Intraspinal opioids in frogs: a new behavioral model for the assessment of opioid action.
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Acetates↗
Biomedical subjects
C W Stevens
Publications and source records attributed to C W Stevens.
Interaction of intrathecal morphine and ST-91 on antinociception in the rat: dose-response analysis, antagonism and clearance.
Physiological data suggest that the direct effect of spinal opiates as well as the activation of adrenergic bulbospinal pathways each results in a reduction in the gain of the stimulus response function in dorsal horn neurons. In its simplest form, this suggests the hypothesis that co-activation of spinal alpha2 and opioid receptors should be manifested as a synergistic interaction in which in its simplest form the net effect would be a product of the effect produced by either drug alone. To assess this hypothesis, rats were prepared with chronically implanted intrathecal (IT) catheters. Dose-response curves for IT morphine were obtained in the presence of fixed doses (0.01 nmol, 0.03 nmol, 0.1 nmol, 0.3 nmol) of 2-[2,6-dimethylphenylamino]-2-imidazoline (ST-91), an alpha 2 agonist. Such concurrent administration of ST-91 resulted in highly significant leftward shifts in the effect of morphine on the hot plate (52.5 degrees C) measure with a significant increase in dose-response curve slopes. To minimize the effects of the cut-off time necessary in an antinociceptive measure, a "Cox proportional hazard" analysis was used. The (log) Hazard function log[h(t)] is expressed as a linear function of the effects resulting from the action of morphine, the action of ST-91 and as a function of an interaction of morphine and ST-91, e.g., the general form is: log[h(t)] = alpha o(t) + beta 1.log doseM + beta 2.log doseST + beta 12.log doseM.log doseST Estimates of the principal coefficients beta 1, beta 2 and beta 12 corresponding to the overall effect of morphine alone, ST-91 alone and the interaction between the two were calculated: beta 1, beta 2 and beta 12. A statistical test of the interaction coefficient revealed that beta 12 was significantly (p less than .001) different from zero, indicating the powerful synergy between IT ST-91 and morphine. Confirmation of the synergistic nature of spinal opioid alpha 2 receptors was provided by the fact that IT injection of naloxone (90 nmol) or phentolamine (100 nmol) after IT injection of various combinations of morphine and ST-91 immediately and completely abolished the potentiating effect of the combination. The clearance of IT [3H]morphine from the thoracic and lumbar spinal cord was not changed in the presence of ST-91. These observations suggest a potent synergistic interaction between spinal mu and alpha 2 adrenergic receptor systems.
Adrenergic alpha-Agonists↗
The antiseizure activity of dihydropyridine calcium channel antagonists in the conscious rat.
By using a rat seizure model, a comparison of the antiseizure activity of 12 dihydropyridine calcium channel antagonists (administered i.c.v.) to their binding affinities for the neuronal site known to regulate L-type calcium channels was made. For these dihydropyridine calcium channel antagonists a correlation between physiologic activity and binding affinities would provide evidence that these agents exert their antiseizure actions via a mechanism involving a binding site that regulates L-type neuronal calcium channels. Despite i.c.v. administration, a parallel in antiseizure activity and binding affinities could not be demonstrated precisely, suggesting that the dihydropyridines may be exerting their antiseizure activity by more than just simple neuronal calcium channel blockade.
Animals↗
Endogenous opioid system down-regulation during hibernation in amphibians.
In late summer, Northern grass frogs, Rana pipiens, intraspinally administered dynorphin produces a potent, dose-dependent antinociceptive action as measured by the acetic acid test used to evoke a hindlimb wiping response. Surprisingly, in fall, frogs which have entered hibernation, intraspinal dynorphin produces no antinociception action. Intraspinal morphine shows a decreased effect in fall frogs while systemic morphine is equi-effective in summer and fall frogs. Immobilization stress, previously shown to be mediated by endogenous opioid systems in this amphibian, produces a robust increase in nociceptive thresholds in summer frogs while the nociceptive thresholds of fall frogs are unaffected by this procedure. Summer frogs adapted to cold room (4 degrees C) show a significant decrease in nociceptive thresholds compared to cohorts kept at room temperature, and cold-adapted frogs returned to room temperature show a naloxone-attenuated increase in nociceptive threshold. Collectively, these data suggest that endogenous opioid systems in these northern frogs are down-regulated during fall hibernation.
Animals↗
Magnitude of opioid dependence after continuous intrathecal infusion of mu- and delta-selective opioids in the rat.
