Biochemical and behavioral alterations in developing rats treated with 5,7-dihydroxytryptamine.

Intracisternal administration of 5,7-dihydroxytryptamine (5,7-DHT) to immature rats produced a marked reduction of brain norepinephrine and serotonin. Accompanying these reductions of brain amines were a decrease in body weight and alterations in behavior. After treatment with 5,7-DHT at 3 days of age, locomotor activity was significantly elevated at 14 days of age, but was reduced at 28 days of age. 5,7-DHT alone also induced a significant deficit in acquisition of the shuttle-box avoidance response and blocked body movements observed after decapitation. Treatment with either pargyline or desipramine before injection of 5,7-DHT eliminated the effect of 5,7-DHT on noradrenergic fibers while enhancing the effects of 5,7-DHT on brain serotonergic fibers. These treatments also minimized the deficits of 5,7-DHT on growth and on acquisition of the avoidance response and reversed the blockade of decapitation convulsions. However, animals pretreated with pargyline or desipramine before they received 5,7-DHT still demonstrated hyperactivity at 14 days of age equivalent to that observed in neonates that received only 5,7-DHT. Furthermore, a behavioral syndrome induced by 30 mg/kg of 5-hydroxytryptamine was markedly potentiated by all of the 5,7-DHT treatments which suggest that serotonin receptors were supersensitive.     

Spinal antinociception by adenosine analogs and morphine after intrathecal administration of the neurotoxins capsaicin, 6-hydroxydopamine and 5,7-dihydroxytryptamine

The effects of intrathecal pretreatment with the neurotoxins capsaicin, 6-hydroxydopamine and 5,7-dihydroxytryptamine on spinal antinociception by adenosine analogs (NECA, 5'-N-ethylcarboxamido adenosine and CHA, N6-cyclohexyl adenosine) and morphine were examined using the rat tail flick and hot plate tests. Pretreatment with 50 micrograms capsaicin for 7 to 11 days (which reduced substance P immunoreactivity in the superficial layers of the dorsal spinal cord) produced a slight increase in the action of NECA and CHA, and reduced the action on morphine in the hot plate test but not in the tail flick test. Pretreatment with 50 to 100 micrograms 6-hydroxydopamine for 7 to 14 days (which reduced spinal cord noradrenaline levels by 54-65%) reduced spinal antinociception by NECA and CHA but not that by morphine. Pretreatment with 50 micrograms 5,7-dihydroxytryptamine (which reduced spinal cord serotonin levels by 74-89%) had no effect on any agent. Acute pretreatment with 7.5-30 micrograms phentolamine reduced the spinal antinociceptive action of noradrenaline, NECA and CHA, primarily in the hot plate test. Phentolamine (30 micrograms) also reduced the action of morphine (hot plate greater than tail flick), but did not affect the action of L-baclofen. These results suggest that spinal antinociception by adenosine analogs: 1) occurs primarily at a postsynaptic site of action (capsaicin results), and 2) is dependent on release of endogenous noradrenaline and activation of spinal adrenergic receptors (6-hydroxydopamine and phentolamine results). The reduction in the effect of morphine by capsaicin (removes a source of adenosine release) and phentolamine (antagonizes the action of endogenously released adenosine) can be explained in terms of the adenosine release hypothesis of morphine action within the spinal cord.     

Morphine pharmacokinetics and pain assessment after intracerebroventricular administration in patients with terminal cancer

Morphine pharmacokinetics and pain relief were evaluated after intracerebroventricular administration of morphine (0.4 +/- 0.11 mg) in seven patients with cancer suffering from intractable pain. Ventricular cerebrospinal fluid (CSF), lumbar CSF, and plasma morphine concentrations were analyzed by a specific morphine radioimmunoassay. A two-compartment model was sufficient to describe the kinetics of morphine in ventricular CSF. Morphine diffuses to the lumbar level, and the mean maximum concentration was 192 +/- 105 ng/ml at 4.5 +/- 1.3 hours. Ventricular and lumbar CSF morphine kinetics showed a similar decline during the elimination phase, with terminal half-lives of 3.8 +/- 0.6 hours and 4.2 +/- 1.6 hours, respectively. Pain relief was evaluated by a visual analog scale: the test showed a rapid onset of analgesia (less than 10 minutes). Analgesic effectiveness reached a maximum between 6 and 10 hours. The relationship between pharmacologic effect and morphine concentrations in ventricular CSF resulted in an anticlockwise hysteresis curve. The presence of morphine in lumbar CSF suggested an additive spinal action of morphine, which probably plays a role in the duration of analgesia.     

