The alpha-adrenoceptor antagonist, zolertine, inhibits alpha1D- and alpha1A-adrenoceptor-mediated vasoconstriction in vitro

1. The antagonist effect of zolertine (4-phenyl-1-[2-(5-tetrazolyl)ethyl]piperazine trihydrochloride), on vascular contraction elicited by noradrenaline in aorta, carotid (alpha1D-adrenoceptors), mesenteric (alpha1A/D-adrenoceptors) and caudal arteries (alpha1A-adrenoceptors) from Wistar Kyoto (WKY) and spontaneously hypertensive (SHR) rats and rabbit aorta (alpha1B-adrenoceptors), was investigated in endothelium-denuded arterial rings. 2. The selective alpha1D-adrenoceptor agonist, noradrenaline, elicited concentration-dependent contractions in all arterial rings from both species. Noradrenaline selectivity was: carotid = aorta >> mesenteric = rabbit aorta > caudal arteries. 3. The contractile responses induced by noradrenaline were competitively antagonized by zolertine in rat carotid and aorta arteries, yielding pA2 values of WKY, 7.48 +/- 0.18; SHR, 7.43 +/- 0.13 and WKY, 7.57 +/- 0.24; SHR, 7.40 +/- 0.08, respectively. Zolertine was a non-competitive antagonist in some blood vessels as Schild plot slopes were lower than unity. The pKb estimates for zolertine were WKY, 6.98 +/- 0.16; SHR, 6.81 +/- 0.18 in the mesenteric artery, WKY, 5.73 +/- 0.11; SHR, 5.87 +/- 0.25 in the caudal artery and 6.65 +/- 0.09 in rabbit aorta. 4. Competition binding experiments using the alpha1-adrenoceptor antagonist [3H]prazosin showed a zolertine pKi of 6.81 +/- 0.02 in rat liver (alpha1B-adrenoceptors) and 6.35 +/- 0.04 in rabbit liver (alpha1A-adrenoceptors) membranes. 5. Zolertine showed higher affinity for alpha1D-adrenoceptors compared to alpha1A-adrenoceptors, while it had an intermediate affinity for alpha1B-adrenoceptors. The ability of the alpha1-adrenoceptor antagonist zolertine to block alpha1D-adrenoceptor-mediated constriction in different vessels of WKY and SHR rats may explain its antihypertensive efficacy despite its low order of potency.

Normative and validation studies of the Nine-hole Peg Test with children

This study evaluated norms for fine motor dexterity skills on elementary school children of ages 5 through 10 and conducted reliability and validity stud ies utilizing the Nine-hole Peg Test. The sample included 826 students in 10 elementary schools. Moderately high test-retest reliability (rs = .81 and .79) and high interrater agreement (rs > .99) were obtained. Older students had shorter completion time that measured fine motor dexterity than younger students. Significant sex differences were found in completion time, but only for the dominant hand. Correlations of -.80 and -.74 between the scores on the Nine hole Peg Test and Purdue Pegboard Test at all tested ages indicated adequate concurrent validity of the measures and a significant difference in test scores between regular and special education groups provided further evidence of construct validity. The findings supported the Nine-hole Peg Test as an effective screening tool for fine motor dexterity of school-age children.

Influence of admixed citric acid on the release profile of pelanserin hydrochloride from HPMC matrix tablets

Pelanserin is a weakly basic experimental drug with a short half-life and a prolonged release formulation was developed using hydroxypropyl methylcellulose (HPMC) and citric acid to set up a system bringing about gradual release of this drug. For this purpose powder mixtures were wet granulated with water and compressed with a hydraulic press at 55 MPa. Dissolution studies were made using 900 ml HCl 0.1 N, the first 3 h, and phosphate buffer pH 7.4, h 3-8. Dissolution curves were described by M(t)/M(inf)=kt(n), applied separately for each dissolution medium. The dissolution mechanism involved a coupled diffusion/relaxation with a trend favoring the diffusion mechanism with increasing citric acid concentrations. Increasing concentrations of citric acid produced increasing values of the kinetic constants, in a cubic relationship. Higher HPMC proportions produced slower dissolution rates but with a citric acid compensating more clearly a decreased solubility of pelanserin at pH 7.4. Individually calculated dissolution curves showed experimental 8 h pelanserin dissolution in a range of 65-99% for matrices with 100 mg HPMC/tab., while those with 200 mg HPMC/tab. were in the range 57-73%.

Analgesic efficacy and bioavailability of ketorolac in postoperative pain: a probability analysis

BACKGROUND

The analgesic efficacy and bioavailability of 30 mg intramuscular ketorolac was studied in 24 patients with severe or very severe postoperative pain.

METHODS

Pain and pain relief were determined by a five-point verbal rating scale and data were submitted to a probability analysis. Ketorolac plasma levels were determined by high-performance liquid chromatography.

RESULTS

Two patients chose not to finish the study; 22 patients completed the study achieving at least good pain relief. Of these 22 patients, 13 reached complete pain relief. Ketorolac was rapidly absorbed. Notwithstanding, pain relief increased gradually, showing considerable delay with regard to plasma concentrations. Analysis of the probability-time curves revealed that 25% of the patients obtained moderate pain relief at 7 min after ketorolac administration, 50% at 11 min, 75% at 29 min, and 95% at 60 min. Good pain relief was achieved in 25, 50, and 75% of the patients at 1.1, 1.8, and 2.7 h, respectively. Complete pain relief was achieved in 25% and 50% of the patients at 2.6 h and 3.7 h, respectively. The probability of exhibiting an acceptable pain relief in responsive patients for more than 5 h was 0.97. No serious side effects were detected.

CONCLUSIONS

Results show that 30 mg intramuscular ketorolac is an adequate treatment for postoperative pain in the Mexican population. Therefore, the use of higher doses is not justified. Due to gradual installation of analgesia, administration of additional analgesic medication before 1 h is not recommended.

