RNA interference and functional characterization of a tergal gland alpha amylase in the German cockroach, Blattella germanica L.

German cockroach males possess tergal glands that secrete a combination of oligosaccharides, lipids and proteins. Four major proteins occur in the secretion, with one being the 63 kDa alpha-amylase Blattella germanica Tergal Gland protein-1 (BGTG-1). Denaturing and starch gel electrophoresis coupled with peptide sequencing verified amylase activity for the BGTG-1 protein. BGTG-1 gene expression profiles were determined by using quantitative real-time PCR to compare messenger RNA abundance among isolated tissues of males, females and gravid females. Differences in BGTG-1 gene expression occurred among male tissues, with tergal gland tissue showing the highest expression. Tissues of nongravid and gravid females had significantly lower expression in comparison with male tergal glands (gravid females lowest). RNA interference (RNAi) was used to silence BGTG-1 gene expression by injecting BGTG-1 homologous double-stranded RNA (dsRNA) into male cockroaches. Groups injected with BGTG-1 dsRNA showed ∼90% lower BGTG-1 gene and protein expression compared to controls, which correlated with lower amylase activity in colorimetric assays. However, behavioural assays comparing precopulatory behaviour and mating success between RNAi and control males did not reveal differences. These results connect amylase gene expression and activity in tergal gland tissue but suggest other factors, such as other tergal gland components, may contribute more strongly to mating success.

Visualization and Transport of Positron Emission from Proton Activation in vivo.

Heavy charged particle beams can be widely used for cancer therapy if control in heterogeneous tissue is proved practical. A beam of protons at 200 million electron volts has been visualized in plastic and in a living animal by using an on-line positron camera. The fraction of the activity retained in the radiation site was found to be at least 70 percent of that produced in a dead animal. The sensitivity of the technique was established for a typical geometry.

Effects of chronic infusion of neurotensin and a neurotensin NT1 selective analogue PD149163 on amphetamine-induced hyperlocomotion.

Neurotensin (NT) has been proposed as an endogenous antipsychotic based in part on the similarity in behavioural effects to antipsychotic drugs, for example, attenuation of both amphetamine-induced hyperlocomotion (AH) and amphetamine disrupted pre-pulse inhibition in the rat. However, there is some evidence that repeated administration of NT or an analogue produces behavioural tolerance to such effects. The present experiments sought to confirm and extend these findings by testing the effects on AH of 7 days central administration of NT and the NT1 selective analogue PD 149163 and the effects of 21 days central administration of NT. NT and PD149163 continuously administered for 7 days produced no effect on AH (in contrast to attenuation with a single injection here and previously reported), whereas 21 days of NT administration potentiated AH. Together, these studies report that the effects of NT or a NT analogue on AH depends on the duration of administration of peptide. The results are discussed in comparison with the reported antipsychotic properties of acute administration of NT and possible mechanisms involving NT1 receptors.

Thyrotrophin-releasing hormone decreases feeding and increases body temperature, activity and oxygen consumption in Siberian hamsters.

Thyrotrophin-releasing hormone (TRH) is known to play an important role in the control of food intake and energy metabolism in addition to its actions on the pituitary-thyroid axis. We have previously shown that central administration of TRH decreases food intake in Siberian hamsters. This species is being increasingly used as a physiological rodent model in which to understand hypothalamic control of long-term changes in energy balance because it accumulates fat reserves in long summer photoperiods, and decreases food intake and body weight when exposed to short winter photoperiods. The objectives of our study in Siberian hamsters were: (i) to investigate whether peripheral administration of TRH would mimic the effects of central administration of TRH on food intake and whether these effects would differ dependent upon the ambient photoperiod; (ii) to determine whether TRH would have an effect on energy expenditure; and (iii) to investigate the potential sites of action of TRH. Both peripheral (5-50 mg/kg body weight; i.p.) and central (0.5 microg/ml; i.c.v.) administration of TRH decreased food intake, and increased locomotor activity, body temperature and oxygen consumption in the Siberian hamster, with a rapid onset and short duration of action. Systemic treatment with TRH was equally effective in suppressing feeding regardless of ambient photoperiod. The acute effects of TRH are likely to be centrally mediated and independent of its role in the control of the production of thyroid hormones. We conclude that TRH functions to promote a catabolic energetic state by co-ordinating acute central and chronic peripheral (thyroid-mediated) function.

Diagnostic procedures employed by dental practitioners in Australia with a focus on endodontic diagnostic procedures.

