The effect of tryptamine on serotonin release from hypothalamic slices is mediated by a cholinergic interneurone

Tryptamine produced a concentration-related inhibition of potassium-evoked release of tritium from slices of rat hypothalamus preloaded with ³H-serotonin. This effect of tryptamine was blocked by a series of serotonin antagonists with a relative order of potency which suggested that tryptamine was acting on a post-junctional serotonin receptor. However, the response to tryptamine was also blocked by tetrodotoxin, indicating that tryptamine may be acting indirectly via the release of a second neurotransmitter. The finding that physostigmine enhanced, whilst atropine antagonised the effect of tryptamine suggests that the second neurotransmitter may be acetylcholine. This possibility is discussed.     

Inhibition by naloxone of the rise in hypothalamic dopamine and serum prolactin induced by ethanol

We investigated the effect of naloxone on the concentration of dopamine in the hypothalamus and on the concentration of prolactin in serum and anterior pituitary of male rats acutely treated with ethanol. Acute ethanol administration increased serum prolactin levels and hypothalamic dopamine concentration. Pituitary prolactin was not modified by this treatment. Naloxone administered 15 min before the animals were sacrificed decreased serum prolactin levels and hypothalamic dopamine concentration in ethanol-treated rats. These results suggest that ethanol increases prolactin secretion because it decreases the release of dopamine by the hypothalamus. Naloxone decreases prolactin release probably because it antagonizes the inhibitory action of opioids on dopaminergic neurons.     

pH敏感型羟丙甲基纤维素衍生物的控释研究

目的制备羟丙甲基纤维素接枝共聚物缓释片并研究此缓释片的体外释放行为。方法选用茶碱为模型药物,以不同DM含量的羟丙甲基纤维素接枝共聚物水分散体进行包衣,考察包衣片在蒸馏水和模拟胃液中的缓释效果。结果 DM含量为2.5%和5%时,包衣片在水中和模拟胃液中的释放符合Higuchi缓释释放模式,DM含量达到7%时片剂释放明显加快。结论羟丙甲基纤维素接枝共聚物是pH敏感型缓释包衣材料。     

Effect of intraperitoneally administered GABA on the locomotor activity of mice

Gammaaminobutyric acid (GABA) was injected intraperitoneally (i.p.) into mice at doses from 25–2000 mg/kg, and spontaneous locomotor activity was recorded for the following 20 min. A slight but significant decrease in the spontaneous locomotor activity was noted only with the highest dose. The stimulation of motor activity induced by ethanol (2.4 g/kg i.p.) was significantly counteracted by GABA (100 mg/kg i.p. and upwards). A further suppression of ethanol-induced hyperactivity was reached by pretreatment with aminooxyacetic acid (AOAA, 15 mg/kg i.p.). The stimulation of motor activity induced by morphine (10 mg/kg i.p.) remained unaffected by even high doses of i.p. GABA. Motility produced by activation of postsynaptic catecholamine receptors, i.e., by apomorphine (3 mg/kg i.p.) and clonidine (3 mg/kg i.p.) following reserpine (10 mg/kg i.p.) and -methyltyrosine (250 mg/kg i.p.) pretreatment, was not affected by i.p. GABA injections, whereas hypomotility caused by a low dose of haloperidol (150 g/kg i.p.) was enhanced.In conjunction with earlier biochemical data, these results suggest a certain access of blood-borne GABA to the CNS, leading to inhibition of dopaminergic neurons involved in motility regulation.     

In vivo release of endogenous GABA in the cat hypothalamus

Summary The posterior hypothalamus of anaesthetized cats was superfused with artificial cerebrospinal fluid through a push-pull cannula and the release of endogenous GABA from the hypothalamus into the superfusate was studied. The resting release of GABA varied rhythmically, since phases of high rate of release were separated from each other by phases of low rate of release. The time interval between two adjacent phases of high rate of release was about 70 min. Electrical stimulation of the posterior hypothalamus with the tip of the cannula enhanced the rate of release of GABA in a frequency-dependent way. Superfusion of the hypothalamus with CSF which contained a high concentration of potassium and a low concentration of sodium increased the rate of release of GABA; this effect was dependent on the presence of calcium ions in the superfusing fluid. Pretreatment of the cats with reserpine reduced the levels of GABA in hypothalamus and rest of brain and the concentration of GABA in the superfusate as well. Stimulation of the locus coeruleus with a bipolar electrode elicited an increased release of GABA in the hypothalamus.Part of the results was presented at the Spring Meeting of the German Pharmacological Society, Mainz, March 1978This work was supported by the Deutsche Forschungsgemeinschaft     

