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Biomedical subjects

R B Raffa

Publications and source records attributed to R B Raffa.

At least 109 records · Page 6Linked to original sources
PubMed1989

In vivo demonstration of the enhancement of MK-801 by L-glutamate.

MK-801 infused bilaterally into the nucleus accumbens of rats produced a dose-related increase in locomotor activity that was not blocked by intra-accumbens infusion of haloperidol (2.5 micrograms). Intra-accumbens infusion of L-glutamate (1.0 microgram) was without effect when administered alone, but significantly enhanced the increase in locomotor activity produced by MK-801 (5.0 micrograms). The inactive isomer of MK-801 did not produce hypermotility and L-glutamate did not enhance amphetamine(intra-accumbens)-induced hypermotility. These results extend to an in vivo model electrophysiological and radioligand binding studies demonstrating an enhancement of MK-801 activity by L-glutamate. The results also reinforce the concept that such an enhancement would occur during an escalation of excitatory amino acid levels accompanying pathological overload and, thus, would trigger a compensatory neuronal protection by MK-801.

Animals↗
PubMed1989

Obligatory role of B cells and adherent accessory cells in the transfer of a defect in morphine-mediated antinociception in C57BL/6J-bg/bg (beige-J) mice.

C57BL/6J-bg/bg (beige-J) mice have a blunted antinociceptive response to intracerebroventricularly (i.c.v.) injected morphine in the tail-flick test. Beige-J mice are also immunologically defective and exhibit the pathology of Chediak-Higashi syndrome (CHS). We transferred by i.v. injection 2 x 10(7) mononuclear spleen cells, devoid of PMNs, obtained from beige-J mice to normal C57BL/6J-bg/+ littermates that do not exhibit CHS or a blunted antinociceptive response to morphine. After 8 days, the normal littermates demonstrated significant (P less than 0.05) reduction in their analgesic responsiveness to morphine. This phenomenon was found to require B-cells and adherent cells in the adoptively transferred spleen cells. B-cells that had been purified by panning on anti-Ig-coated plates were sufficient to transfer the analgesic defect unless adherent cells were removed prior to immunocytoadherence. T-cells, in the presence or absence of adherent cells, failed to transfer the decreased sensitivity to morphine. These results demonstrate a novel neuroimmune interaction whereby B-lymphocytes and adherent cells, or a substance derived from them, are able to affect the antinociceptive action of morphine.

Animals↗
PubMed1989

Can equal pA2 values be compatible with receptor differences?

Situations exist in which pA2 analysis leads to conclusions about receptor differentiation that conflict with those drawn from other convincing lines of evidence. Robert Raffa and colleagues address this issue in its broadest context, particularly in relationship to the concept of accessory binding sites, using the controversy of delta-opioid receptor-mediated antinociception as an example. When the possibility of accessory binding sites is considered, it becomes clear that the finding of equal pA2 values does not necessarily mean action at the same receptor, and that the finding of unequal pA2 values does not necessarily confirm action at different receptors.

Chemical Phenomena↗
PubMed1988

Reciprocal hindlimb scratching and putative subtype-selective muscarinic agents.

We have previously proposed that the reciprocal hindlimb scratching (RHS) of mice elicited by intrathecal injection of muscarinic agents is mediated by M1 muscarinic receptors. In this study, benzhexol potently inhibited pilocarpine-induced RHS (ID50 = 0.5 ng), methoctramine did not fully block RHS and RS 86 neither produced nor blocked RHS. These data (1) differentiate the three muscarinic agents using this in vivo endpoint, (2) substantiate binding studies characterizing benzhexol and methoctramine as putative M2 and M2 antagonists, respectively, and (3) further support using RHS for studying muscarinic agents.

Animals↗
PubMed1988

Mu-, but not delta-, opioid receptor-mediated antinociception in mice is attenuated by gamma-irradiation.

Mice were exposed to whole-body irradiation (500 rads) from a 137Cs gamma-source and tested 2 h later for antinociception (tail-flick test) produced by intracerebroventricular administration of morphine or the more delta-selective opioid peptide, [D-Pen2,L-Pen5]enkephalin (DPLPE). Irradiation significantly attenuated the antinociception produced by morphine, but not by DPLPE. These results demonstrate a differential sensitivity of mu- and delta-opioid receptors to gamma-irradiation and, in addition, may be of clinical relevance for cancer patients receiving concurrent radiation therapy and opioid analgesics.

