Counteracting effect of papaverine on morphine inhibition of gastrointestinal transit in mice

Oral papaverine has been shown to be capable of antagonizing the constipation induced by a single dose of oral morphine. The primary aim of the present study was to ascertain whether papaverine is also capable of counteracting morphine-induced decrease of upper gastrointestinal transit (UGT) after repeated parenteral administration of the opioid. We next investigated the mechanisms(s) responsible for the counteracting effect of papaverine, by analysing whether this effect was changed by pretreatment with N(G)-nitro-L-arginine methyl ester (L-NAME), dexamethasone, indomethacin or capsaicin. Papaverine, co-administered with morphine, counteracted the morphine-induced decrease in UGT in mice pretreated with morphine for 3 days but did not do so in naive animals. The counteracting effect of papaverine was antagonized by L-NAME, but not by indomethacin. In mice pretreated with both morphine and dexamethasone, papaverine failed to antagonize the effect of morphine. Capsaicin pretreatment completely abolished the effect of a single dose of morphine, the effect being partially restored by the 3 days pretreatment with morphine. In mice pretreated with both capsaicin and morphine, the UGT decrease elicited by morphine was lower than in the other experimental groups and was not modified by papaverine. Our results show that papaverine can counteract the morphine inhibition of UGT in mice repeatedly exposed to the opioid. Papaverine exerts its action through a nitric oxide synthase-mediated mechanism; this mechanism is only effective after repeated morphine administration and does not operate when capsaicin-sensitive afferent neurones are ablated.

Role of the cholinergic system and of apamin-sensitive Ca2+-activated K+ channels on rabbit jejunum spontaneous activity and on the inhibitory effects of adrenoceptor agonists

1. One reason why rabbit jejunum is suitable for studying the mechanisms underlying the actions of the various neurotransmitters and their interactions is its spontaneous motility. The main regulator of spontaneous motility is the cholinergic system. How the cholinergic system regulates the spontaneous activity in the rabbit jejunum and how it affects the inhibitory action of alpha- and beta-adrenoceptor agonists remains unclear. 2. We studied the influence of the cholinergic system and apamin-sensitive Ca2+-activated K+ channels on spontaneous contractions in the rabbit jejunum and on the inhibitory effects of alpha1- and beta-adrenoceptor agonists. 3. In naïve tissues, atropine (ATR, 7.4 x 10(-8) m) and tetrodotoxin (8 x 10(-8) m) almost completely inhibited - to a similar extent - the amplitude of spontaneous activity. Despite the presence of ATR or TDX, tissue contraction gradually recovered to about 50% of the baseline amplitude within 5-10 min. When ATR or TDX, respectively, were added to the TDX- or ATR-treated tissues, the recovered activity decreased weakly but significantly. After washout and a 45-min rest the contraction amplitude returned to baseline values. A further exposure to ATR or TDX reduced the contraction to a level significantly lower than the one obtained after TDX or ATR added 5 min after ATR or TDX, respectively. In preparations prestimulated for 10 min with acetylcholine (ACh), ATR abolished the TDX-resistant recovered spontaneous activity. 4. Adrenaline (ADR, 0.5-5 x 10(-7) m) and phenylephrine (PHE, 1-10 x 10(-7) m) inhibited tissue motility in naïve and in ATR- and in TDX-exposed preparations. But whereas in naïve preparations the alpha1-adrenoceptor antagonists completely antagonized inhibition induced by both drugs, in ATR- and TDX-exposed tissues they did so only partially for ADR. Agonist-induced inhibition had a rapid onset but rapidly faded; pendular movements took significantly longer to recover in ATR- and TDX-treated tissues than in naïve tissues. In tissues exposed for 2 min to ADR (0.5-5 x 10(-7) m) or PHE (1-10 x 10(-7) m), washout or addition of alpha1-adrenoceptor antagonists caused an immediate short-lasting increase in contraction amplitude. 5. Apamin (APAM, 5 x 10(-9) m) caused a rapid and persistent increase in the amplitude of contractions. It also blocked the inhibitory responses to ADR and PHE, and removed washout-induced contractions. The APAM-induced increase in the contraction amplitude correlated with the increase obtained by washing out ADR or PHE. 6. Isoprenaline (at concentrations up to 2.8 x 10(-7) m) produced no inhibitory response in naïve tissues, but it invariably blocked (at a concentration of 0.7 x 10(-7) m) the recovered spontaneous activity (and sometimes depressed muscletone) in tissues exposed to ATR or TDX. Neither propranolol (3.4 x 10(-7) m) nor APAM (5 x 10(-9) m) counteracted these inhibitory effects. 7. These results indicate that spontaneous motility in the rabbit jejunum is predominantly mediated by neuronal release of ACh and by some other unidentified neuronal activity. Released ACh inhibits myogenic activity and strongly antagonizes beta-adrenoceptor-induced APAM-insensitive inhibition but leaves alpha1 agonist-induced APAM-sensitive inhibition unchanged.

