Fasting glycaemia to simplify screening for gestational diabetes.

OBJECTIVE: Recommendations in Switzerland on screening for gestational diabetes endorse the International Association of Diabetes in Pregnancy Study Group consensus. As universal testing is time consuming and glucose loading is unpleasant, the recommendations include a simplification, not performing the glucose loading in women with fasting glycaemia <4.4 mmol/l. Our objective was to evaluate the diagnostic performance of this simplified strategy, compared with the complete test, in our population with a low prevalence of gestational diabetes. DESIGN: We collected 2298 complete 75-g glucose tolerance tests. We simulated stopping the test, so avoiding the glucose loading and further glycaemia, if fasting glycaemia was <4.4 or ≥5.1 mmol/l. SETTING AND POPULATION: Unselected pregnant women from Geneva and Basel, at 24-28 weeks of gestation. METHODS: We calculated the sensitivity, and the percentage of women who would avoid the complete test with the strategy based on fasting glycaemia. RESULTS: The prevalence of gestational diabetes was 10.9% in our population. Among 251 women with gestational diabetes, fasting glycaemia was ≥5.1 mmol/l in 119 women (47.4%), between 4.4 and <5.1 mmol/l in 78 women (31.1%) and <4.4 mmol/l in 54 women (21.5%). Proceeding with the complete test only in women with fasting glycaemia between 4.4 and <5.1 mmol/l will result in a sensitivity of 78.5%. This strategy would avoid glucose loading in 63.8% of women. CONCLUSIONS: Screening with fasting glycaemia is an attractive alternative to universal screening with the complete 75-g glucose tolerance test. This strategy is, however, slightly less sensitive than previously reported in higher-risk populations. TWEETABLE ABSTRACT: Fasting glycaemia can be considered as an alternative to the complete test for gestational diabetes screening.

3-Deazaguanine: inhibition of initiation of translation in L1210 cells.

In L1210 cells in culture, 3-deazaguanine (DG), a relatively new purine analog, was found to inhibit DNA and protein synthesis but not total RNA synthesis. The effect of the drug on protein synthesis was therefore further examined. Polyadenylic acid-containing RNA synthesis was not decreased by DG treatment, suggesting that the inhibiton of protein synthesis was a function of an alteration in the process of translation. DG altered the polyribosome sedimentation profile in a dose-dependent manner, increasing the numbers of monosomes and smaller polysomes and decreasing the number of larger polysomes. The nascent polypeptides in DG-treated cells were labeled with [3H]leucine, and the increased number of monosomes was not associated with a proportionate amount of [3H]leucine when compared to the polysomes. This indicated that the monosomes had not been derived directly from the breakdown of active polysomes. The shift in the polysome profile was reversed by cycloheximide, suggesting that DG profile inhibited the initiation of translation. This was confirmed by the demonstration of the inhibition of DG of the formation of the 43S preinitiation complex. The inhibition of the initiation of protein synthesis by DG may contribute to the antitumor actions of this new purine analog.

Phase I clinical and pharmacokinetic study of mitoxantrone given to patients by intraperitoneal administration.

On the basis of its high degree of cytotoxicity against fresh human ovarian cancers and its relative lack of vesicant activity, mitoxantrone administered by the i.p. route was studied in a Phase I and pharmacokinetic trial. Thirty-three patients with good performance status and diagnoses of metastatic or recurrent ovarian (31 patients) and colon (two patients) cancers were treated with 12- to 38-mg/m2 doses, administered by the i.p. route every 4 wk for up to ten treatment courses. Mitoxantrone doses were escalated at 2- to 3-mg/m2 increments in groups of three to 11 patients. Thirty-eight mg/m2 (by i.p. dwell without removal) were considered the maximally tolerated dose in that, of eight treated patients, four experienced severe leukopenia and six experienced severe abdominal pain. Response to i.p. mitoxantrone was evaluable in 17 patients. None of seven patients with clinically measurable intraabdominal or pelvic tumor masses responded; however, in three (50%) of six patients with nonmeasurable disease, there was normalization of previously elevated serum CA-125 concentrations for 3, 17, and 24 mo. Additionally, two (50%) of four patients who underwent third-look laparotomies were found to have greater than 75% reductions in i.p. tumor masses with response lasting 24 and 25 mo. At 38 mg/m2, mitoxantrone was associated with a mean concentration.time product of 100 micrograms.h/ml in the i.p. space and of 0.071 micrograms.h/ml in plasma, yielding an i.p./plasma area under the curve ratio of 1408. We conclude that chemical peritonitis is the dose-limiting toxicity of i.p. administered mitoxantrone and that a dose of 23 mg/m2 every 3 to 4 wk should be used in future Phase II trials in ovarian cancer patients with minimal residual intraabdominal and pelvic disease following second-look laparotomy.

