Biomedical subjects

A Baamonde

Publications and source records attributed to A Baamonde.

At least 19 recordsLinked to original sources

PubMed2001

Effects of the calcium release inhibitor dantrolene and the Ca2+-ATPase inhibitor thapsigargin on spinal nociception in rats.

The effects produced by the intrathecal administration of dantrolene and thapsigargin, measured in several analgesic tests in the rat are described. Dantrolene decreases the release of calcium from intracellular stores and thapsigargin is able to inhibit the reticular Ca2+-ATPase, avoiding intracellular calcium storage. Dantrolene (30-300 nmol/rat) and thapsigargin (3-30 nmol/rat) reduced the nociceptive behavior (biting, scratching, licking; BSL) produced by the NK(1) receptor agonist septide (0.5 microg), without affecting the BSL induced by AMPA (2 microg) or NMDA (4 microg). Also, both drugs elicited analgesia in the tail-flick test but not in the formalin test. The antinociceptive effects induced by thapsigargin were more intense and long-lasting than those produced by dantrolene. These results seem to indicate that the intracellular modulation of calcium homeostasis could be an interesting target in order to induce spinal analgesia.

Analgesics↗

PubMed2000

Intrathecal N-methyl-D-aspartate (NMDA) induces paradoxical analgesia in the tail-flick test in rats.

The intrathecal (IT) administration of NMDA in rodents has usually been reported to produce hyperalgesic reactions, although some articles describe that spinal NMDA can lead to analgesia. We show here that the nociceptive behavior (biting, scratching, licking; BSL) observed after NMDA injection (1-8 microg/rat; IT) is followed by a long period of increased tail-flick latencies, not longer detected 24 h after NMDA administration. The NMDA-receptor antagonist CPP (10-100 ng/rat; IT) blocked the BSL behavior induced by NMDA. In the tail-flick test, this antagonist induced analgesia by itself, and was able, at 30 ng/rat, to prevent the NMDA-mediated analgesia. The implication of opiate mechanisms was discarded since naloxone (3 and 10 mg/kg; IP) did not antagonize NMDA-induced analgesia. Finally, the involvement of the intracellular calcium binding protein calmodulin was assessed. The calmodulin inhibitor, calmidazolium (30-300 microg/rat; IT) only blocked the excitatory effect (BSL) without modifying the tail-flick analgesia produced by NMDA (4 microg). These results show that a single intrathecal administration of NMDA sequentially induces both nociceptive and antinociceptive, nonopiate responses in rats.

Analgesics, Non-Narcotic↗

PubMed2000

Effects of intraplantar morphine in the mouse formalin test.

We studied the effects of intraplantar morphine in the formalin test in mice. Intraplantarly administered morphine (30 - 300 microg) induced analgesic effects at lower doses than intraperitoneally administered morphine. Following the administration of [3H]morphine, the % of radioactivity present in brain was the same by either route. In contrast, higher radioactivity values appeared in the injected paw in those mice intraplantarly injected. Since local morphine induces analgesia at doses lower than the intraperitoneally administered drug, especially in the second phase of the test, and the access to brain is undistinguishable, we propose that local morphine enhances central opiate analgesia in the formalin test in mice.

Analgesics, Opioid↗

PubMed2000

Effects of DAGO on the rodent hippocampal evoked potentials using different perfusion solutions.

Opioid receptor agonists exert excitatory effects in the hippocampus by inhibiting GABA release. We report that the mu-opioid agonist, DAGO, increases the amplitude of the population spikes (PS) measured in the stratum pyramidale of the CA1 cell layer in mouse and rat hippocampal slices perfused with an artificial cerebrospinal fluid (ACSF), but not when perfused in Krebs solution. The GABAA agonist, 3-APS, induces inhibitory responses when perfused in either ACSF or Krebs. Also, the field excitatory postsynaptic potentials (EPSP) measured on stratum radiatum do not differ when the slice is perfused with either ACSF or Krebs. The increase in the amplitude of the PS induced by DAGO is not obtained when perfused in a modified. ACSF whose concentration of MgSO4 was lowered to its concentration in the Krebs solution (from 2.4 mM to 1.2 mM). Thus, changes in the concentration of MgSO4 seem to be responsible for the different responses induced by DAGO.