肺靶向阿霉素微球的体外释放度测定方法的建立

目的建立肺靶向阿霉素明胶微球(ADM-GMS)体外释放度测定的方法。方法以透析法考察阿霉素明胶微球的体外释放度,采用紫外分光光度法在波长254nm处测定阿霉素明胶微球的体外释药量。结果阿霉素微球体外释药量在1~40mg/L浓度范围内线性关系良好,平均回收率为99.63%,RSD为1.16%。结论该方法简便、快速、准确,可作为阿霉素微球体外释放度的测定方法。     

3H-ACh release from guinea pig gallbladder evoked by GABA through the bicuculline-sensitive GABA receptor

Summary We investigated the effect of GABA on the spontaneous efflux of ³H-acetylcholine (ACh) from the isolated guinea pig gallbladder loaded with ³H-choline. Application of GABA (10^–5 M) caused a significant increase in the fractional rate of tritium efflux. This GABA-evoked efflux of ACh was inhibited by the perfusion of tetrodotoxin (10^–6 M) and Ca-free medium. Nipecotic acid (10^–4 M) did not affect the GABA-evoked release of ACh, indicating that ACh was not released by the entry of GABA into cholinergic nerve terminals. Bicuculline (10^–6 M) and furosemide (10^–6 M), the chloride ion channel blocker, inhibited the GABA-evoked ACh release. The application of muscimol (10^–5 M), but not baclofen (10^–5 M) also produced an increase in the fractional rate of ACh release. Thus, the GABA receptors involved in the increase of ACh release are bicuculline-sensitive. The GABA-evoked release of ACh was not altered by the perfusion with hexamethonium (10^–5 M), thus indicating the presence of GABA receptors on the postganglionic cholinergic neurons.These findings suggest that bicuculline-sensitive GABA receptors probably coupled to a Cl^– ionophore are present on postganglionic cholinergic neurons and are involved in the increase of ACh release in guinea pig gallbladder.This paper is part of a dissertation submitted by N. Saito to Kobe University School of Medicine, for the requirement of Doctor of Philosophy     

Effect of the GABA uptake inhibitor tiagabine on sleep and EEG power spectra in the rat

1. The sleep profiles induced by agonists and agonistic modulators of γ-aminobutyric acid_A (GABA_A) receptors differ markedly. With regard to GABA_A agonists, the effects may be due to the fact that these agents are poor substrates for uptake and are therefore likely to activate GABA_A receptors tonically. To investigate this possibility, we assessed the sleep effects of two doses (2 and 10 mg kg⁻¹) of the GABA re-uptake inhibitor tiagabine, administered intraperitoneally at light onset in 8 rats. Electroencephalogram (EEG) and electromyogram were recorded during the first 8 h after the injection.
2. Compared with vehicle, tiagabine had minimal effects on the temporal pattern of non-rapid eye movement sleep (non-REMS) and on the total time spent therein. However, tiagabine dose-dependently elevated EEG activity during non-REMs, most prominently in the lower frequencies (1–8 Hz) and least pronounced in the frequencies between 11 and 16 Hz. During the first 2 h after the injection, 10 mg kg⁻¹ tiagabine elicited repetitive episodes of hypersynchronous EEG waves during wakefulness and slightly suppressed REMS. Except for these effects, tiagabine hardly influenced the time spent in and EEG activity during wakefulness and REMS.
3. The effects of tiagabine on state-specific EEG activity were qualitatively very similar to those elicited by GABA_A agonists. These findings support the hypothesis that the influence of GABA_A agonists on EEG signals may be caused by tonic stimulation of GABA_A receptors.