Resistance to methotrexate due to gene amplification in a patient with acute leukemia.

A patient is described with acute myelocytic leukemia refractory to conventional therapy, who also became highly resistant to methotrexate (MTX) after repeated courses of this drug. Leukemia cells from this patient were found to contain an elevated level of dihydrofolate reductase (DHFR) activity, with no change in the affinity of the enzyme for MTX. A sensitive "dot blot" assay revealed a fourfold increase in the gene copy number of DHFR. Southern blot analysis with a human DHFR cDNA probe confirmed this increase in the gene copy number, and demonstrated a similar restriction pattern with Eco R1, Hind III, and Pst 1 as seen with a highly amplified human leukemia cell line, K562. Additional DHFR fragments were detected, not seen in the K562 blot, suggesting the presence of pseudogenes, or a result of gene rearrangements occurring as part of the amplification process. Resistance to MTX in this patient was therefore ascribed to gene amplification and overproduction of DHFR.

Taste-induced changes in plasma insulin and glucose turnover in lean and genetically obese rats.

Cephalic-phase insulin release (CPIR) and the changes in glucose turnover induced by saccharin ingestion were studied in freely moving lean and genetically obese fa/fa rats equipped with chronic catheters for blood sampling. Six-hour-fasted lean and obese rats were trained to drink 1 ml sodium saccharin (0.15%) or 1 ml glucose (70%), and blood samples were taken before and after the stimuli. As early as 1-1.5 min poststimulus, there was a significant increase in CPIR in lean and obese rats. The amplitude of the CPIR induced either by saccharin or by glucose in the obese rats was significantly higher than it was in the lean rats. The effect of saccharin ingestion on the hepatic glucose production (HGP) and the rate of glucose disappearance (Rd) was studied in 6-h-fasted lean and obese rats, under non-steady-state conditions, according to a method previously validated. Saccharin ingestion produced a significant increase in HGP and Rd in lean and obese rats compared with basal values. The saccharin-induced increments in HGP and Rd were higher in the obese than in the lean animals. We conclude that saccharin (through taste) appears to elicit parasympathetic (insulin release) and sympathetic (HGP increase) reflexes in lean and obese rats. These taste-induced changes in plasma insulin and glucose turnover are exaggerated in the obese rats and may participate in obesity and in insulin resistance of the overall syndrome.

Effects of leptin on corticotropin-releasing factor (CRF) synthesis and CRF neuron activation in the paraventricular hypothalamic nucleus of obese (ob/ob) mice.

The effects of leptin on the levels of CRF messenger RNA (mRNA) in the paraventricular hypothalamic nucleus (PVN), on the activation of the PVN CRF cells, and on the plasma levels of corticosterone were investigated in lean (+/?) and obese (ob/ob) C57BL/6J male mice. Murine leptin was s.c. infused using osmotic minipumps. The treatment period extended to 7 days, and the daily dose of leptin delivered was 100 microg/kg. The mice were killed either in a fed state or following 24 h of total food deprivation. The starvation paradigm was employed to enhance the activity of the hypothalamic-pituitary-adrenal axis in obese mice. In situ hybridization histochemistry was performed to determine the PVN levels of CRF mRNA and the arcuate nucleus levels of neuropeptide Y mRNA. The activity of the PVN CRF cells was estimated from the number of PVN cells colocalizing CRF mRNA and the protein Fos. Leptin led to a reduction in body weight gain and fat deposition. These effects were seen in both +/? and ob/ob mice and were observed to be particularly striking in obese mutants, in which leptin also caused an important reduction in food intake. Leptin also was found to affect plasma levels of corticosterone. It lowered the high corticosterone levels of obese mutants, an effect that appeared more evident in food-deprived than in fed mice. Finally, leptin prevented the induction of CRF synthesis in the PVN and the activation of the PVN CRF neurons observed in food-deprived ob/ob mice and hindered the elevation of arcuate nucleus neuropeptide Y synthesis in ob/ob mice. Together these results suggest a role for leptin in the excessive response of the hypophysiotropic CRF system of the ob/ob mouse.