Analgesics↗

PubMed1999

Effects of diethylstilbestrol on mouse hippocampal evoked potentials in vitro.

1. Several steroids and related compounds can bind to central opiate receptors in whole-brain mouse homogenates. Among these drugs, the synthetic estrogen, diethylstilbestrol (DES), exhibits one of the highest affinities in binding experiments labeling opiate receptors with the nonselective opiate antagonist, [3H]diprenorphine. 2. In the search for a functional correlate to this biochemical finding, we have studied the effects of DES on the mouse hippocampal slice in vitro preparation. 3. Previously, binding studies were performed in hippocampal homogenates, labeling opiate receptors with [3H]diprenorphine or with the mu-selective opiate agonist, [3H]DAGO. DES inhibited [3H]diprenorphine and [3H]DAGO binding, the IC50 values obtained being (1.03 +/- 0.16) x 10(-5) and (1 +/- 0.8) x 10(-5) M, respectively. 4. In mice hippocampal slices, we measured the extracellular evoked potentials obtained in the CA1 pyramidal cell layer of the hippocampi and the field excitatory postsynaptic potentials (EPSP) obtained in the stratum radiatum. The presence of DES (10(-5) M) induced an increase in the amplitude of the population spikes measured in the pyramidal layer without modifying the field EPSP. This effect is similar to that obtained in the presence of DAGO in this preparation. The effect produced by DES was not modified by the presence of the opiate competitive antagonist, naloxone (10(-5) M), or by the opiate alkylating agent, beta-chlornaltrexamine (10(-5) M). Conversely, in the presence of the transcription inhibitor, actinomycin D (5 micrograms/ml), the effect produced by DES was inhibited. 5. Our results with DES support the general idea that estrogens increase central excitability. Although diethylstilbestrol can bind to opiate receptors in the hippocampus, the effect induced by this estrogen on hippocampal excitability seems unrelated to a direct action on opiate receptors, and an intracellular effect is suggested.

Animals↗

PubMed1999

Spinal effects of the calmodulin inhibitor calmidazolium on dorsal horn neurons in the rat.

Drugs able to inhibit calmodulin activation can prevent some consequences of the rise in intracellular calcium. It has recently been shown that intrathecal injection of calmodulin inhibitors induce analgesia in rats. We study here the effect induced by the calmodulin inhibitor, calmidazolium, on the activity of dorsal horn neurons driven by noxious and non-noxious stimuli. Extracellular recordings of convergent (n = 12), low-threshold mechanoreceptive (n = 5) and proprioceptive (n = 5) units were made in the presence of calmidazolium. Calmidazolium (600 micrograms) reduced the noxious (50 degrees C) heat-evoked responses obtained in convergent neurons. On the contrary, the non-noxious tactile responses obtained in low-threshold mechanoreceptive neurons as well as the joint movement-evoked responses obtained in proprioceptive units remained unmodified. We conclude that calmidazolium can block nociceptive processing in the spinal cord and that this fact can help to explain the analgesic effects that intrathecal W-7 and calmidazolium induce in behavioral tests.

Animals↗

PubMed1999

Study of the density of opioid receptors in the male mouse brain at different stages of sexual maturation.

The binding of opiate receptors was evaluated in male Swiss CD1 mice in different stages of maturation, i.e., prepubertal (7 and 20 days old), pubertal (40 days old) and postpubertal (60 days old). The opiate receptors were labeled with [3H]-diprenorphine and the KD and Bmax were measured. A similar KD (0.35-0.42 nM) value was obtained in all age groups tested indicating no changes in opiate affinity with sexual maturation. The maximal opiate binding capacity, Bmax was similar in 20- and 40-day-old mice as compared to 60-day-old mice while lower values were obtained in 7-day-old mice. These data indicate that sexual maturation does not affect the number of opiate receptors. Since different testosterone plasma levels have been described in males of this strain at the different ages included in our study, our results support previous findings showing that testosterone does not influence opiate binding sites in rodents.

Animals↗

PubMed1998

Comparison of the effects of calmidazolium, morphine and bupivacaine on N-methyl-D-aspartate- and septide-induced nociceptive behaviour.

