Changes in the regulation of 5-hydroxytryptamine release by alpha2-adrenoceptors in the rat hippocampus after long-term desipramine treatment.

In vivo microdialysis was used to measure the effects of long-term treatment of rats with desipramine upon the regulation by alpha2-adrenoceptors of serotonin (5-hydroxytryptamine, 5-HT) release from the serotonergic neurons in the hippocampus. Rats were injected with saline or desipramine, 10 mg/kg, i.p., every 12 h for 14 days. When added to the perfusion solution, brimonidine, an alpha2-adrenoceptor agonist, significantly inhibited the K+-evoked release of 5-HT in the hippocampi of saline-treated, control rats. This action of brimonidine was prevented by pretreating the rats with idazoxan, an alpha2-adrenoceptor antagonist. Long-term desipramine treatment significantly reduced the inhibitory effect of brimonidine upon the K+-evoked 5-HT release. With long-term administration of desipramine, noradrenaline content in the hippocampi was significantly decreased as compared with that of the control rats, whereas the basal noradrenaline concentration in the dialysate was significantly increased. On the other hand, both the 5-HT content of the hippocampus and the basal 5-HT concentration in the dialysate were significantly increased. The present study suggests that long-term administration of desipramine causes a functional subsensitivity of the presynaptic alpha2-adrenoceptors that regulate serotonergic neuronal function in the rat hippocampus. It also supports the concept that changes in the sensitivity of alpha2-adrenoceptors that regulate neurotransmitter release play an important role in the mechanism of antidepressant drug action.

Pharmacological characterization of alpha 2-adrenoceptor regulated serotonin release in the rat hippocampus.

The purpose of the present study was to confirm the functional regulation by alpha 2-adrenoceptors of the release of serotonin (5-HT) from the rat hippocampus in vivo. Under several pharmacological conditions, extracellular levels of 5-HT were estimated by assaying its concentrations in the perfusate by high performance liquid chromatography with electrochemical detection. Extracellular 5-HT in the hippocampus was reduced by tetrodotoxin (10 microM) co-perfusion, but increased by perfusion of a selective 5-HT re-uptake inhibitor, fluoxetine (10 microM). Addition of potassium (K+, 120 mM) to the perfusion fluid evoked an approximately 3-fold increase in 5-HT release. When the alpha 2-adrenoceptor agonist UK14,304 (0.1-10 microM) was added to the perfusion solution, the K(+)-evoked 5-HT release was significantly inhibited in a concentration-dependent manner. This inhibitory action of UK14,304 was reversed by pretreatment with an alpha 2-adrenoceptor antagonist, idazoxan (5 mg/kg, i.p.). In rats which were catecholaminergically denervated with 6-hydroxydopamine, UK14,304 (10 microM) still inhibited the K(+)-evoked 5-HT release. Treatment with pertussis toxin (PTX) did not alter the K(+)-evoked release of 5-HT but abolished the inhibitory effect of UK14,304. These findings suggest that 5-HT release is functionally modulated via alpha 2-adrenoceptors located on the serotonergic nerve terminals in the rat hippocampus and furthermore, the possibility that the inhibitory of alpha 2-adrenoceptors is linked to G-proteins which are substrates of PTX.

Effect of preanesthetic intramuscular ranitidine on gastric acidity and volume in children.

STUDY OBJECTIVE: To evaluate the effects of preanesthetic administration of intramuscular (IM) ranitidine on pH and volume of gastric contents in children. DESIGN: Three randomized treatment groups. SETTING: Central operating rooms at a university hospital. PATIENTS: Forty children age 1 to 10 years undergoing a variety of elective surgical procedures requiring general anesthesia with endotracheal intubation. INTERVENTIONS: IM ranitidine 1 mg/kg (n = 15) or 2 mg/kg (n = 15) was administered 2 hours prior to induction of anesthesia. Ten patients without ranitidine served as the control group. An orogastric tube was inserted into each patient. MEASUREMENTS AND MAIN RESULTS: Gastric fluid pH and volume were measured every hour in the three groups. Plasma ranitidine concentrations were measured in ten patients of the ranitidine-treated groups. The mean volume of gastric fluid at induction of anesthesia was significantly lower in the ranitidine-treated patients (2.4 ml for ranitidine 1 mg/kg, 3.2 ml for ranitidine 2 mg/kg) than in the controls (8.6 ml; p less than 0.05). The mean pH values at induction of anesthesia were significantly higher in the ranitidine-treated patients (4.6 for 1 mg/kg, 6.7 for 2 mg/kg) than in the controls (2.1; p less than 0.05). Dose-dependent plasma ranitidine concentrations were obtained. CONCLUSIONS: Preanesthetic IM ranitidine 1 to 2 mg/kg resulted in a higher pH and lower volume of gastric fluid at the time of induction and in a higher pH during 3 hours of anesthesia. This therapy may be a useful adjunct to premedication for children who have a greater than normal risk of pulmonary aspiration during anesthesia.