Analgesics↗
PubMed1988

The analgesic defect of C57BL/6J-bgJ/bgJ (beige-J: Chediak-Higashi syndrome) mice transmitted by adoptive transfer of spleen cells to normal littermates.

We recently discovered and reported that C57BL/6J-bgJ/bgJ (beige-J) mice have a deficiency in their analgesic response to intracerebroventricularly-administered morphine in the tail-flick test. Postulating a link between these findings and the known immunological defect of beige-J mice (Chediak-Higashi syndrome), we examined the effect of splenectomy on beige-J mice and the adoptive transfer of their mononuclear spleen cells to normal littermate controls (2 x 10(7) cells via tail vein). Eight days after these interventions, the splenectomized beige-J mice responded nearly as well as normal mice to centrally administered morphine in the tail-flick test. The adoptive transfer recipients, in contrast, nearly completely lost their response to the analgesic action of morphine in this test. From the combined results, the spleen appears to be a significant factor in the analgesic defect of beige-J mice and, furthermore, mononuclear splenocytes appear to be the source of a substance that can transfer this defect to otherwise normal animals.

Analgesia↗
PubMed1988

Examination of the involvement of supraspinal and spinal mu and delta opioid receptors in analgesia using the mu receptor deficient CXBK mouse.

The role of mu and delta opioid receptors in the spinal and supraspinal analgesic actions of morphine and [D-Pen2, L-Pen5] enkephalin were examined in the tail-flick test utilizing the mu opioid receptor deficient CXBK mouse and BALB/cBy and C57BL/6By, the progenitor strains of CXBK. The analgesic effects of i.c.v. administered morphine were equivalent in the CRS-CD1 (Swiss) standard laboratory mice and the progenitor strains of CXBK. Morphine did not, however, produce analgesia in the CXBK mice at doses greater than 10 times the ED50 dose in the progenitor strains. Similarly, the analgesic effect of i.c.v. [D-Ala2, NMePhe4, Gly-ol]enkephalin, a highly selective mu receptor peptide agonist, also was reduced greatly in the CXBK mice. These data are consistent with the deficiency in mu opioid receptors observed autoradiographically in this strain. In contrast, the highly selective delta opioid receptor peptide agonist [D-Pen2, L-Pen5]enkephalin was equipotent i.c.v. in the CXBK mice and in the progenitor strains of CXBK. In contrast to the effects produced by i.c.v. administration, the analgesic effects of intrathecally administered morphine were similar between CRS-CD1 and CXBX strains of mice. These results suggest that 1) both mu and delta opioid receptors can mediate supraspinal analgesia and 2) that the receptor(s) involved in spinally mediated analgesia is (are) quite distinct from those involved supraspinally.

Analgesia↗
PubMed1987

The effect of Phe-Met-Arg-Phe-NH2 (FMRFamide) on morphine-induced inhibition of colonic propulsive motility in mice.

Morphine and the molluscan neuropeptide Phe-Met-Arg-Phe-NH2 (FMRFamide) were administered to mice alone or in combination intracerebroventricularly (i.c.v.) and the effect on colonic propulsive motility was measured. Both morphine (1.0 microgram, i.c.v.) and FMRFamide (10 and 50 micrograms, i.c.v.) delayed expulsion of a 3 mm glass bead placed in the distal colon of mice compared to vehicle-treated controls. The inhibitory effects of morphine and FMRFamide on expulsion time were additive at the doses used and individually blocked by naloxone. These data suggest that FMRFamide does not antagonize this nonanalgesic effect of morphine, but appears to have opioid agonist properties.

Animals↗
PubMed1987

Colonic bead expulsion time in normal and mu-opioid receptor deficient (CXBK) mice following central (ICV) administration of mu- and delta-opioid agonists.