Behavioral evidence for supersensitivity following destruction of central serotonergic nerve terminals by 5,7-dihydroxytryptamine.

Previous studies have established that a complex behavioral syndrome--consisting of tremor, rigidity, hindlimb abduction. Straub tail, lateral head weaving and reciprocal forepaw treading--is a specific reflection of the activity of central serotonin receptors. This syndrome was utilized in the present study to test for supersensitivity in the central serotonergic system. Specific destruction of central serotonin nerve terminals by intraventricular injection of 5,7-dihydroxytryptamine (5,7-DHT, 50 mug) in adult male rats pretreated with a catecholamine uptake blocking agent resulted in marked supersensitivity to serotonin precursors and agonists. The greatest degree of supersensitivity was observed in response to L-5-hydroxytryptophan, for which the ED50 for elicitation of the syndrome was 20% of the value for control rats. A lesser degree of supersensitivity was seen in response to L-tryptophan (following monoamine oxidase inhibition) and the direct-acting serotonin agonist, 5-methoxy-N,N-dimethyltryptamine, for which the ED50 was approximately 50% of the control value in both cases. Supersensitivity begins to develop within 24 hours and is relatively complete by 96 hours after 5,7-DHT. A marked subsensitivity to the serotonin releasing agent, fenfluramine, was found in 5,7-DHT-treated rats. In contrast to the marked supersensitivity to serotonin precursors and agonists which occurs following 5,7-DHT, chronic administration of a serotonin synthesis inhibitor, p-chlorophenylalanine (400 mg/kg every 3 days for a total of 24 days), did not produce supersensitivity to L-5-hydroxytryptophan or 5-methoxy-N,N-dimethyltryptamine. Possible pre- and postsynaptic mechanisms for the development of supersensitivity are discussed.     

Changes in drinking activity, urine volume and urinary electrolyte excretion after intracerebroventricular administration of diisopropylfluorophosphate

The effects of i.c.v. administration of diisopropylfluorophosphate on drinking activity, urine volume and urinary electrolyte excretion were examined in the conscious, unrestrained rat. An i.c.v. dose of 5 micrograms of diisopropylfluorophosphate was found to inhibit acetylcholinesterase activity in five nuclei in the anterior, dorsal portion of the hypothalamus. This dose of diisopropylfluorophosphate also resulted in a dipsogenic episode, a diuresis and a biphasic effect on urinary sodium and potassium excretion. Each response was independent of the other two responses. The responses were mediated by muscarinic cholinergic receptors other than nicotinic receptors as they were blocked by both atropine and pirenzepine but not mecamylamine. The results suggest that the muscarinic receptors responsible are probably of muscarinic receptor M1 class.     

