Organ of Corti explants direct tonotopically graded morphology of spiral ganglion neurons in vitro

The spiral ganglion is a compelling model system to examine how morphological form contributes to sensory function. While the ganglion is composed mainly of a single class of type I neurons that make simple one-to-one connections with inner hair cell sensory receptors, it has an elaborate overall morphological design. Specific features, such as soma size and axon outgrowth, are graded along the spiral contour of the cochlea. To begin to understand the interplay between different regulators of neuronal morphology, we cocultured neuron explants with peripheral target tissues removed from distinct cochlear locations. Interestingly, these "hair cell microisolates" were capable of both increasing and decreasing neuronal somata size, without adversely affecting survival. Moreover, axon characteristics elaborated de novo by the primary afferents in culture were systematically regulated by the sensory endorgan. Apparent peripheral nervous system (PNS)-like and central nervous system (CNS)-like axonal profiles were established in our cocultures allowing an analysis of putative PNS/CNS axon length ratios. As predicted from the in vivo organization, PNS-like axon bundles elaborated by apical cocultures were longer than their basal counterparts and this phenotype was methodically altered when neuron explants were cocultured with microisolates from disparate cochlear regions. Thus, location-dependent signals within the organ of Corti may set the "address" of neurons within the spiral ganglion, allowing them to elaborate the appropriate tonotopically associated morphological features in order to carry out their signaling function. J. Comp. Neurol. 524:2182-2207, 2016. © 2015 Wiley Periodicals, Inc.

The effect of protein kinase C and G protein-coupled receptor kinase inhibition on tolerance induced by mu-opioid agonists of different efficacy

Differences in the mechanisms underlying tolerance and mu-opioid receptor desensitization resulting from exposure to opioid agonists of different efficacy have been suggested previously. The objective of this study was to determine the effects of protein kinase C (PKC) and G protein-coupled receptor kinase (GRK) inhibition on antinociceptive tolerance in vivo to opioid agonists of different efficacy. A rapid (8-h) tolerance-induction model was used where each opioid was repeatedly administered to naive mice. Animals were then challenged with the opioid after injection of a kinase inhibitor to determine its effects on the level of tolerance. Tolerance to meperidine, morphine, or fentanyl was fully reversed by the PKC inhibitor 12-(2-cyanoethyl)-6,7,12,13-tetrahydro-13-methyl-5-oxo-5H-indolo(2,3-a)pyrrolo(3,4-c)carbazole (Gö6976). However, in vivo tolerance to [d-Ala(2),N-Me-Phe(4),Gly(5)-ol]-enkephalin (DAMGO) was not reversed by PKC inhibition. The novel small-molecule GRK inhibitors beta-adrenergic receptor kinase 1 inhibitor and 2-(8-[(dimethylamino) methyl]-6,7,8,9-tetrahydropyridol[1,2-a]indol-3-yl)-3-(1-methylindol-3-yl)maleimide (Ro 32-0432) did not reverse the tolerance to meperidine, fentanyl, or morphine but did reverse the tolerance to DAMGO. To correlate GRK-dependent DAMGO-induced tolerance with mu-opioid receptor desensitization, we used in vitro whole-cell patch-clamp recording from mouse locus coeruleus neurons and observed that the GRK inhibitors reduced DAMGO-induced desensitization of mu-opioid receptors, whereas the PKC inhibitor had no effect. These results suggest that tolerance induced by low- and moderate-efficacy mu-opioid receptor agonists is dependent on PKC, whereas tolerance induced by the high-efficacy agonist DAMGO is dependent on GRK.

Role of protein kinase C and mu-opioid receptor (MOPr) desensitization in tolerance to morphine in rat locus coeruleus neurons

In morphine tolerance a key question that remains to be answered is whether μ-opioid receptor (MOPr) desensitization contributes to morphine tolerance, and if so by what cellular mechanisms. Here we demonstrate that MOPr desensitization can be observed in single rat brainstem locus coeruleus (LC) neurons following either prolonged (> 4 h) exposure to morphine in vitro or following treatment of animals with morphine in vivo for 3 days. Analysis of receptor function by an operational model indicated that with either treatment morphine could induce a profound degree (70–80%) of loss of receptor function. Ongoing PKC activity in the MOPr-expressing neurons themselves, primarily by PKCα, was required to maintain morphine-induced MOPr desensitization, because exposure to PKC inhibitors for only the last 30–50 min of exposure to morphine reduced the MOPr desensitization that was induced both in vitro and in vivo. The presence of morphine was also required for maintenance of desensitization, as washout of morphine for > 2 h reversed MOPr desensitization. MOPr desensitization was homologous, as there was no change in α₂-adrenoceptor or ORL1 receptor function. These results demonstrate that prolonged morphine treatment induces extensive homologous desensitization of MOPrs in mature neurons, that this desensitization has a significant PKC-dependent component and that this desensitization underlies the maintenance of morphine tolerance.

Involvement of PKC alpha and G-protein-coupled receptor kinase 2 in agonist-selective desensitization of mu-opioid receptors in mature brain neurons

BACKGROUND AND PURPOSE

The ability of an agonist to induce desensitization of the mu-opioid receptor (MOR) depends upon the agonist used. Furthermore, previous data suggest that the intracellular mechanisms underlying desensitization may be agonist-specific. We investigated the mechanisms underlying MOR desensitization, in adult mammalian neurons, caused by morphine (a partial agonist in this system) and DAMGO (a high-efficacy agonist).

EXPERIMENTAL APPROACH

MOR function was measured in locus coeruleus neurons, by using whole-cell patch-clamp electrophysiology, in rat and mouse brain slices (both wild-type and protein kinase C (PKC)alpha knockout mice). Specific isoforms of PKC were inhibited by using inhibitors of the receptors for activated C-kinase (RACK), and in vivo viral-mediated gene-transfer was used to transfect neurons with dominant negative mutants (DNMs) of specific G-protein-coupled receptor kinases (GRKs).

KEY RESULTS

Morphine-induced desensitization was attenuated by using RACK inhibitors that inhibit PKCalpha, but not by other isoform-specific inhibitors. Further, the PKC component of morphine-induced desensitization was absent in locus coeruleus neurons from PKCalpha knockout mice. The PKC-enhanced morphine-induced desensitization was not affected by over-expression of a GRK2 dominant negative mutant (GRK2 DNM). In contrast, DAMGO-induced MOR desensitization was independent of PKC activity but was reduced by over-expression of the GRK2 DNM but not by that of a GRK6 DNM.

CONCLUSIONS AND IMPLICATIONS

In mature mammalian neurons, different MOR agonists can induce MOR desensitization by different mechanisms, morphine by a PKCalpha-mediated, heterologous mechanism and DAMGO by a GRK-mediated, homologous mechanism. These data represent functional selectivity at the level of receptor desensitization.