We have recently shown that spinal calmodulin inhibitors (W-7 and calmidazolium) dose-dependently inhibit the nociceptive reaction (biting, scratching, licking, BSL) evoked by intrathecal N-methyl-D-aspartate (NMDA) and septide, an agonist of the neurokinin (NK) NK1 receptor. To compare this effect with that induced by standard analgesics, we now report a study of the effects of calmidazolium (14420 nmol), bupivacaine (29-582 nmol) and morphine (26-260 nmol) when coadministered intrathecally with either NMDA (4 microg) or septide (0.5 microg). Calmidazolium had the highest potency for inhibiting septide-induced nociceptive behaviour, acting over a dose range of 34-130 nmol (dose eliciting a half-maximal response, ED50, 67 nmol) lower than that of bupivacaine [ED50 234 (115-475) nmol]. Only the highest dose of morphine (260 nmol) inhibited septide-evoked BSL [ED50=133 (69-255) nmol]. Higher doses of morphine could not be tested due to the appearance of an excitatory aversive reaction. Both calmidazolium [ED50=232 (138-388) nmol] and bupivacaine [ED50=123 (59-256) nmol] dose-dependently reduced NMDA-induced BSL reaching an almost maximal inhibition at the highest doses assayed (420 and 291 nmol, respectively). In contrast, morphine had less effect on NMDA-induced behaviour, inducing only a partial reduction of BSL even with the highest dose assayed (260 nmol). Overall, it can be concluded that the calmodulin inhibitor calmidazolium inhibits septide- and NMDA-evoked nociceptive behaviour with a potency and efficacy at least as high as those of morphine and bupivacaine.

Analgesics↗

PubMed1998

Different types of steroids inhibit [3H]diprenorphine binding in mouse brain membranes.

1. The binding of 60 drugs, mainly steroids, to opioid receptors was studied in crude membrane fractions from mouse brains. 2. Competition assays with the different drugs (5 x 10(-7)-10(-4)M) were performed by labeling opiate receptors with [3H]diprenorphine (0.3-0.4 nM). 3. Only 7 drugs (alpha,5beta-tetrahydrodeoxycorticosterone, megestrol acetate, mifepristone, 17alpha-ethynylestradiol, diethylstilbestrol, clomiphene citrate and tamoxifen citrate) inhibited [3H]diprenorphine binding more than 50% at the highest concentration assayed (10(-4) M). The IC50 values ranged between 6x10(-5) M. 4. Thus, the present results show that only a limited number of steroids, from diverse classes, bind to opiate receptors.

Animals↗

PubMed1997

Spinal calmodulin inhibitors reduce N-methyl-D-aspartate- and septide-induced nociceptive behavior.

The effect of two calmodulin inhibitors, W-7 (N-(6-aminohexyl)-5-chloro-1-naphtalenesulfonamide) and calmidazolium, on the nociceptive behavior induced by the intrathecal injection of NMDA (N-methyl-D-aspartate), AMPA (alpha-amino-3-hydroxy-5-methyl-4-iso xazolepropionic acid) or of septide is described. Lumbar intrathecal injection of NMDA, AMPA or septide induced a caudally directed nociceptive reaction (biting, scratching and licking). The nociceptive behavior induced by NMDA (4 microg) was dose dependently inhibited when W-7 (0.25-1 micromol/rat) or calmidazolium (0.12-0.5 micromol/rat) was coinjected. Biting, scratching and licking produced by AMPA (2 microg) were unaffected by intrathecal calmodulin inhibitors. Finally, septide-evoked nociceptive behavior (2 microg) was antagonized by W-7 (0.12-0.5 micromol/rat) and calmidazolium (0.06-0.25 micromol/rat). Thus, calmodulin inhibitors prevent the nociceptive reaction evoked by drugs that modify intracellular Ca2+, NMDA and septide, without affecting the nociceptive response induced by AMPA, for which Ca2+ is not the main second messenger.

Animals↗

PubMed1997

Cyproterone acetate displaces opiate binding in mouse brain.

Drugs acting on androgen receptors modify opioid transmission in the central nervous system. To investigate a direct interaction, we studied whether the binding of [3H]diprenorphine to mouse brain membranes was modified by cyproterone acetate (progesterone derivative with antiandrogen activity), flutamide (non-steroidal antiandrogen), 5alpha-dihydrotestosterone and progesterone. Only cyproterone acetate inhibited [3H]diprenorphine binding (IC50 = (1.62 +/- 0.33) x 10(-6) M) without modifying its association rate. These results suggest that cyproterone acetate binds to opiate receptors independently of its classical androgenic intracellular receptor effect.

