but moderate antiallodynic effects were produced by i.th. administration of fixed ratio (1:1) combinations of morphine with 60 microg each (highest soluble dose) of piroxicam (%MPE = 40.8 +/- 10.2) or NS-398 (%MPE = 32.4 +/- 9.5). Further, the combined i.th. administration of morphine, piroxicam and NS-398 in fixed 1:1:1 ratio (60 microg each) resulted in a supraadditive antiallodynic effect (%MPE = 70.4 +/- 10.8). Finally, morphine, but not ketorolac, given i.th. produced dose-dependent anti nociception in either the tail-flick or the paw-flick tests. However, there was no synergy between morphine and ketorolac against thermal nociception in either of the tests. These findings suggest that spinal prostanoids produced via both COX1 and COX2 pathways may play a role in neuropathic pain states and suggest the clinical utility of opioid plus COX-inhibitor combination therapy.

Analgesics, Opioid↗
PubMedDate not supplied

A reverse-phase HPLC and fluorescence detection method for measurement of 5-hydroxytryptamine (serotonin) in Planaria.

INTRODUCTION: Planaria have proven to be a good model system in which to investigate mammalian behaviors and responses to drugs. We have recently studied the response of planarians to dopaminergic ligands and to the effects of cocaine and opioids. To correlate behavior (specifically, drug withdrawal) with neurotransmitter levels, we developed a method to quantify 5-hydroxytryptamine (5-HT; serotonin) in planarians. METHODS: Following the homogenization of planarians in aqueous solvent (perchloric acid, L-cystine, and Na(2)EDTA) and centrifugation of supernatant (14,000 x g at 4 degrees C for 20 min), 5-HT was measured using HPLC (aqueous citric acid buffer mobile phase; 5-microm C(18) column with fluorescence detection, 280/340 nm). N(omega)-methyl-5-HT was used as an internal standard (IS). RESULTS: 5-HT was rapidly extracted and conveniently measured from the planarians. The detection limit of the procedure (0.35 ng) was below the amount of 5-HT in one animal. DISCUSSION: The ability to measure neurotransmitter levels provides a methodological opportunity to correlate behavior with biochemical changes in planarians and to extend behavioral observations to intracellular transmitter and second messenger transduction pathways.

Animals↗