Expression of corticotropin-releasing factor and its receptors in the brain of lean and obese Zucker rats.

Expression of CRF messenger RNA (mRNA) and heteronuclear RNA (hnRNA) as well as the mRNAs encoding the CRF receptors of type 1 (CRF1R) and type 2 alpha (CFR2R) in the brain has been investigated in lean (Fa/?) and obese (fa/fa) Zucker rats. Exonic and intronic in situ hybridization histochemistry was employed to measure the mRNA and hnRNA levels in rats killed before (resting state), during, and 120 min after a treadmill running session. The resting expression of CRF hnRNA in the hypothalamic paraventricular nucleus (PVN) of obese rats was minimal and comparable to that of lean rats. However, during treadmill running, this expression was higher in obese than in lean rats. In obese rats, the transcription of the CRF1R mRNA in the PVN was high under resting conditions, dropped considerably during running, and rose again to elevated levels 120 min after the treadmill session. In lean rats, CRF1R mRNA in the PVN was minimal before and during running, but rose to a value similar to that in obese rats 120 min after running. In the PVN of obese rats, expression of the CRF1R gene measured during resting conditions was comparable to the level seen after running and proved to be dependent upon the feeding state of the rats. Expression of the CRF2R transcript was reduced in the ventromedial nucleus of the hypothalamus (VMH) of the obese rat. Plasma ACTH concentrations during treadmill running were lower in obese than in lean animals. Basal and postrunning levels of circulating corticosterone were higher in fa/fa than in Fa/? rats. However, there was no difference in corticosterone levels between lean and obese animals during running. The present results provide evidence for differences between lean and obese rats in the expression of CRF and its receptor within selective hypothalamic nuclei. Given the anorectic and thermogenic properties of CRF and the roles of PVN and VMH in the regulation of energy balance, it can be argued that the observed alterations in the biosynthesis of CRF and its receptors within the PVN and VMH might be related to the development of obesity.

Daily administration of melatonin delays rat vaginal opening and disrupts the first estrous cycles: evidence that these effects are synchronized by the onset of light.

The effect of daily melatonin administration was investigated in the immature female rat. Starting on day 15 of age, 100 micrograms melatonin were injected sc at different times of the day in animals housed in 12 h of light, 12 h of darkness or 16 h of light, 8 h of darkness. Melatonin given 9-11 h after the onset of light in both lighting regimens resulted in a 10-day delay of vaginal opening, a dissociation of the relation between vaginal opening and first proestrus, and a disruption of the initial estrous cycles. The same dose of melatonin given at other times during the photoperiod had no effect on sexual maturation. GnRH secretion in melatonin-treated animals was decreased, as judged by 30% lower pituitary GnRH receptor number in animals killed after opening of the vagina. During the diestrous phases, plasma levels of LH, FSH, and 17 beta-estradiol were similar to those in control rats, but during proestrus, the surge of FSH was higher, and the peak of estradiol was higher and of a longer duration. This hormonal pattern suggests a build-up of hormones in secreting cells, which follows the lower incidence of proestrous phases in melatonin-treated rats. This build-up of FSH was indeed present, with higher concentrations in the pituitary during diestrus after melatonin treatment, while pituitaries removed during proestrus had lower contents of FSH. These results confirm that chronic melatonin administration delays sexual maturation of female rat, probably by retarding maturation of hypothalamic GnRH-producing cells. Thus, melatonin could modify basal GnRH secretion or pulsatile release. Pituitary and ovarian responsiveness do not seem to be affected, since proestrous surges of 17 beta-estradiol, LH, and FSH occur, albeit at a reduced frequency. The results also show that there is a window of maximum sensitivity to administration of melatonin 9-11 h after the onset of light, and that this window of sensitivity is synchronized by the onset of light. This raises the possibility that the abnormal presence of endogenous melatonin during this period of the day could induce abnormal sexual development.