Early changes in nitric oxide synthase activity in atrial intramural arteries following experimental spinal cord injury in rats

Previously, we have shown that immediately after an experimental spinal cord injury (SCI) in anaesthetized rats, there is a large fall in mean arterial pressure (MAP) and heart rate (HR), followed by an abrupt increase in MAP. To evaluate the participation of nitric oxide (NO), we evaluated the activity of nitric oxide synthase (NOS) using Nicotinamide adenine dinucleotide phosphate (NADPH) diaphorase histochemistry in sections of atria at several post-injury time-intervals. Staining increased at 3 min, reached a maximum at 9 min and diminished 30 min after injury. Pretreatment with atropine prevented changes in MAP, HR and NADPH-d staining suggesting that such modifications result from an increased vagal stimulation. In conclusion, the NOS activity is transiently elevated in the atrial intramural arteries of rats subjected to an SCI.

5-HT1A receptors modulate the consolidation of learning in normal and cognitively impaired rats

Attempts were made to further analyze the role of 5-HT1A receptors in consolidation of learning by evaluating the role of these receptors in cognitively normal and impaired animals. The effects of post-training administration of 8-OH-DPAT and 5-HT1A receptor antagonists, WAY 100135, WAY 100635, and S-UH-301, plus the cholinergic and glutamatergic antagonists, scopolamine and dizolcipine, respectively, were determined using an autoshaping learning task. The results showed that 8-OH-DPAT increased the number of conditioned responses, whereas WAY100135, WAY100635, and S-UH-301, and the 5-HT depleter, p-chloroamphetamine (PCA), had no effect. PCA did not change the silent properties of the 5-HT1A receptor antagonists. PCA, WAY100635, and S-UH-301, but not GR127935 (a 5-HT1B/1D-receptor antagonist) or MDL100907 (a 5-HT2A receptor antagonist), reversed the effect to 8-OH-DPAT. Ketanserin (a 5-HT2A/2C receptor antagonist) and ondansetron (a 5-HT3 receptor antagonist), at a dose that increased the conditioned responses by itself, reversed the effect of 8-OH-DPAT. Moreover, 8-OH-DPAT or S-UH-301 reversed the learning deficit induced by scopolamine and dizocilpine whereas WAY100635 reversed the effect of scopolamine only. These data confirm a role for presynaptic 5-HT1A receptors during the consolidation of learning and support the hypothesis that serotonergic, cholinergic, and glutamatergic systems interact in cognitively impaired animals.

Discriminative stimulus properties of indorenate, a serotonin agonist

OBJECTIVE

To determine whether indorenate, a serotonin-receptor agonist, can exert discriminative control over operant responses, to establish the temporal course of discriminative control and to compare its stimulus properties to a (5-HT)IA receptor agonist. [3H]-8-hydroxy-2-(di-N-propylamino) tetralin (8-OH-DPAT).

DESIGN

Prospective animal study.

ANIMALS

Ten male Wistar rats.

INTERVENTIONS

Rats were trained to press either of 2 levers for sucrose solution according to a fixed ratio schedule, which was gradually increased. Rats were given injections of either indorenate or saline solution during discrimination training. Once they had achieved an 83% accuracy rate, rats underwent generalization tests after having received a different dose of indorenate, the training dose of indorenate at various intervals before the test, various doses of 8-OH-DPT, or NAN-190 administered before indorenate or 8-OH-DPAT.

OUTCOME MEASURES

Distribution of responses between the 2 levers before the first reinforcer of the session, response rate for all the responses in the session, and a discrimination index that expressed the drug-appropriate responses as a proportion of the total responses.

RESULTS

Indorenate administration resulted in discriminative control over operant responses, maintained at fixed ratio 10, at a dose of 10.0 mg/kg (but not 3.0 mg/kg). When the interval between the administration of indorenate and the start of the session was varied, the time course of its cue properties followed that of its described effects on 5-HT turnover. In generalization tests, the discrimination index was a function of the dose of indorenate employed; moreover, administration of 8-OH-DPAT (from 0.1 to 1.0 mg/kg) fully mimicked the stimulus properties of indorenate in a dose-dependent way. The (5-HT)IA antagonist NAN-190 prevented the stimulus generalization from indorenate to 8-OH-DPAT. Also, NAN-190 antagonized the stimulus control of indorenate when administered 45 minutes before the session, but not when administered 105 minutes before the session (i.e., 15 minutes before the administration of indorenate).

CONCLUSION

(5-HT)IA receptors are of relevance to the stimulus function of indorenate. However, other receptor subtypes may also be involved. Hence, other agonists and specific antagonists should be studied before definite conclusions are drawn.

Optimisation of Candida albicans typing by pulsed-field gel electrophoresis

Six strains of Candida albicans were subjected to pulsed-field gel electrophoresis (PFGE) using the CHEF-DRIII system (BioRad). Hansenula mingei YB-4662-VIA and Saccharomyces cerevisiae YNN 295 (BioRad) were used as size markers (1.05-3.13 and 0.22-2.2 megabase pairs [Mbp] respectively) for comparison of DNA molecules. The DNAs were resolved by a three-block protocol with pulse times of 120 s for 24 h, 240 s for 36 h and 300 s for 17 h. The voltage was set at 4.5 V/cm for the first two blocks and 4.0 V/cm for the final block. PFGE was carried out under these conditions using different agarose concentrations, types and concentrations of buffer, temperatures, and sizes of agarose gel plug. The resolution and mobility of DNAs were affected by some of these variables. Separation of C. albicans by PFGE was optimal at 12 degrees C with 1.0 x Tris-borate-EDTA (TBE) buffer using 1.2% agarose. Resolution of banding patterns was dependent on size of DNA plug used.