BACKGROUND: An accurate diagnosis is the foundation for determining prognosis and appropriate management. This study adds to pre-existing (albeit limited) evidence by exploring the use of diagnostic techniques amongst dental practitioners. The main aim of the study was to identify the availability, usage and clinician preference for specific diagnostic tests. A secondary aim was to investigate the use of diagnostic tests for common clinical scenarios. METHODS: A cross-sectional survey was distributed online to dental practitioners registered with the Australian Dental Association. Quantitative data on clinician demography, and the availability and preference of diagnostic tests was summarized with Stata 13 software. Pearson's chi-squared test was used to determine associations. RESULTS: General dental practitioners (GDP) and specialists comprised 86% and 14% of the 433 respondents, respectively. Unlike light transillumination, most GDP had radiography, biting tests and pulp sensibility tests available. The electric pulp test and ethyl chloride were first choices of most practitioners despite markedly lower availability relative to cold spray. Symptoms and endodontic assessments generally attracted wider usage of pulp testing. CONCLUSIONS: More dental practitioners should utilize diagnostic testing in order to arrive at accurate diagnoses. The availability of diagnostic tests did not completely translate to usage and none of the scenarios presented warranted pulp sensibility testing from all respondents.

Two hexamerin genes from the termite Reticulitermes flavipes: Sequence, expression, and proposed functions in caste regulation.

Previous molecular studies on the termite Reticulitermes flavipes have revealed that two hexamerin proteins serve an important status quo role in the regulation of juvenile hormone (JH)-dependent caste differentiation. Here, we report sequence data and other experimental evidence suggesting how these two hexamerins function in achieving caste regulation. The two hexamerin genes, named Hex-1 and Hex-2, encode highly unique sequence features relative to the 100+ other known insect hexamerins. These features include a long hydrophobic tail and prenylation motif in Hex-1, and a long hydrophilic insertion plus several putative protease cleavage sites in Hex-2. Both hexamerin genes are primarily expressed in fat body tissue, but only Hex-2 expression is substantially induced by JH. SDS-PAGE showed that the hexamerin proteins constitute a major proportion of total soluble termite protein. Also, although each protein occurs in both the membrane and soluble protein fractions, Hex-2 has stronger membrane affinity. Anti-JH antiserum specifically recognizes hemolymph-soluble Hex-1 protein, supporting that the unique prenylation site in Hex-1 facilitates covalent JH binding to the primary amino acid chain. Finally, increased ratios of Hex-2 to Hex-1 transcription occur in caste phenotypes and developmental stages that differentiate in response to rising JH titers. Two main conclusions can be taken from these studies. First, elevated ratios of Hex-2 to Hex-1 expression are associated with caste phenotypes that differentiate in response to rising JH titers (i.e., workers, presoldiers and soldiers). Second, due to their unique structural features and other observed characteristics, our findings support the hypothesis that the two hexamerins participate in the regulation of caste-differentiation by modulating JH availability.

Thyrotropin-releasing hormone (TRH)-like immunoreactivity in the grey monkey (Macaca fascicularis) spinal cord and medulla oblongata with special emphasis on the bulbospinal tract.

The distribution of thyrotropin-releasing hormone (TRH)-like immunoreactivity (LI) has been studied in the grey monkey (Macaca fascicularis) spinal cord and medulla oblongata by the use of indirect immunofluorescence and the peroxidase-antiperoxidase (PAP) technique. Furthermore, double-labeling experiments were performed in order to study colocalization of 5-hydroxytryptamine (5-HT)- and substance P-LI. A dense innervation of TRH-immunoreactive (IR) varicose fibers was found in the ventral horn motor nuclei, in the region surrounding the central canal, in the intermediolateral cell column, and in the dorsal horn laminae II and III. In addition, cell bodies harboring TRH-LI were found in the dorsal horn laminae II-IV. In the ventral horn, many of the large cell bodies and their proximal dendrites were totally encapsulated by TRH-IR fibers. From double-labeled sections a high degree of coexistence could be established between TRH-/5-HT-LI, TRH-/substance P-LI, and 5-HT-/substance P-LI in fibers in the motor nuclei; as a consequence, a large proportion of these fibers should harbor TRH-/5-HT-/substance P-LI. A coexistence between TRH-/5-HT-LI could also be demonstrated in the intermediolateral cell column. However, no unequivocal coexistence could be found between TRH-/substance P-LI and 5-HT-/substance P-LI in this region. In the dorsal horn, no clear coexistence could be encountered for any of the above indicated combinations. Electron microscopic analysis of material from the lumbar lateral motor nucleus demonstrated TRH-IR terminals making synapses with large cell bodies and dendrites. In addition, contacts lacking synaptic specializations could also be verified. In the medulla oblongata, with the use of the PAP technique, a large number of cell bodies containing TRH-LI were encountered in the midline raphe nuclei and in nucleus reticularis lateralis. A similar distribution pattern could be found for 5-HT-LI, but no cell bodies containing substance P-LI could be seen in these regions. Chemical analysis of specimens from cervical, thoracic, and lumbar spinal cord revealed higher concentrations of TRH- and 5-HT-LI in the ventral quadrants, whereas substance P-LI dominated in the dorsal quadrants. Thus, the concentrations of TRH-, 5-HT-, and substance P-LI was in accordance with the observed regional variation in density of IR-fibers and varicosities found in the spinal cord. We have shown that TRH-LI has a distribution in the monkey spinal cord and medulla oblongata similar to that previously demonstrated in other species.(ABSTRACT TRUNCATED AT 400 WORDS)