Intracellular signal transduction pathways as targets for neurotoxicants

The multiple cascades of signal transduction pathways that lead from receptors on the cell membrane to the nucleus, thus translating extracellular signals into changes in gene expression, may represent important targets for neurotoxic compounds. Among the biochemical steps and pathways that have been investigated are the metabolism of cyclic nucleotides, the formation of nitric oxide, the metabolism of membrane phospholipids, the activation of a multitude of protein kinases and the induction of transcription factors. This brief review will focus on the interactions of three known neurotoxicants, lead, ethanol and polychlorinated biphenyls, with signal transduction pathways, particularly the family of protein kinase C isozymes, and discusses how such effects may be involved in their neurotoxicity.

Modulation of DNA synthesis by muscarinic cholinergic receptors

Acetylcholine muscarinic receptors are a family of five G-protein-coupled receptors widely distributed in the central nervous system and in peripheral organs. Activation of certain subtypes of muscarinic receptors (M1, M3, M5) has been found to modulate DNA synthesis in a number of cell types. In several cell types acetylcholine, by activating endogenous or transfected muscarinic receptors, can indeed elicit cell proliferation. In other cell types, however, or under different experimental conditions, activation of muscarinic receptors has no effect, or inhibits DNA synthesis. A large number of intracellular pathways are being investigated to define the mechanisms involved in these effects of muscarinic receptors; these include among others, phospholipase D, protein kinases C and mitogen-activated-protein kinases. The ability of acetylcholine to modulate DNA synthesis through muscarinic receptors may be relevant in the context of brain development and neoplastic growth.

Interactions between cholecystokinin and opioids in the isolated guinea-pig ileum

1. Although cholecystokinin octapeptide sulphate (CCK-8) activates the opioid system of isolated guinea-pig ileum (GPI) whether it activates the mu- or kappa-system, or both, remains unclear. Neither is it known whether CCK-8 influences the withdrawal responses in GPI preparations briefly exposed to opioid agonists. This study was designed to clarify whether CCK-8 activates mu- or kappa-opioid systems or both; and to investigate its effect on the withdrawal contractures in GPI exposed to mu- or kappa-agonists and on the development of tolerance to the withdrawal response. 2. In GPI exposed to CCK-8, the selective kappa-antagonist nor-binaltorphimine elicited contractile responses that were concentration-related to CCK-8 whereas the selective mu-antagonist cyprodime did not. 3. In GPI preparations briefly exposed to the selective mu-agonist, dermorphin, or the selective kappa-agonist, U-50, 488H, and then challenged with naloxone, CCK-8 strongly enhanced the withdrawal contractures. 4. During repeated opioid agonist/CCK-8/opioid antagonist tests tolerance to opioid-induced withdrawal responses did not develop. 5. These results show that CCK-8 preferentially activates the GPI kappa-opioid system and antagonizes the mechanism(s) that control the expression of acute dependence in the GPI.

Mu and kappa opioid system interactions in the expression of acute opioid dependence in isolated guinea-pig ileum

In vivo studies have suggested that the kappa opioid system can partially inhibit the development of physical dependence to mu agonists. Vice versa, activation of mu receptors may inhibit the expression of physical dependence to kappa agonists. We studied mu-kappa interactions in the isolated guinea-pig ileum (GPI). In the isolated GPI briefly exposed to mu or kappa agonists the addition of the respective antagonists precipitated a withdrawal contracture. After a first withdrawal response, however, some tissues failed to exhibit subsequent mu or kappa withdrawal contractures. A withdrawal contracture to the selective mu antagonist, cyprodime, after repeated exposures to a selective mu agonist, dermorphin, was restored by nor-binaltorphimine (BNI), a selective kappa antagonist. Vice versa, after repeated exposures to the kappa agonist, U-50,488H, cyprodime restored tissue responsiveness to BNI. Tissues repeatedly exposed to dermorphin and washed after each exposure contracted to the addition of BNI. Tissues repeatedly exposed to U-50,488H contracted on the addition of cyprodime. These findings strongly suggest that exogenous agonist-elicited stimulation of the mu (or kappa) opioid system indirectly activates the endogenous kappa (or mu) system. The indirectly-activated endogenous system inhibits the withdrawal response to the exogenously-stimulated opioid system. In isolated GPI the mu and kappa opioid systems thus appear to interact, regulating each other.