The continuous intrathecal infusion of morphine (2, 6, 20 nmol/h), sufentanil (0.06, 0.2, 0.6 nmol/h), [D-Ala2,MePhe4, Gly-ol5]enkephalin (DAMGO) (0.1, 0.3, 1.0 nmol/h) or [D-Ala2,D-Leu5]enkephalin (DADLE) (2, 6, 20 nmol/h) in unanesthetized rats produces a dose-dependent increase in hot plate latency 1 day after pump implant followed by a gradual return to baseline values by days 3-4, i.e. tolerance. Rats assessed for opioid dependence after 7 days of intrathecal (i.t.) infusion of opioids show a withdrawal syndrome most readily noted by withdrawal body shakes (WBS) after injection of the opioid antagonist, naloxone (1 mg/kg i.p.). The number of WBS was proportional to the infusion dose of opioid agonist. Although each tolerance-producing agent was infused in one of three log-spaced (low, medium, high) doses, selected to have approximately equal antinociceptive activity across agents, the agents varied in the apparent degree of dependence. Thus, at the highest infusion dose, the average number of WBS observed was greatest for DADLE (32.8), morphine (30.2) and sufentanil (25.0) while animals treated with DAMGO displayed a significantly less degree of opioid dependence (8.7).
Animals↗
Diltiazem enhances and flunarizine inhibits nimodipine's antiseizure effects.
The dihydropyridine calcium channel antagonist, nimodipine has antiepileptic and anticonvulsive properties that are thought to be mediated through neuronal calcium channel blockade. The dihydropyridine binding site can be positively and negatively allosterically regulated by the benzothiazepines and the phenylalkylamines/piperazines, respectively. We investigated this binding interaction at the physiologic level by examining the effects of diltiazem (a benzothiazepine) and flunarizine (a piperazine) on the antiseizure activity of nimodipine. Seizures were induced with pentylenetetrazole in awake rats with chronically implanted EEG electrodes. Calcium channel antagonists were administered intracerebroventricularly 30 min after pentylenetetrazole at doses given at 15 min intervals. Diltiazem and flunarizine alone lacked antiseizure properties. The calculated ED50 values for nimodipine were: nimodipine alone = 135 micrograms; nimodipine + diltiazem (100 micrograms) = 67 micrograms. Nimodipine + flunarizine (10 micrograms) completely suppressed nimodipine's antiseizure activity. These findings may reflect the interaction observed among these agents at binding sites associated with the calcium channel and supports the idea that dihydropyridines mediate their antiseizure actions through neuronal calcium channel antagonism.
Animals↗
Benzo[a]pyrene-diol-epoxide-induced anchorage-independence in diploid human fibroblasts. Analysis of cellular protooncogenes.
Treatment of diploid human fibroblasts with stereoisomeric benzo[alpha]pyrene anti and syn diol epoxides has been shown to induce anchorage-independent clones of cells with a dose dependence and frequency [(0.5-12) X 10(-4)] not significantly different from mutations at the hypoxanthine-guanine phosphoribosyltransferase locus [(1-8) X 10(-4)] in these cells. The majority of the anchorage-independent clones that were picked retained their mutagen-induced, anchorage-independent phenotype through at least 20 generations of expansion in monolayer culture. No variant cells showing extended life-span were detected among survivors in any of the mutagen treatment groups (less than 1.6 X 10(-7) frequency). Extensive analysis of a pool of 15 cellular protooncogenes (Ha-ras, Ki-ras, N-ras, mos, fos, fes, myc, abl, sis, myb, erbA, erbB, src, raf, N-myc), using Southern and northern blot analysis, was done to determine whether mutagen-induced rearrangement, amplification or overexpression of any of these genes was responsible for the mutagen-induced, anchorage-independent phenotype. We found no evidence that the genomic arrangement or expression level of any of these genes had been altered, thus indicating that an alternative form of mutation, or an alternative gene not included in this screening was responsible for the mutagen-induced, anchorage-independent phenotype.
7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide↗
Use of CA 125 to monitor patients with ovarian epithelial carcinomas.