美金胺重复用药对新生大鼠的毒性反应

目的N-甲基-D-天冬氨酸受体离子通道拮抗剂美金胺对缺氧缺血具有明显的脑保护效果,观察重复应用大剂量美金胺对SD新生大鼠可能造成的不良影响。方法实验于2003-10/2004-03在新华医院中心实验室进行。选用7日龄SD新生大鼠80只,随机分为美金胺54,35,23m g/(kg·d)组及对照组4组,每组20只。连续14d分别经腹腔注射美金胺54,35,23mg/(kg·d)或注射用水(10μL/g)。14d后每组取13只大鼠给予断头处死,余7只大鼠停药恢复1周后断头处死,分别观察大鼠用药后的毒性反应及体质量增长情况。结果78只大鼠进入结果分析。①各剂量美金胺组动物在用药后均有不同程度的不良反应,主要发生在用药后第1～5天,但均能在用药后三四个小时内恢复正常。②美金胺54,35,23m g/(kg·d)组分别在用药后第6,5,4天出现耐受。其中美金胺54m g/(kg·d)组2只大鼠分别在连续用药第10天和第12天死亡,其他动物均存活。③各剂量组动物在用药后均有不同程度的体质量增长减缓,连续用药14d后美金胺54,35,23mg/(kg·d)组大鼠体质量明显低于对照组[(29.26±3.61),(30.46±4.10),(30.57±2.82),(37.72±3.04)g,P<0.01]。④停药7d后,美金胺35,23mg/(kg·d)组大鼠体质量与对照组比较差异已不明显,但美金胺54mg/(kg·d)组大鼠体质量仍显著低于对照组[(56.52±10.68),(74.05±5.13)g,P<0.01]。结论①不同剂量的美金胺连续应用14d,可能会对大鼠的生长有抑制作用,但停药后可获代偿性恢复。②新生大鼠对美金胺有较好的耐受性。     

美金胺重复用药对新生大鼠的毒性反应

目的：N-甲基-D-天冬氨酸受体离子通道拮抗剂美金胺对缺氧缺血具有明显的脑保护效果，观察重复应用大剂量美金胺对SD薪生大鼠可能造成的不良影响。方法：实验于2003—10／2004-03在新华医院中心实验室进行。选用7日龄SD新生大鼠80只，随机分为美金胺54，35，23mg／（kg&;#183;d）组及对照组4组，每组20只。连续14d分别经腹腔注射美金胺54，35，23mg/（kg&;#183;d）或注射用水（10μL／g）。14d后每组取13只大鼠给予断头处死，余7只大鼠停药恢复1周后断头处死，分别观察大鼠用药后的毒性反应及体质量增长情况。结果：78只大鼠进入结果分析。①各剂量美金胺组动物在用药后均有不同程度的不良反应，主要发生在用药后第1～5天，但均能在用药后三四个小时内恢复正常。②美金胺54，35，23mg／（kg&;#183;d）组分别在用药后第6，5，4天出现耐受。其中美金胺54mg／（kg&;#183;d）组2只大鼠分别在连续用药第10天和第12天死亡，其他动物均存活。（④各剂量组动物在用药后均有不同程度的体质量增长减缓，连续用药14d后美金胺54，35，23mg∥（kg&;#183;d）组大鼠体质量明显低于对照组【（2926&;#177;3.61），（30.46&;#177;10），（30.37&;#177;2.82），（37．72&;#177;3．04）g，P〈0．01]。（4）药7d后，美金胺35，23mg/（kg&;#183;d）组大鼠体质量与对照组比较差异已不明显，但美金胺54mg／（kg&;#183;d）组大鼠体质量仍显著低于对照组【（56．52&;#177;10．68），（74．05&;#177;5．13）g,P〈0．01]。结论：①不同剂量的美金胺连续应用14d，可能会对大鼠的生长有抑制作用，但停药后可获代偿性恢复。②新生大鼠对美金胺有较好的耐受性。     

Toxicological evaluation of azumolene after repeated intraperitoneal administration in rats

We investigated the toxicity of azumolene (Az), a more water‐soluble compound than dantrolene, after 14 days of intraperitoneal (i.p.) administration in rats at doses of 1, 2.5 or 10 mg/kg/day. No animals died or presented signs of toxicity. No significant differences in water and food consumption or weight gain were noted among the groups. Blood analysis revealed no significant alteration by Az treatment in the number of blood cells. However, Az treatment induced a perivascular inflammatory reaction in the liver and non‐diffuse necrosis of skeletal muscle, both of which occurred only at the highest dose of Az and were completely reversed 14 days after cessation of treatment. Congestion and inflammation in the kidneys were only partially reversed. Caffeine‐induced contracture of skeletal muscle was not altered during 7 days of i.p. injection of Az (2.5 mg/kg/day). In conclusion, Az is a safe compound for long‐term administration, but does cause a mild, reversible reaction in skeletal muscle and kidney.     

