Thyroid surgery for tumours: the Semon Lecture, presented at the RSM November 1996

1,1,1-Trichloroethane (TRI) is a commonly used industrial solvent with a considerable potential for inhalation abuse. Previous studies in our laboratory and elsewhere have shown that this agent exerts a suppressant effect on operant responding, as well as a number of additional neurobehavioral effects that are similar to those of central nervous system (CNS) depressant drugs. In an effort to provide information relevant to potential mechanisms involved in the behavioral effects and abuse potential of TRI, the present study evaluated the acute effects of this agent on the activity of the hypothalamo-pituitary-adrenal (HPA) axis . Male Sprague-Dawley rats were exposed to 3500 or 5000 ppm TRI by inhalation for 10 or 30 min. Following exposure, plasma levels of adrenocorticotropic hormone (ACTH) and corticosterone and levels of ACTH and corticotropin-releasing factor (CRF) in three brain regions--hypothalamus, hippocampus, and frontal cortex--were determined by selective radioimmunoassays. Levels of TRI in the three brain regions as well as blood were measured by headspace gas chromatography to determine the target tissue concentrations responsible for neuroendocrine changes. Uptake of TRI in blood and all brain regions was very rapid, with stable concentrations apparently achieved within 10 min and maintained for 30 min. During this time course, a significant decrease in plasma corticosterone was produced at 30 min but no significant change in plasma ACTH was observed with 3500 ppm TRI. However, after exposure to 5000 ppm, both plasma ACTH and plasma corticosterone were significantly reduced at 10 and 30 min. ACTH levels in the three brain regions were not significantly changed by TRI, while hypothalamic CRF was significantly increased during exposure to 3500 ppm. However, hypothalamic concentrations of CRF declined following 30 min at 3500 ppm and were not significantly changed by 5000 ppm. This complexity of effects on the regulation of HPA axis activity likely precluded the establishment of consistent relationships between changes in hormonal levels and blood or regional brain concentrations of the inhalant. However, these actions of TRI were strikingly similar to those previously reported for the benzodiazepines.     

Gonadal steroids have paradoxical effects on brain oxytocin receptors

Specific brain receptors for oxytocin have been described in several mammalian species. The distribution of these receptors differs greatly across species and in the rat, receptor binding in specific brain regions appears to depend upon gonadal steroids. This study used in vitro receptor autoradiography to examine the effects of testosterone on oxytocin receptor binding in the mouse forebrain. Three groups of male mice were compared: castrates treated with blank capsules, castrates treated with testosterone filled capsules, and intact males. Irrespective of steroid treatment, the distribution of oxytocin receptors in mouse forebrain differed markedly from patterns previously described in the rat. In addition to these species differences in receptor distribution, testosterone had effects in the mouse which differed from the induction of receptors previously reported in the rat. In the mouse ventromedial nucleus of the hypothalamus, binding in the untreated castrate males was approximately double that observed in either the intact or the testosterone-treated castrates. In other regions of the mouse brain, such as the intermediate zone of the lateral septum, binding to oxytocin receptors was increased with testosterone treatment. These results suggest that the brain oxytocin receptor varies across species not only in its distribution but also in its regional regulation by gonadal steroids. These apparently paradoxical changes in oxytocin receptor binding may result from either direct or indirect effects of gonadal steroids in mouse brain.     

Regional distribution and production rate of 3-methoxy-4-hydroxyphenylethyleneglycol sulphate (MHPG-SO4) in rat brain

The levels of noradrenaline (NA) and 3-methoxy-4-hydroxyphenylethyleneglycol sulphate (MHPG-SO4) in 15 brain regions showed a parallel distribution in male Wistar rats. The differences in regional distribution of MHPG-SO4 were similar to those in the rate of NA turnover reported by other investigators. The accumulation rates of MHPG-SO4 during 45 and 90 min after probenecid injection significantly correlated to the steady state levels of MHPG-SO4 in nine regions studied. With the results, the regional levels of MHPG-SO4 either in untreated or in probenecid-treated rats, are considered to be a useful index of NA turnover.     