     

In vivo release of newly synthesized catecholamines from the hypothalamus by amphetamine

Summary The posterior hypothalamus of cats immobilized with gallamine was superfused through a push-pull cannula with artificial cerebrospinal fluid. Addition of³H-tyrosine into the superfusing fluid led to synthesis of³H-catecholamines which were released spontaneously. Separation of the³H-catecholamines by column chromatography or their acetylation and separation by paper chromatography revealed that both³H-noradrenaline and³H-dopamine were released. In most experiments³H-noradrenaline represented about 10 to 25% of total³H-catecholamines. Superfusion of the hypothalamus with amphetamine (1×10^–5 M) enhanced the release of total³H-catecholamines, the release of³H-noradrenaline being relatively more enhanced than that of³H-dopamine. Determination of the readioactive compounds in the hypothalamus at the end of the experiments showed that total³H-catecholamines represented 3% of³H-tyrosine. About 15% of the total³H-catecholamines were due to³H-noradrenaline and 85% to³H-dopamine.     

Effects of early maternal separation on ethanol intake,GABA receptors and metabolizing enzymes in adult rats

Rationale Maternal separation (MS) in neonatal rats affects ethanol self-administration (SA) in adulthood; however, the conditions and mechanisms need to be clarified. Objectives The goal of this study was to determine the effect of MS on ethanol SA in adulthood in different groups of rats, which control for time of separation, handling, and rearing conditions and, for mechanistic assessment, to examine GABA-A receptors in the central nucleus of the amygdala (CeA) and levels of liver metabolizing enzymes. Methods Newborn, male Long–Evans rats were randomly assigned to different groups and treated over postnatal days 2–14. The rats were picked up by their tails and put back down with no separation (MS0), separated from their mother for 15 min/day (MS15), separated from their mother for 180 min/day (MS180), handled once for a bedding change (NH), or were animal facility reared (AFR). In adulthood, these rats were allowed 5-day continuous access to ethanol, and GABA-A receptors and liver enzymes were measured. Results The MS15 group consumed and preferred significantly less ethanol (about one third) than the MS180 group; however, neither group was different from the MS0 or the AFR group. The NH group consumed and preferred significantly more ethanol than all other groups, at least twice that of the MS180s. GABA-A receptors were increased in the CeA in MS15s, which could help explain the effects. Alcohol dehydrogenase may have been altered in the AFRs. Conclusions Various treatments in neonates affect ethanol intake and GABA-A receptors, and possibly ethanol metabolism, in adulthood. These changes were not simply related to time of separation but were also due to the degree of handling.     

The GABA/benzodiazepine receptor chloride channel complex during repeated episodes of physical ethanol dependence in the rat

The GABA/benzodiazepine (BZ) receptor chloride channel complex was investigated during repeated episodes of ethanol intoxication and withdrawal in the rat; the intragastric intoxication technique was applied and the severity of intoxication, withdrawal and number of seizures were recorded. The following groups were studied after decapitation during withdrawal 10–16 h after the last ethanol feeding: A) isocalorically fed controls not receiving ethanol; B) isocalorical controls subjected to a single ethanol intoxication period; C) animals subjected to 15 intoxication-withdrawal episodes (spontaneous seizures); D) same as C, but without developing seizures. A radio receptor technique was applied in the characterization of the receptor complex comprising specific binding to the BZ-receptor, the chloride channel and the GABA receptor by ³H-diazepam, ³⁵S-TBPS and ³H-muscimol, respectively. The allosteric couplings among the components of the receptor complex were studied by ³H-diazepam and ³⁵S-TBPS binding enhancement tests involving muscimol, ZK 93423 and DMCM. Cortex, hippocampus and cerebellum were the brain regions studied. Except for a reduced specific binding of ³H-diazepam in cerebellum, there were no indications of changes in specific binding to any part of the receptor complex. The allosteric coupling of BZ and GABA receptors as well as chloride channel-BZ receptors were unchanged in all groups. It is notable that no changes at all could be related to number of intoxication-withdrawal episodes or to the development of seizures. Thus, the present study gave no indication that the GABA/benzodiazepine receptor chloride channel complex is directly involved in the augmentation of cerebral nervous system excitability (seizures) during repeated episodes of physical ethanol dependence.     