Acute withdrawal after bremazocine and the interaction between mu- and kappa-opioid receptors in isolated gut tissues

1. This study was undertaken to investigate whether, after a brief exposure of guinea-pig isolated ileum and rabbit jejunum to bremazocine, a kappa-opioid agonist also possessing antagonist activity at mu-opioid receptors, the addition of opioid antagonists produced withdrawal contractures. Our aim was to verify in these tissues the existence of an interaction between the mu- and kappa-opioid systems. 2. In guinea-pig ileum preparations previously exposed for 5 min to bremazocine at 5.7 x 10(-7) M and 5.7 x 10(-8) M, naloxone (5 x 10(-7) M) elicited no response whereas in tissues exposed to a lower bremazocine concentration (5.7 x 10(-9) M), naloxone (5 x 10(-7) M) and the selective kappa-opioid antagonist, nor-binaltorphimine (3.4 x 10(-8) M) both produced a strong contracture. 3. Bremazocine (5.7 x 10(-7) M) administered to guinea-pig isolated ileum, previously exposed for 5 min to morphine (10(-7) M), induced a withdrawal contracture. In contrast, lower bremazocine concentrations (1.4 and 7.1 x 10(-8) M) did not elicit a withdrawal contracture. 4. Naloxone (5 x 10(-7) M), added to the bath after a 5 min exposure of guinea-pig ileum to morphine (10(-7) M), elicited the characteristic withdrawal contracture. Bremazocine (1.4-7.1 x 10(-8) M) added 1 min before naloxone (5 x 10(-7) M) inhibited the naloxone withdrawal contracture in a dose-related way whereas naloxone 5 x 10(-8) M added 1 min before naloxone 5 x 10(-7) M, did not affect the withdrawal response. 5. In the rabbit jejunum, bremazocine (1.4-7.1 x 10-8 M) caused a decrease in amplitude in the spontaneous tissue activity. In tissues exposed to these bremazocine concentrations, naloxone(5 x 10-7 M) elicited a marked contracture. A similar contracture occurred when nor-binaltorphimine(3.4 x 10-8 M) was added in place of naloxone. These effects were dose-related to the bremazocine concentration. The specific K-agonist, U-50,488H (5 x 10-8 M), elicited the same effects as bremazocine.6. These findings show that stimulation of K-opioid receptors induces a state of dependence that is not prevented by blocking the pi-opioid system. The observation that low bremazocine concentrations inhibit the morphine-induced withdrawal contractures, indicates an interaction between the micro- and K-opioid system in guinea-pig isolated ileum, similar to that observed in the whole animal.

Total body irradiation and prednimustine in chronic lymphocytic leukemia and low grade non-Hodgkin's lymphomas. A 9-year experience at a single institution

BACKGROUND

The efficacy and toxicity of total body irradiation (TBI) in patients with chronic lymphocytic leukemia (CLL) and low grade non-Hodgkin's lymphomas (NHL) were evaluated.

METHODS

Between January 1984 and September 1992, 81 consecutive patients, 40 affected with CLL and 41 with low grade NHL, with symptomatic Stage III and IV disease, were treated with TBI followed by prednimustine. TBI was given with a 6 MV linear accelerator, applying two opposite alternating fields, including total body, with two fractions of 15 cGy given per week (3-day interval). A total dose of 150 cGy was given over 5 weeks. Six to nine courses of prednimustine (100 mg/m2 orally for 5 consecutive days every 4 weeks) was administered 2 months after TBI treatment as consolidation therapy.

RESULTS

Of 40 patients with CLL, 18 (Group I; median age 58.5 years) were younger than 65 years and 22 (Group II; median age 73 years) were older. The overall response rates were 78% in Group I and 91% in Group II, with a median response time of 16.5 and 16 months, respectively. Hematologic toxicity was 72% in Group I and 73% in Group II. It was reversible in all but one heavily pretreated patient who died of progressive anemia and thrombocytopenia after TBI alone. In the 40 patients with CLL, the response rate was 85%; there were 5 complete responses (CRs) (12.5%) and 29 partial responses (PRs) (72.5%). Of the 41 patients with NHL, 29 (Group I; median age 55 years) were younger than 65 years and 12 (Group II; median age 71.5) were older. The overall response rate in both groups was 83%, with median response times of 18.5+ and 14.5+ months for Groups I and II, respectively. Hematologic toxicity was 59% in Group I, whereas it was 50% in Group II. It was reversible in all patients. Overall, in the 41 patients with symptomatic Stage III and IV low grade NHL, the response rate was 82.8%; there were 10 CRs (24.3%) and 24 PRs (58.5%). The prednimustine regimen was generally well tolerated.

CONCLUSIONS

In our experience, TBI given in a dose of 150 cGy in 10 fractions twice a week, followed by prednimustine, is an effective treatment for patients with CLL and patients with low grade NHL. This treatment also is effective in patients older than 65 years. The toxicity is acceptable, particularly when TBI and prednimustine are given as initial treatment. Pretreated patients should be monitored strictly.

The role of opioid mechanisms in the anorectic effects of stimulants: U50,488H enhances amphetamine inhibition of free feeding in rats

The influences of the kappa-opiate agonist U50,488H (U50; 4 mg/kg IP), the neuroleptic haloperidol (HAL; 0.3 mg/kg IP), and MK-801 (0.2 mg/kg IP), a noncompetitive antagonist for NMDA receptors, were compared on the effects of nine days of d-amphetamine (AMPH) treatment (3 mg/kg IP) on food and water intake and urine output. AMPH prevented feeding stimulation produced by U50 during the first 2 h, whereas U50 inhibited the hyperphagic phase that rats showed between 2 and 5 h after AMPH administration. Tolerance did not develop to the first 2-h suppression of feeding; in contrast, the late hyperphagic phase slowly recovered across the nine days of treatment. Combined administration of the two drugs barely affected water intake but considerably increased urine output. Unlike U50, HAL left the late hyperphagic response to AMPH unchanged and delayed the development of hyperdipsia. In our study MK-801 had one effect only: It significantly reduced amphetamine diuresis. These results suggest that by inhibiting the late hyperphagic response U50 enhances the anorectic effects of AMPH, but that dopamine probably has no direct role in this interaction.