Faecal elimination of steroids in rats after oral administration of mepartricin

Treatment of both male and female rats with 5 IU/day mepartricin for 7-10 days administered by gastric tubing resulted in an increased faecal excretion of some steroids. Mean rate of elimination of total oestrogens was enhanced by 45% in male rats and by 14% in female rats, and the average excretion of conjugated oestrogen was also increased in the female animals. Faecal elimination of cholesterol was 37% and 42% higher in male and female rats, respectively, after mepartricin treatment, and in male rats plasma concentrations of cholesterol were reduced following treatment. It is suggested mepartricin acts either by changing the intestinal flora or by acting directly on the steroid moieties, and it is speculated that a similar mechanism may occur in man.     

Differential effects of subcutaneous and intrathecal morphine administration on blood glucose in mice: comparison with intracerebroventricular administration

The s.c. administration of morphine (2.5-80 mg/kg) produced a dose-dependent hyperglycemia, whereas morphine (12.5-50 micrograms) given i.t. in the lumbar region caused a dose-dependent hypoglycemia in unanesthetized mice. Both effects on blood glucose were antagonized by s.c. naloxone, although inhibition of i.t. morphine required a higher naloxone dose. Naloxone pretreatment with 2 mg/kg, but not 1 mg/kg s.c., potentiated a hyperglycemic response to i.t. saline. High i.t. doses of morphine caused an early (within 2 min) scratching behavior that was not inhibited by naloxone or glucose loading and a later (greater than 20 min) tonic convulsive behavior (opisthotonus). Lethality was partially inhibited by glucose loading which delayed, but did not prevent, the hypoglycemic effect of i.t. morphine. The hypoglycemic effect of i.t. morphine was also delayed in streptozotocin-diabetic ICR mice and diabetic (db/db) C57BL/KsJ mice, but the latter were more sensitive to lethality, which occurred without hypoglycemia or seizures. All these effects of i.t. morphine were completely blocked by acute spinal transection of T10-T11, but the nociceptive, hypoglycemic and opisthotonic effects were not mimicked by i.c.v. morphine (6.25-50 micrograms) in ICR mice, which showed a bell-shaped hyperglycemic dose-response relationship and a brief explosive motor behavior at the higher doses (25-50 micrograms). It is concluded that the effects of morphine on blood glucose and on behavior are dependent upon the route of administration, and that the convulsive effect of i.t. morphine may be facilitated by the production of a profound hypoglycemia, which involves a spinal, rather than supraspinal or systemic, action of morphine.     

The effect of intracerebroventricular dopamine administration on the respiratory response to hypoxia

Acute hypoxia produces an increase in ventilation. When the hypoxia is sustained, the initial increase in ventilation is followed a decrease in ventilation. The precise mechanism of this decline in ventilation during sustained hypoxia is unknown. Recent studies hypothesized that the accumulation of dopamine in the central nervous system might have a major role in production of hypoxic respiratory depression. The purpose of this study was to examine whether dopamine has an effect on occurance of central ventilatory depression which is seen in acute hypoxia in peripheral chemoreceptors denervated animals. The experiment were conducted in rabbits anesthetized with Na-pentobarbital (25 mg x kg(-1) i.v.). For intracerebroventricular (i.c.v.) injections of dopamine (1 microg) in each animal, canula was placed in left lateral cerebral ventricle by stereotaxic method. Respiratory frequency (f x min(-1)), tidal volume (V(T)) ventilation minute volume (V(E)) and systemic arterial blood pressure (BP) were recorded during air and 3 minutes hypoxic gas mixture (8%O2-92%N2) breathing. I.c.v. administration of dopamine during normoxia decreased V(T), f, V(E) and BP, significantly. When rabbits were injected with an i.c.v. dopamine on hypoxic gas mixture breathing in control animals, there was depression of hypoxic ventilatory responses. After i.c.v. administration of dopamine antagonists haloperidol (0.1 mg) and domperidone (0.07 mg) in chemodenervated rabbits, the significant increases in V(T), V(E) and BP were observed. On the breathing of hypoxic gas mixture of chemodenervated and i.c.v. dopamine antagonists administrated rabbits, hypoxic depression was completely abolished. These results of this study show that accumulation of dopamine in the brain seems to reduce the response of the central control mechanisms to chemoreceptor impulses during normoxia and hypoxia. In conclusion present study suggests important role played by central dopaminergic pathways in the occurence of acute hypoxic ventilatory depression.     