The protective action of amlodipine on cardiac negative inotropism caused by prolonged incubation in vitro

The mechanism of the antihypertensive action of the 1,4-dihydropyridine Ca2+ antagonist amlodipine was studied in isolated ventricular strips and aortic rings from Wistar rats after oral treatment with amlodipine 15 mg/kg/day for one week. The contractions evoked by electrical stimulation of isolated strips from right ventricles pretreated with amlodipine (5 nM) were unaffected during the first hour after mounting, but they decreased in magnitude after prolonged incubation (4 hr). However, the decrease in response of these preparations after prolonged incubation was less than that observed in strips prepared from untreated rats. A negative inotropic effect of amlodipine was observed at concentrations higher than 300 nM. In the presence of lower concentrations of amlodipine (5 nM-30 nM) after prolonged incubation, the contractions of ventricular strips were significantly more sustained than in the absence of amlodipine. Likewise, the decrease in contractility evoked by increasing the stimulation frequency from 1 to 3 Hz was reduced in amlodipine treated rats. The recovery of contractility was improved when stimulation frequency was returned to 1 Hz. On the other hand, when rat ventricular strips pretreated with amlodipine (5 nM) were exposed to isoprenaline (3 microM), the contractions evoked by isoprenaline were enhanced. The isoprenaline effect was not altered with 300 nM amlodipine, but with 3 microM became weak and was significantly lower than in strips treated with isoprenaline alone. In addition, treatment with amlodipine produced a marked decrease in the contractions evoked by 100 mM KCl solution in isolated aortic rings when compared to untreated rats. This inhibition was produced in a time-dependent manner with an IC50 equal to 30 and 3 nM after 2 and 45 min of contraction, respectively. Ex vivo results show that amlodipine treatment decreased aortic contractility without producing a negative inotropic effect although there was an occupation of cardiac Ca2+ channels. These results suggest that a protective effect of amlodipine on cardiac negative inotropism is produced by prolonged incubation in vitro.

The role of nitric oxide in angiotensin II-induced renal vasoconstriction in renovascular hypertension

OBJECTIVE

To evaluate the contribution of nitric oxide to the regulation of angiotensin II-induced renal vasoconstriction in normotensive rats and in rats with aortic coarctation-induced hypertension.

METHODS

We evaluated the renal vascular reactivity of nonischemic kidney to angiotensin II with and without nitric oxide synthesis inhibitor (NG-nitro-L-arginine methyl ester) in the isolated perfused kidney. The nitrite concentration in renal perfusate of nonischemic kidney was measured as an index of nitric oxide released and the activity of nitric oxide synthase in renal tissue was determined by production of [3H]-L-citrulline.

RESULTS

The perfusion of NG-nitro-L-arginine methyl ester potentiated angiotensin II-induced renal vasoconstriction in normotensive rats but had no effect on hypertensive rats. The release of nitrites in kidneys from hypertensive rats was lower than that in kidneys from normotensive rats. The activity of renal nitric oxide synthase was less in the hypertensive rats than it was in the normotensive rats.

CONCLUSIONS

Nitric oxide counteracts the vasoconstrictor effect of angiotensin II in normotensive rats, whereas this protective mechanism is impaired in hypertensive rats. This impairment potentiates effect of angiotensin II on vascular resistance, thereby contributing to the development of high blood pressure.

Spontaneously hypertensive rats: a potential model to identify drugs for treatment of learning disorders

Spontaneously hypertensive rats (SHR) of 3 to 12 months of age learned and retrieved less information than normotensive Wistar-Kyoto rats (WKY), although no difference was found with animals from 18 and 24 months of age. The combined influence of hypertension and aging had an additive detrimental effect on cognitive functions. Notwithstanding these deficiencies in learning and memory, SHR have seldom been used as a model in the screening of drugs with therapeutic potential for treatment of disorders of cognitive processes. Moreover, the calcium channel blocker nimodipine has beneficial effects on learning in both aged and hypertensive animals and humans. However, no attempt has been made to investigate whether nimodipine can reverse the additive deleterious effects of aging and hypertension in the same subject. We recently reported that deteriorated animals (middle-aged and/or hypertensive) chronically treated with nimodipine (via osmotic minipumps) exhibit higher learning scores. This information indicates that nimodipine can reverse the impairing effects of either aging or hypertension on learning; the presence of the two conditions, however, produces a severe impairment that can be partially reversed by this drug. Therefore, we propose that mature and middle-aged SHR represent a model for the screening of potentially useful drugs in the treatment of learning disorders, probably associated with hypertension and/or aging. Nevertheless, it must be remembered that the SHR is a genetic model and the appearance of neural disturbances could be a parallel genetic phenomenon and not necessarily or exclusively related to hypertension per se.

Effects of the 5-HT receptor antagonists GR127935 (5-HT1B/1D) and MDL100907 (5-HT2A) in the consolidation of learning

We have previously reported that 5-HT1B/1D and 5-HT2A/2B/2C receptors play a role in learning and memory. The present investigation was devoted to analyze further in the autoshaping learning task: (1) the effects of the 5-HT1A/1B/1D receptor agonist, GR46611, the 5-HT1B/1D receptor antagonist, GR127935, and the selective 5-HT2A receptor antagonist, MDL100907. Consistent with a role of 5-HT1B/1D receptors in learning, the post-training injection of GR46611 (1-10 mg/kg) decreased the consolidation of learning whereas GR127935 (10 mg/kg) increased it; the effects of both drugs were reversed by PCA pretreatment. GR127935 abolished the decrease induced by GR46611, TFMPP and mCPP, whereas MDL100907 (0.1-3.0 mg/kg) had no effect by itself but abolished the effects of DOI, ketanserin and TFMPP and moderately inhibited the effects elicited by mCPP, 1-NP and mesulergine. Neither did GR127935 nor MDL100907 significantly modify the increase in the consolidation of learning induced by 8-OH-DPAT. Thus, the present findings suggest that stimulation of presynaptic 5-HT1B/1D receptors impairs the consolidation of learning whilst stimulation of 5-HT2A/2C receptors enhances it; the blockade of 5-HT2A receptors has no effects. In addition, 5-HT2 receptors seem to modulate this cognitive stage.