The effects of GABA and benzodiazepine receptor antagonists on the anti-conflict actions of diazepam or ethanol

The effects of picrotoxin, bicuculline or RO 15-1788 on the anti-conflict action(s) of diazepam or ethanol were studied in rats using a modified Vogel's conflict test procedure. RO 15-1788 antagonized the anti-punishment effects of diazepam (2.5 mg/kg, IP), whereas various doses of bicuculline or picrotoxin did not interfere with diazepam's anti-conflict effect in this test situation. The anti-conflict action of ethanol (2 g/kg, IP) was antagonized by picrotoxin (1.0 mg/kg, IP), whereas both bicuculline and RO 15-1788 were without effect on the increased punishment response produced by ethanol. These data suggest that the anti-conflict properties of ethanol are at least partially mediated through an enhancement of central GABAergic activity.     

黄芩素固体脂质纳米粒包封率测定及体外释放度考察

目的测定黄芩素固体脂质纳米粒的包封率,并考察其体外释放规律。方法溶剂扩散法制备脂质纳米粒,高速离心法分离纳米粒和游离药物,HPLC法测定包封率并考察其体外释放规律。结果测得纳米粒的平均包封率为60.73%,其体外释放规律符合H iguch i动力学方程。结论黄芩素固体脂质纳米粒有较高的包封率,在体外具有良好的缓释作用。     

Effect of acute and chronic ethanol treatment on hepatic triglyceride release from the rat perfused liver

Rats were fed ethanol (30% of total calory intake) for 5 weeks (chronic ethanol treatment), while isocaloric sucrose replaced ethanol in controls. Livers from both ethanol-treated and control rats were perfused with ethanol (acute ethanol treatment), and without ethanol. The hepatic lipid levels and the release of triglycerides and lipoproteins from the livers to the perfusates were measured. Neither chronic nor acute ethanol treatment changed the liver lipid levels.Chronic ethanol treatment reduced the release of triglycerides and preβ-lipoproteins. Acute administration of ethanol increased the release of triglycerides and lipoprotiens in chronically ethanol-treated rats.The chronic effect of ethanol may be related to reduced protein synthesis in these livers, while the acute effect may be secondary to the established effect of ethanol on triglyceride synthesis or to a direct effect on hepatic triglyceride release.     

人参总皂苷渗透泵片体外释药的影响因素

目的建立测定人参总皂苷渗透泵片体外释放度的方法,考察不同因素对该剂型体外释药行为的影响规律。方法用UV法和体外释放度试验,考察渗透泵片在不同溶出方法、释放介质、搅拌桨转速下的累积释放度。结果溶出方法、搅拌桨转速、溶出介质pH3.5~7.6对渗透泵片体外释放行为无显著影响;渗透压对体外释放行为有显著影响。结论确定了不同因素对渗透泵片体外释放度的影响规律。     

GABA induced changes in acetylcholine release from slices of guinea-pig brain

Summary The effect of GABA on acetylcholine (ACh) release was investigated on superfused slices of guinea-pig cerebral cortex (CC), caudate nucleus (CN), tuberculum olfactorium and brain stem.GABA (1–6×10^–3 mol/l) increased the spontaneous and KCl-evoked ACh overflow in CC and CN, reduced the electrically-evoked release in all areas tested (most evidently in CC and CN) and lowered the threshold of electric stimulation-induced ACh release in CC. These effects were also caused by 3-amino-1-propane sulphonic acid (1×10^–3mol/l) and ethanolamine-O-sulphate (2×10^–4mol/l), were reduced by bicuculline (1×10^–4mol/l) and fully antagonized by picrotoxin (8×10^–5mol/l), but they were not influenced by phentolamine, methysergide, spiroperidol or strychnine.Tetrodotoxin (TTX) (5×10^–7mol/l) blocked the facilitation of spontaneous ACh release by GABA only when the slices were perfused with normal Krebs solution, but not when perfused with a KCl-enriched medium. These results suggest that GABA affects the cholinergic transmitter release through bicuculline- and picrotoxin-sensitive receptors, showing low affinity toward the agonist. Moreover GABA modulation of resting ACh release requires action potentials only in normal [K⁺]₀, but not in high [K⁺]₀, suggesting that GABA-receptive sites are located at cholinergic terminals.     