Increase in levels and ex vivo release of thyrotrophin-releasing hormone (TRH) in specific regions of the CNS of the rat by chronic treatment with antidepressants.

This study has investigated the effects of chronic treatment with amitriptyline, chlorimipramine, mianserin and metergoline on levels and ex vivo release of thyrotrophin-releasing hormone (TRH), 5-hydroxytryptamine (5-HT) and 5-hydroxyindoleacetic acid (5-HIAA) in specific regions of the brain and lumbar spinal cord of the rat. All four treatments caused a significant increase in levels of TRH in the lumbar spinal cord with amitriptyline producing the most marked effect. Amitriptyline alone caused a similar marked increase in levels of TRH in the nucleus accumbens and suprachiasmatic nucleus but none of the treatments had a significant effect on the TRH content of the median eminence or septal nuclei. Potassium-induced release of TRH and 5-HT ex vivo was measured from tissue slices of the nucleus accumbens, septal nuclei and lumbar spinal cord after treatment with amitriptyline and mianserin. An increase in release of TRH was observed only from tissue slices of areas where increased levels of the peptide had occurred; namely nucleus accumbens and lumbar spinal cord after administration of amitriptyline and lumbar spinal cord after mianserin. None of the drugs significantly altered the ex vivo release of 5-HT or 5-HIAA. The results are discussed in relation to a possible interaction between TRH and 5-HT receptors in the antidepressant action of these drugs.

The effects of 5,7-dihydroxytryptamine and p-chlorophenylalanine on thyrotrophin-releasing hormone in regions of the brain and spinal cord of the rat.

The distribution of thyrotrophin-releasing hormone (TRH) and 5-hydroxytryptamine (5-HT) were compared in ten regions of the rat brain and in lumbar spinal cord. After dissection, using a cutting box and tissue punches, TRH was measured by radioimmunoassay and 5-HT by HPLC with electrochemical detection. Within the brain the highest levels of TRH were found in the median eminence and the remaining hypothalamus. There were also relatively high levels in the suprachiasmatic nucleus, septal nuclei and nucleus accumbens. Highest levels of 5-HT were found in the raphe nuclei, hypothalamic nuclei, nucleus accumbens, stria terminalis, septal nuclei and hippocampus. 5,7-Dihydroxytryptamine (5,7-DHT; 200 micrograms, i.c.v.) markedly reduced levels of 5-HT in brain and spinal cord. In the ventral lumbar cord there was a comparable decrease of TRH and 5-HT (-80%) and a smaller but significant decrease in the nucleus accumbens (-55%) and septal nuclei (-38%). p-Chlorophenylalanine (PCPA; 250 mg/kg X 2) reduced levels of 5-HT (-80%), without significantly altering those of noradrenaline. p-Chlorophenylalanine also significantly reduced levels of TRH in the nucleus accumbens (-72%) but not in the other regions of brain or spinal cord taken. The results are discussed in relation to the previously described co-existence of TRH and 5-HT in the spinal cord and the possible alternative forms of interactions between amine and peptide in the nucleus accumbens.

Involvement of catecholaminergic neurones and alpha-adrenoceptors in the wet-dog shake and forepaw licking behaviour produced by the intrathecal injection of an analogue of thyrotrophin-releasing hormone (CG 3509).