Ocular absorption and distribution of bendazac after topical administration to rabbits with different vehicles

Ocular and systemic absorption of bendazac was investigated after topical administration to rabbits of 0.5% solutions of bendazac lysine in different polysaccharide vehicles. The results show that the drug is absorbed into the retina-choroid via an extracorneal, or sclero-conjunctival route; the iris and the ciliary body are presumably supplied via both the transcorneal and the extracorneal pathways. The extent of absorption via the extracorneal route is not related to vehicle viscosity but rather to the chemical features of vehicle. The transcorneal penetration appears to be hindered by the binding of the drug to corneal tissues.

The presence of L-carnitine in ocular tissues of the rabbit

Carnitine plays an important role in the metabolism of fatty acids. Its presence is considerable in tissues that use fatty acids as an important source of energy, such as the heart and skeletal muscle. Free carnitine and acid soluble acylcarnitines are present in various tissues of the rabbit eye. The lowest concentration of carnitine was observed in the vitreous humor and the highest in the lens. The ratio, acid soluble acylcarnitine/free carnitine, was lower in the cornea, aqueous humor, vitreous humor and lens, than in iris, ciliary body and choroid-retina. The topical administration of carnitine increased both free carnitine and acetylcarnitine in cornea, and only free carnitine in aqueous humor and choroid retina. Only after intravenous administration, did the levels of free and acyl-carnitine increase in the iris and ciliary body. Neither of the two carnitine species was changed in vitreous humor. The determination of the activity of carnitine acetyltransferase in the eye showed that in the ciliary body the values of activity were three times higher than those in the iris and choroid-retina. The elevated ratio of acid soluble acylcarnitines with respect to free carnitine in iris, ciliary body, choroid-retina as well as the higher activity of carnitine acetyltransferase in the ciliary body, suggest that carnitine plays an important role in those tissues of the eye where cells of a muscular nature are present and may represent, after esterification, an important energy reserve.

Withdrawal contractures of guinea-pig isolated ileum after acute activation of kappa-opioid receptors

1. The present study was undertaken to investigate firstly whether a brief exposure for 5 min of guinea-pig isolated ileum to the kappa-opioid agonist, U-50,488H produced a withdrawal contracture on addition of naloxone and secondly to ascertain whether the response was due to the activation of kappa-opioid receptors. 2. Naloxone (10(-6) M) did not elicit a response in preparations exposed to U-50,488H (5 x 10(-7) M-2 x 10(-6) M). However, after exposure to U-50,488H (5 x 10(-7) M), naloxone (10(-6) M) produced a strong contracture if the agonist was washed out 1 min before the addition of the antagonist. 3. The addition of naloxone (10(-6) M) to the ileum preparation exposed to U-50,488H (10(-7) M or lower) caused a response of similar intensity irrespective of whether the agonist had been washed out. 4. The selective kappa-opioid antagonist, nor-binaltorphimine (2.7 x 10(-9) M and 2.7 x 10(-7) M), injected before the opioid agonists, prevented the naloxone-induced contracture after exposure to U-50,488H (8 x 10(-8) M) but did not affect the contracture after exposure to morphine (5 x 10(-7) M). 5. Nor-binaltorphimine (2.7 x 10(-9) M) caused a contraction of the ileum preparation when injected 5 min after exposure to U-50,488H (8 x 10(-8) M) but not after morphine (5 x 10(-7) M). 6. The alpha 2-adrenoceptor agonist, clonidine (3 x 10-8 M) and the calcium channel blocker, nifedipine(3 x 10-8 M), injected 1 min before naloxone, blocked the ileum contraction to naloxone after exposure to U-50,488H (8 x 10-8 M). The results demonstrate that the stimulation of Kappa-opioid receptors can induce a similar dependence in guinea-pig ileum to that produced by activation of micro receptors.