Repeated trimipramine induces dopamine D2/D3 and alpha1-adrenergic up-regulation

Trimipramine (TRI), which shows a clinical antidepressant activity, is chemically related to imipramine but does not inhibit the reuptake of noradrenaline and 5-hydroxytryptamine, nor does it induce beta-adrenergic down-regulation. The mechanism of its antidepressant activity is still unknown. The aim of the present study was to find out whether TRI given repeatedly was able to induce adaptive changes in the dopaminergic and alpha1-adrenergic systems, demonstrated by us previously for various antidepressants. TRI was given to male Wistar rats and male Albino Swiss mice perorally twice daily for 14 days. In the acute experiment TRI (given i.p.) does not antagonize the reserpine hypothermia in mice and does not potentiate the 5-hydroxytryptophan head twitches in rats. TRI given repeatedly to rats increases the locomotor hyperactivity induced by d-amphetamine, quinpirole and (+)-7-hydroxy-dipropyloaminotetralin (dopamine D2 and D3 effects). The stereotypies induced by d-amphetamine or apomorphine are not potentiated by TRI. It increases the behaviour stimulation evoked by phenylephrine (given intraventricularly) in rats, evaluated in the open field test as well as the aggressiveness evoked by clonidine in mice, both these effects being mediated by an alpha1-adrenergic receptor. It may be concluded that, like other tricyclic antidepressants studied previously, TRI given repeatedly increases the responsiveness of brain dopamine D2 and D3 (locomotor activity but not stereotypy) as well as alpha1-adrenergic receptors to their agonists. A question arises whether the reuptake inhibition is of any importance to the adaptive changes induced by repeated antidepressants, suggested to be responsible for the antidepressant activity.     

Allogeneic stem cell transplantation for multiple myeloma

Ethanol is added to unleaded gasoline as an oxygenate to decrease carbon monoxide automobile emissions. This introduces inhalation as a new possible route of environmental exposure to humans. Knowledge of the pharmacokinetics of inhaled ethanol is critical for adequately assessing the dosimetry of this chemical in humans. The purpose of this study was to characterize the pharmacokinetics of inhaled ethanol in male and female B6C3F1 mice and F344 rats and to develop a physiologically based pharmacokinetic (PBPK) model for inhaled ethanol in mice, rats, and humans. During exposure to 600 ppm for 6 hr, steady-state blood ethanol concentrations (BEC) were reached within 30 min in rats and within 5 min in mice. Maximum BEC ranged from 71 microM in rats to 105 microM in mice. Exposure to 200 ppm ethanol for 30 min resulted in peak BEC of approximately 25 microM in mice and approximately 15 microM in rats. Peak BEC of about 10 microM were measured following exposure to 50 ppm in female rats and male and female mice, while blood ethanol was undetectable in male rats. No sex-dependent differences in peak BEC at any exposure level were observed. Species-dependent differences were found following exposure to 200 and 600 ppm. A blood flow limited PBPK model for ethanol inhalation was developed in mice, rats, and humans which accounted for a fractional absorption of ethanol. Compartments for the model included the pulmonary blood and air, brain, liver, fat, and rapidly perfused and slowly perfused tissues. The PBPK model accurately simulated BEC in rats and mice at all exposure levels, as well as BEC reported in human males in previously published studies. Simulated peak BEC in human males following exposure to 50 and 600 ppm ranged from 7 to 23 microM and 86 and 293 microM, respectively. These results illustrate that inhalation of ethanol at or above the concentrations expected to occur upon refueling results in minimal BEC and are unlikely to result in toxicity.     