The CA 125 radioimmunoassay has been increasingly used to monitor the course of patients with ovarian epithelial carcinomas. The purpose of this report is to describe our experience in the use of this assay and to better define its clinical utility. Fifty-one patients had serum CA 125 follow-up during primary chemotherapy. All 51 patients demonstrated either a normal CA 125 level at the completion of chemotherapy or a substantial fall in CA 125 values with treatment. In 48 of 51 patients, the drop in CA 125 levels was temporally related to the clinical regression or remission of tumor. Forty of these patients underwent second-look laparotomy; 23 patients (58%) had residual disease. A total of 45 patients had serum CA 125 determinations at the time of second-look laparotomy. Eight patients with microscopic disease and 11 of 18 patients with gross residual disease had a "negative" (less than 35 U/ml) CA 125 level. The predictive value of an elevated CA 125 level was 1.00. However, the predictive value of a negative value was only 0.50. Hence, a negative CA 125 level cannot be a substitute for a second-look laparotomy. Only 7 of 18 patients (39%) with gross residual disease at second-look surgery had an elevated CA 125 level. Patients with an elevated CA 125 and gross residual tumor at the second-look laparotomy uniformly demonstrated large, bulky disease. Furthermore, the survival of patients with gross residual disease at second-look laparotomy correlated with the preoperative CA 125 value. Serum CA 125 determinations also show promise in the follow-up of patients with a negative second-look laparotomy. The serum CA 125 level from patients with a "negative" second-look laparotomy can become elevated months before recurrent disease is appreciated.
Actuarial Analysis↗
Management of malignant, mixed mesodermal tumors of the uterus.
Forty-two patients with malignant, mixed mesodermal tumors of the uterus were identified by retrospective chart review. Only 2 patients were premenopausal at the time of diagnosis. Six of the patients had previously received pelvic radiotherapy. Surgical/pathologic findings were inconsistent with clinical staging in 17 of the patients. Patients with stage I tumors were found to have extrauterine extension of tumor in 39% of the cases. Overall, 2- and 5-year actuarial survival rates were 40 and 18%, respectively. The surgical extent of disease was a major prognostic factor in patient survival (P = 0.006). Patients with tumors showing no invasion or invasion limited to the inner two-thirds of the myometrium also demonstrated a significant survival advantage as compared to those with deeper myometrial invasion (P = 0.02). However, no statistically significant relationship was demonstrated between survival and patient age, the nature of the sarcomatous element (homologous or heterologous), or the presence of cervical involvement. Patients with recurrent or persistent disease did poorly; only 4 patients have survived more than 1 year after documentation of recurrent disease. Two patients had prolonged disease stabilization with radiotherapy and cisplatin. Another patient with pulmonary metastases had a 6-month, complete response to cisplatin.
Adult↗
Potency of infused spinal antinociceptive agents is inversely related to magnitude of tolerance after continuous infusion.
By employing a constant-rate (1 microliter/hr) constant-dose intrathecal infusion pump in rats, groups received a 7-day infusion of one of three concentrations (in nmol/hr) of each of the following receptor preferring ligands: morphine (mu: 2, 6, 20), sufentanil (mu: 0.06, 0.2, 0.6), DAMGO (mu: 0.1, 0.3, 1.0), DADLE (delta: 2, 6, 20) or ST-91 (alpha-2: 3, 10, 30). On day 7 the magnitude of tolerance was assessed by establishing i.t. dose-response curves for the effect of the chronic drug given as a bolus. Each infused animal was used for one bolus injection. It was observed that for all drugs, a parallel rightward shift in the dose-response curve was produced with the degree of shift proportional to the log of the infusion dose. Of particular significance was the finding that drugs differed significantly in the magnitude of the shift produced by the chronic infusion of equieffective concentrations. Thus, at the intermediate infusion dose, the degree of the shift in the bolus dose-response curve (i.e., magnitude of tolerance) for morphine, DADLE, ST-91, DAMGO and sufentanil was 55, 46, 29, 7 and 2, respectively. These data are interpreted to suggest that agents with high potency and a significant receptor reserve will produce a smaller shift in the dose-response curve (e.g., sufentanil and DAMGO) than the similar infusion of an equieffective dose of another agent with less potency and a smaller population of spare receptors (morphine).
Analgesics↗
The significance of atypical cervical cytology in an older population.