Androgen Antagonists↗

PubMed1996

Calmodulin inhibitors induce spinal analgesia in rats.

Calcium is an important intracellular messenger that interacts with Ca(2+)-binding proteins, such as calmodulin (CaM), to activate several intracellular enzymes. The involvement of Ca2+ in the transmission of nociceptive signals has been demonstrated at the spina level. Specifically, spinal sensitization induced by persistent nociceptive stimulation seems to be related to an increase of cytosolic calcium and the subsequent activation of several enzymes, some of which are Ca2+/CaM dependent. In order to elucidate the possible implication of calmodulin in these pain processes, we have studied the effect of two calmodulin inhibitors (W-7 and calmidazolium) or the formalin and tail-flick tests in rats after their intrathecal administration. Antinociceptive effects were observed in both tests by injecting 0.12-1 mumol/rat of calmidazolium and 0.25-2 mumol/rat of W-7. Calmidazolium was more potent than W-7 in inhibiting both phases of the formalin test, whereas lower doses of W-7 in comparison to calmidazolium affected the tail-flick latencies. In addition, both drugs induced, at high doses, a muscular flaccidity of the hindlimbs that impaired normal walking in the rats. This effect caused; significant reduction of the rotarod performance when 1 mumol/rat of calmidazolium or 2 mumol/rat of W-7 were injected. Overall, our results show that calmodulin inhibitors are capable of producing spinal analgesia on phasic and tonic noxious stimuli in rats, thus rendering them a promising potential as analgesics.

Analgesia, Epidural↗

PubMed1996

Interaction among alfaxalone, pregnenolone sulfate, and two GABAA agonists on hippocampal slices.

GABAA agonists do not respond to the same degree to allosteric modulators of the GABAA receptor complex such as benzodiazepines. We report there the effects of two steroids (alfaxalone and pregnenolone sulfate) on the inhibition induced by two GABAA agonists, 3-amino propane sulphonic acid (3-APS) and muscimol, on the extracellular evoked potentials obtained in CA1 of mice hippocampi. Alfaxalone (1 microM) potentiates the effects of both agonists, although incubation times longer than 15 minutes are required to potentiate the inhibitory effect of muscimol. Lower doses of pregnenolone sulfate at shorter incubation periods are able to inhibit the effects produced by single doses of 3-APS as compared to muscimol (15 microM during 5 min vs 30 microM during 5 min). Our results confirm the possibility that there might be differences in the interaction between GABAA agonists and modulatory steroids.

Allosteric Regulation↗

PubMed1996

Calcium and depolarization-dependent effect of pregnenolone derivatives on uterine smooth muscle.

1. The effects of several gestagens (pregnenolone [1 to 30 microM], 20 alpha-hydroxy-pregnenolone [1 to 30 microM], and 20 beta-hydroxypregnenolone [1 to 30 micro M]) on rat uterine contraction induced by KCl (60 mM) and CaCl2 (30 microM to 6 mM) have been assayed. 2. The three drugs relaxed the tonic contraction induced by KCl in a concentration-dependent way. The respective EC50 values were: 27.6 +/- 1.58 microM (pregnenolone), 4.1 +/- 0.12 microM (20 alpha-hydroxy-pregnenolone), and 11.2 +/- 1.04 microM (20 beta-hydroxypregnenolone). CaCl2 (1 to 10 mM) totally counteracted the relaxing effect of pregnenolone but only partially compared to that of 20 alpha- or 20 beta-hydroxy-pregnenolone. 3. CaCl2 (30 microM to 6 mM) produced concentration-dependent contraction of rat uterus in medium lacking calcium plus 30, 60, or 90 mM of KCl. The EC50 values of CaCl2 were: 0.38 +/- 0.072, 0.183 +/- 0.015, and 0.183 +/- 0.015 mM in a medium with 30, 60, or 90 mM of KCl, respectively. 4. Pregnenolone (10 microM) did not significantly modify the EC50 of CaCl2 in a medium with 30, 60, or 90 mM of KCl. However, 20 beta-hydroxypregnenolone (10 microM) antagonized, in a noncompetitive manner, the concentration-response curve to CaCl2. 5. 20 alpha-Hydroxypregnenolone (4 microM) antagonized the concentration-response curve to CaCl2 in a competitive manner. This antagonism was directly related to the concentration of KCl in the medium. 6. Our results suggest a different calcium antagonist effect of the three gestagens assayed.