Region-dependent attenuation of mu opioid receptor-mediated G-protein activation in mouse CNS as a function of morphine tolerance

BACKGROUND AND PURPOSE

Chronic morphine administration produces tolerance in vivo and attenuation of mu opioid receptor (MOR)-mediated G-protein activation measured in vitro, but the relationship between these adaptations is not clear. The present study examined MOR-mediated G-protein activation in the CNS of mice with different levels of morphine tolerance.

EXPERIMENTAL APPROACH

Mice were implanted with morphine pellets, with or without supplemental morphine injections, to induce differing levels of tolerance as determined by a range of MOR-mediated behaviours. MOR function was measured using agonist-stimulated [(35)S]guanylyl-5'-O-(gamma-thio)-triphosphate ([(35)S]GTPgammaS) and receptor binding throughout the CNS.

KEY RESULTS

Morphine pellet implantation produced 6-12-fold tolerance in antinociceptive assays, hypothermia and Straub tail, as measured by the ratio of morphine ED(50) values between morphine-treated and control groups. Pellet implantation plus supplemental injections produced 25-50-fold tolerance in these tests. In morphine pellet-implanted mice, MOR-stimulated [(35)S]GTPgammaS binding was significantly reduced only in the nucleus tractus solitarius (NTS) and spinal cord dorsal horn in tissue sections from morphine pellet-implanted mice. In contrast, MOR-stimulated [(35)S]GTPgammaS binding was significantly decreased in most regions examined in morphine pellet+morphine injected mice, including nucleus accumbens, caudate-putamen, periaqueductal gray, parabrachial nucleus, NTS and spinal cord.

CONCLUSIONS AND IMPLICATIONS

Tolerance and the regional pattern of apparent MOR desensitization were influenced positively by the level of morphine exposure. These results indicate that desensitization of MOR-mediated G-protein activity is more regionally widespread upon induction of high levels of tolerance, suggesting that this response contributes more to high than low levels of tolerance to CNS-mediated effects of morphine.

Influence of Voltage-sensitive Ca(++) channel drugs on bupivacaine infiltration anesthesia in mice

BACKGROUND

Local anesthesia has been traditionally associated with blockade of voltage-sensitive sodium (Na(+)) channels. Yet in vitro evidence indicates that local anesthetic mechanisms are more complex than previously understood. For example, local anesthetics bind and allosterically modify 1,4-dihydropyridine-sensitive Ca(++) channels and can reduce Ca(++) influx in tissues. The current study examines the influence of voltage-sensitive Ca(++) channels in bupivacaine infiltration anesthesia.

METHODS

Baseline tail-flick latencies to radiant heat nociception were obtained before subcutaneous infiltration of bupivacaine and Ca(++)-modulating drugs in the tails of mice. No musculature is contained in the tail that could result in motor block. The magnitude of infiltration anesthesia over time, as well as the potency of bupivacaine alone or in the presence of Ca(++)-modulating drug, was assessed by obtaining test latencies.

RESULTS

The 1,4-dihydropyridine L-type Ca(++) channel agonist S(-)-BayK-8644 reduced the duration of action and potency of bupivacaine anesthesia. In opposite fashion, nifedipine and nicardipine increased the effects of bupivacaine. Neither nifedipine nor nicardipine alone elicited anesthesia. Alternatively, the phenylalkylamine L-type blocker verapamil elicited concentration-dependent anesthesia. Other Ca(++) channel subtype blockers were investigated as well. The N-, T-, P-, and Q-type channel blockers, omega-conotoxin GVIA, flunarizine, omega-agatoxin IVA, and omega-conotoxin MVIIC, respectively, were unable to modify bupivacaine anesthesia.

CONCLUSIONS

These results indicate that heat nociception stimulates Ca(++) influx through L-type channels on nociceptors in skin. Although other voltage-sensitive Ca(++) channels may be located on skin nociceptors, only the L-type channel drugs affected bupivacaine in the radiant heat test.

Removal of ammonia from contaminated air by trickle bed air biofilters

A trickle bed air biofilter (TBAB) was evaluated for the oxidation of NH3 from an airstream. Six-millimeter Celite pellets (R-635) were used for the biological attachment medium. The efficiency of the biofilter in oxidizing NH3 was evaluated using NH3 loading rates as high as 48 mol NH3/m3 hr and empty-bed residence times (EBRTs) as low as 1 min. Excess biomass was controlled through periodic backwashing of the biofilter with water at a rate sufficient to fluidize the medium. The main goal was to demonstrate that high removal efficiencies could be sustained over long periods of operation. Ammonia oxidation efficiencies in excess of 99% were consistently achieved when the pH of the liquid nutrient feed was maintained at 8.5. Quick recovery of the biofilter after backwashing was observed after only 20 min. Evaluation of biofilter performance with depth revealed that NH3 did not persist in the gas phase beyond 0.3 m into the depth of the medium (26% of total medium depth).

Buprenorphine substitution ameliorates spontaneous withdrawal in fentanyl-dependent rat pups

Iatrogenic physical dependence has been documented in human infants infused i.v. with fentanyl or morphine to maintain continuous analgesia and sedation during extracorporeal membrane oxygenation and mechanical ventilation. Many infants are slowly weaned from the opioid. However, this approach requires extended hospital stays. Little is known about the potential benefits of substitution therapy to prevent abstinence. Therefore, the hypothesis was tested that s.c. and p.o. buprenorphine substitution would ameliorate spontaneous withdrawal in fentanyl-dependent rat pups. Analgesia in the tail-flick test was used to indicate behaviorally active doses of buprenorphine in opioid-naïve postnatal day 17 rats. Other postnatal day 14 rat pups were surgically implanted with osmotic minipumps that infused saline (1 microL/h) or fentanyl (60 microg/kg/h) for 72 h. Vehicle or buprenorphine was administered s.c. or p.o. before the initiation of spontaneous withdrawal brought about the removal of the osmotic minipumps. The major withdrawal signs of wet-dog shakes, jumping, wall climbing, forepaw tremor, and mastication were counted during a 3-h period of withdrawal. The major scored sign, scream on touch, was assessed every 15 min for 3 h. Injection of naloxone after the 3-h observation did not reveal any residual dependence. Subcutaneous buprenorphine administration significantly ameliorated all signs of withdrawal. Surprisingly, p.o. buprenorphine was nearly as efficacious as the s.c. route of administration. These results indicate that buprenorphine substitution therapy may be effective in fentanyl-dependent human infants.