A novel neurotoxin, cobrotoxin b, from Naja naja atra (Taiwan cobra) venom: purification, characterization, and gene organization

A novel neurotoxin, cobrotoxin b, was isolated from Naja naja atra (Taiwan cobra) venom by successive chromatographies on gel filtration and SP-Sephadex C-25 columns. The yield of this novel toxin was 5% of that of cobrotoxin from the same venom. Its neurotoxicity determined as the inhibition of acetylcholine-induced muscle contractions was approximately 50% of that of cobrotoxin. Cobrotoxin b consists of 61 amino acid residues including 8 cysteine residues. Moreover, there are 12 amino acid substitutions between cobrotoxin b and cobrotoxin. The genomic DNA, with a size of 2,386bp, encoding the precursor of cobrotoxin b was isolated from the liver of N. naja atra. The gene consists of three exons separated by two introns. This exon/intron structure is essentially the same as that reported for the cobrotoxin gene. Moreover, the nucleotide sequences of the two neurotoxin genes exhibit 92% identity. These results highly suggest that the cobrotoxin b and cobrotoxin genes are derived from a common ancestor. Comparative analyses of cobrotoxin b and cobrotoxin precursors showed that the protein-coding regions of the exons are more diverse than introns, except for in the signal peptide domain. This indicates that the protein-coding regions may have arised via accelerated evolution. BLAST searches for sequence similarity in the GeneBank databases showed that intron 1 of the cobrotoxin b and cobrotoxin genes encodes a small nucleolar RNA (snoRNA). However, the snoRNA gene is absent from the gene encoding the Laticauda semifasciata erabutoxin c precursor (L. semifasciata and N. naja atra are sea and land snakes, respectively). Since previous studies suggested the potential mobility of snoRNA genes during evolution, we propose that intron insertions or deletions of snoRNA genes occurred with the evolutionary divergence between the sea snake and land snake neurotoxins.

Genomic structures of cardiotoxin 4 and cobrotoxin from Naja naja atra (Taiwan cobra)

Two genomic DNAs with the size of 2.3 kb and 2.4 kb, which were isolated from the liver of Naja naja atra (Taiwan cobra), encoded the precursors of cardiotoxin 4 and cobrotoxin, respectively. Both genes shared virtually identical overall organization with three exons separated by two introns, which were inserted in the similar positions of the gene's coding regions. Moreover, their nucleotide sequences shared approximately 84.2% identity. This result reveals the evolutionary relationship between cardiotoxin and cobrotoxin. The exon/intron structures of cardiotoxin 4 and cobrotoxin genes were similar to that reported for erabutoxin c gene, a neurotoxin genomic DNA from a sea snake (Laticauda semifasciata). However, in contrast to the finding that the intron 2 of these genes had a similar size, a notable variation with the size of intron 1 was observed (1233 bp, 1269 bp and 197 bp for cardiotoxin 4, cobrotoxin and erabutoxin c genes, respectively). The different size with intron 1 is due to the middle region at the first intron of cardiotoxin 4 and cobrotoxin genes, which encoded small nucleolar RNA (snoRNA), being absent in that of erabutoxin c gene. These results, together with the finding of the potential mobility of snoRNA genes during evolution, suggest that intron insertions or deletions of snoRNA genes occur with the evolutionary divergence of snake neurotoxins and cardiotoxins.

Possible involvement of endothelium-derived hyperpolarizing factor in vascular responses of abdominal aorta from pregnant rats

Increased relaxant response to acetylcholine during pregnancy is proposed to be due to an estrogen-mediated increase in nitric oxide release. We studied acetylcholine-induced pathways of relaxation in the thoracic and abdominal aortic rings from pregnant and nonpregnant Wistar-Kyoto rats and measured basal and stimulated release of nitrites in these vessels. Endothelium-dependent relaxation was significantly greater in pregnant than in nonpregnant rats. Acetylcholine provoked a concentration-dependent relaxation on thoracic and abdominal aortic rings from nonpregnant and pregnant rats. After N118-nitro-L-arginine methyl ester pretreatment, the relaxation was significantly inhibited in the two preparations of nonpregnant and pregnant rodents. The relaxation was not inhibited by indomethacin in any of the aortic segments from pregnant and nonpregnant rats. After cytochrome P450 arachidonic acid metabolism inhibitor clotrimazole, a nonsignificant decrease in the Emax to acetylcholine-induced relaxation was observed in the thoracic segments of pregnant and nonpregnant rats. On the other hand, in abdominal aorta, clotrimazole decreased maximal relaxation in rings from pregnant rats (P<.05) but did not change the acetylcholine-induced relaxation from nonpregnant rats. Our results show an increase in the acetylcholine-stimulated release of nitrites in thoracic aortic rings from pregnant rats compared with rings from nonpregnant rats, which cannot be evidenced in abdominal aortic rings. These results suggest that acetylcholine-induced vasodilation in the abdominal segment from pregnant rats is mediated only in part by nitric oxide, the remainder apparently due to an endothelium-derived vasodilator, cytochrome P450-dependent, which may be endothelium-derived hyperpolarizing factor/epoxyeicosatrienoic acid.

Role of 5-HT1B, 5-HT2A and 5-HT2C receptors in learning

The effects of post-training (i.p.) injection of TFMPP, mCPP, DOI or 1-NP in the autoshaping learning task was explored. Furthermore, the post-training effects of these agonists after treatment with the antagonists (+/-)-pindolol, (+/-)-propranolol, NAN-190, ketanserin, ritanserin, mesulergine, MDL-72222 or p-chloroamphetamine (5-HT depleter) were studied. Rats were individually trained with a lever-press response (conditioned response; CR) on the autoshaping task and tested 24 h later. The results showed that the injection of TFMPP (1-10 mg/kg), mCPP (1-10 mg/kg), 1-NP (0.1-1.0 mg/kg) or mesulergine (0.4 mg/kg) decreased the rate of CR, while DOI (0.01-0.1 mg/kg) and ritanserin (0.5 mg/kg) and ketanserin (0.001-0.1 mg/kg) increased it. However, the effect induced by TFMPP was reversed by (+/-)-pindolol, ketanserin, ritanserin and PCA; the mCPP-induced effect was antagonized by (+/-)-propranolol, ketanserin, ritanserin and MDL-72222; and the effect produced by 1-NP was reversed by ketanserin, ritanserin and PCA. In addition, the increment in CR provoked by DOI was enhanced by ketanserin, and reversed by ritanserin, mesulergine and PCA. These findings suggest that TFMPP, 1-NP and DOI exerted their effects via stimulation of presynaptic 5-HT receptors. The effects of mCPP most probably reflect activation of postsynaptic receptors. The present data suggest that both 5-HT1B and 5-HT2A-2C receptors play a significant role in the consolidation of learning.