Hydrodynamic properties of nitrogenase--the MoFe protein from Azotobacter vinelandii studied by dynamic light scattering and hydrodynamic modelling

Trichloroethylene (TRI) is an industrial solvent with a history of use in anesthesia, and is a common groundwater contaminant. Cytochrome P450 (CYP)-dependent metabolism of TRI produces chloral hydrate (CH) and is rate limiting in the ultimate production of trichloro- and/or dichloroacetic acid from TRI. Exposure of rodents to TRI results in lung and liver tumors (mice) and nephrotoxicity (rats). The toxicity is exacerbated by pretreatment of mice with CYP inducers. We report significant variability in TRI metabolism in a sample of 23 human hepatic microsomal samples and demonstrate the dependence of TRI metabolism on CYP2E1. K(m) values in this limited sample population are not normally distributed. We have correlated microsomal CH formation with the activity toward routine CYP2E1 substrates and with immunologically detectable CYP2E1 protein. Further, TRI metabolism in microsomes from lymphoblastoid cell lines expressing CYP2E1, CYP1A1, CYP1A2, or CYP3A4 indicated minimal involvement of the latter forms, with CYP2E1 catalyzing more than 60% of total microsomal TRI metabolism. These results indicate that humans are not uniform in their capacity for CYP-dependent metabolism of TRI and increased CYP2E1 activity may increase susceptibility to TRI-induced toxicity in the human.     

NMDA-NR1 receptor subunit mRNA expression in rat brain after 6-OH-dopamine induced lesions: a non-isotopic in situ hybridization study

Antisense digoxigenin-labeled deoxyoligonucleotides probes and non-isotopic in situ hybridization (HIS) techniques have been used to explore the NMDA-NR1 receptor subunit mRNA distribution in different brain areas of rats which had their dopaminergic nigrostriatal pathway previously lesioned with intracerebral administration of 6-OH-dopamine (6-OH-DA). Intense and significant hybridization signals for NR1 mRNA were found in dentate gyrus and regions CA1-CA2-CA3 of the hippocampus, in layers II-III and V-VI of the cerebral cortex, and in the cerebellum of sham-treated rats. Basal ganglia structures such as the striatum exhibited few NR1 mRNA hybridization signals as compared to the hippocampus and cerebral cortex. In contrast, both zona compacta and reticulata of substantia nigra (SN) showed a reduced number of cells with nevertheless intense NR1 mRNA HIS signals. The NR1 mRNA distribution in the brain was affected in a brain regional selective manner by 6-OH-DA induced lesions of DA neuronal systems. A striking increase in NR1 mRNA HIS signals was observed in both striata after unilateral lesioning with 6-OH-DA. Instead, in SN compacta but not in reticulata, a moderate but significant bilateral reduction of NR1 mRNA was observed after unilateral 6-OH-DA injection. No significant changes in NR1 mRNA were detected in cerebral cortex and other brain regions after 6-OH-DA treatment. These studies, and others reported in the literature, support the view that extensive lesions of nigrostriatal DA-containing neurons in the brain may trigger compensatory or adaptative responses in basal ganglia structures such as striatum and substantia nigra which involve glutamateric neurons and the genic expression of NMDA receptors.     

BBB transport and P-glycoprotein functionality using MDR1A (-/-) and wild-type mice. Total brain versus microdialysis concentration profiles of rhodamine-123

PURPOSE: The effect of P-glycoprotein (Pgp) on brain distribution using mdr1a (-/-) mice was investigated. METHODS: Fluorescein (Flu) and FD-4 were used to check whether blood-brain barrier (BBB) integrity was maintained in mdr1a (-/-) mice. The Pgp substrate rhodamine-123 (R123) was infused and total brain, blood and brain microdialysate concentrations in mdr1a (-/-) mice and wild-type mice were compared. RESULTS: Maintenance of BBB integrity was indicated by equal total brain/blood ratios of Flu and FD-4 in both mice types. R123 concentrations in brain after i.v. infusion were about 4-fold higher in mdr1a (-/-) than in wild-type mice (P < 0.05), without changes in blood levels. After microdialysis experiments the same results were found, excluding artifacts in the interpretation of Pgp functionality by the use of this technique. However the 4-fold ratio in brain was not reflected in corresponding microdialysates. No local differences of R123 in the brain were found. By the no-net-flux method in vivo recovery appeared to 4.6-fold lower in mdrla (-/-) mice compared with wild-type mice. CONCLUSIONS: Pgp plays an important role in R123 distribution into the brain. Using intracerebral microdialysis, changes in in vivo recovery by the absence or inhibition of Pgp (or active efflux in general) need to be considered carefully.     