Sedative tolerance accompanies tolerance to the analgesic effects of fentanyl in infant rats

Iatrogenic tolerance and physical dependence have been documented in human neonates and infants infused with fentanyl or morphine i.v. to maintain continuous analgesia and sedation during extracorporeal membrane oxygenation (ECMO) and mechanical ventilation for the treatment of life-threatening pulmonary diseases. Using postnatal d 17 infant rats, the hypothesis was tested that sedative tolerance accompanies tolerance to fentanyl analgesia in the tail-flick test. Postnatal d 14 infant rats remained naive or received osmotic minipumps infusing saline (1 microL/h) or fentanyl citrate (60 microg x kg(-1) h(-1)). Seventy-two hours later, fentanyl's antinociceptive potency was reduced 3.1-fold in fentanyl-infused rats. Conscious sedation and deep sedation were examined with the cliff-avoidance and the righting-reflex procedures, respectively. Fentanyl-infused infants were tolerant to both the conscious and deep sedative effects of fentanyl. Another hypothesis tested was that very high receptor intrinsic activity opioids are less likely to produce tolerance, or to be cross-tolerant to other opioids. Dihydroetorphine is 5,000 to 10,000 times more potent than morphine. However, fentanyl-infused infant rats were cross-tolerant to the analgesic and sedative effects of dihydroetorphine. Interestingly, dihydroetorphine's analgesic efficacy was significantly reduced to a maximum analgesic efficacy (Emax) value of 40% maximum possible effect (MPE). Another concern was whether fentanyl tolerance would generalize to another class of sedatives, the benzodiazepines. This was especially relevant considering the widespread use of benzodiazepines like midazolam in ECMO and mechanical ventilation. Midazolam elicited no analgesia in the tail-flick test. Furthermore, fentanyl-tolerant rats were not cross-tolerant to the conscious or deep sedative effects of midazolam.

Fentanyl self-administration in juvenile rats that were tolerant and dependent to fentanyl as infants

Human neonates and infants can become tolerant and dependent during continuous fentanyl or morphine administration. The long-term consequences in these individuals as juveniles and adults are unknown. This study compared fentanyl self-administration behavior in juvenile rats that were opioid naive or were exposed chronically to fentanyl as infants. Postnatal day 14 infant rats remained naive or were implanted with saline- or fentanyl-filled Alzet minipumps. After 72 h, fentanyl's antinociceptive potency was 3.0-fold lower in the fentanyl-infused rats. Naloxone precipitated withdrawal occurred only in the fentanyl-infused animals. Other similarly treated infant rats were allowed to mature into P42 juvenile rats before enrolling them in an oral fentanyl self-administration study. Rats from each group consumed significantly more fentanyl than quinine. However, those rats, tolerant and dependent to fentanyl as infants, did not self-administer more fentanyl than their opiate-naive littermates. The issue of whether fentanyl was consumed for its reinforcing properties was demonstrated when noncontingent administration of opiate antagonists significantly reduced fentanyl intake in another group of juvenile rats. These data indicate that fentanyl is consumed for its reinforcing properties, but that infant fentanyl tolerance and dependence did not predispose them to self-administer more fentanyl than opiate-naive animals.

Involvement of phospholipid signal transduction pathways in morphine tolerance in mice

1. Opioid tolerance involves an alteration in the activity of intracellular kinases such as cyclic AMP-dependent protein kinase (PKA). Drugs that inhibit PKA reverse morphine antinociceptive tolerance. The hypothesis was tested that phospholipid pathways are also altered in morphine tolerance. Inhibitors of the phosphatidylinositol and phosphatidylcholine pathways were injected i.c.v. in an attempt to acutely reverse morphine antinociceptive tolerance. 2. Seventy-two hours after implantation of placebo or 75 mg morphine pellets, mice injected i.c.v. with inhibitor drug were challenged with morphine s.c. for generation of dose-response curves in the tail-flick test. Placebo pellet-implanted mice received doses of inhibitor drug having no effect on morphine's potency, in order to test for tolerance reversal in morphine pellet-implanted mice. Injection of the phosphatidylinositol-specific phospholipase C inhibitor ET-18-OCH3 significantly reversed tolerance, indicating a potential role for inositol 1,4,5-trisphosphate (IP3) and protein kinase C (PKC) in tolerance. Alternatively, phosphatidylcholine-specific phospholipase C increases the production of diacylglycerol and activation of PKC, without concomitant production of IP3. D609, an inhibitor of phosphatidylserine-specific phospholipase C, also reversed tolerance. Heparin is an IP3 receptor antagonist. Injection of low molecular weight heparin also reversed tolerance. PKC was also examined with three structurally dissimilar inhibitors. Bisindolylmaleimide I, Go-7874, and sangivamycin significantly reversed tolerance. 3. Chronic opioid exposure leads to changes in phospholipid metabolism that have a direct role in maintaining a state of tolerance. Evidence is accumulating that opioid tolerance disrupts the homeostatic balance of several important signal transduction pathways.

Enhancement mu opioid antinociception by oral delta9-tetrahydrocannabinol: dose-response analysis and receptor identification

The antinociceptive effects of various mu opioids given p.o. alone and in combination with Delta-9-tetrahydrocannabinol (Delta9-THC) were evaluated using the tail-flick test. Morphine preceded by Delta9-THC treatment (20 mg/kg) was significantly more potent than morphine alone, with an ED50 shift from 28.8 to 13.1 mg/kg. Codeine showed the greatest shift in ED50 value when administered after Delta9-THC (139.9 to 5.9 mg/kg). The dose-response curves for oxymorphone and hydromorphone were shifted 5- and 12.6-fold, respectively. Methadone was enhanced 4-fold, whereas its derivative, l-alpha-acetylmethadol, was enhanced 3-fold. The potency ratios after pretreatment with Delta9-THC for heroin and meperidine indicated significant enhancement (4.1 and 8.9, respectively). Pentazocine did not show a parallel shift in its dose-response curve with Delta9-THC. Naloxone administration (1 mg/kg s.c.) completely blocked the antinociceptive effects of morphine p.o. and codeine p.o. The Delta9-THC-induced enhancement of morphine and codeine was also significantly decreased by naloxone administration. Naltrindole (2 mg/kg s.c.) did not affect morphine or codeine antinociception but did block the enhancement of these two opioids by Delta9-THC. No effect was seen when nor-binaltorphimine was administered 2 mg/kg s.c. before morphine or codeine. Furthermore, the enhancements of morphine and codeine were not blocked by nor-binaltorphimine. We find that many mu opioids are enhanced by an inactive dose of Delta9-THC p.o. The exact nature of this enhancement is unknown. We show evidence of involvement of mu and possibly delta opioid receptors as a portion of this signaling pathway that leads to a decrease in pain perception.

Involvement of intracellular calcium in morphine tolerance in mice

Opioid analgesic tolerance is associated with a disruption in Ca++ homeostasis. Drugs reducing Ca++ influx can prevent and reverse tolerance. The hypothesis was tested that both Ca++ influx and mobilization from intracellular pools maintains the expression of morphine tolerance. Ca++ modulating drugs were injected ICV at doses not affecting morphine's potency in placebo pellet-implanted mice, in order to determine whether tolerance would be reversed in morphine pellet-implanted mice. The Ca++ chelator EGTA significantly reversed tolerance. The Ca++ channel antagonists nifedipine and omega-conotoxin GVIA also reversed tolerance. The role of intracellular Ca++ was investigated using the membrane permeable intracellular Ca++ chelator EGTA-AM. EGTA-AM reversed tolerance at lower morphine doses, but not at higher morphine doses. Thus, mobilization of intracellular Ca++ contributes to the expression of tolerance. Finally, 1,4-dihydropyridine-sensitive Ca++ channels are known to stimulate Ca++-induced Ca++ release (CICR) from Ca++/caffeine-sensitive microsomal pools possessing ryanodine receptors. We examined whether blocking Ca++ mobilization from these pools with ryanodine would reverse morphine tolerance. Ryanodine's effects were similar to EGTA-AM. Tolerance was reversed at lower morphine doses, but not at higher doses. Thus, morphine tolerance appears to be associated with increases in Ca++ influx and mobilization from Ca++/caffeine-sensitive pools.