Novel SnoRNAs from Naja naja atra (Taiwan cobra) and Bungarus multicinctus (Taiwan banded krait), form extended sequence complementarity to 5S rRNA

During the mapping and sequencing of Naja naja atra cobrotoxin and cardiotoxin 4 genes, we have found that novel small nucleolar RNAs (snoRNAs) are encoded in the first intron of the two genes. The snoRNAs in Naja naja atra were amplified from the venom glands cDNA mixtures of Naja naja atra by reverse transcription-polymerase chain reaction using the primers designed from the first intronic sequences of cobrotoxin and cardiotoxin 4 genes. Likewise, the snoRNAs in Bungarus multicinctus were also amplified by the same primers. Comparison of these snoRNA genes reveals that the regions involved in binding to 5S rRNA are highly conserved among these genes, and form 12-nt and 15-nt tracts of complementarity to phylogenetically invariant sequences in eukaryotic 5S rRNAs. The box C sequence in these snoRNAs is consensus, however, variations with the sequence of box D motif are observed. The present study is the first case of intron-encoded snoRNAs contain extended regions of perfect complementarity to mature 5S rRNA.

Effects of nimodipine on learning in normotensive and spontaneously hypertensive rats

It is well known that the calcium channel blocker, nimodipine, has beneficial effects on learning in either aged or hypertensive animals and humans. However, no attempts have been made to investigate if nimodipine can reverse the synergistic deleterious effects of aging and hypertension in the same subject. Therefore, this study investigated the effects of stable infusions of nimodipine in the autoshaping learning task using middle-aged normotensive (WKY) and hypertensive (SHR) rats. WKY and SHR of 12 months of age were implanted with osmotic minipumps releasing either vehicle or nimodipine (0.4 mg/kg/day). After 3 weeks of treatment, the animals received autoshaping training sessions during 4 consecutive days. The WKY animals treated with nimodipine exhibited the highest levels of learning during the last session, the rank order being WKY-nimodipine > SHR-nimodipine > WKY-vehicle > SHR-vehicle. These results confirm that nimodipine can reverse the impairing effects of either aging or hypertension on learning; the presence of both conditions, however, might produce more severe dysfunctional changes that cannot be totally reversed by nimodipine.

Synthesis of 3-amino-2-(3-indolyl)propanol and propanoate derivatives and preliminary cardiovascular evaluation in rats

A series of tryptamine analogues has been prepared and tested for their 5-HT1 receptor agonist properties. The incorporation of an alkoxy group at the C-5 position of the indole nucleus resulted in a short-lived and dose-dependent immediate antihypertensive and bradycardic response in anaesthetized spontaneously hypertensive rats (SHR). In addition, a carbomethoxy function at the beta-position of the side-chain of the tryptamines significantly increased the mean resting arterial blood pressure (MAP) in pithed rats and also produced contraction of the canine basilar artery in a dose-dependent fashion. Structure-activity relationships (SAR) suggest that the 5-alkoxy group is an important pharmacophore in the production of the antihypertensive effect and that the introduction of a hydroxymethylene group on the side-chain, instead of the carbomethoxy group, changed the receptor affinity profile.

Effects of 5-HT4 receptor agonists and antagonists in learning

In the present work, the effects of pre- or post-training (ip) injection of BIMU1 and BIMU8 (5-HT4 agonists) were figured out in the autoshaping learning task. Furthermore, the post-training effects of these agonists after treatment with SDZ 205-557 and GR 125487D (5-HT4 antagonists) or p-Chloroamphetamine (PCA) were also explored. Animals were individually trained in a lever-press response on the autoshaping task and 24 hours later were tested. The results showed that pre-training injection of BIMU1 (5 20 mg/Kg) or BIMU8 (20 mg/Kg) increased the CR; in contrast, the post-training administration of BIMU1 (10-20 mg/Kg) or BIMU8 (5 and 20 mg/Kg) decreased it. Further experiments revealed that the post-training injections of SDZ 205-557 (1.0-10.0 mg/Kg) or GR 125487D (0.39-1.56 mg/Kg) by themselves did not alter the CR. When BIMU1 or BIMU8 was administered to rats pretreated with SDZ 205-557 (10 mg/Kg) or GR 125487D (0.78 mg/Kg), the decrement induced by 5-HT4 the agonists was reversed; in contrast, the administration of PCA failed to modify the CR or the agonist-induced responses. The findings showed that the pre-training stimulation of 5-HT4 receptors enhanced the acquisition of CR, while, post-training activation of 5-HT4 receptors, impaired the consolidation of learning. The latter effect was not altered by PCA pretreatment. The data show that 5-HT4 receptors are involved in the acquisition and consolidation of learning. It seems that postsynaptic 5-HT4 receptors are involved in the latter effect.

A pharmacological analysis of serotonergic receptors: effects of their activation of blockade in learning

1. The authors have tested several 5-HT selective agonists and antagonists (5-HT1A/1B, 5-HT2A/2B/2C, 5-HT3 or 5-HT4), an uptake inhibitor and 5-HT depletors in the autoshaping learning task. 2. The present work deals with the receptors whose stimulation increases or decreases learning. 3. Impaired consolidation of learning was observed after the presynaptic activation of 5-HT1B, 5-HT3 or 5-HT4 or the blockade of postsynaptic 5-HT2C/2B receptors. 4. In contrast, an improvement occurred after the presynaptic activation of 5-HT1A, 5-HT2C, and the blockade of presynaptic 5-HT2A, 5-HT2C and 5-HT3 receptors. 5. The blockade of postsynaptic 5-HT1A, 5-HT1B, 5-HT3 or 5-HT4 receptors and 5-HT inhibition of synthesis and its depletion did no alter learning by themselves. 6. The present data suggest that multiple pre- and postsynaptic serotonergic receptors are involved in the consolidation of learning. 7. Stimulation of most 5-HT receptors increases learning, however, some of 5-HT subtypes seem to limit the data storage. 8. Furthermore, the role of 5-HT receptors in learning seem to require an interaction with glutamatergic, GABAergic and cholinergic neurotransmission systems.