Plasma growth hormone (GH) response to intravenous GH-releasing factor (GRF) in adult rats: evidence for transient pituitary desensitization after GRF stimulation.

The ability of human (h)GRF-(1-29)NH2 to stimulate GH secretion was studied in cannulated adult rats. In order to suppress endogenous GRF secretion and the inhibitory action of hypothalamic somatostatin (SRIF), rats were anesthetized with sodium pentobarbital. Intravenous administration of hGRF-(1-29)NH2 elicited a dose-dependent response of plasma GH, with 250 ng/kg being the smallest effective dose in male rats. In female rats, for each dose tested (250 to 70,000 ng/kg), the GH response represented only about 60% that of male rats. Repeated iv stimulations with hGRF-(1-29)NH2 at short time intervals (45 min) produced transient desensitization of pituitary responsiveness to GRF: a blunted GH response to the second and third stimulations was observed both in male and in female rats and for each dose tested. Similar blunted responses were also obtained with repeated injections of native hGRF-(1-44)NH2. The possibility that these blunted responses could be due to incomplete suppression of hypothalamic SRIF secretion by sodium pentobarbital was excluded by the use of rats that were passively immunized against SRIF; in these rats, it was shown that at least 65% of the inhibition of the GH response after the second GRF stimulation was unrelated to SRIF action. Similar transient desensitization to repeated hGRF-(1-29)NH2 stimulations was also observed in conscious rats that were passively immunized against SRIF. This occurrence of blunted responses was shown to be related to the length of the time interval between GRF stimulations, with longer intervals resulting in less or no desensitization. It appears thus that modulation of pituitary responsiveness to the action of GRF is mediated by at least two independent mechanisms in the rat: in addition to the inhibitory action imposed by hypothalamic SRIF, which induces periods of refractoriness to the action of GRF, it was shown in this study that in the pituitary level each GRF stimulation also induces a transient desensitization of somatotrophs for about 1 h. This period of refractoriness might not be due to excessive stimulation with GRF, since it was also observed with the lowest dose of hGRF-(1-29)NH2 that gave a significant release of GH. Finally, a sex difference was confirmed for the response of anesthetized adult rats to stimulation with hGRF-(1-29)NH2, reflecting a sex steroid-induced modification of pituitary responsiveness to GRF stimulation.

Daily afternoon administration of melatonin does not irreversibly inhibit sexual maturation in the male rat.

Previous studies from our laboratory demonstrated that daily afternoon melatonin injections from 20-40 days of age inhibited sexual development of young male rats, whereas in adult animals, similar injections had no effect. The present study was designed to determine more precisely the critical age period during which melatonin exerts its inhibiting effect and to see whether spontaneous sexual maturation resumes after discontinuation of melatonin administration at 45 days of age or even during continuous administration of melatonin until 115 days of age. Sexual maturation was evaluated using weights of seminal vesicles and testes; plasma levels of testosterone, FSH, and LH; pituitary contents and concentrations of FSH and LH; and, finally, pituitary content of GnRH receptors. Administration of melatonin to young male rats from 20-30 days of life had the same inhibitory effect on sexual maturation at 40 days as melatonin injections from 20-40 days. In contrast, administration of melatonin from 30-40 days only slightly decreased plasma testosterone concentration, weight of seminal vesicles, and pituitary GnRH receptor content. Melatonin administration from 38-40 days had no effect. Daily melatonin administration from 20-45 days of age was followed by resumption of sexual maturation, as observed at 70 days. The recovery was complete by 80 days of age when all of the parameters studied reflected complete sexual maturation. Finally, in rats treated continuously with melatonin from days 20 until 115, sexual maturation occurred but was delayed by about 20-30 days. Beginning of sexual development was observed at 60 days of life, and full development was attained only at 100 days. These data confirm that melatonin delays sexual maturation in the young male rat when administered daily in the afternoon. They demonstrate that this inhibitory action of melatonin is most critical between 20 and 30 days of life and is reversible regardless of whether melatonin administration is discontinued after 45 days of life. The suppression of the pubertal peaks of pituitary GnRH receptor number and pituitary and plasma FSH concentrations in treated rats suggests that melatonin interferes with the pubertal increase in GnRH secretion. In conclusion, these reversible effects of melatonin suggest that this pineal indolamine represents an important factor for the timing of sexual maturation.