Extracellular signal-regulated protein kinases (ERKs) and ERK kinase (MEK) in brain: regional distribution and regulation by chronic morphine

Quantitative blot immunolabeling techniques were used to determine the concentrations of ERK1 (M(r) 44 kDa) and ERK2 (M(r) 42 kDa), the two major extracellular signal-regulated protein kinases, in different regions of rat brain. The aggregate ERK concentrations (ERK1 and ERK2) were relatively high in each of the brain regions studied, ranging from approximately 0.35 ng/microgram protein in cerebellum to approximately 1.2 ng/microgram protein in nucleus accumbens. However, differences in the regional distributions of ERK1 and ERK2 resulted in ratios of their relative abundance that differed by close to 10-fold among the regions studied. The ratios of ERK1 protein to ERK2 protein varied along a rostral-caudal gradient from a low of 0.16 in frontal cortex to a high of 1.5 in pons/medulla. In hypotonic homogenates from regions at either extreme of the gradient, ERK1 and ERK2 were both found to be predominantly (> 80%) soluble. In subcellular fractions prepared from sucrose homogenates of frontal cortex and pons/medulla, both ERK1 and ERK2 were enriched in the synaptosomal and cytosolic fractions, whereas ERK2 was also enriched in the microsomal fraction. By contrast, in subfractions containing purified nuclei, levels of ERK1 and ERK2 were about one-third of those seen in homogenates and, in subfractions enriched in mitochondria, both ERK1 and ERK2 were barely detectable. The catalytic activity of the ERKs paralleled their protein levels in all of the brain regions except the hippocampus, in which the activity and phosphotyrosine content were disproportionately high. As a possible explanation for this apparent disparity, the regional distribution of ERK kinase (MEK), which phosphorylates and activates the ERKs, was also investigated. The levels of immunoreactivity of the M(r) 45 kDa ERK kinase band differed by about threefold among the brain regions, with the highest levels being present in nucleus accumbens, hippocampus, substantia nigra, and caudate/putamen. Therefore, a higher concentration of ERK kinase immunoreactivity did not appear to account for the disproportionate levels of ERK activity and phosphotyrosine content in the hippocampus. Potential regulation of ERK and ERK kinase levels was also investigated in rats subjected to chronic morphine treatment. ERK1 and ERK2 levels were increased selectively in locus coeruleus and caudate/putamen after chronic morphine treatment, whereas ERK kinase immunoreactivity remained unchanged in all of the brain regions analyzed. In summary, the regional differences in ERK and ERK kinase expression and the region-specific regulation of ERK expression suggest that ERK-related signaling may play an important role in CNS function and its adaptive responses.     

Genetic and ontogenetic variability in the noradrenergic regulation of adrenocortical function

Corticosterone levels in the blood under restriction positively correlated with the hormone response to i.c.v. norepinephrine injection in 7 genetic groups of rats. Reactions to stress and norepinephrine simultaneously decreased in adult rats after prenatal glucocorticoid treatment. Prenatal stress or corticosterone treatment have a lasting effect on typosine hydroxylase (TH) activity and adrenoligands binding in the mice brain. Prenatal treatment increased TH activity in the noradrenergic system of the brain and decreased binding of radiolabelled prazosin, clonidine and dihydroalprenolol in some brain regions as well as stress reaction in mice. Thus, individual variations in adrenocortical stress response may be related to the differences in the function of the brain noradrenergic system.     