To ascertain the significance of squamous atypia encountered during routine Papanicolaou smear screening in an older population, we reviewed 115 consecutive patients over age 50 seen during a 3-year period. Evaluation included repeating the smear and performing colposcopy in all patients. Colposcopically directed biopsy and endocervical curettage were performed when appropriate. Sixty-seven patients (58.3%) had atrophy, 43 (37.4%) were normal, two (1.7%) had cervical intraepithelial neoplasia grade 1, two (1.7%) had cervical intraepithelial neoplasia grade 2, and one (0.9%) had human papillomavirus (HPV) infection. There was a strong association between squamous atypia and estrogen deficiency. With the correction of the estrogen deficiency, the squamous atypia reverted to normal in a statistically significant percentage of patients. A Papanicolaou smear report of squamous atypia in women over age 50 should not be considered normal; further evaluation is required. The incidence of cervical or vaginal intraepithelial neoplasia and HPV infection is much lower than reported in studies involving younger patients.
Aged↗
Squamous atypia on cytology. The influence of age.
The optimal management of squamous atypia on cytology has not been determined. Colposcopy has been recommended because of the high false-negative rate of cytology. To evaluate colposcopy, 1,074 consecutive, nonpregnant women presenting with squamous atypia on cytology were examined prospectively with colposcopy and simultaneous repeat cytology. No specific treatment was given prior to evaluation. Biopsy and endocervical curettage were performed when clinically indicated. Two hundred two women (18.8%) had abnormal cervical or vaginal biopsies, 74 had human papillomavirus, and 128 had cervical intraepithelial neoplasia with or without associated papillomavirus infection. Invasive cancer was not detected. Repeat cytology suggested intraepithelial neoplasia in 60 women, 37 (61%) of whom had positive biopsy findings. Such biopsy findings were obtained in 89 of 306 women (29.1%) with repeat squamous atypia on cytology and in 76 of 708 women (10.8%) with repeat negative cytology. When the data were stratified in terms of age, 184/787 (19.6%) abnormal biopsies occurred in women less than or equal to 40 years of age and 18/287 (6.3%) in women greater than or equal to 41. Squamous atypia on cytology should not be ignored. However, women greater than or equal to 41 are at lower risk of having colposcopically detectable abnormalities and can be followed more conservatively.
Adolescent↗
Opioid dependence after continuous intrathecal infusion of mu and delta opioids in the rat.
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Analgesics, Opioid↗
Assessment of the role of A1/A2 adenosine receptors mediating the purine antinociception, motor and autonomic function in the rat spinal cord.
The effects on nociception, motor and autonomic function produced by the intrathecal administration of three adenosine analogs: N6-(L-2-phenylisopropyl)-adenosine, N6-cyclohexyladenosine and 5'-(N-ethylcarboxamido)-adenosine were examined in rats. Over the range of 0.3 to 1.0 nmol these agents produced a dose-dependent antinociception in the hot plate and tail-flick tests. In addition, 5'-(N-ethylcarboxamido)-adenosine and N6-(L-2-phenylisopropyl)-adenosine both suppressed the chemically evoked writhing response as well as the touch-evoked hyperesthesia normally observed in rats receiving low doses of intrathecal strychnine. These adenosine analogs examined at doses higher than 1.5 nmol produced a dose-dependent motor impairment as measured behaviorally and by electromyography, and an increase in the volume distention required to evoke micturition. Statistically significant effects on heart rate or blood pressure were not observed at any of the doses tested. The effects of the adenosine analogs on nociceptive and motor endpoints were partially antagonized by pretreatment with intrathecal caffeine (2 mumol). These results suggest a probable association of spinal adenosine receptors with a number of spinal sensory and motor systems other than those involved with nociceptive processing.
Adenosine↗
Time course characteristics of tolerance development to continuously infused antinociceptive agents in rat spinal cord.
By using a constant-rate, fixed concentration intrathecal infusion model, the time course of change in hot plate (HP) response latencies over a 7-day period was examined in rats receiving constant infusion of saline (vehicle), morphine (MOR (2, 6 or 20 nmol/hr), sufentanil (SUF) (0.06, 0.2 or 0.6 nmol/hr), D-Ala2-MePhe4-Gly-ol5-enkephalin (DAMGO) (0.1, 0.3 or 1.0 nmol/hr) (mu opioids), D-Ala2-D-Leu5-enkephalin (DADLE) (2,6 or 20 nmol/hr) (delta opioid), ST-91 (3, 10 or 30 nmol/hr) (alpha-2 agonist) or the combination of ST-91 + MOR. Three important observations were made: 1) A concentration-dependent elevation in HP latency was observed on day 1 (order of potency: DAMGO = SUF greater than MOR greater than or equal to DADLE greater than or equal to ST-91 + MOR greater than or equal to ST-91) with a gradual return to saline-infused values observed for all concentrations of all drugs by 3 to 5 days. 2) The rate of tolerance development, estimated by calculation of the exponential decay half-life from peak day 1 HP, was not different as a function of drug dose. The area under the 7-day tolerance curve (response latency x day) was directly proportional to infusion concentration and to peak HP effect on day 1. These two calculations both suggest that the rate at which the tolerance adaptation of drug occurs to agonist effects is similar for agents acting upon mu, delta and alpha-2 receptors in rat spinal cord.(ABSTRACT TRUNCATED AT 250 WORDS)
Analgesics↗
Chronic intraventricular administration of cholecystokinin octapeptide (CCK-8) suppresses feeding in rats.