Long-term alterations in opiate antinociception resulting from infant fentanyl tolerance and dependence

Postnatal day-14 (P14) infant rats remained naive or were implanted with osmotic minipumps infusing saline or fentanyl (50 microg kg(-1) h(-1)). Fentanyl was administered 72 h later for measurement of antinociception in the tail-flick test. The potency of fentanyl was 3.0-fold lower in fentanyl-infused compared to saline-infused P17 rats. Fentanyl-infused P17 rats injected with naloxone underwent withdrawal characterized by increases in spontaneous activity, wall climbing, diarrhea, abdominal stretching, forepaw treading/tremors, wet-dog shakes, jumping, ptosis, rhinorrhea and hypothermia. Other naive, saline-infused and fentanyl-infused P17 rats not challenged with fentanyl or naloxone were housed until maturing into P42 juveniles. Fentanyl's potency was equal among each treatment group. However, morphine's potency was reduced in juveniles tolerant to fentanyl as infants. Morphine was also less potent in P90 adults tolerant to fentanyl as infants. Thus, chronic opiate exposure during infancy may affect the developing central nervous system, and desensitize animals and humans to opiate analgesia throughout life.

Evaluation of trickle bed air biofilter performance as a function of inlet VOC concentration and loading, and biomass control

The 1990 Amendments to the Clear Air Act have stimulated strong interest in the use of biofiltration for the economical, engineered control of volatile organic compounds (VOCs) in effluent air streams. Trickle bed air biofilters (TBABs) are especially applicable for treating VOCs at high loadings. For long-term stable operation of highly loaded TBABs, removal of excess accumulated biomass is essential. Our previous research demonstrated that suitable biomass control for TBABs was achievable by periodic backwashing of the biofilter medium. Backwashing was performed by fluidizing the pelletized biological attachment medium with warm water to about a 40% bed expansion. This paper presents an evaluation of the impact of backwashing on the performance of four such TBABs highly loaded with toluene. The inlet VOC concentrations studied were 250 and 500 ppmv toluene, and the loadings were 4.1 and 6.2 kg COD/m3 day (55 and 83 g toluene/m3 hr). Loading is defined as kg of chemical oxygen demand per cubic meter of medium per day. Performance deterioration at the higher loading was apparently due to a reduction of the specific surface of the attached biofilm resulting from the accumulation of excess biomass. For a toluene loading of 4.1 kg COD/m3 day, it was demonstrated that the long-term performance of biofilters with either inlet concentration could be maintained at over 99.9% VOC removal by employing a backwashing strategy consisting of a frequency of every other day and a duration of 1 hr.

The enhancement of morphine antinociception in mice by delta9-tetrahydrocannabinol

We have previously reported that intracerebroventricular or intrathecal administration of inactive doses of delta9-tetrahydrocannabinol (THC) greatly enhance the antinociceptive potency of morphine in the mouse tail-flick test. Experiments were conducted to test the hypothesis that morphine's potency would be enhanced in mice receiving THC and morphine by conventional per os (p.o.) and subcutaneously (s.c.) routes of administration. Antinociception was measured in the tail-flick test of radiant heat after administration of different combinations of THC and morphine p.o. and s.c. Subcutaneous administration of THC (4 and 25 mg/kg) increased the potency of s.c. morphine 8.5- and 22.3-fold, respectively, while s.c. THC (25 mg/kg) increased the potency of p.o. morphine 3.1-fold. Per os administration of THC (10 and 20 mg/kg) increased the potency of s.c. and p.o. morphine 11.4-fold and 7.6-fold, respectively. Thus, morphine's potency was significantly increased regardless of the enteral and parenteral routes of THC and morphine administration. The synthetic receptor selective cannabinoid CP-55, 940 (0.1 mg/kg, s.c.) also enhanced morphine's potency. Finally, the ability of the CB1 receptor antagonist SR141716A to antagonize the enhancement of morphine by THC indicates that THC was acting through a cannabinoid receptor mechanism.

Characterization of delta9-tetrahydrocannabinol and anandamide antinociception in nonarthritic and arthritic rats

Little is known about the effectiveness of delta9-tetrahydrocannabinol (THC) and anandamide in blocking mechanical nociception. Even less is known about their antinociceptive efficacy in chronic inflammatory arthritis induced by Freund's complete adjuvant. The hypothesis was tested that THC and anandamide elicit antinociception in the paw pressure test, and that arthritic rats would exhibit a different response. In nonarthritic rats, THC- and anandamide-induced antinociception lasted 90 min and 15 min, respectively, while antinociception lasted 90 min and 30 min, respectively, in arthritic rats. Area under the curve calculations revealed no effect of arthritis on THC- and anandamide-induced antinociception. Another hypothesis was that paw pressure thresholds in arthritic rats reflect chronic cannabinoid receptor stimulation due to elevations in free anandamide levels. Yet, the CB1 receptor antagonist SR141716A failed to alter paw pressure thresholds in either nonarthritic or arthritic rats. Further investigation revealed that SR141716A significantly blocked THC antinociception, with no effect on anandamide. Thus, anandamide's effects did not result from CB1 receptor stimulation, and any potential contribution of endogenous anandamide in arthritis was not revealed. Finally, THC and anandamide appear to release an as yet unknown endogenous opioid, because naloxone significantly blocked their effects. This study indicates that anandamide and THC may act at different receptor sites to modulate endogenous opioid levels in mechanical nociception.

Ontogeny of mu opioid agonist anti-nociception in postnatal rats

Mu opiate agonists morphine, fentanyl and meperidine are administered short-term to pediatric patients, from the neonatal period through adolescence. However, there has been no assessment of the effect of age on the analgesic efficacy or the concentration-response relationship for these opioids in human pediatric patients. Few studies in animals have correlated opioid anti-nociception and tissue levels of these opioids commonly administered to pediatric patients. The present study was conducted to examined the role of age on opioid anti-nociceptive potency and efficacy and brain and plasma opioid levels to provide predictive information on the effect of opioids in developing humans. Administration of trace amounts of tritiated drug with anti-nociceptive doses of unlabeled drug was used for the assessment of anti-nociception in the tail-flick test and for the measurement of brain and plasma drug equivalent levels in postnatal rats (PND 3-21). Morphine and fentanyl were completely efficacious in all postnatal ages examined, although age-related differences in drug potency, as well as, differences in brain and plasma levels were observed. There was a good correlation between morphine (r = 0.96) and fentanyl (r = 0.89) ED(50) values and their respective brain and plasma EC(50) equivalent levels. Meperidine had limited efficacy in young rats (PND 3-9) but was completely efficacious in older rats (PND 14-17). However, PND 21 rats experienced tonic-clonic seizures which limited its efficacy to 70% anti-nociception. Our data suggest that pharmacokinetics, the development of the blood-brain barrier and ontogeny of opioid receptor function may play important roles in the sensitivity of postnatal rats to mu receptor agonists.