cDNA sequence analysis and expression of kappa-bungarotoxin from Taiwan banded krait

The cDNAs encoding kappa-bungarotoxin was constructed from the cellular RNA isolated from the venom glands of Bungarus multicinctus by reverse transcription-polymerase chain reaction. A high degree of nucleotide sequence homology was observed between kappa-bungarotoxin and other kappa-neurotoxins. The kappa-bungarotoxin was subcloned into the expression vector pET32a(+) and transformed into BL21(DE3) E. coli strain. The recombinant toxin was expressed as a fusion protein. Recombinant kappa-bungarotoxin was separated from the fused protein by cleavage with CNBr and purified by reversed phase high performance liquid chromatography. In addition to kappa-bungarotoxin, the cDNA fragment encoding kappa3-bungarotoxin was also found in the cDNA mixtures prepared from the cellular RNA of the venom glands of the same snake. This result suggests that the venom glands of Taiwanese B. multicinctus should secrete at least two kinds of kappa-neurotoxins.

A pathway for targeting soluble misfolded proteins to the yeast vacuole

We have evaluated the fate of misfolded protein domains in the Saccharomyces cerevisiae secretory pathway by fusing mutant forms of the NH2-terminal domain of lambda repressor protein to the secreted protein invertase. The hybrid protein carrying the wild-type repressor domain is mostly secreted to the cell surface, whereas hybrid proteins with amino acid substitutions that cause the repressor domain to be thermodynamically unstable are retained intracellularly. Surprisingly, the retained hybrids are found in the vacuole, where the repressor moiety is degraded by vacuolar proteases. The following observations indicate that receptor-mediated recognition of the mutant repressor domain in the Golgi lumen targets these hybrid fusions to the vacuole. (a) The invertase-repressor fusions, like wild-type invertase, behave as soluble proteins in the ER lumen. (b) Targeting to the vacuole is saturable since overexpression of the hybrids carrying mutant repressor increases the fraction of fusion protein that appears at the cell surface. (c) Finally, deletion of the VPS10 gene, which encodes the transmembrane Golgi receptor responsible for targeting carboxypeptidase Y to the vacuole, causes the mutant hybrids to be diverted to the cell surface. Together these findings suggest that yeast have a salvage pathway for degradation of nonnative luminal proteins by receptor-mediated transport to the vacuole.

Genotoxic effects of metronidazole

Metronidazole (MTZ) is an effective agent used in the treatment of parasitic infections. Its genotoxic effects have been shown in a variety of prokaryotic systems; however, negative results have been reported in human in vivo studies. Due to its wide spread use, a study was performed to evaluate the chromosomal aberration frequencies in peripheral blood lymphocyte cultures from 10 individuals, before and after metronidazole treatment. A significant increase in the percentage of cells with chromatid and isochromatid breaks was observed after metronidazole treatment (1500 mg per day for 10 days). The percentages of cells with aberrations did not correlate with the levels of MTZ found in plasma. Individual variability was observed with respect to both the induction of aberrations and the concentration of MTZ in plasma. They could represent differences at the metabolic level, since metronidazole is known to be biotransformed by a polymorphic P450 cytochrome, and its metabolites have shown mutagenic activity.

Effects of aging and hypertension on learning, memory, and activity in rats

A comparison between behavioral alterations induced by hypertension and aging was made in spontaneously hypertensive (SHR) and Wistar-Kyoto rats (WKY) of different ages (3-24 months old), trained to perform autoshaping learning and activity tasks. Food-deprived rats received autoshaping training sessions during 6 days; the animals were retrained 1 month later. Two weeks after autoshaping training, the animals were evaluated in the spontaneous activity task during 2 consecutive days. The results show an age-related decrease in learning, memory, and spontaneous activity. Independently of the age group compared, WKY, though showing lower activity, learned and retrieved more than SHR. Accordingly, the reductions in learning and memory were correlated with both aging and hypertension. The combined influence of these two factors had synergistic detrimental effects on cognitive functions.

Anthelmintic properties of alpha-sanshool from Zanthoxylum liebmannianum

The decoction of the stem bark of Zanthoxylum liebmannianum (Engelm.) P. Wilson (Rutaceae) decreased the count of intestinal nematode eggs in naturally infected sheep. In addition, the chloroformic extract was toxic to Ascaris suum. Fractionation of the organic extract guided by the Ascaris suum lethality test led to the isolation of alpha-sanshool (LC50 = 83.4 x 10(-5)M) as the only active compound. On the other hand, alpha-sanshool induced tonic-clonic seizures when it was injected intraperitoneally to mice. This finding could be a warning regarding the potential toxicity of this plant.

Systemic injection of p-chloroamphetamine eliminates the effect of the 5-HT3 compounds on learning

There is evidence that 5-HT3 antagonists enhance learning and memory; however, their mechanisms of action are unknown. The aim of the present work was to investigate further the role of 5-HT3 receptors involved in learning, using the specific 5-HT3 agonist 1-(m-chlorophenyl)-biguanide (mCPBG) and the 5-HT3 antagonists ondansetron and tropisetron. p-Chloroamphetamine (PCA) pretreatment was used to determine whether pre- or postsynaptic 5-HT3 receptors are involved in learning. The posttraining intraperitoneal (IP) injection of each drug was analyzed on a lever-press response on autoshaping, which is an associative learning task. The results showed that mCPBG impaired retention of the conditioned response (CR), whereas tropisetron and ondansetron improved it. In other animals, PCA alone did not affect CR but was able to block the effects of the 5-HT3 ligands. The present data suggest that the actions of 5-HT3 compounds could be due to their interaction with presynaptic 5-HT3 receptors.