Effect of nonsteroidal anti-inflammatory drugs on withdrawal responses in guinea pig ileum after a brief exposure to morphine

The inhibition mechanism of nonsteroidal anti-inflammatory drugs (NSAIDs) on withdrawal response was examined in vitro. Naloxone elicited a strong contraction in the isolated guinea pig ileum after a 5-min exposure of the tissue to morphine. The contraction was inhibited by aspirin, indomethacin and salicylic acid, administered concomitantly to morphine or 1 min before the opioid antagonist. The short contact time of NSAIDs with the isolated preparations seems to indicate that mechanisms other than inhibition of prostaglandins synthesis are implicated in this action. NSAIDs depressed the ileum contraction to naloxone after stimulation of the tissue with cholecystokinin, when injected into the bath 1 min before the peptide. The contraction to naloxone after exposure to indirect excitatory peptides was very similar to withdrawal contraction. After maximal ileum stimulation with prostaglandin E1, naloxone induced a strong contraction indicating that this substance activates the opioid system, as occurs with cholecystokinin. NSAIDs, at concentrations that inhibit naloxone-induced contractions, did not depress the maximal contracture to cholecystokinin and prostaglandin E1, but inhibited the submaximal one. These results suggest that the inhibition of withdrawal contraction by NSAIDs in acute dependence is due mainly to their ability to block the contraction caused by substances whose action is neuronally mediated, which are released to counteract the opioid action. Prostaglandin E1 may be part of this system of action and reaction.

Manifestations of acute opiate withdrawal contracture in rabbit jejunum after mu-, kappa- and delta-receptor agonist exposure

1. Following a 5 min in vitro exposure to morphine (1.3 x 10(-7) M), U-50,488H (2.5 x 10(-8) M) and deltorphin (1.6 x 10(-8)-6.5 x 10(-9) M), the rabbit isolated jejunum exhibited a precipitated contracture after the addition of naloxone (2.75 x 10(-7) M). 2. The precipitated responses to U-50,488H and deltorphin but not to morphine were reproducible in the same tissue. 3. The precipitated contractures were blocked completely by tetrodotoxin (3 x 10(-7) M), partially by atropine (1.5 x 10(-7) M) and not affected by hexamethonium (1.4 x 10(-5) M). 4. Naloxone administration (2.75 x 10(-7) M) before the agonist prevented the development of the adaptive response to morphine and U-50,488H but not to deltorphin. 5. The selective antagonists norbinaltorphimine (2.7 x 10(-8)-2.7 x 10(-9) M) and naltrindole (1.1 x 10(-7) M) prevented the adaptive response development only to the respective agonists. 6. The opioid agonists partially inhibited the spontaneous activity of the tissue. This study has shown that independent activation of mu-, kappa- and delta-opioid receptors can induce dependence in this isolated tissue. Rabbit jejunum is a suitable tissue for studying the acute effects of opioids on the adaptative processes determined by their administration.

The α1-blocker dapiprazole inhibits diuresis but not drinking and feeding induced by U-50,488H

To further explore the interaction between opiates and catecholamines in the control of water balance, we studied the effects of the alpha 1-adrenoceptor antagonist dapiprazole on the modifications in drinking and diuresis produced by U-50,488H (a selective kappa-opiate agonist), morphine, naloxone, and amphetamine in rats. Because animals were maintained in a free-feeding paradigm and water intake is also controlled by feeding (prandial drinking), food intake was also measured. At doses administered (3-6 mg/kg, IP), dapiprazole had no effect on basal food and water intake or on diuresis. Nor did it modify changes in feeding and drinking produced by U-50,488H, morphine, naloxone, and amphetamine. It did, however, antagonize the diuretic effect of both U-50,488H and amphetamine. In addition, suppression of diuresis was obtained by combining doses of dapiprazole and morphine or naloxone that were devoid of antidiuretic effects when administered independently. A further experiment showed that diuresis produced by water load was also prevented by dapiprazole. alpha 1-Adrenoceptors thus appear to play a role in the regulation of water balance in a condition of free access to water, inhibiting diuresis without affecting drinking.

Dapiprazol prevents U50,488H-mediated suppression of preparatory components of drinking behavior in rats

In a previous study, we found that the kappa opioid agonist U50,488H (U50) suppresses both appetitive and consummatory components of drinking behavior in rats trained to negotiate water in a straight runway. U50 also activates diuresis. Kappa opioid mechanisms could therefore play a dissipative role in the body's water balance. Since naloxone inhibits diuresis, but not hypodipsia produced by U50, these effects are probably mediated also by nonopioid mechanisms. In rats trained to negotiate water in a straight runway, we have studied the influence on the hypodipsic effects of U50 of the selective alpha-1 adrenoceptor antagonist dapiprazol (DAP), which we found to inhibit U50-mediated diuresis. When given alone, DAP (3 and 6 mg/kg IP) influenced neither running for water nor water intake; neither did it prevent the suppression of water intake produced by U50 (8 mg/kg IP) across the test. However, it did antagonize the U50-mediated slowing of running for water. Alpha-1 adrenoceptors thus appear to play a role in U50's effects on diuresis and the appetitive, but not consummatory, aspects of drinking.