Animals↗

PubMed1995

Non-immunological hydrops fetalis and intrapericardial teratoma: case report and review.

A large intrapericardial teratoma was found at necropsy in a 38-week stillborn fetus, in which prenatal diagnosis of hydrops fetalis and an echogenic cardiac mass had been made. Clinical and pathological data are reported. In utero intrapericardial teratomata lead to different outcomes depending on whether fetal hydrops is associated. When generalized fetal hydrops is not present, the outcome is good, even in cases with large pericardial effusions. When generalized fetal hydrops occurs, it often results in a poor outcome. In our literature review, we have found eight perinatal deaths in nine similar cases reported.

Adult↗

PubMed1994

Gender and test dependence of a type of kappa mediated stress induced analgesia in mice.

1. In male mice, 80 inescapable footshocks (S-80) induce analgesic responses measured by the tail flick test that are blocked by naloxone and the kappa opioid antagonist, nor-binaltorphimine. We now study the nociceptive responses, induced after this particular stress, measured by the writhing test, the tail immersion test and a high intensity tail immersion test both in male and female mice. 2. In stressed males, analgesic responses are seen in all the nociceptive tests. Naloxone (10 mg/kg) does not prevent them. 3. In stressed females, in contrast with males, no analgesia is produced in the tail flick test. The writhing test and the tail immersion test registered analgesic responses that were not prevented by naloxone (10 mg/kg). 4. We conclude that only the antinociceptive kappa opioid mediated component of the stress we study is strongly dependent on gender, in contrast to other types of analgesia triggered by the same stress.

Analgesia↗

PubMed1993

Involvement of spinal kappa opioid receptors in a type of footshock induced analgesia in mice.

We have studied the effects of several opioid antagonists on a type of footshock stress-induced analgesia (FSIA) measured by the tail-flick test in male mice. Naloxone injected either subcutaneously (0.1-10 mg/kg) or intrathecally (1-20 micrograms) antagonized FSIA at higher doses than those that blocked a similar degree of analgesia induced by morphine. Intracerebroventricular (i.c.v.) naloxone (1-20 micrograms) did not modify the FSIA while antagonizing the i.c.v. morphine-induced analgesia. As a consequence, the antagonism of the FSIA by naloxone probably occurs at the level of the spinal cord and through receptors different than mu. The delta selective antagonist naltrindole (0.1-3 mg/kg s.c.) did not antagonize the analgesic effects of the stress. Nor-binaltorphimine, a kappa selective antagonist, blocked the FSIA when administered systemically (1-4 mg/kg i.p.) or locally (0.1-1 microgram i.t.). These results strongly suggest that spinal kappa opioid receptors are responsible for this type of endogenous analgesia.

Analgesia↗

PubMed1993

Opioid footshock-induced analgesia in mice acutely falls by stress prolongation.

The application of 80 footshocks (S-80) to mice induces a decrease in nociceptive responses as measured by the tail-flick test, which is opioid mediated as well as prevented by naloxone (10 mg/kg, SC). When the stress is prolonged up to 240 shocks (S-240) (i.e., from 6 min 40 s to 20 min), no analgesia can be seen immediately after the stress. We have examined the two most obvious possibilities, but they do not seem to be responsible for this fact. When morphine (1-5 mg/kg IP) is injected in the S-240 situation, a potentiation of its analgesic effects is seen, so that a desensitization of mu opioid receptors is unlikely. On the other hand, although cortisol (3-30 mg/kg IP) inhibits the analgesic response to S-80, metyrapone (40 and 80 mg/kg IP) and cortexolone (3-18 mg/kg IP) do not cause S-240 to be analgesic. Thus, an increase of endogenous glucocorticoids released during the long-duration stress does not seem responsible for the lack of analgesia after S-240.

Animals↗