Cholecystokinin octapeptide (CCK-8) is known to suppress feeding in sheep, pigs, golden hamsters and rats following acute intracerebroventricular (i.c.v.) injection. In this study, we report the effects of chronically administered i.c.v. CCK-8 on long-term food intake in rats. After baseline food intake was established over a period of 3 days, rats were implanted with Alzet osmotic minipumps, which delivered 1.0 microliter/h. Three groups of animals were prepared which received saline (vehicle) or CCK-8 at 12.25 micrograms/day (low dose) or CCK-8 at 122.5 micrograms/day (high dose). Surgical preparation of the animals with the intraventricular cannula and the osmotic minipump resulted in an initial reduction in food consumption in all groups. In the saline group daily food consumption returned to presurgery values by day 4. Similar results were observed with the low dose of CCK-8. In contrast, in animals receiving the high concentrations of CCK-8, the initial fall in feeding was more prominent and though it rose during the 7-day infusion interval, it remained statistically below control during this period. After termination of the infusion, daily food consumption rose to normal levels during the next 3 days. For comparison, the cumulative difference between daily food consumption over the period of 8 days during infusion and pre-infusion control was 39.9 +/- 10.0 g/24 h in the saline group. In CCK-8-infused animals, food consumption after pump implantation was reduced by an integrated value of 35.5 +/- 5.0 g/24 h at low dose and 117.4 +/- 20.2 g/24 h at high dose.(ABSTRACT TRUNCATED AT 250 WORDS)
Animals↗
Opioid antinociception in amphibians.
Systemic and spinal administration of opioids produces a behaviorally defined antinociception in a variety of mammalian models. Although endogenous opioid peptides and opioid binding sites are ubiquitous throughout phylogeny, little attention has been paid to the function of endogenous opioid system(s) or development of nociceptive models in nonmammalian species. Recent work has shown that the amphibian, Rana pipiens, provides an appropriate model for assessment of opioid antinociception and that endogenous opioid systems may likewise modulate the central processing of noxious information in amphibians as well as mammals.
Amphibians↗
Characterization of mutagen-activated cellular oncogenes that confer anchorage independence to human fibroblasts and tumorigenicity to NIH 3T3 cells: sequence analysis of an enzymatically amplified mutant HRAS allele.
Treatment of diploid human fibroblasts with an alkylating mutagen has been shown to induce stable, anchorage-independent cell populations at frequencies (11 X 10(-4) consistent with an activating mutation. After treatment of human foreskin fibroblasts with the mutagen benzo[a]pyrene (+/-)anti- 7,8-dihydrodiol 9,10-epoxide and selection in soft agar, 17 anchorage-independent clones were isolated and expanded, and their cellular DNA was used to cotransfect NIH 3T3 cells along with pSV2neo. DNA from 11 of the 17 clones induced multiple NIH 3T3 cell tumors in recipient nude mice. Southern blot analyses showed the presence of human Alu repetitive sequences in all of the NIH 3T3 tumor cell DNAs. Intact, human HRAS sequences were observed in 2 of the 11 tumor groups, whereas no hybridization was detected when human KRAS or NRAS probes were used. Slow-migrating ras p21 proteins, consistent with codon 12 mutations, were observed i in the same two NIH 3T3 tumor cell groups that contained the human HRAS bands. Genomic DNA from one of these two human anchorage-independent cell populations (clone 21A) was used to enzymatically amplify a portion of exon 1 of the HRAS gene. Direct sequence analysis of the amplified DNA indicated equal presence of a wild-type (GGC) and mutant (GTC) allele of the HRAS gene. The results demonstrate that exposure of normal human cells to a common environmental mutagen yields HRAS GC----TA codon 12 transversions that have been commonly observed in human tumors. This oncogene as well as yet to be identified oncogene are also shown to stably confer anchorage-independence to human cells.
7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide↗