马来酸曲美布汀缓释片体外释放特征与体内J＇b~H关性研究

目的考察马来酸曲美布汀缓释片体外药物释放特征与体内外相关性。方法分别采用①水、②0．1mol／L盐酸、③0．01mol／L盐酸等三种溶剂作为释放介质,考察释放介质对释放度的影响。用Wagner—Nelson方程法计算马来酸曲美布汀缓释片在健康男性受试者体内吸收百分数,并与相应时间体外累积释放度线性回归,进行体内外相关性考察。结果马来酸曲美布汀缓释片在不同释放介质中的释放度一致,均符合零级动力学。将体内累积吸收百分数y与相应时间在0．01mol／L盐酸释放介质中的体外释放百分数X进行线性回归（n=7）,回归方程为Y=1．0093x一0．3329,r：0．9600（P=0．000601〈0．001）,表明具有良好的体内外相关性,呈A级相关。结论马来酸曲美布汀缓释片的释放度不受三种释放介质影响,释药恒速。体外释放累积百分数与体内吸收百分数呈A级相关。     

Effect of GABA Analogues on Blood Pressure and Central GABA Metabolism in the Rat

Abstract: Gamma aminobutyric acid (GABA) and different GABA analogues were examined for their cardiovascular actions and their influence on striatal dopamine (DA) levels and GABA accumulation after aminooxyacetic acid (AOAA). Gamma hydroxybutyric acid (GHBA) and baclofen caused hypertension and tachycardia after systemic as well as intracerebroventricular administration, while the opposite was true for GABA and muscimol. The hypertension after GHBA and baclofen was not reduced by picrotoxin or bicuculline and was not influenced by varying GABA levels by 3-mercaptopropionic acid (3-MPA)or AOAA. GHBA and muscimol but not baclofen reduced GABA accumulation induced by AOAA. Picrotoxin in a subconvulsive dose increased GABA accumulation and antagonized the inhibition after GHBA or muscimol. Bicuculline and a moderate dose of picrotoxin tended to decrease GABA accumulation by themselves and if anything augmented the effects of GHBA and muscimol. GHBA and baclofen but not muscimol in combination with AOAA increased DA levels, which was not prevented by picrotoxin or bicuculline. We conclude that the cardiovascular actions of GHBA and baclofen are probably not mediated by mechanisms identical to those of muscimol or exogenous GABA. In view of the biochemical results their actions would however be compatible with a concept of different GABA receptors.     

Met-enkephalin inhibition of K+-induced LHRH and ARIF release from rat mediobasal hypothalamic slices

Unilateral application of picrotoxin or (+)-γ-acetylenic GABA ((+)GAG) on the cortex of rats produces a characteristic dyskinetic syndrome. Using stereotaxic coordinates, the cortical localization of these abnormal movements was mapped and found to be similar to that previously described after electrical stimulation of these cortical areas: Abnormal movements of the head and forelimb were produced by picrotoxin or (+)GAG applied to sites more anteriorly and of the hindlimb more posteriorly. The degree of enzyme inhibition following application of (+)GAG was used to demonstrate a very limited degree of drug diffusion. These results suggest that interferences with GABAergic function in well-defined cortical areas may play a role in dyskinetic movement disorders.     

Effect of fenfluramine administration on synaptosomal uptake of some neurotransmitters and on synaptosomal enzymes which metabolise GABA

Summary Fenfluramine has been considered to deplete neuronal 5-hydroxytryptamine (5-HT). This compound is able to reduce the synaptosomal uptake of 5-HT and other neurotransmitters such as GABA and glutamic acid (Glu). The effects of fenfluramine on these three compounds considered as neurotransmitters are different. The inhibition is of competitive type for 5-HT and non-competitive for GABA and Glu. Concerning the enzymes involved in GABA synthesis and degradation, Fenfluramine increases Glutamic acid decarboxylase activity and decreases GABA-transaminase activity in synaptosomes. Decreased synaptosomal GABA levels could be attributed to a lower uptake. An enzymatic regulating system may be responsible in restoring the GABA level. A similar mechanism concerning serotonin has been previously suggested (Costa et al., 1971).