Differences between circadian and ultradian organization of cortisol and melatonin rhythms during activity and rest.

We compared the cortisol and melatonin circadian and ultradian rhythms in normal men using two approaches: 1) the men were exposed successively to two conditions, one normal and a second chosen to alter differently each of the hormones, i.e. complete bedrest for 34 h (supine, fasting, and under dim light), and 2) analyses of the rhythms using a combination of curve smoothing for the description of the 24-h rhythm, and peak detection and spectral analysis for the measurement of periodic phenomena. Blood was sampled every 30 min from 0700-0700 h. A diurnal rhythm was detected for both hormones, with different underlying frequencies. Plasma cortisol had an ultradian rhythm of 8 h. From 0000-0800 h (night) and 0830-1600 h (early day), the pulsatile activity and baseline values of cortisol were high, while from 1630-2400 h (late day), these variables were low. During complete bedrest, pulsatile activity and baseline values were even higher during the night period, and the nocturnal peak of cortisol, usually present between 0300-1000 h, was split in two, with an early peak at 0000-0400 h. There were two specific events during the day associated with synchronous, high amplitude pulses: awakening and eating at noon. No such pulses occurred at suppertime or when the men fasted. Melatonin secretion was organized around a 5.5-h period. In the rest condition, plasma melatonin values were higher during the night. The 24-h rhythms of cortisol and melatonin were temporally related. Plasma melatonin began to rise when plasma cortisol was at its lowest, it peaked when cortisol began to rise, and it began to decrease when cortisol reached its peak, with a 5-h phase delay between plasma cortisol and melatonin rise at night. In summary, melatonin and cortisol rhythms have different ultradian frequencies, suggesting an intrinsic difference in the mechanisms controlling their secretion. In addition, their responses to restricted physical activity in an environment with dim light were completely different; for plasma melatonin, the change was primarily quantitative, with an increase in total production especially at night, while for plasma cortisol, there was more of a qualitative change, with different patterns of pulsatile activity and possible splitting of the nocturnal peak. The differences in the ultradian organization of these two hormones imply that the correlation between their peaks must depend on a third factor, which is likely to be the 24-h organization of the day.

Distribution of the uncoupling protein 2 mRNA in the mouse brain.

The present study was conducted to investigate the brain distribution of the recently cloned uncoupling protein 2 (UCP2). Northern blot analyses were first carried out to confirm the presence of UCP2 in the brain. These analyses revealed the brain presence of UCP2 mRNA and the absence of the mRNAs encoding uncoupling protein 1 and uncoupling protein 3. They also demonstrate that UCP2 mRNA expression was abundant in the hypothalamus and not affected by cold acclimation. In situ hybridization histochemistry was used to determine the brain distribution of the mRNA encoding UCP2. A markedly intense hybridization signal was found in the hypothalamus, the ventral septal region, the caudal hindbrain (medulla), the ventricular region, and the cerebellum. A very highly intense hybridization signal was apparent in the suprachiasmatic nucleus, the medial parvicellular part of the paraventricular hypothalamic nucleus, the arcuate nucleus, the dorsal motor nucleus of the vagus nerve, and the choroid plexus. The specifically localized expression of UCP2 mRNA suggests that this mRNA has a neuronal localization. Neuronal expression was particularly manifest in the nucleus of the horizontal limb of the diagonal band, the submedius thalamic nucleus and the dorsal motor nucleus of the vagus nerve, where agglomerations of the silver grains delineated individual cells. The role played by UCP2 in the brain has yet to be fully described, but the pattern of distribution of the transcript suggests that this mitochondrial protein is part of neuronal circuitries controlling neuroendocrine functions, autonomic responses, and the general arousal of the brain. Given the involvement of the proteins from the uncoupling protein's family in the uncoupling of cellular respiration, it can be argued that UCP2 contributes to the metabolic rate and thermoregulation of these circuitries. In addition, by promoting oxygen consumption in the brain, UCP2 could control the production of reactive oxygen species and thereby influence the process of neural degeneration.