Characterization of neonatal rat morphine tolerance and dependence

The administration of morphine and fentanyl by continuous intravenous infusion has been shown to produce analgesic tolerance and physical dependence in human neonates. In animals, daily repeated morphine bolus injections is a common method of inducing neonatal rat tolerance and dependence. Yet this method differs from the intravenous route reported to affect human neonates. Alzet osmotic minipumps were implanted in postnatal day 14 rats to provide a continuous morphine infusion more closely mimicking the clinical picture. Rats remained naive or were infused with saline or morphine (0.7 mg/kg/h) for 72 h. Morphine's antinociceptive potency was similar between naive and saline-infused animals, while morphine-infused animals were tolerant. Gender did not contribute to the degree of tolerance observed. Naloxone precipitated withdrawal in the morphine pump-implanted rats was similar to that reported by others. Thus, minipumps provide a useful model for assessing the tolerance and dependence liability of different opioids.

Morphine tolerance-induced modulation of [3H]glyburide binding to mouse brain and spinal cord

Modulation by opioids of ATP-gated potassium channels, which regulate in part intracellular calcium levels, was measured by the binding of [3H]glyburide. Scatchard analyses generated a KD for whole brain of vehicle-pretreated mice of 288 pM with a Bmax of 694 fmol/mg protein. In the spinal cord the KD was 0.94 nM and the Bmax was 184 fmol/mg protein. Acute morphine decreased the KD in brain and spinal cord with no change in Bmax. Morphine tolerance increased the KD in brain and spinal cord 2.6- and 2.9-fold, respectively, concurrent with 1.6- and 3.4-fold increases in Bmax. Modulation by morphine of glyburide-sensitive binding sites may contribute at least in part to tolerance to morphine via alterations in intracellular calcium levels in neurons.

Characterization of neonatal rat fentanyl tolerance and dependence

Fentanyl and morphine are administered to human neonates and infants to provide analgesia and sedation during painful and stressful procedures. These opioids have often been shown to produce tolerance and dependence during continuous intravenous infusion. In neonatal animals, morphine produces tolerance and dependence, yet little is known about fentanyl. This report describes the first model for studying opioid tolerance and dependence in neonatal animals with use of osmotic minipumps. Postnatal day 6 rat pups were anesthetized and then remained naive or were surgically implanted subcutaneously with Alzet osmotic minipumps containing either saline or fentanyl (100 microg/kg/hr). Tolerance and dependence were assessed 72 hr after implantation. The ED50 values for fentanyl antinociception in the tail-flick test were not different between naive and saline pump-implanted animals. However, the fentanyl pump-implanted animals were tolerant to fentanyl. The tolerance observed was not the result of gender, developmental changes, fentanyl distribution or changes in fentanyl metabolism. These results indicate that continuous administration of fentanyl via osmotic minipump can render normal neonatal rats tolerant and physically dependent on fentanyl in 72 hr. Withdrawal precipitated by naloxone (5 mg/kg s.c.) in the fentanyl pump-implanted animals was characterized by increased spontaneous activity, micturition/defecation, wall climbing, abdominal stretching, tremors, scream on touch and spontaneous vocalization. This new model may provide a tool for studying the long-term consequences of neonatal opioid exposure in juvenile and adult animals.

Regional cutaneous differences in the duration of bupivacaine local anesthesia in mice

At this time little is know about local anesthesia of the skin, and the sensitivity of different cutaneous regions to local anesthetics. Studies were conducted in mice to test the hypothesis that cutaneous regions are differentially sensitive to bupivacaine, and to the ability of epinephrine (EPI) to prolong local anesthesia. Infiltration of 0.25% and 0.5% bupivacaine s.c. in the dorsal aspect of the mouse tail produced local anesthesia that lasted 15 and 45 min, respectively, against radiant heat nociception. EPI (1:200,000) prolonged the local anesthetic effects of the 0.25% concentration by 45 min, whereas the effect of the 0.5% concentration was extended by only 15 min. Bupivacaine (0.25% and 0.5%) infiltrated in the dorsal aspect of the hind-paw produced local anesthesia that lasted 5 and 30 min, respectively. EPI prolonged the local anesthetic effects of the 0.25% concentration by only 10 min, whereas EPI did not prolong anesthesia but appeared to increase the efficacy of the 0.5% concentration. These results provide evidence of regional differences in cutaneous sensitivity to local anesthetics, and the ability of EPI to extend the duration of anesthesia.

Calcium modulation of morphine analgesia: role of calcium channels and intracellular pool calcium

Calcium (Ca++) administered into the i.c.v. space of mice has been reported to block opioid-induced antinociception dose dependently. These studies were conducted to test the hypothesis that Ca++ i.c.v. blocks the antinociceptive effects of morphine i.c.v. as a consequence of transmembrane Ca++ influx and Ca++ release from intracellular pools. Mice were injected with voltage-sensitive Ca++ channel antagonists at a dose that did not affect morphine antinociception to determine whether this pretreatment would prevent the inhibitory effects of Ca++. Nimodipine (12 nmol i.c.v.) was ineffective in preventing the inhibitory effects of Ca++ (100 nmol i.c.v.), whereas omega-conotoxin GVIA (3.3 pmol i.c.v.) completely prevented the inhibition by Ca++ of morphine antinociception. Other experiments were conducted to determine whether blocking Ca++ release from Ca++/caffeine-sensitive microsomal pools with ryanodine would prevent the inhibitory effects of Ca++. Ryanodine (2 nmol i.c.v.) significantly attenuated the inhibition by Ca++ of morphine antinociception. Another hypothesis to be tested was that stimulation of Ca++ release from intracellular pools would, like Ca++, block morphine antinociception. Thapsigargin (0.002-30 nmol i.c.v.), which increases cytosolic Ca++ by depleting Ca++ from inositol 1,4,5-trisphosphate-sensitive microsomal pools, dose-dependently blocked the antinociceptive effects of morphine. The results of this study indicate that Ca++ blocked morphine antinociception by stimulating Ca++ influx through omega-conotoxin GVIA-sensitive channels and by stimulating Ca++ release from Ca++/caffeine-sensitive microsomal pools.