[Pneumonia due to aspiration of povidone-iodine during anesthesia--a case report].

We report a case of pneumonia secondary to aspiration of povidone-iodine, which was used as an oral antiseptic. The patient was 17 y.o. female (body weight: 70 kg) who underwent a transsphenoidal resection of pituitary adenoma. Although she had a history of asthma during her childhood, no asthmatic attacks occurred for the past 10 yrs. After satisfactory anesthesia induction and tracheal intubation, 60 ml of 0.7% povidone-iodine solution was used to clean the oral cavity by a surgeon. Insufficient sealing by the cuff occurred after suturing the tube, which had made a needle hole in the cuff. Arterial oxygen saturation dropped to 90% and an increased resistance in the lungs was noted. The trachea was reintubated and she was transferred to the ICU. Her chest X-ray revealed signs of pneumonia and atelectasis in the right upper lobe. Mechanical ventilation with PEEP and periodical bronchial toilet were performed during her stay in the ICU for 42 hrs. A week was needed for the improvement of her X-ray findings. Although povidone-iodine is thought to be safe and affective antiseptics, severe complications from its aspiration may occur in patients whose airways are sensitive as observed in this case.

[The effect of dopamine or dobutamine on plasma concentration of magnesium in dogs].

Plasma magnesium (Mg) concentration of dogs was determined with atomic absorption spectrophotometry during the infusion of dopamine (DOA) or dobutamine (DOB). Other electrolytes were also measured with same samples. Normoventilation was maintained during this experiment in order to avoid the respiratory interference. DOA 15-20 micrograms.kg-1.min-1 decreased Mg concentration significantly. DOB 5-20 micrograms.kg-1.min-1 did not change Mg concentration. Potassium (K) values were almost constant during infusion of both drugs, but DOB reduced K concentration at the dose of 20 micrograms.kg-1.min-1. Ionized calcium ion tended to decrease in DOA and to increase in DOB while the dose of the catecholamines was increased. These were not significant changes. These changes of concentration returned to control values 1 hour after stopping drug administrations. We speculate that beta-receptor, especially beta 2-receptor stimulation by DOA is responsible for the decrease of Mg in the mechanism of Mg uptake into cells of such tissues as liver or muscle.

[A psychological burden on patients with clinical trials during anesthesia].

We investigated with questionnaires, psychological outline of 30 patients, who were requested to participate in clinical trials of anti-tachycardia drugs during anesthesia. Although 14 patients consented to the trial, the consent was not based on adequate understanding or volunteerism in 3 patients. Nine patients of the consented group were anxious about the possible use of the trial drug. Eight patients of the rejected group felt anxiety on surgery and anesthesia, which was the most common reason for rejection. Forty % of refused patients felt a guilty conscience or embarrassed. Although we tried to obtain patients' consent following governmental and institutional regulations and guidelines, not only the consented but also the refused patients suffer from psychological burden with the clinical trial. It is of concern that recruitment to the trial enhances anxiety of the patients as they already feel uneasiness, unrest, and insecurity facing anesthesia and surgery. To avoid entry of less informed or unwilling patients to the clinical trial, we must secure patients' veto, and recruitment should be performed by clinicians who are not involved in anesthesia practice.

[Pharmacological characterization of alpha 2-adrenoceptor regulated 5-HT release in the rat hippocampus].