Neurotensin causes a greater increase in the metabolism of dopamine in the accumbens than in the striatum in vivo.

Differential pulse voltammetry with carbon fibre electrodes was used to study the effect of central administration of neurotensin on the extracellular level of 3,4-dihydroxyphenylacetic acid (DOPAC) in the nucleus accumbens and the striatum in anaesthetised rats. Intracerebroventricular injection of neurotensin (10 micrograms) increased the peak height for DOPAC 20 min after administration in the nucleus accumbens but only after 40 min in the striatum. The maximum increase was similar in both regions, with 30% and 27% above the pre-injection basal level, respectively. Neurotensin (1 micrograms) however increased the extracellular level of DOPAC in the nucleus accumbens alone. Neurotensin (0.1, 1.0 and 3.0 micrograms/0.5 microliter), injected into the ventral tegmental area, induced a potent and long-lasting elevation of the peak height for DOPAC in the nucleus accumbens, while the same doses in the substantia nigra produced effects on the metabolism of dopamine in the striatum of smaller amplitude and shorter duration. The maximum effect of each dose was about 2.5 times greater in the mesolimbic, compared to the nigrostriatal system. Amphetamine (2 mg/kg, s.c.) decreased the extracellular level of DOPAC with a similar magnitude, both in the nucleus accumbens (52%) and the striatum (47%). Intracerebroventricular administration of neurotensin (1 micrograms), 5 min after amphetamine, did not alter the effect of amphetamine on the extracellular level of DOPAC either in the nucleus accumbens or the striatum. However, neurotensin (10 micrograms) partially reversed the effect of amphetamine in the nucleus accumbens and had a similar but smaller and delayed effect in the striatum. The results from the present study, together with previous neurobehavioural studies, suggest that neurotensin has a relatively selective action on the mesolimbic dopaminergic system in the rat.

Structure-activity studies of neurotensin on muscular rigidity and tremors induced by 6-hydroxydopamine lesions in the posterolateral hypothalamus of the rat.

It has previously been reported that intracerebroventricular administration of neurotensin (30 micrograms) reduced muscular rigidity and tremors, induced by a neurochemical lesion with 6-hydroxydopamine in the posterolateral hypothalamus of rats. In the present study, the effects of two fragments (NT1-10 and NT8-13) and two analogues ([D-Tyr11]-NT and [Ala11]-NT) of neurotensin on the grasping time (index of muscle rigidity) and tremors in 6-hydroxydopamine-lesioned rats are reported. Intracerebroventricular administration with 120 micrograms of NT1-10 and [Ala11]-NT had no effect on the muscle rigidity and tremors induced by the neurochemical lesion. The administration of NT8-13 60 micrograms) significantly attenuated both behavioural responses. The analogue [D-Tyr11]-NT produced a much greater attenuation of the muscle rigidity and tremors. The dose of 1.8 micrograms of [D-Tyr11]-NT significantly reduced the grasping time, while the number of tremors was attenuated with the threshold dose of 0.9 micrograms. Together, these results suggest that the effects of neurotensin on muscle rigidity and tremors, induced by pretreatment with 6-hydroxydopamine injected into the posterolateral hypothalamus, were not caused by non-specific effects but largely depended on the carboxy terminal of the peptide. The tyrosine residue in position 11 of the molecule plays a critical role in the action of neurotensin, as shown with the high potency and duration of action of the analogue [D-Tyr11]-NT. As previously suggested, the greater effect with [D-Tyr11]-NT may be due to greater resistance of the analogue to enzymatic degradation because of the incorporation of the D-Tyr amino acid, in position 11 of neurotensin.

Posterior hypothalamic receptors involved in the cardiovascular changes elicited by electrical stimulation of the rostral ventrolateral medulla.