A method utilizing the insertion of a 3 mm glass bead into the distal colon was used to evaluate the activity of intracerebroventricularly (ICV) administered mu- and delta-opioid agonists on colonic bead expulsion time in mice. Specifically, the ability of two mu-opioid receptor agonists, morphine and [D-Ala2,NMePhe4, Gly-ol5]-enkephalin (DAGO) and a selective delta-opioid receptor agonist, [D-Pen2,L-Pen5]-enkephalin (DPLPE), to inhibit colonic bead expulsion time was measured in normal (Swiss) and mu-opioid deficient (CXBK) mice. All three compounds maximally inhibited colonic bead expulsion time in normal mice. All three compounds also inhibited colonic bead expulsion time in CXBK mice, but none maximally. These results are in contrast to previous work in which clear differential analgesic sensitivity of CXBK mice to centrally administered mu- and delta-opioid receptor agonists was observed in the tail-flick test. Taken together, the results suggest (a) that mu-, and possibly delta-, opioid receptors can mediate supraspinal inhibition of colonic bead expulsion in mice and (b) that the genetic deficits of mu-receptor number or genetically-induced alteration in receptor function in CXBK mice do not equally affect inhibition of colonic bead expulsion and tail-flick antinociception.

Animals↗
PubMed1987

Evidence that reciprocal hindlimb scratching elicited in mice by intrathecal administration of muscarinic agonists is mediated through M1 type receptors.

Intrathecal (IT) administration of pilocarpine to mice produces a vigorous and dose-related reciprocal hindlimb scratching (RHS) response (ED50 = 0.6 microgram) that is potently blocked by simultaneous IT administration of atropine (ID50 = 0.002 microgram). We now report that RHS is (1) also elicited by the more selective M1 agonist McN-A-343-11 (ED50 = 11.6 micrograms), (2) blocked by the selective M1 antagonist pirenzepine (ID50 = 0.001 microgram), and (3) is not blocked by the selective M2 antagonist AF-DX 116 BS at a dose up to 100 times the ID50 dose of pirenzepine. These results extend our earlier findings and suggest that the RHS elicited in mice by IT injection of muscarinic agonists is mediated through pirenzepine-sensitive (presumably M1) receptors and that RHS may be a convenient in vivo centrally mediated M1 endpoint.

(4-(m-Chlorophenylcarbamoyloxy)-2-butynyl)trimethy↗
PubMed1987

Restoration of analgesic response of C57BL/6J-bgJ (beige-J) mice to morphine by carbachol.

C57BL/6J-bgJ (beige-J) mice respond poorly to the analgesic effects of centrally administered (intracerebroventricular; i.c.v.) morphine in the tail-flick test. In the present study C57BL/6J-bgJ mice, their littermate (heterozygous) controls, and normal Swiss mice were given carbachol (200 micrograms/ml) in their drinking water for three weeks. Carbachol had no effect on control animals. However, the carbachol-treated beige-J mice responded to i.c.v.-administered morphine (1 microgram) significantly better than untreated beige-J mice and nearly as well as the normal mice.

Animals↗
PubMed1987

C57BL/6J-bgJ (beige) mice: differential sensitivity in the tail flick test to centrally administered mu- and delta-opioid receptor agonists.

The antinociceptive effects of two mu-opioid receptor agonists, morphine and [D-Ala2, MePhe4, Gly-ol5]enkephalin (DAGO), and a selective delta-receptor agonist, [D-Pen2, L-Pen5]enkephalin (DPLPE), were determined in C57BL/6J-bgJ (beige) and control mice (CRS-CDl and C57BL/6By) using a standard tail-flick assay. The antinociceptive response of C57BL/6J-bgJ mice to intracerebro-ventricularly administered morphine and DAGO was significantly reduced compared to controls, but there was no difference in the antinociceptive response to DPLPE. These results suggest that there is a genetic deficit of mu-opioid receptor number or a genetically-induced alteration in receptor function in regions of C57BL/6J-bgJ brains involved in antinociception, that delta-opioid receptors can mediate antinociception in mice, and that the C57BL/6J-bgJ strain may offer a practical new animal model for studying the function of opioid receptor subtypes.

Animals↗
PubMed1987

Pilocarpine-induced reciprocal hindlimb scratching in mice.