Exercise testing in patients with electrocardiographic evidence of left ventricular hypertrophy

The purpose of this study was to determine the influence of left ventricular hypertrophy, based on electrocardiographic evidence, on the results of exercise thallium testing. Patients with electrocardiographic evidence of left ventricular hypertrophy (ECG-LVH) and suspected of having coronary artery disease underwent exercise thallium testing. Retrospective analysis of 107 consecutive patients with ECG-LVH showed transient myocardial perfusion defects (TMPD) in 12 (11%), indicative of myocardial ischemia; 12 (11%) had fixed myocardial perfusion defects (FMPD), indicative of probable myocardial infarction; 5 had TMPD plus FMPD (5%), and scan results for 78 were normal (73%). In patients with ECG-LVH, additional ST changes were observed in 76% and chest pain in 7% of patients with ECG-LVH. In a matched comparison group of 255 patients not prescreened for ECG-LVH, TMPD was observed in 20%, FMPD in 16%, and TMPD plus FMPD in 26% of patients, and normal results were found in 38%. Electrocardiographic changes were found in 49% and chest pain in 20%. Hemodynamic responses to exercise were comparable between subgroups. Lung thallium uptake was quantified as the lung-to-heart thallium activity ratio (L-H) on the immediate exercise anterior planar images. In controls, a significant increase in L-H was observed in patients with TMPD and TMPD plus FMPD. This was not observed in patients with ECG-LVH, possibly because of elevated thallium myocardial activity as a result of increased left ventricular mass. The conclusion is that patients with ECG-LVH often had normal perfusion scan results (73%) on exercise despite a high incidence of additional ECG changes (76%).(ABSTRACT TRUNCATED AT 250 WORDS)

Endogenous opioids released by suspending mice by the tail selectively enhance spinal mu opioid analgesia

In studying the interactions between handling mice and their subsequent analgesic response to an intrathecally (i.t.) administered mu-opioid agonist, DAMGO, it was found that suspending ICR mice by the tail for 1, 5, or 20 sec, 10 min before the tail-flick test, enhanced DAMGO by 5.3-, 7.4- and 23.6-fold, respectively, compared with mice maintained in a level posture. This enhancement was not accompanied by a change in the rostral flow of [3H]-DAMGO (25 ng, i.t.) to the brain (3.7% in 10 min), in its distribution along the neuraxis or in its systemic absorption. However, i.c.v. administration of beta-endorphin (1-27), an antagonist of epsilon opioid receptors, abolished the enhancement of i.t. DAMGO without affecting its basal analgesic potency. Pretreatment with the delta-opioid antagonist naltrindole (5.6 nmol, i.t.,-30 min) also blocked the enhancement of DAMGO without significantly affecting its basal analgesic potency. Alternatively, this same dose of naltrindole injected i.c.v. failed to block the enhancement of DAMGO in suspended mice. A 20-sec suspension failed to enhance i.t. kappa and delta-agonists, but it did enhance i.t. morphine. In mouse strain comparisons, i.t. DAMGO was more potent in C57BL/6J and DBA/2J mice than in C3H/HeJ and ICR mice, but DAMGO was enhanced by a 20-sec suspension in all strains tested. Thus suspending mice by the tail evoked a reflex enhancement of spinal mu agonist-induced analgesia that probably involved both the supraspinal release of beta-endorphin (an endogenous epsilon agonist) and the subsequent spinal release of an endogenous delta-receptor agonist in the reflex pathway.

The hypothermic and antinociceptive effects of intrathecal injection of CGRP (8-37) in mice

Calcitonin gene-related peptide (CGRP) and the selective antagonist properties of the peptide fragment of CGRP [CGRP (8-37)] have been the subjects of numerous investigations. These data represent the first demonstration of the hypothermic and antinociceptive effects of CGRP (8-37). Intrathecal injection of CGRP (8-37) in mice produced hypothermia which differed from that produced by CGRP in time course, duration of action and potency. CGRP and CGRP (8-37) did not alter blood flow. Thus, a direct vasodilatory action was not responsible for the acute hypothermic effects of the drugs. The combination of CGRP and CGRP (8-37) resulted in a decrease in body temperature which was no greater than that of either drug alone. We failed to observe any significant antinociceptive effect in the tail-flick assay after i.t. injection of CGRP (8-37), but dose-dependent antinociception was produced by CGRP (8-37) in the p-phenylquinone (PPQ) assay, with an ED50 value of 6.0 micrograms. However, CGRP (8-37) failed to block or enhance the antinociception produced by CGRP over a wide dose range. In addition to demonstrating an agonist-like effect for CGRP (8-37), these data also indicate that CGRP and CGRP (8-37) may not act through a common mechanism.

The role of endogenous opioids as mediators of the hypothermic effects of intrathecally administered calcium and calcitonin gene-related peptide in mice

To the authors' knowledge, the effect of i.t. administered calcium on thermoregulation in mice has not been investigated. Calcium administration (i.t.) induced hypothermia in mice. It was found that calcitonin gene-related peptide (CGRP) (i.t.) also produced hypothermia. Because opioids have well documented thermoregulatory effects, the authors evaluated whether the hypothermia induced by calcium and CGRP was the result of the release of opioids. Calcium induced hypothermia at different ambient temperatures (4 degrees C, 22 degrees C and 30 degrees C) in intact mice. Similarly treated spinalized mice maintained body temperature. Using laser Doppler flowmetry, there was a significant increase in blood flow in the tails of calcium-injected mice vs. those of vehicle-injected mice. Both naloxone and naltrindole failed to block the hypothermic effects of calcium (i.t.). Nor-binaltorphimine (i.t.) significantly blocked calcium (i.t.)-induced changes in body temperature. CGRP (i.t.) produced hypothermia for 15 hr postinjection, with the maximum decrease at 3 hr. CGRP induced hypothermia in intact and sham-lesioned mice but not in spinalized mice. CGRP (i.c.v.) also produced hypothermia (onset, 15-min postinjection) followed by the peak effect at 1 hr with recovery to baseline temperature by 2 hr. Subthreshold doses of calcium and CGRP given in combination produced greater than additive hypothermia. The hypothermic effects of CGRP were reversed by naloxone, naltrindole and nor-binaltorphimine. CGRP produced significant hypothermia in both morphine-tolerant and nontolerant mice. Chronic administration of CGRP in nontolerant and morphine-tolerant mice did not alter hypothermia after pretreatment with CGRP (i.t.).(ABSTRACT TRUNCATED AT 250 WORDS)

Endogenous dynorphin modulates calcium-mediated antinociception in mice

We previously reported that calcium administered IT produces antinociception by stimulating spinal Met-enkephalin release. However, at times the antinociceptive effects of calcium in the tail-flick test are greatly diminished. The results of this study indicates that during these periods calcium also stimulates endogenous dynorphin release. Dynorphin has been reported to block opiate-induced antinociception. Calcium-injected mice (150-600 nmol, IT) pretreated with vehicle IP displayed a poor degree of antinociception. Alternatively, pretreating mice with pentobarbital (45 mg/kg, IP) restored the antinociceptive effects of calcium. Low doses of naloxone and norbinaltorphimine (BNI) did not produce antinociception but restored the antinociceptive effects of calcium. Dynorphin (1-17) (Dyn 1-17), and Dyn (1-13), but not Dyn (1-8), blocked the antinociceptive effects of calcium restored with pentobarbital. These results indicate that calcium-mediated antinociception was sensitive to injected dynorphins. In additional experiments, antiserum to Dyn (1-13) was found to restore the antinociceptive effects of calcium, presumably by binding dynorphin released by calcium.