(-)-Norpseudoephedrine, but not (+/-)-amphetamine, prevents the increase in fluid intake associated with ethanol presentation in rats

The effects of daily intraperitoneal administration of (+/-)-amphetamine (AMPH: 4 mg/kg) and (-)-norpseudoephedrine (NPE: 15 or 30 mg/kg) on drinking were evaluated in rats allowed to drink water or a 5% ethanol solution during the 5 h following drug administration. AMPH, but not NPE, significantly increased water intake. Substitution of ethanol for water produced a significant increase in fluid intake in the control group, whereas drinking levels remained unchanged in both AMPH and NPE treated rats. Discontinuation of drug treatment during the regimen of ethanol presentation produced a prompt increase in fluid intake in the NPE, but not AMPH, treated groups. Finally, substitution of water for ethanol led to a significant reduction of fluid intake in all the groups. These results suggest that a light (i.e. NPE), but not a strong (i.e. AMPH) psychomotor stimulant, is able to weaken rewarding properties of diluted ethanol.

Effects of trazodone and m-chlorophenylpiperazine (m-CPP) on acute dependence in mice

The antidepressant trazodone and its main metabolite, m-CPP, having an antiserotoninergic and serotoninergic activity respectively, were studied in an acute dependence model in mice, to establish whether 5-hydroxytryptaminergic systems are involved in the manifestations of acute opiate dependence and in its development. When drugs were administered 15 min before naloxone, all signs of abstinence decreased, with the exception of teeth chattering that was increased by m-CPP and unaffected by trazodone. When injected 15 min before morphine, jump episodes were decreased by the highest doses of both drugs, while teeth chattering was decreased by m-CPP only. When administered 1 h before morphine, trazodone increased paw and head shakes and mCPP decreased teeth chattering and both left the other signs unaffected. Serotoninergic systems seem to have a significant role in events involved in the withdrawal syndrome and a minor one in those leading to the development of dependence.

Misleading results in studying pharmacodynamic interaction with oral anticoagulant

We described an experimental condition, in which the i.p. administration of rats of irritants produces a misleading increase of the anticoagulant effect of warfarin. Group of 10 adult Wistar rats were treated i.p. or i.v. with HCl 0.1N plus warfarin p.o.; 24 hr after warfarin administration, prothrombin time was determined on citrate blood specimens and the animals were submitted to autopsy. When HCl is given i.p., a significant increase of prothrombin time is observed. On the contrary following i.v. administration no interference with the anticoagulant effect of warfarin is observed. Abdomen exploration of rats shows the presence of serum exudate following i.p. but not i.v. administration of HCl. The synergistic effect of i.p. administration of HCl on anticoagulant effect of warfarin appears an experimental artifact, probably attributable to a non-specific local irritating effect. This result stresses the need of caution in interpreting animal data indicating a synergism with oral anticoagulant.

Facilitating effect of amphetamine on the response of rabbit aortic strips to adrenaline, dopamine and serotonin

Amphetamine increased the response of rabbit aortic strips to adrenaline, dopamine and serotonin at consistently lower doses than those exerting a direct contracting effect. The amphetamine-facilitated contraction had the same shape as that produced by biogenic amines alone, whereas the contraction produced by amphetamine alone was more delayed and flatter. Serotonin and dopamine facilitated each other, but less markedly and with a narrower interval between facilitating and contracting doses than amphetamine. Pargyline exerted no facilitating effect on biogenic amines. Phentolamine and prazosin inhibited the direct response to adrenaline, dopamine and amphetamine, and the amphetamine-facilitated response to adrenaline and dopamine; they were inactive against serotonin alone and combined with a facilitating dose of amphetamine or dopamine. Cyproheptadine inhibited the direct response to serotonin and amphetamine, and the amphetamine-facilitated response to serotonin; it was inactive against dopamine and adrenaline both alone and combined with a facilitating dose of amphetamine or serotonin.

Antinociceptive effects of trazodone and m-chlorophenylpiperazine (mCPP) in mice: interaction with morphine

1. The antidepressant trazodone and its main metabolite m-chlorophenylpiperazine (mCPP) were investigated for their analgesic properties and their sensitivity to a threshold dose of morphine in acetic acid abdominal constriction and hot plate tests. 2. The drugs elicited hypoalgesic effects at about the same doses in the two analgesic assays. 3. Naloxone (2 mg/kg i.p.) prevented the hypoalgesia of trazodone but not of mCPP in the hot plate test. The opiate antagonist did not affect the responses of both drugs to the writhing test. 4. Subanalgesic doses of the two drugs increased the sensitivity to morphine in both assays. The results further support the suggested role played by opioid and 5-HT systems on depression.

Ocular disposition of acetaminophen and its metabolites following intravenous administration in rabbits

Time-courses of both 'total' (unchanged plus metabolized) and unmetabolized acetaminophen were investigated in plasma and ocular tissues of rabbit after intravenous administration. The drug freely diffuses across the haemato-ocular barriers, reaching eye levels equal to those in the plasma; ocular concentrations are higher than those of all other investigated drugs. The time-course in aqueous is superimposable to that observed in the plasma; in other ocular tissues it is much slower. There is evidence of an ocular metabolism or a concentration into the eye of minor metabolites formed elsewhere.