The posterior hypothalamic receptors involved in the cardiovascular responses to electrical stimulation of the rostral ventrolateral medulla were investigated in urethane-anaesthetized rats. Electrical stimulation of the rostral ventrolateral medulla produced a significant increase in systolic blood pressure. This response was significantly attenuated by the prior administration of d,l-propranolol (20 micrograms), clonidine (8 micrograms), atropine (8 micrograms) or methysergide (10 micrograms) into the posterior hypothalamus, but not by cimetidine (11 micrograms), chlorpheniramine (12 micrograms), naloxone (10 micrograms) or a vasopressin V1 antagonist (100 ng). The effect of clonidine (8 micrograms) on the pressor response to stimulation of the rostral ventrolateral medulla was antagonized by idazoxan (66 micrograms). These results confirm that the cardiovascular changes elicited by stimulation of the rostral ventrolateral medulla area are, in part, centrally modulated by alpha 2 and beta-adrenoceptors in the posterior hypothalamus which exert respectively, inhibitory and stimulatory effect. Furthermore the results indicate the involvement of posterior hypothalamic cholinergic and serotonergic receptors in the pressor response produced by stimulation of the rostral ventrolateral medulla.

Muscarinic antagonists attenuate neurotensin-stimulated accumbens and striatal dopamine metabolism.

The effect of scopolamine and atropine upon the increase in extracellular 3,4-dihydroxyphenylacetic acid induced by central injection of neurotensin was examined in the nucleus accumbens and the striatum of anaesthetized rats using in vivo differential pulse voltammetry with carbon fibre electrodes. Scopolamine (1 and 3 mg/kg, i.p.) and atropine (20 micrograms, i.c.v.) did not alter the 3,4-dihydroxyphenylacetic acid level in the nucleus accumbens or the striatum, measured for 60 min after administration. Neurotensin (10 micrograms, i.c.v.) increased the 3,4-dihydroxyphenylacetic acid peak height in both regions. Pretreatment with scopolamine (1 mg/kg) 15 min before neurotensin injection blocked the increase in extracellular 3,4-dihydroxyphenylacetic acid in the striatum but not in the nucleus accumbens whilst scopolamine (3 mg/kg) partially attenuated the effect of neurotensin in the nucleus accumbens and blocked the increase in 3,4-dihydroxyphenylacetic acid in the striatum. Atropine partially attenuated the effect produced by neurotensin in the nucleus accumbens and blocked the increase in 3,4-dihydroxyphenylacetic acid induced by the peptide in the striatum. However, the increase in extracellular 3,4-dihydroxyphenylacetic acid induced by haloperidol (1 mg/kg, s.c.) was not altered by scopolamine (1 mg/kg) or atropine. Also, the increase in dopamine metabolism in the nucleus accumbens and the striatum after centrally injected haloperidol (10 micrograms, i.c.v.) was not altered by atropine (20 micrograms, i.c.v.). Together, the results demonstrate a functional interaction between muscarinic antagonists and neurotensin on in vivo dopamine metabolism in the nucleus accumbens and the striatum but with a greater effect in the latter region.

Muscarinic antagonists attenuate the increase in accumbens and striatum dopamine metabolism produced by clozapine but not by haloperidol.

1. The effect of the muscarinic antagonists, scopolamine and atropine, were examined on the increase in extracellular 3,4-dihydroxyphenylacetic acid (DOPAC) in the nucleus accumbens and the striatum induced by haloperidol and clozapine by use of in vivo differential pulse voltammetry with carbon fibre electrodes in anaesthetized rats. 2. Animals received saline (1 ml kg-1, s.c.), scopolamine (1 mg kg-1, o.p.) or atropine (20 micrograms, i.c.v.) followed 15 min later by saline (10 microliters, i.c.v.), haloperidol (1 mg kg-1, s.c.) or clozapine (30 mg kg-1, i.p.) and extracellular DOPAC was simultaneously recorded in the nucleus accumbens and the striatum every 5 min for 60 min after drug administration. 3. Scopolamine or atropine alone had no effect on the DOPAC peak height but attenuated the increase in extracellular DOPAC induced by clozapine in both brain regions. Neither scopolamine nor atropine altered the haloperidol-induced increase in accumbens or striatal extracellular DOPAC. 4. The present results demonstrate that muscarinic antagonists attenuate the increase in accumbens and striatal dopamine metabolism in vivo produced by the atypical neuroleptic clozapine but not the haloperidol-induced increase in dopamine metabolism. The results indicate that central muscarinic receptors are involved in the actions on dopaminergic function of clozapine but not haloperidol.