Evidence that endogenous opioids mediate the antinociceptive effects of intrathecally administered calcium in mice

Mice injected with calcium in the intrathecal (i.t.) space display dose-dependent antinociception in the tail-flick test. The aims of this study were to evaluate whether endogenous opioids mediate the antinociceptive effects of calcium (i.t.) and to determine if antinociception resulted from calcium acting directly in segmental spinal sites. Mice spinalized at T6 to T8 were more sensitive to the antinociceptive effects of calcium (150-600 nmol i.t.) than sham-lesioned mice. In intact mice, naloxone (138-275 pmol i.t.) and naltrindole (2.8-22 nmol i.t.) dose-dependently blocked the antinociceptive effects of calcium (600 nmol i.t.), with inhibitory dose-50 (ID50) values of 235 picomol and 11.4 nanomol, respectively. nor-Binaltorphimine (nor-BNI) (14-54 nmol i.t.) did not antagonize the antinociceptive effects of calcium (i.t.). Furthermore, the calcium (i.t.) dose-response curve was shifted right-ward by naloxone (206 pmol i.t.) and naltrindole (5.5 nmol i.t.). nor-BNI (54 nmol i.t.) was ineffective in shifting the dose-response curve. In spinalized mice, naloxone (206-687 pmol i.t.) and naltrindole (11-44 nmol i.t.) blocked the antinociceptive effects of calcium (i.t.), with ID50 values of 342 and 19.2 nmol, respectively. nor-BNI did not antagonize antinociception. In addition, the calcium (i.t.) dose-response curve was shifted right-ward by naloxone (275 pmol i.t.) and naltrindole (11 nmol i.t.). The dose-response curve was not shifted by nor-BNI (54 nmol i.t.). A 4-hr pretreatment with the irreversible mu receptor antagonist beta-funaltrexamine (0.01-0.4 nmol i.t.) blocked [D-Ala2, N-Me-Phe4, Gly5-ol]enkephalin but not [D-Pen2,5]enkephalin or calcium (i.t.)-mediated antinociception.(ABSTRACT TRUNCATED AT 250 WORDS)

Influence of dopaminergic and serotonergic neurons on intravenous ethanol self-administration in the rat

Rats implanted with chronic indwelling intravenous catheters and allowed access to a self-administration apparatus learned to self-inject intravenous ethanol. Ethanol concentrations of 0.5, 1.0, and 2.0%, corresponding to a dose/injection of 1, 2, and 4 mg/kg, respectively, were consistently self-injected. Self-injection was not acquired or maintained with ethanol doses of 0.5 or 8 mg/kg/injection. Saline replacement of ethanol reservoirs led to marked increases in lever-pressing response in animals self-injecting 1, 2, and 4 mg/kg ethanol/injection but not with 0.5 or 8 mg/kg/injection. Neurotoxin-induced lesions of dopamine-(DA) containing neurons in nucleus accumbens septi failed to alter the acquisition or maintenance of ethanol self-injection. Pretreatment with haloperidol (0.05 and 0.1 mg/kg, SC) failed to alter hourly or daily self-injection rates. On the other hand, p-chlorophenylalanine pretreatment increased, while fluoxetine (2.5 and 5.0 mg/kg) administration significantly reduced, self-injected intravenous ethanol. These data suggest that ethanol is self-injected by the rat in a narrow dose range and that 5-hydroxytryptamine (5-HT), but not DA-containing neurons, subserves some function in the reinforcing or aversive affects of ethanol.

Cellular effects of piezoelectric versus electrohydraulic high energy shock waves

High energy shock waves produced by a piezoelectric lithotripter, (EDAP LT.01) and an electrohydraulic lithotripter, (Dornier HM3) were examined for their effects on Chinese hamster ovary cells in suspension. The EDAP caused acute lactate dehydrogenase release, consistent with severe membrane disruption in a proportion of cells, with the remaining proportion of cells replicating normally as measured by clonogenic assay. Similarly, the Dornier also caused lactate dehydrogenase release. However, a significant proportion of cells which remained "viable" after Dornier treatment, (intact to lactate dehydrogenase), did not replicate by clonogenic assay. The Dornier HM3 lithotripter has been reported to produce free radicals in aqueous solution. In the current investigation, we could not detect significant free radical formation from the EDAP LT.01. Chinese hamster ovary cell killing by the Dornier HM3 was significantly augmented by radiosensitizers, 5-iodo-2-deoxyuridine or buthionine sulfoximine, while radioprotectors cysteamine and WR-1065 had no protective effect. EDAP cell killing was not influenced by either radioprotectors or radiosensitizers. The mechanism of in vitro cytotoxicity differs between piezoelectric and electrohydraulic high energy shock wave delivery.

Surgery for duplex kidneys with ectopic ureters: ipsilateral ureteroureterostomy versus polar nephrectomy

Conventional surgery for the ectopic ureter stresses polar nephrectomy, while preserving a functioning upper pole by ipsilateral ureteroureterostomy is performed less commonly. During the last 15 years we operated on 35 children for ectopic ureter. High ipsilateral ureteroureterostomy (15 patients) was performed when the upper pole cortex appeared to be smooth and pink, and the anastomosis was surgically feasible. Upper pole nephrectomy and upper ureterectomy (21 patients) were performed when the involved segment appeared grossly to be pale, cystic or otherwise abnormal. One low ipsilateral ureteroureterostomy was performed concomitant with contralateral ureteral reimplantation. Complications after ipsilateral ureteroureterostomy and partial nephrectomy were similar. Histological evidence of dysplasia of the polar nephrectomy specimens was focal in 7 patients (33 per cent), marked in 2 (10 per cent) and not detected in 12 (57 per cent). Ipsilateral ureteroureterostomy is an appropriate means to manage the ectopic ureter in selected cases because dysplasia in these upper pole renal units seldom is significant, and because ipsilateral ureteroureterostomy and polar nephrectomy have similar postoperative morbidity rates.

Subclavian-external carotid artery bypass graft. Restoring blood flow to the brain

This article describes an unusual surgery for a type of carotid artery disease. The perioperative nurse has an important role on the vascular team when performing this procedure. For this reason, a thorough knowledge of the events and possible complications are important in the care of these patients. Careful preoperative nursing assessment and postoperative follow-up will help prevent any complications and promote a successful outcome in these patients.

A case report of three synchronous stage I malignant neoplasms

A patient with three synchronous, Stage I neoplasms of the ovary, kidney, and lung, who underwent resection of all lesions at the same operative procedure, is presented. The incidence of multiple primary malignancies and the prognosis for Stage I cancers of the ovary, kidney, and lung are reviewed.