Misleading results in studying pharmacodynamic interaction with oral anticoagulants

An experimental conditions is described in which the i.p. administration to rats of irritants produces a misleading increase of the anticoagulant effect of warfarin. Groups of 10 adult Wistar rats were treated i.p. or i.v. with HCl 0.1N plus warfarin p.o.; 24 hr after warfarin administration, prothrombin time was determined on citrate blood specimens and the animals were submitted to autopsy. When HCl is given i.p., a significant increase of prothrombin time is observed. On the contrary following i.v. administration no interference with the anticoagulant effect of warfarin is observed. Abdomen exploration of rats shows the presence of serum exudate following i.p. but not i.v. administration of HCl. The synergistic effect of i.p. administration of HCl on anticoagulant effect of warfarin appears an experimental artifact, probably attributable to a non-specific local irritating effect. This result stresses the need of caution in interpreting animal data indicating a synergism with oral anticoagulants.

Some pharmacological characteristics of the guinea pig ileum opioid system activated by cholecystokinin

Naloxone, added after contractions induced by CCK-8 on the guinea pig ileum preparation, elicited a contraction attributed to the release of endogenous opioid which could inhibit the excitatory action of the peptide. With large concentrations of CCK-8, the preparation gave reproducible responses with time. Naloxone, added before the peptide, protracted the excitatory response to CCK-8, but not its height. Morphine decreased the response to CCK-8 but simultaneously raised the response to naloxone. The latter effect appeared very similar to the withdrawal contraction observed after brief exposure of the opioid in the guinea pig ileum to opioids. Clonidine, and alpha-2 adrenoceptor agonist, and nifedipine, a calcium channel antagonist, both known to interfere with tolerance and physical dependence, affected the excitatory response to CCK-8 and the subsequent response to naloxone in a different way.

Reproducible withdrawal contractions of isolated guinea-pig ileum after brief morphine exposure: effects of clonidine and nifedipine

Guinea-pig ileum stored for 30 min in Krebs solution and then mounted in Tyrode solution gave reproducible contracture responses to naloxone after brief exposure to morphine. The preparation lasted for several hours and a variety of pharmacological tests could be made. Clonidine, an alpha 2-adrenoceptor agonist, and nifedipine, a calcium channel antagonist, both known to interfere with tolerance and physical dependence, inhibited naloxone withdrawal contractures in a dose related way. Their action seemed to be receptor-mediated since yohimbine and Bay k 8644, respectively, reversed their inhibitory effect.

Ocular absorption of benzydamine by the rabbit

An aqueous solution of 0.15 per cent benzydamine hydrochloride, a non-steroidal anti-inflammatory drug, was applied to the rabbit eye. Following topical application to the cornea, the drug was soon detected in the aqueous fluid of the treated eye, whereas the plasma levels were negligible. The possibility that benzydamine can inhibit inflammatory processes in the eye without the risk of side-effects is discussed.

Effects of dapiprazole, clonidine and yohimbine on the development of dependence and withdrawal behaviour in mice

There is evidence that central noradrenergic hyperactivity is involved in the manifestation of the major signs and symptoms of the opiate withdrawal syndrome. In order to assess whether or not the noradrenergic system is also implicated in the development of opiate dependence, we studied dapiprazole, an alpha-1 selective adrenoceptor antagonist, clonidine and yohimbine using the acute dependence model in mice. When administered just before naloxone, after dependence development, all three drugs reduce abstinence signs. When injected 15 min before morphine to observe the drugs' effects on the development of dependence, dapiprazole depresses all the symptoms registered while clonidine decreases only jumping, but increases paw and head shakes. None of these drugs affects the naloxone precipitated withdrawal syndrome when injected 1 h before morphine. It is suggested that the noradrenergic system is involved in both the manifestation of the withdrawal syndrome and in the development of opiate dependence. Diapiprazole may be a useful tool in patients and in pharmacological studies of dependence and abstinence.

Ocular distribution of aspirin and salicylate following systematic administration of aspirin to rabbits

The distribution of aspirin and salicylate 30 min after the intravenous administration of different doses of aspirin has been investigated in the rabbit eye. HPLC enabled a rapid and sensitive determination of both substances. A considerable dose-dependent penetration into all ocular tissues was observed with both aspirin and salicylate. Aspirin concentrations were higher than in plasma in all ocular tissues with the exception of the lens. These results show that an unhydrolysed drug may have a direct local effect by acetylating lens protein or other ocular constituents.

Third outbreak of trichinellosis caused by consumption of horse meat in Italy

The clinical and epidemiological aspects of the largest Italian outbreak of human trichinellosis which occurred in Northern Italy in August 1986 are reported. About 300 people who ate raw horse meat were involved. The clinical and biological aspects of 161 patients were studied. None died. The causal parasite, isolated from a patient, was identified through isoenzymatic typing as Trichinella nelsoni. Fever, oedema, myalgia and headache were the most common signs and symptoms. The Fluorescent Antibody Test (FAT) proved positive for 96 percent of the patients showing clinical manifestations. Essential laboratory data are reported.