Effects of testosterone upon MPTP-induced neurotoxicity of the nigrostriatal dopaminergic system of C57/B1 mice

We have recently reported that treatment of gonadectomized female and male C57/B1 mice with the gonadal steroid hormone, estrogen, reduced nigrostriatal dopaminergic neurotoxicity resulting from the Parkinson's-like inducing agent 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). In the present report we examined whether the predominantly male gonadal steroid hormone, testosterone, would similarly modulate MPTP-induced neurotoxicity. Male C57/B1 mice were assigned to one of the following five treatment conditions: (1) Intact, (2) Orchidectomized, (3) Intact + MPTP, (4) Orchidectomized + Testosterone + MPTP and (5) Orchidectomized + MPTP. Corpus striatal and olfactory tubercle dopamine. DOPAC and norepinephrine concentrations were determined from the animals within each of the five treatment conditions. Orchidectomy alone failed to alter striatal dopamine and DOPAC concentrations, with levels obtained being similar to that of Intact animals. MPTP treatment significantly reduced striatal reduced striatal dopamine and DOPAC concentrations, regardless of hormonal condition of the animal. Similar results were obtained for olfactory tubercle determinations, with the exception that DOPAC levels from Orchidectomized mice were significantly greater than Intact males. No significant differences were obtained for norepinephrine within either brain area sampled. These results show that unlike estrogen, testosterone is devoid of any capacity to modulate nigrostriatal dopaminergic neurotoxicity resulting from MPTP. These findings may be related to the gender differences which exist in the prevalence of Parkinson's disease.     

Fat: can''t live with it, can''t live without it. Part I

Manganese (Mn) complexes are unstable and dissociate in vivo. Because of the release of this metal, there exists some concern about the potential long-term neurotoxicity associated with the use of Mn-based contrast agents. This latter problem arises because manganese is known to accumulate in specific regions of the brain of people intoxicated by this metal. It was previously demonstrated that Mn can accumulate in the mice brain after administration of 5 micromol/kg of MnCl2, Mn-diethylenetriaminepentaacetate (Mn-DTPA), or Mn-dipyridoxal diphosphate (Mn-DPDP). In order to better characterize the behavior of Mn complexes after administration, this study assesses the regional distribution of Mn in the brain after i.v. injection of a single dose of MnCl2 or Mn-DTPA. Male Wistar rats received an i.v. injection of 5 micromol/kg of 54Mn as MnCl2 or Mn-DTPA. The rats were killed at one and two weeks post exposure. The distribution of the radioactivity in the slices was monitored by autoradiography. For both MnCl2 or Mn-DTPA, we observed that the radioactivity was dispersed in the entire brain, but the radioactivity was higher in several regions. No difference was observed between MnCl2 or Mn-DTPA in the regional distribution of Mn, and no difference was observed between the two times of exposure (1 week or 2 weeks). The uptake of Mn was minimal in corpus callosum. Maximal Mn concentration was observed in the hippocampal region, thalamus, colliculi, amygdala, olfactory nuclei, and cerebellum.     

Using asymmetric jaws to junction with previously treated areas

This study was conducted to determine and compare the activities of glutathione-S-transferase (GST) in red blood cells of cattle, horses, pigs, goats, dogs, rabbits, rats and mice. The highest GST activity was found in mouse red blood cells followed by that of rats, dogs, cattle, pigs, goats and horses with the lowest activity in rabbits. There were significant differences between the GST activities from these various species. The species differences in GST activities correlate with the reported variable responses of the different species to different toxicants since erythrocyte GST plays a significant role in the detoxification of circulating xenobiotics.     

Sex and species differences in mouse and rat forebrain commissures depend on the method of adjusting for brain size

Sex differences in the forebrain commissures (corpus callosum, hippocampal commissure, and anterior commissure) were examined in B6D2F2 hybrid mice and Sprague-Dawley rats. Twenty-four male-female littermate pairs of mice were perfused at each of 21, 42 and 63 days of age and the midsagittal area of the commissures was measured from en bloc stained tissue. Twenty-two male-female littermate pairs of rats were examined at 110 days of age using the same methods. Male mice had larger bodies than females but no sex differences were found for mouse brain weight or commissure areas. In contrast, a significant sex difference was found for rat body, brain, corpus callosum and hippocampal commissure sizes. Four methods were used to adjust for differences in brain size (ratio, geometric, linear regression, and allometric). When the two species were analysed separately, neither mice nor rats showed significant sex differences in commissure areas relative to brain size if regression or allometric adjustments were made. Even when data from mice and rats were combined into one large group with a wide range of values, no species or sex differences were apparent after adjustments were made for brain size with either the regression or allometric methods. The use of ratios to adjust for differences in overall size is not recommended, especially because this method does not effectively remove the influence of brain size from commissure size; a substantial correlation is often present between the ratio and brain size.     