Central administration of GPR55 receptor agonist and antagonist modulates anxiety‐related behaviors in rats

G‐protein‐coupled receptor 55 (GPR55) has been proposed as an atypical cannabinoid receptor, which is activated by lysophosphatidylinositols and some synthetic or endogenous cannabinoid molecules. The exact role of GPR55 receptors in the central nervous system especially in anxiety needs to be evaluated. In this study, the effects of intracerebroventricular (i.c.v.) administration of agonist and antagonist of GPR55 receptor on anxiety‐related behaviors in rats were investigated. Here, O‐1602 (GPR55 agonist) at the doses of 0.2, 1, and 5 μg/rat increased %OAT and %OAE but not the locomotor activity, showing an anxiolytic response, whereas i.c.v. injection of ML193 (GPR55 antagonist) at the doses of 0.1 and 1 μg/rat increased anxiety‐like behaviors while causing locomotor impairment. The antagonistic effect of ML193 on the anxiolytic‐like effect of O‐1602 was also evaluated. The results showed that ML193 decreased the anxiolytic‐like effect of O‐1602. Based on these results, it may be concluded that central GPR55 may have a role in modulation of anxiety‐like behaviors in rats. Further experiments are needed to elucidate the exact role of these receptors in anxiety.     

Augmentation of AAV-mediated cardiac gene transfer after systemic administration in adult rats

Adeno-associated virus (AAV)-6 or -9-pseudotyped vectors are suitable for efficient cardiac gene transfer after intravenous injection in mice. However, a systemic application in larger animals or humans would require very high doses of viral particles. Therefore, the aim of our study was to test if ultrasound-targeted microbubble destruction could augment cardiac transduction of AAV vectors after intravenous administration in rats. To analyze efficiency and specificity of gene transfer, microbubbles loaded with AAV-6 or -9 harboring a luciferase or enhanced green fluorescent protein (EGFP) reporter gene were infused into the jugular vein of adult Sprague-Dawley rats. During the infusion, high mechanical index ultrasound was administered to the heart. Control rats received the same amount of virus without microbubbles, but with ultrasound. After 4 weeks, organs were harvested and analyzed for reporter gene expression. In contrast to low cardiac expression after systemic transfer of the vector solution without microbubbles, ultrasound-targeted destruction of microbubbles significantly increased cardiac reporter activities between 6- and 20-fold. Analysis of spatial distribution of transgene expression using an AAV-9 vector encoding for EGFP revealed transmural expression predominantly in the left ventricular anterior wall. In conclusion, ultrasound targeted microbubble destruction augments cardiac transduction of AAV vectors in rats. This approach may be suitable for efficient, specific and noninvasive AAV-mediated gene transfer in larger animals or humans.     

Severe pulmonary pathology after intravenous administration of vectors in cirrhotic rats.

After an intravascular injection, adenoviral vectors are normally taken up by the reticuloendothelial system in the liver, where they rapidly trigger an innate response. However, we have previously found that the biodistribution of adenoviral vectors is altered in cirrhotic rats due to the presence of pulmonary intravascular macrophages, which cause a shift in vector uptake from the liver to the lungs. We now report that this is correlated with fatal pulmonary hemorrhagic edema in cirrhotic rats. In addition, cirrhotic rats reacted to vector with enormous increases in TNF-alpha and IL-6 and markedly prolonged coagulation times. Although we also saw fatal reactions to high doses of adenoviral vectors in normal rats, the time course and symptoms were very different, and pulmonary hemorrhagic edema was seen only in cirrhotic rats. Because abnormal pulmonary reticuloendothelial uptake is known to occur in humans during cirrhosis and other diseases, there is the potential that intravascular administration of adenoviral vectors might cause lung pathology in such patients.     