Absorption of bendazac lysine after topical application to the rabbit eye

A water solution of 0.5% 14C-3-bendazac lysine was administered to the rabbit eye. Following single application to the cornea, the drug was found in different ocular compartments including the lens. Although in the lens the concentrations are lower as compared to the iris, retina ciliary bodies and aqueous humor, they last longer.

Ocular pharmacokinetics of dapiprazole

Dapiprazole is a drug having specific alpha 1 adrenergic blocking properties. Following topical instillation on the eye, it crosses the corneal epithelium reaching high concentrations in the ocular tissue and producing a prompt miotic and hypotensive effect. The high concentration ratio between ciliary bodies and iris versus aqueous humor suggests a peculiar affinity for these structures containing adrenoceptors of the alpha type. The very low concentrations in the plasma, as compared to those after systemic administration, and in the fellow eye indicate that the systemic absorption is negligible.

Investigations on the ocular pharmacokinetics of bendazac in rabbits

The ocular pharmacokinetics of bendazac were studied in rabbits, following intravenous administration of bendazac lysine. The compound and its 5-hydroxyderivative were determined in different eye compartments and plasma by radioassay, using [14C]bendazac, and HPLC. The highest concentrations were found in the iris and in descending order in the ciliary body, retina, cornea, tears, aqueous humor, vitreous, and lens. The time course of concentrations in the plasma, aqueous and vitreous humor, ciliary body, and retina showed kinetics described by the exponential equation y = aebx with a half-life of 2.47, 4.56, 3.59, and 3.22 hr, respectively; in the lens the half-life was 17.77 hr.

Tissue distribution, urinary, fecal and biliary excretion of 14C bendazac L-lysine salt in rats

The distribution of bendazac in the plasma and some rat tissues was studied after single oral administration of 14C bendazac L-lysine salt. The drug is distributed in varying amounts in the liver, kidneys, spleen, muscle, plasma and lens. In these tissues, the drug kinetics is similar, except for the lens where elimination of the drug is slower. More than 80% of the radioactivity administered is excreted through the urine and feces. Fecal excretion is due to the high biliary excretion.

Distribution and excretion of 3H-dapiprazole in the rat

Tissue distribution as well as biliary, urinary and fecal excretion of 3H-dapiprazole was studied in the rat. The product is found in many tissues, including the brain. About 23 and 57% of the dose is excreted in the urine and feces and about 65% is eliminated in the bile.

A comparative pharmacological study of trazodone, etoperidone and 1-(m-chlorophenyl)piperazine

Since 1-(m-chlorophenyl)piperazine (mCPP) is a metabolite of trazodone (TRZ) and etoperidone (ETO), two atypical antidepressants, a pharmacological study was undertaken to establish the possible contribution of mCPP to the effects of the parent compounds. Behavioral effects of mCPP in rats consist in head shakes and other signs of serotoninergic stimulation; subtoxic doses also produce clonic convulsions and prostration. TRZ and ETO produce sedation and signs of alpha-adrenergic blockade; subtoxic doses produce tremors, clonic convulsions and prostration. Peripheral effects of norepinephrine (NE) and serotonin (5-HT) in rats are potentiated by mCPP and inhibited by TRZ and ETO. 5-hydroxytriptophan (5-HTP)-induced head twitches in mice are inhibited by TRZ and ETO and unaffected by mCPP. At similar doses mCPP, TRZ and ETO inhibit some nociceptive responses in rats and mice.

Trazodone, a new avenue in the treatment of depression

Pharmacological and biochemical data on trazodone are reviewed in order to compare this drug to imipramine and other tricyclics both from the point of view of the mechanism of action and preferential clinical indications. Trazodone tends to inhibit biochemical and pharmacological functions depending on the catecholaminergic system, whereas imipramine has a potentiating activity. However, both these drugs decrease the density of beta-receptors following repeated administrations. Trazodone and imipramine have similar effects on the serotoninergic system. The two drugs also share an antinociceptive activity. It is stressed that this activity has been of critical importance in the discovery of trazodone. In fact, the development of this drug was based on the working hypothesis that a disturbance in the perception of unpleasant experience has a role in the pathogenesis of depression. Some medical implications of the alpha-blocking activity of trazodone are discussed. Trazodone is preferable to other antidepressant treatment when depression is associated with angle-closure glucoma, cardiovascular disturbances depending on noradrenaline release, tremor, some psychotic conditions and alcoholism.

Possible dopaminergic involvement in biting compulsion induced by large doses of clonidine

The effects of amphetamine, scopolamine, phenoxybenzamine, haloperidol and clozapine on biting compulsion induced by large doses of clonidine were studied in mice. Clonidine-induced biting compulsion was potentiated by amphetamine and scopolamine, and inhibited by phenoxybenzamine, haloperidol and clozapine. It appears that biting compulsion elicited by clonidine is mediated by the stimulation of both noradrenaline and dopamine in the brain. Since clorapine, an atypical neuroleptic agent, inhibits this response, the possibility is discussed to use clonidine-induced biting compulsion to detect neuroleptic agents devoid of extrapyramidal side effects.