Altered regional blood volume in chronic cannabis smokers.

The quantitative measurement of cerebral perfusion is crucial for the study of both normal and impaired human brain function. Although cannabis is the most commonly abused illicit substance in the United States, its effects on cerebral blood volume (CBV) have not been fully examined. The objective of the present study was to examine differences in relative regional blood volume in focal regions of interest--including the frontal lobe, the temporal lobe, and the cerebellum--during a period of supervised abstinence from cannabis. Dynamic susceptibility contrast MRI data were collected on 12 current, long-term daily cannabis users between 6 and 36 hr after the subjects' last reported cannabis use. Resting-state CBV images were also acquired in 17 healthy comparison subjects. Data were acquired in the axial plane with a 1.5-Tesla GE Signa scanner following a bolus of gadolinium contrast agent. Cannabis users demonstrated significantly increased blood volumes in the right frontal area ( p     

Lithium protection against oxygen toxicity in rats: ammonia and amino acid metabolism

1. The use of Li pre-treatment in rats before high pressure oxygen exposure has been reported effective in controlling convulsions. This is an effect which is better demonstrated if exposure to oxygen follows shortly after Li injection than exposure following several hours later. 2. This study has investigated the hypothesis that the protective action of Li may be exerted, in the short term, by its removing ammonia from the blood and alleviating the latter's known toxic action. 3. A normal Li distribution time profile in unstressed rat brain and blood following intraperitoneal injection has been established. Brain and blood ammonia, amino acids and Li concentrations were also measured in Li-treated animals exposed and convulsed by oxygen. These measurements were made both shortly (15 min) and also several hours after (24 hr) Li treatment. Ammonia and amino acid values in Li-protected groups were compared to normal unstressed animal values and also to values in animals convulsed by oxygen unprotected by Li pre-treatment. 4. In rat brain abd blood significant (P less than 0-001) elevation of ammonia and glutamine and depression of gamma-amino butyric acid (brain only) and glutamate was noted following oxygen treatment in unprotected animals. Prior injection of Li 15 min before high pressure oxygen exposure delayed convulsions twice as long. Additionally if these animals were only exposed to oxygen for a period of time equal to that which would normally produce convulsions in unprotected animals, brain and blood ammonia and amino acids were maintained near to unstressed animal levels. Concomitantly, blood Li concentrations were considerably depressed below the values one would expect from the previously determined Li distribution time profile. 5. In rats exposed to high pressure oxygen 24 hr after Li treatment there was no protective action against high pressure oxygen convulsion, rather a potentiating effect for convulsion was seen. 6. These data present compelling evidence for the controlling effect of Li in rats, on rising blood ammonia concentration which occurs in high pressure oxygen exposure. The effect might well be due to the known chelating properties of Li with ammonia.     

Characterization of native corticotropin-releasing factor receptor type 1 (CRFR1) in the rat and mouse central nervous system

Corticotropin releasing factor (CRF), the most important regulator of various responses to stress, acts through CRF receptors (CRFR). For their characterization in brain tissue of Sprague-Dawley rats and C57BL/6J mice, a recently described polyclonal antibody directed against the N-terminus of rat CRFR1 (rCRFR1) was used. The molecular weights of rat and mouse brain receptors were determined by Western blot analysis to be 80,000-76,000 and 83,000-79,000, respectively, whereas molecular weights of 72,000-59,000 were observed for CRFR1 from rat and mouse pituitary. Immunohistochemical analysis was performed with brain sections of naive rats and mice. Strong CRFR1 staining was detected in the cortex, cerebellum, mesencephalon and pons of both species, whereas weak staining was observed in amygdala and hippocampus. The striatum did not show immunoreactivity. The density of immunostaining was significantly lower in murine than in rat cortex. In contrast, in the pons and mesencephalon of mice, higher density of immunostaining was observed than in the same brain structures of rats. On the basis of the observed differences, it is suggested that CRFR1 is differentially processed in rats and mice. In addition, the density of CRFR1 staining differed between both species.     