Intrathecal (IT) administration of pilocarpine (0.25-2.0 micrograms) to mice produced a vigorous and dose-related reciprocal hindlimb scratching response that lasted for 10-15 minutes. Neither the intracerebroventricular administration of pilocarpine at up to 10 times the intrathecal ED90 dose nor the subcutaneous administration of 10 mg/kg pilocarpine caused as robust an effect as IT administration. The reciprocal hindlimb scratching produced by the ED90 dose of pilocarpine (2 micrograms, IT) was antagonized in a dose-related manner by simultaneous IT administration of atropine (ID50 = 0.002 micrograms), methysergide (ID50 = 1.89 micrograms), the substance P antagonist [D-Pro2,D-Trp7,9]-SP (ID50 = 4.94 micrograms), and the putative neurokinin B antagonist [D-Pro2,D-Trp6,8,Nle10]-NK (ID50 = 3.33 micrograms), but not by yohimbine (5 micrograms), phentolamine (2 micrograms), or naloxone (2.5 micrograms). These results suggest that pilocarpine-induced reciprocal hindlimb scratching is mediated spinally, that the effect is produced by an action of pilocarpine on muscarinic receptors in the spinal cord, and that neurokinin, and perhaps 5-HT, mechanisms might also be involved.

Animals↗
PubMed1987

Reversible inhibition of acetylcholine contracture of molluscan smooth muscle by heavy metals: correlation to Ca++ and metal content.

The present study examined the effects of three heavy metals on the acetylcholine (ACh) contracture and Ca++ kinetics of the anterior byssus retractor muscle of Mytilus edulis. An isolated tissue bioassay using anterior byssus retractor muscle was prepared according to standard procedures and the isometric tension produced in response to ACh was measured. Ten millimolar Ni++, Co++ or Cd++ reduced the maximum contracture response to ACh in zero-Ca medium in a time-dependent manner. The inhibition was reversed upon restoration of medium containing 10 mM Ca++. The loss (and re-establishment) of contracture response to ACh corresponded to the influx (and efflux) of the heavy metal ions opposite to the direction of Ca++ flow. These results are consistent with the concept that the loss of the ACh contracture response is attributable to the displacement of tissue Ca++ from release sites by heavy metals.

Acetylcholine↗
PubMed1986

Evidence for a role of conditioning in the development of tolerance to morphine-induced inhibition of gastrointestinal transit in rats.

Groups of rats were administered s.c. saline or morphine for 14 consecutive days and received morphine, saline or no treatment on day 15. Significant and consistent environmental cues were established through the treatment and test periods. Transit of a charcoal meal along the gastrointestinal tract, measured on day 15, was significantly greater in rats conditioned to daily morphine, followed by saline on day 15, than in any other group. This enhanced transit was approximately equal in magnitude to the amount of developed tolerance to morphine. These results support the hypothesis that tolerance to opiates may be partly explained by a compensatory conditioned physiological response opposing the acute effect.

Animals↗
PubMed1986

Intrathecal FMRFamide (Phe-Met-Arg-Phe-NH2) induces excessive grooming behavior in mice.

The molluscan neuropeptide Phe-Met-Arg-Phe-NH2 (FMRFamide) was administered intrathecally (i.t.) to mice and their behavior was monitored for 30 min. FMRFamide induced a dramatic and dose-related (5-12 micrograms) increase in grooming-related activities compared to saline-treated controls. The grooming behavior produced by 8 micrograms FMRFamide was not blocked by simultaneous i.t. administration of 10 micrograms of the following antagonists: atropine, phentolamine, methysergide, naloxone or spantide; peripheral administration of naloxone (3.5 mg/kg, s.c.) also failed to antagonize FMRFamide grooming. These data constitute the first report that FMRFamide produces behavioral changes in mammals.

Animals↗
PubMed1986

Antagonism of receptor-activated biological effects mediated by second messenger pathways.

It is generally held that many biologically active compounds produce their effects through a sequence of events that are initiated when the substances combine with selective receptors located on the cell surface membrane. Activation of these receptors produces a stimulus that is somehow transmitted intracellularly. The transduction between the stimulus and the response is now known to be mediated, in many systems, by an intracellular intermediary or second messenger. A model describing the relation of agonist concentration, receptor occupation, and biological response in such a system is herein extended to include antagonist binding at two target sites the cell-surface receptor and the receptor for the second messenger. It is demonstrated that the shift of an agonist's dose-response curve is characteristic of the site of antagonism and that analysis of this shift can reveal the existence of a second messenger pathway or, if this is known, the site of action of the antagonist.

Binding, Competitive↗