Role of specific dopamine receptor subtypes in amphetamine discrimination

Biochemical, electrophysiological, and behavioral experiments suggest that the dopamine D-1 and D-2 receptor subtypes functionally interact. In rats trained to discriminate 1.0 mg/kg d-amphetamine, substitution with the D-2 agonist quinpirole (0.1-2.0 mg/kg) produces amphetamine-lever responding, whereas the D-1 agonist SKF 38393 (0.3-10.0 mg/kg) elicits only saline-appropriate responding. Combining either quinpirole (0.05-0.5 mg/kg) or SKF 38393 (0.5-10.0 mg/kg) with 0.3 mg/kg d-amphetamine results in dose-dependent increases in amphetamine-lever responding. Conversely, the D-1 antagonist SCH 23390 (0.02-0.1 mg/kg) antagonizes the discrimination produced by 0.7 mg/kg d-amphetamine. Additional combination studies examined the effect of DA receptor drugs on discrimination when quinpirole is substituted in d-amphetamine trained rats. SKF 38393 (0.5-7.0 mg/kg) fails to increase the amphetamine-appropriate lever response produced by either 0.05 or 0.2 mg/kg quinpirole. Similarly, SCH 23390 (0.01-0.1 mg/kg) fails to antagonize the amphetamine-lever responding produced by either 0.2 or 0.5 mg/kg quinpirole. Haloperidol (0.02-0.2 mg/kg) does antagonize the amphetamine-appropriate response produced by quinpirole substitution. The d-amphetamine discrimination studies indicate that stimulating D-2 receptors alone or D-1 receptors in the presence of d-amphetamine yields d-amphetamine-lever responding, and suggests that D-1/D-2 receptors can functionally interact to alter discrimination behavior. Quinpirole substitution, on the other hand, shows an insensitivity to D-1 receptor manipulations.

Morphine self-administration in the rat during adjuvant-induced arthritis

Rats injected with Freund's adjuvant develop a syndrome resembling human rheumatoid arthritis complete with paw swelling, edema and persistent pain. At the onset of pain, arthritic rats and their pain-free littermate controls (vehicle injection) were allowed to self-administer intravenous morphine (5.0 mg/kg/injection) in a 24 hr/day schedule. Self-injected morphine appeared to provide analgesia in arthritic rats as demonstrated by a decreased sensitivity to applied tail pressure. Arthritic rats self-inject significantly less morphine than pain-free animals. Injection of indomethacin, which alleviates the pain and inflammation of the adjuvant-induced disease, reduces, at least initially, morphine self-injection in the arthritic but not pain-free animals. As the adjuvant-induced inflammation and pain dissipated, arthritic rats rapidly began to increase opioid intake. The presence of persistent pain apparently reduces the addictive properties of morphine.

Transrectal aspiration biopsy of the prostate: the importance of atypia

Transrectal aspiration biopsy is useful as an alternative method to examine the prostate. As a means to improve the sensitivity of this method we investigated the significance of cellular atypia. Transrectal aspiration biopsy revealed highly atypical cells in 30 of 225 patients and in 17 patients slightly atypical cells were found. Biopsy was repeated in 22 patients with highly atypical cells and cancer was confirmed in 17 (77 per cent). In the group with only slight atypia 2 of 6 patients had cancer upon repeat prostatic biopsy. When transrectal aspiration biopsy contains highly atypical cells biopsy should be repeated to avoid a false negative diagnosis. These results suggest that atypia is an abnormal finding that must be followed clearly to maintain a high sensitivity with this biopsy method.

Tyrosine influence on amphetamine self-administration and brain catecholamines in the rat

Earlier work had shown that L-tyrosine administration, precursor to both dopamine (DA) and norepinephrine (NE), could increase brain DA metabolite concentrations after amphetamine treatment and restore amphetamine-induced decreases in whole brain NE. Both monoamines have been suggested to participate in some aspects of continued drug abuse. Rats trained to self-administer IV d-amphetamine were treated with IP tyrosine during test sessions to examine the behavioral and neurochemical response. In animals with less than 35 days of amphetamine exposure, L-tyrosine treatments did not alter amphetamine self-administration. Experiments using a computer-controlled injection apparatus which administered IV amphetamine to naive rats in patterns mimicking those of self-administration animals indicated tyrosine could antagonize amphetamine-induced NE depletions. The increases in DA metabolite dihydroxyphenylacetic acid (DOPAC) were found limited to the striatum, an area not involved in the positive reinforcing effects of amphetamine. Concentrations of DOPAC in nucleus accumbens septi were unchanged by the amphetamine or the amphetamine-tyrosine regimen. In rats with 4-6 months of chronic amphetamine exposure, however, L-tyrosine administration significantly reduced daily drug self-injection. While neurochemical responses to tyrosine could not be performed, it is speculated that chronic long-term amphetamine abuse might alter the tyrosine-induced changes in DA and/or NE synthesis and release compared to that in the acute or short-term amphetamine abuse animals. These data suggest that the success or failure of an experimental pharmacologic treatment strategy in psychomotor stimulant abusers might be dependent on the subjects history of drug abuse.

Fluoxetine-induced attenuation of amphetamine self-administration in rats

Daily injections of fluoxetine (5.0 mg/kg i.p.) to rats trained to self-administer intravenous d-amphetamine produced marked decreases in drug intake on three successive days of treatment. After fluoxetine injections were stopped, the number of daily amphetamine self-injections was still significantly reduced for an additional 2 days. When trained amphetamine self-administration animals were placed in an apparatus which delivered i.v. saline with each lever press, increased self-injection is observed. Acute fluoxetine injection did not alter this response. However, if fluoxetine is given prior to amphetamine exposure for 1 day and animals are then tested for the saline response, lever pressing activity is significantly reduced. These data might suggest that 5-hydroxytryptaminergic neurons mediate some aversive or negative reinforcing property of amphetamine. If true, this finding could be exploited clinically in cases of human psychomotor stimulant addiction.

Dietary tryptophan supplements attenuate amphetamine self-administration in the rat

Previously, it had been shown that lesions of cerebral 5-hydroxytryptamine (5-HT)-containing neurons and injections of drugs affecting 5-HT synthesis or receptor mediated function would alter amphetamine self-administration in the rat. The present study sought to ascertain whether diets enriched in L-tryptophan (L-TRY), the amino acid precursor to 5-HT, would: elevate cerebral 5-HT concentrations and affect amphetamine self-administration behavior. Diets containing 2.0 and 4.0% L-TRY increased cerebral 5-HT concentrations above those of rats on normal rat chow (0.26% L-TRY). The 4.0% diet elevated brain 5-HT to the same degree in rats exposed to the diet for 1, 2 or 3 days. When normal diets were restored, brain 5-HT concentrations rapidly returned to normal. Animals trained to self-administer d-amphetamine, when given access to the L-TRY enriched diets, significantly reduced their daily amphetamine self-injection during exposure periods. When normal rat chow was restored a delay in recovery to pre-diet amphetamine self-administration was observed: 1 day with the 2.0% L-TRY diet and 2 days with the 4.0% L-TRY diet. The 4.0% L-TRY diet failed to alter saline-frustration responding indicating the diet did not produce decrements in motor performance. When animals were placed on the 4.0% L-TRY diet and allowed access to amphetamine for 1 day then exposed to saline, a profound decrease in saline-frustration responding was observed.(ABSTRACT TRUNCATED AT 250 WORDS)