Heterogeneous photobleaching in confocal microscopy caused by differences in refractive index and excitation mode

Changes in brain 5-HT turnover which have been associated with portal-systemic encephalopathy (PSE) in man were studied in rats with experimental PSE for intervals up to 15 weeks following the surgical construction of end-to-side portacaval shunts (PCS). These were compared to changes measured in portacaval transposed rats (PCT) which, show little hepatic dysfunction or cerebral abnormalities but, in common with the PCS rat, sustain total portal-systemic diversion. Thus any differences between these two groups were indicative of hepatic dysfunction and not the systemic diversion of portal blood. After 15 weeks, sustained increases were measured in brainstem and cerebral concentrations of the catabolite of 5-hydroxytryptamine (5-HT), 5-hydroxyindole acetic acid (5-HIAA), from 0.25+/-0.01 to 0.68+/-0.01*** microg g(-1) brain and from 0.18+/-0.01 to 0.31+/-0.03*** microg g(-1) brain respectively in PCS rats and were statistically greater to those measured in the brainstem and cerebrum of PCT and control rats. Sustained increases in cerebral concentrations alone of 5-hydroxytryptophan (5-HTP), the precursor of 5-HT, from 0.17+/-0.01 to 0.23+/-0.02 microg g(-1) brain were measured in PCS rats and were significantly*** greater than in PCT control rats after 15 weeks. Some early increases in 5-HTP were measured in PCS above control rats but these were not significant after 15 weeks. No sustained significant differences between the 3 groups were measured in 5-HT after 15 weeks. These data confirm previous evidence that the elevations in 5-HTP and 5-HIAA concentrations observed in experimental chronic liver failure and PSE are due to liver dysfunction and not portal-systemic diversion and may contribute additional information regarding the role of derangements in central 5-HT turnover as one of the causes of PSE. ***p<0.001, Newman-Keuls ANOVAR followed by Student's unpaired t-test for individual comparisons, (data shown are mean +/- SEM).     

Quantitative autoradiographic mapping of mu-, delta- and kappa-opioid receptors in knockout mice lacking the mu-opioid receptor gene

Mice lacking the mu-opioid receptor (MOR) gene have been successfully developed by homologous recombination and these animals show complete loss of analgesic responses to morphine as well as loss of place-preference activity and physical dependence on this opioid. We report here quantitative autoradiographic mapping of opioid receptor subtypes in the brains of wild-type, heterozygous and homozygous mutant mice to demonstrate the deletion of the MOR gene, to investigate the possible existence of any mu-receptor subtypes derived from a different gene and to determine any modification in the expression of other opioid receptors. Mu-, delta-, kappa1- and total kappa-receptors, in adjacent coronal sections in fore- and midbrain and in sagittal sections, were labelled with [3H]DAMGO (D-Ala2-MePhe4-Gly-ol5 enkephalin), [3H]DELTI (D-Ala2 deltorphinI), [3H]CI-977 and [3H]bremazocine (in the presence of DAMGO and DPDPE) respectively. In heterozygous mice, deficient in one copy of the MOR gene, mu-receptors were detectable throughout the brain at about 50% compared to wild-type. In brains from mu-knockout mice there were no detectable mu-receptors in any brain regions and no evidence for mu-receptors derived from another gene. Delta-, kappa1- and total kappa-receptor binding was present in all brain regions in mutant mice where binding was detected in wild-type animals. There were no major quantitative differences in kappa- or delta-binding in mutant mice although there were some small regional decreases. The results indicate only subtle changes in delta- and kappa-receptors throughout the brains of animals deficient in mu-receptors.