Role of alpha1-adrenoceptors in the reduction of external carotid blood flow induced by buspirone and ipsapirone in the dog

The effects of the 5-HT1A receptor agonist with anxiolytic properties, buspirone and ipsapirone, in the external carotid bed of anaesthetized dogs were analyzed. Since these agonists produce several vascular effects via activation of both 5-HT receptors and alpha1-adrenoceptors, their effects were compared with those elicited by the 5-HT agonist, quipazine, and the alpha1-adrenoceptor agonist, methoxamine. 1-Min intracarotid (i.c.) infusions of buspirone (300 microgram/min), ipsapirone (40 microgram/min), quipazine (300 microgram/min) and methoxamine (15 microgram/min) produced consistent decreases in external carotid blood flow (ECBF); since these changes in blood flow were not accompanied by modifications in systemic blood pressure, the agonists produced parallel increases in external carotid resistance. After interruption of the sympathetic tone by bilateral cervical vagosympathectomy, the vasoconstrictor responses to all the agonists remained unaffected. The intravenous (i.v.) administration of the nonselective 5-HT1-like receptor antagonist, methiothepin (1-100 microgram/kg), potently and dose-dependently antagonized buspirone-, ipsapirone- and quipazine-induced vasoconstriction; methiothepin similarly antagonized the vasoconstrictor responses to methoxamine. Interestingly, the alpha1-adrenoceptor antagonist, prazosin (1-100 microgram/kg, i.v.), also antagonized the vasoconstrictor responses to buspirone, ipsapirone and methoxamine in a dose-dependent manner. Finally, buspirone (300 microgram/min, i.c.) and ipsapirone (40 microgram/min, i.c.) did not modify the responses to noradrenaline (10 microgram/min, i.c.) or tyramine (100 microgram/min, i.c.). It is concluded that canine external carotid vasoconstriction induced by buspirone and ipsapirone is mainly mediated by activation of alpha1-adrenoceptors located in vascular smooth muscle. These data further highlight the ability of the above anxiolytics to produce significant vascular effects under in vivo conditions.

Reflex circulatory collapse following intrapulmonary entrapment of activated platelets: mediation via 5-HT3 receptor stimulation

1. The role of 5-HT2 and 5-HT3 receptors in the mediation of direct and reflex vascular responses to intrapulmonary platelet activation was investigated. 2. Anaesthetized rabbits were challenged intravenously with an emulsion of autologous bone marrow that produced a sharp increase in pulmonary blood pressure, a fall in systemic blood pressure, platelet consumption and death. 3. Platelet depletion before the challenge nearly abolished all the cardiovascular effects and prevented death. Bilateral vagotomy prevented the fall in systemic blood pressure and death but did no prevent the increase in pulmonary pressure. The intravenous administration of the 5-HT2 antagonist, ketanserin, only reduced the increase in pulmonary pressure without affecting the systemic response or mortality. 4. The effects of intravenous 5-HT and of electrical stimulation of the cephalic ends of the cut vagi nerves were also explored. 5-HT injection increased the pulmonary vascular pressure but its effects on systemic blood pressure were variable. These response were modified by the 5-HT antagonists in a manner that resembles their effects on bone marrow embolism. Afferent vagal stimulation produced a fall in systemic blood pressure that was not prevented by MDL-7222. 5. This study indicates that a centrally mediated reduction of peripheral vascular tone is the cause of the potentially lethal circulatory collapse that follows the intrapulmonary entrapment of activated platelets. This reflex is initiated by the action of 5-HT on 5-HT3 receptors in the lung.

Effect of fluoxetine on learning and memory involves multiple 5-HT systems

Diverse evidence suggests that 5-HT uptake blockers enhance learning and memory. However, there is no information about the mechanisms of action involved in such effects. The aim of the present work was to investigate the nature of the receptors involved in the effects of fluoxetine on learning. Therefore, a dose-response curve of posttraining injection (intraperitoneal) of fluoxetine was carried out in an associative learning task (auto-shaping). Fluoxetine or the vehicle was injected 10 min after 5-HT antagonists: (+/-)-pindolol, (+/-)-propanolol, NAN-190, ketanserin, ritanserin, mesulergine, MDL 72222, or SDZ 205-557. Presynaptic activity was eliminated by means of chloroamphetamine pretreatment. Scopolamine (an anticholinergic) and dizocilpine (a noncompetitive NMDA receptor antagonist) were also used. Results showed that fluoxetine enhanced learning of the conditioned response (CR) in a dose-dependent fashion. All 5-HT antagonists had no effects by themselves but inhibited the effects of fluoxetine at different degrees. Decrement of CR produced by scopolamine was reversed by fluoxetine. Dizocilpine did not affect CR but prevented the effects of fluoxetine. The present findings suggest that the actions of fluoxetine on learning are due to an interaction with multiple receptors of postsynaptic nature.

[Differences between the effects of indorenate and other 5-HT1A agonists on the rabbit aorta]

The aim of this study was to determine if like buspirone, ipsapirone and 8-hydroxy-2(di-N-propylamino)tetralin (8-OH-DPAT), the alpha 1-adrenoceptors are involved in the responses elicited by indorenate in rabbit aorta. Exception made of ipsapirone, all the 5-HT1A agonists above mentioned contracted aortic rings. The contraction elicited by buspirone and 8-OH-DPAT was blocked with prazosin (alpha 1-adrenergic antagonist), whereas the effect of indorenate was unaffected with this blocker but it was inhibited with ritanserin (5-HT2 antagonist). On the other hand, buspirone, ipsapirone and 8-OH-DPAT but not indorenate relaxed arteries precontracted with methoxamine (alpha 1-adrenergic agonist) and none of the agonists relaxed preparations precontracted with acetylcholine or KCl. The results indicate that buspirone and 8-OH-DPAT are partial alpha 1-adrenoceptor agonists since they elicited contractions which are blocked with prazosin and relaxed only rings precontracted with methoxamine. Ipsapirone behaved as an alpha 1-adrenoceptor antagonist since it showed the relaxant but not the contractile effect. Finally, we found no evidence that indorenate has afinity for alpha 1-adrenoceptors. Contraction elicited by this agonist seems to be mediated by 5-HT2 receptors, inasmuch it was blocked with ritanserin.