The role of 5-hydroxytryptamine 7 receptors in the phencyclidine-induced novel object recognition deficit in rats

The role of 5-hydroxytryptamine (serotonin) (5-HT)(7) receptor antagonism in the actions of atypical antipsychotic drugs (APDs), e.g., amisulpride, clozapine, and lurasidone, if any, is uncertain. We examined the ability of 5-HT(7) receptor antagonism alone and as a component of amisulpride and lurasidone to reverse deficits in rat novel object recognition (NOR) produced by subchronic treatment with the N-methyl-D-aspartate receptor antagonist phencyclidine (PCP), and we examined the ability of supplemental 5-HT(7) antagonism to augment the inability of sulpiride, haloperidol, and (1R,4R,5S,6R)-4-amino-2-oxabicyclo[3.1.0]hexane-4,6-dicarboxylic acid (LY379268), a metabotropic glutamate receptor (mGluR) 2/3 agonist, which lack 5-HT(7) antagonism, to reverse the NOR deficit. The 5-HT(7) receptor antagonist, (2R)-1-[(3-hydroxyphenyl)sulfonyl]-2-[2-(4-methyl-1-piperidinyl)ethyl]pyrrolidine (SB269970) (0.1-1 mg/kg) dose-dependently reversed PCP-induced NOR deficits. In addition, the ability of lurasidone (0.1 mg/kg) and amisulpride (3 mg/kg) to reverse this deficit was blocked by cotreatment with the 5-HT(7) receptor agonist (2S)-(+)-5-(1,3,5-trimethylpyrazol-4-yl)-2-(dimethylamino)tetralin (AS19) (5-10 mg/kg), which did not affect NOR in naive rats. Sulpiride, a less potent 5-HT(7) antagonist than amisulpride, did not itself improve the PCP-induced NOR deficit. However, a subeffective dose of SB269970 (0.1 mg/kg) in combination with subeffective doses of lurasidone (0.03 mg/kg), amisulpride (1 mg/kg), or sulpiride (20 mg/kg), also reversed the PCP-induced NOR deficit. Pimavanserin, a 5-HT(2A) inverse agonist, LY379268, and haloperidol did not potentiate the ability of subeffective SB269970 to improve the NOR deficit. Furthermore, the mGluR2/3 antagonist (2S)-2-amino-2-[(1S,2S)-2-carboxycycloprop-1-yl]-3-(xanth-9-yl)propanoic acid (LY341495), which blocks the effect of clozapine to reverse the NOR deficit, did not block the SB269970-induced amelioration of the NOR deficit. These results suggest 5-HT(7) antagonism may contribute to the efficacy of some atypical APDs in the treatment of cognitive impairment in schizophrenia and may itself have some benefit in this regard.     

Quantitative liver function and morphology after paracetamol administration to rats

Abstract . The functional status of the liver after paracetamol administration to rats was dissociated with regard to cytosolic and microsomal functions. The cytosolic function, measured as galactose elimination capacity, was unchanged even after high doses of paracetamol. The microsomal function, measured as the prothrombin time, was reversibly decreased to a minimum 12 h after paracetamol administration and showed dose dependence. The structural changes of the liver cells were centrilobular necroses and dilatation of the endoplasmic reticulum. They were most marked 36 h after paracetamol and were not correlated to the functional impairment. We conclude that during acute paracetamol induced liver damage to rats different functions of the liver are unequally influenced and that the structural changes occur later than the functional ones. The paracetamol intoxicated rat is a promising model for further investigation of dissociation of subcellular functions during acute liver damage.     

Aphrodisiac evaluation in non-copulator male rats after chronic administration of Eurycoma longifolia Jack

The aphrodisiac effect of Eurycoma longifolia Jack (0.5 g/kg) was evaluated in noncopulator male rats using an electrical cage. Fractions of E. longifolia Jack decreased the hesitation time of noncopulator male rats, throughout the investigation period. Furthermore, it possessed a transient increase in the percentage of the male rats responding to the right choice, more than 50% of the male rats scored "right choice" after 3 weeks post-treatment and the effect became more prominent after 8 weeks post-treatment (only 40-50% of the control male rats responded to the right choice) using the electrical copulation cage. Hence, this study lends further support to the use of the plant by indigenous populations as a traditional medicine for its aphrodisiac property.