The purpose of the present study is to confirm the functional regulation of alpha 2-adrenoceptor on the release of serotonin (5-HT) from the rat hippocampus in vivo. Under several pharmacological conditions, extracellular levels of 5-HT were estimated by assaying its concentrations in the perfusion fluid through the use of high-performance liquid chromatography with electrochemical detection. Extracellular 5-HT in the hippocampus was reduced by tetrodotoxin, 10 microM co-perfusion and was increased by perfusion with a selective 5-HT reuptake inhibitor, fluoxetine, 10 microM. Addition of potassium (K+; 120 mM) to the perfusion fluid evoked an approximately 3-fold increase in 5-HT release, and a calcium free medium completely prevented this K(+)-evoked 5-HT release. Potassium-evoked 5-HT release from the hippocampus of freely moving rats was significantly and concentration-dependently inhibited when alpha 2-adrenoceptor agonist, UK14,304, 0.1 microM to 10 microM was added to the perfusion solution, while the output of a 5-HT major metabolite, 5-hydroxyindoleacetic acid (5-HIAA), remained unchanged. This action of UK14,304 was prevented by pretreatment with idazoxan, 5 mg/kg, i. p., an alpha 2-adrenoceptor antagonist. In rats that were catecholaminergically denervated with 6-hydroxydopamine, UK14,304, 10 microM also inhibited the potassium-evoked 5-HT release, but had no effect on the 5-HIAA output. The UK14,304-induced inhibition of 5-HT release was prevented by pretreatment with pertussis toxin (PTX). These findings suggest that 5-HT release is functionally modulated via alpha 2-adrenoceptors located on the serotonergic nerve terminals in the rat hippocampus. They also indicate the possibility that the inhibition of 5-HT release via alpha 2-adrenoceptors is linked to G-proteins which are substrates of PTX.

Cloning and expression of Pseudomonas putida esterase gene in Escherichia coli and its use in enzymatic production of D-beta-acetylthioisobutyric acid.

The esterase catalyzes the stereoselective hydrolysis of methyl DL-beta-acetylthioisobutyrate (DL-ester) to give D-beta-acetylthioisobutyric acid (DAT). To use the enzyme for DAT production, the esterase gene of Pseudomonas putida was cloned and expressed in E. coli. The recombinant E. coli containing the esterase gene produced a large amount of the enzyme in an active form. This strain could be used for the asymmetric synthesis of DAT.

Does preoperative oral clonidine inhibit salivary secretion during general anesthesia?

Clonidine is known to inhibit salivary secretions and cause dryness of the mouth. We evaluated the effect of preoperative oral clonidine on salivary secretions before and during general anesthesia. Twenty-eight adult patients, equally divided into four groups, received the following premedication 2 hr prior to induction of anesthesia. Group 1 patients received oral ranitidine 5 mg.kg(-1) alone. Groups 2 and 3 patients received oral clonidine 1 microg.kg(-1) and 3 microg.kg(-1) respectively with oral ranitidine 5 mg.kg(-1). Group 4 patients received no premedication and served as control. The volume of salivary secretions was determined by calculating the change in weight of four cotton wool cylinders placed in the oral space 10 min before and 30, 60 and 120 min after induction of anesthesia. Salivary volume was significantly less in the clonidine treatment groups before induction of anesthesia. After induction of anesthesia, there were no significant differences in salivary secretions among the four groups. No severe hypotension or bradycardia was seen in any patient of four groups. Preoperative oral ranitidine 5 mg.kg(-1) had no effect on salivary secretion. In conclusion, clonidine did not decrease salivary secretions further over the already decreased level during general anesthesia.

Nucleotide sequence of the gene for a thermostable esterase from Pseudomonas putida MR-2068.

The esterase gene (est) of Pseudomonas putida MR-2068 was cloned into Escherichia coli JM109. An 8-kb inserted DNA directed synthesis of an esterase in E. coli. The esterase gene was in a 1.1-kb PstI-ClaI fragment within the insert DNA. The complete nucleotides of the DNA fragment containing the esterase gene were sequenced and found to include a single open reading frame of 828 bp coding for a protein of 276 amino acid residues. The open reading frame was confirmed by N-terminal amino acid sequence analysis of the purified esterase. A potential Shine-Dalgarno sequence is followed by the open reading frame. The esterase activity of the recombinant E. coli was more than 200 times higher than that of parental strain, P. putida MR-2068.

Chemical Racemization of Methyl L-ß-Acetylthioisobutyrate.

Methyl L-ß-acetylthioisobutyrate was racemized with 1,8-diazabicyclo-[5.4.0]-undecene-7 as a catalyst. Methyl methacrylate and thioacetic acid were identified as the intermediates of the reaction. Thioacetic acid was relatively unstable and susceptible to decomposition during the racemization process. The addition of excess methyl mechacrylate to the reaction mixture prevented a decrease of the racemate. The racemized ester was confirmed to be usable as a substrate for the enzymatic production of D-ß-acetylthioisobutyric acid.