Differential activation of the pituitary-adrenocortical axis after stress in the rat: use of two genetically selected lines (Roman low- and high-avoidance rats) as a model.

We have examined the activation of the pituitary-adrenal axis in two lines of rats, the Roman high (RHA)- and low (RLA)-avoidance rats known to be emotionally different. These rats are selected for rapid acquisition of a conditioned avoidance response (RHA) compared with failure to acquire this response (RLA). In this study the endocrine response (ACTH, corticosterone, aldosterone) of RLA and RHA rats to two types of stress was examined: exposure to open-field stress for 10 min (Op) or exposure to ether vapours for 3 min (E). Basal plasma ACTH concentrations were lower in RLA than in RHA rats (RLA: 110.8 +/- 24.5 ng/l; RHA: 252.7 +/- 60.8 ng/l, P less than 0.05) but the absolute values of ACTH reached after both types of stress were comparable between RLA and RHA rats. Plasma corticosterone and aldosterone under resting conditions were not different between RLA and RHA rats. Plasma corticosterone was higher in RLA following openfield stress (P less than 0.05) while no differences between RLA and RHA were observed after ether stress (RHA: basal = 66 +/- 14.nmol/l, Op = 384 +/- 55, E = 606 +/- 75; RLA: basal = 121 +/- 52, Op = 612 +/- 92, E = 698 +/- 89). Stress-induced increases in plasma aldosterone were higher in the RLA line after both types of stress (RHA: basal = 175 +/- 36 pmol/l, Op = 546 +/- 53, E = 563 +/- 47; RLA: basal = 272 +/- 64, Op = 1246 +/- 91, E = 863 +/- 72).

Inhibition of initiation of translation in L1210 cells by 8-azaguanine.

The inhibition of protein synthesis by 8-azaguanine (azaG) in L1210 cells in culture was investigated. AzaG selectively inhibited protein synthesis at concentrations where viability was decreased significantly. AzaG altered the polyribosome sedimentation profile, increasing the numbers of monosomes and smaller polysomes and decreasing the number of larger polysomes. The reversal by cycloheximide of the alterations in the polysome profile suggested that azaG inhibited the initiation of translation. This was confirmed by the demonstration of inhibition of the formation of the 43S and 80S initiation complexes.

Ovariectomy and estradiol treatment affect the dopamine transporter and its gene expression in the rat brain.

The impact of gonadal hormone withdrawal and estrogen therapy was investigated on the rat dopamine transporter (DAT). Short-term ovariectomized (ST-OVX, 2 weeks) and long-term ovariectomized (LT-OVX, 3 months) rats were treated or not with 17beta-estradiol (E2) for 2 weeks. DAT mRNA expression was measured by in situ hybridization in the substantia nigra pars compacta (SNc) for the nigrostriatal pathway and the ventral tegmental area (VTA) for the mesolimbic pathway whereas DAT levels were assessed by [3H]GBR-12935 autoradiography, respectively, in the striatum and the nucleus accumbens. Ovariectomy produced a time-dependent decrease of the DAT density in the striatum and the nucleus accumbens and the E2 treatment did not significantly restore these DAT levels. Neither ST-OVX nor E2 treatment of the ST-OVX animals altered the DAT mRNA expression in the SNc and the VTA. However, LT-OVX animals showed increased DAT mRNA levels in these regions. E2 treatment of LT-OVX animals partially restored DAT mRNA levels in the SNc and left these levels unchanged in the VTA. These opposite variations induced by OVX on the DAT density and their mRNA levels suggest the involvement of non-genomic mechanisms, such as post-transcriptional events and/or membrane effects. Altered neurotransmission following gonadal hormone withdrawal may contribute to CNS disorders occurring at menopause in predisposed women. Ovariectomized rats constitute a useful model to study the changes in neurotransmitters balance occurring after menopause.