[Evaluation of the toxicity of indorenate on reproduction]

Indorenate (TR3369) a new antihypertensive drug, was examined for effects upon general reproductive performance, for peri-postnatal and embryofetal toxicity in the rat at doses of 0, 10, 20, 40 and 60 mg/kg/day by oral administration. Excluding the 60 mg/kg dose, in the fertility study, any dose produced neither decrement of body weight gain of progenitors, fertility, fetal weight nor survival rate. Retardation of the surface righting, pinnal unfolding or startle response were not observed. On the other hand, 40 and 60 mg/kg significantly increased the number of resorptions. In the peri-postnatal study, doses of 40 and 60 mg/kg incremented the number of dead pups at birth, and the later also affected the survival rate, growing and air righting reflex. Reproductive performance of the F1 offsprings was unimpaired. Indorenate in contrast to serotonin, from which it is a structural derivative, gave no evidence of teratogenicity when administered during the period of organogenesis. It was concluded that the parameters of fetal development were not affected by doses of up to 20 mg/kg, which represents approximately 1200 times the proposed dose for hypertensive patients.

Evidence against the participation of mu- and kappa-opioid receptors in the analgesic activity of ketorolac in rats

The possibility that activation of opioid receptors is involved in the analgesic activity of ketorolac was explored. The analgesic effects of ketorolac, of ketocyclazocine, the prototype kappa-agonist, and of morphine, the prototype mu-agonist, were assayed in the pain-induced functional impairment model in the rat. All three drugs induced a significant analgesic effect in this model. Naloxone was able to antagonize the effects of ketocyclazocine and morphine. However, the effect of ketorolac was not blocked by naloxone, although a high dose, 3.2 mg kg-1, capable of blocking kappa-receptors was used. It is concluded that activation of mu- or kappa-opioid receptors, by either a direct or an indirect mechanism, does not play a role in the analgesic activity of ketorolac.

The 5-HT2 receptor antagonist, pelanserin, inhibits alpha 1-adrenoceptor-mediated vasoconstriction in vitro

The antagonism by pelanserin (2,4(1H,3H)-quinazolinedione,3-[3-(4-phenyl-1- piperazinyl)-propyl]-HCl), a potent 5-HT2 receptor antagonist, of alpha 1-adrenoceptor-mediated contractions of endothelium-denuded carotid, aorta, mesenteric and caudal arteries of both normotensive Wistar-Kyoto (WKY) and spontaneously hypertensive (SHR) rats was investigated. The selective alpha 1-adrenoceptor agonist methoxamine elicited concentration-dependent contractions in all four arterial rings, an effect which was competitively antagonized by pelanserin. pA2 values for pelanserin were in the 7.67-8.11 range when evaluated against the alpha 1-adrenoceptor agonist in arteries from normotensive or hypertensive rats. These data support the conclusion that pelanserin displays alpha 1-adrenoceptor blocking properties. The ability of the 5-HT2 receptor antagonist pelanserin to additionally block alpha 1-adrenoceptor-mediated constriction in different vessels of WKY and SHR may potentially contribute to its blood pressure lowering effects.

Relationship between pharmacokinetics and the analgesic effect of ketorolac in the rat

The relationship between the pharmacokinetic properties and the analgesic effect of ketorolac was evaluated with the pain-induced functional impairment model in the rat. Female Wistar rats were injected with uric acid in the knee of the right hind limb to produce dysfunction. Then, animals received an oral dose of 0.3, 1, 1.8, 3.2 or 5.6 mg/kg of ketorolac tromethamine and analgesic effect and blood concentration, determined by high-performance liquid chromatography, were evaluated at selected times for a period of 4 hr. Ketorolac produced a dose-dependent analgesic effect, measured as a recovery of the functionality of the injured limb, which reached its maximal effect at doses of 3.2 mg/kg or higher. When functionality index was plotted against ketorolac blood concentration, a direct relationship was observed that was well described by the sigmoidal maximal effect model. The data strongly suggest that ketorolac's analgesic effect depends on the blood concentration of the drug.

Mechanism of action of 8-OH-DPAT on learning and memory

It has been previously demonstrated that pretraining injection of 8-hydroxy-2-(di-n-propilamino)tetralin (8-OH-DPAT, a 5-HT1A agonist) impairs conditioned response (CR) in an autoshaping learning task. Therefore, in the present work we intended to determine whether such an effect could be prevented by pretraining, and whether pre- or postsynaptic 5-HT receptors are involved. Groups of rats received or did not receive food magazine training. On the next day, all groups in both conditions, pre- or posttraining, were treated with 8-OH-DPAT (0, 0.062, or 0.250 mg/kg). Posttraining groups were tested on a second session of autoshaping 24 h later. In a second experiment, naive rats received para-chlorophenylalanine (PCPA) (300 mg/kg x 3 days) before pre- or posttraining injection of 8-OH-DPAT. Results showed that in those groups trained to food magazine and treated 24 h later with 8-OH-DPAT, CR was not affected or enhanced. PCPA injection had no effect by itself, but blocked or attenuated the effect of a post- or pretraining injection of 8-OH-DPAT. The present data suggest that a) the pretraining effect of 8-OH-DPAT eliciting a decrease in CR can be eliminated by a food magazine training session; and b) presynaptic 5-HT1A receptors are involved in the effect of 8-OH-DPAT on the acquisition and consolidation of learning.

Hydrophilic-hydrophobic biodegradable polymers: release characteristics of hydrogen-bonded, ring-containing polymer matrices

Biodegradable hydrogen-bonded, ring-containing polymers were prepared. These included poly(enolketones) by the controlled oxidation of poly(vinyl alcohol), and poly(amide-amines) and poly(amide-enamine-esters) by the reaction of diketene with diamines. These polymers had both hydrophilic and hydrophobic properties and are potentially matrix materials for the controlled release of drugs.

Determination of ketorolac in blood and plasma samples by high-performance liquid chromatography

A new method for determination of ketorolac in blood or plasma samples by reversed-phase high-performance liquid chromatography has been developed. The method includes a double extraction with diethyl ether and detection by absorbance at 313 nm. Quantitation was performed by height ratios of ketorolac and the internal standard (sodium tolmetin). Detection limit of the method was 3 ng/ml using 1 ml of plasma and 10 ng/ml using 0.2 ml of blood. The method is linear in the range of concentrations typically obtained after therapeutic doses of the drug, has the advantages of using low volume of body fluid and the internal standard used is commercially available. Those characteristics allow us to conclude that this method is suitable for pharmacokinetic or drug monitoring studies.