Intrathecal injection of the analogue of TRH, CG 3509, into conscious rats produced dose-related wet-dog shakes and forepaw licking, which showed a bell-shaped relationship of intensity to dose. Pretreatment with alpha-MPT intraperitoneally, markedly reduced levels of noradrenaline and dopamine in the spinal cord and brainstem and attenuated both CG 3509-induced responses, while intrathecal treatment with DSP4 selectively reduced noradrenaline in the spinal cord without affecting either behaviour. Since denervation supersensitivity may develop following treatment with DSP4, these results are not inconsistent with a proposal that bulbospinal noradrenergic neurones modulate the behaviour induced by CG 3509. Wet-dog shakes and forepaw licking induced by CG 3509 were reduced by pretreatment with phenoxybenzamine or prazosin, suggesting that a tonic noradrenergic pathway may facilitate both behavioural responses through alpha 1-adrenoceptors. Methoxamine, combined with CG 3509 partially attenuated the wet dog shake behaviour, but methoxamine produced marked hindlimb jerking which might physiologically antagonise wet-dog shakes. Concomitant administration of clonidine and CG 3509 potently reduced wet-dog shakes in a dose-related manner but did not significantly affect forepaw licking, while idazoxan did not significantly affect either response. The latter findings imply that alpha 2-adrenoceptors play different roles in modulating the two behavioural responses and the possible synaptic location of the receptors is discussed. Taken together these results suggest that CG 3509 may release noradrenaline from bulbospinal neurones regulating motor function.

The TRH analogue CG3509 increases in vivo catechol/ascorbate oxidation in the N. accumbens but not in the striatum of the rat.

The effects of injection of the thyrotrophin-releasing hormone (TRH) analogue, orotyl-histidyl-proline amide (CG3509) into the accumbens and striatum, was studied on dopamine metabolism by means of in vivo voltammetry. Forty minutes after infusion of CG3509 (1-5 micrograms) into the n. accumbens there was a significant dose-related increase in the oxidation peak, corresponding to the oxidation of the dopamine metabolite, dihydroxyphenylacetic acid (DOPAC) and ascorbic acid. The size of this peak returned to normal by 80 min after the infusion. There was no change in the indole oxidation peak. Infusion of CG3509 (5 micrograms) had no effect on the size of either the catechol or the indole oxidation peaks recorded in the striatum. Intraventricular injection of CG3509 (10 micrograms) also increased DOPAC/ascorbic acid oxidation peak recorded in the n. accumbens, without altering the indole peak. While the voltammetric technique used in the present experiments is not able fully to separate ascorbic acid and DOPAC in vivo, the results support the view that TRH and its analogues selectively increase dopaminergic activity in the mesolimbic region.

Comparative behavioural and biochemical effects of repeated intrathecal administration of thyrotrophin-releasing hormone (TRH) or two analogues of TRH in adult rats.

The effect of repeated intrathecal injection of thyrotrophin-releasing hormone (TRH) and two analogues of TRH, C-terminally modified RX 77638 and N-terminally modified CG 3509, were examined on behavioural (wet-dog shakes and forepaw licking) and biochemical markers for spinal motoneurones, bulbospinal raphe nerve terminals and the pituitary-thyroid axis in rats. Saline (10 microliters washed in with 15 microliters), TRH (20 micrograms), RX 77368 (2 micrograms) or CG 3509 (2 micrograms) were administered intrathecally (twice daily for 3 or 5 days), after which levels of plasma-free thyroxine and thyroid-stimulating hormone (TSH) were measured and the dorsal and ventral portions of the thoracolumbar spinal cord, brainstem and hypothalamus were assayed for TRH- and calcitonin gene-related peptide (CGRP)-like immunoreactivity, levels of indoleamines and the activity of choline acetyltransferase (ChAT). Behavioural tolerance developed rapidly with consecutive injections of RX 77368, such that wet-dog shakes were significantly reduced and forepaw-licking tended to be decreased by the third intrathecal injection. Five, but not 3, days of administration of RX 77368 selectively elevated levels of 5-hydroxytryptamine (5-HT) and 5-hydroxyindoleacetic acid in the ventral spinal cord, where these substances are principally located in bulbospinal raphe nerve terminals. The time course of the change in indoleamines suggests that administration of TRH peptides elevated the synthesis, rather than the release, of 5-HT from these nerve terminals.(ABSTRACT TRUNCATED AT 250 WORDS)

Analeptic effects of centrally injected TRH and analogues of TRH in the pentobarbitone-anaesthetized rat.

The effect of intracerebral injection of TRH and several biologically stable TRH analogues in the pentobarbitone anaesthetized rat was examined. Bilateral injection of TRH (5.0 micrograms total dose) and the analogues RX 77368 (0.01-1.0 microgram), CG 3509 (0.1-1.0 microgram), DN-1417 (1.0 microgram) and MK-771 (1.0 microgram) into the nucleus accumbens reduced the pentobarbitone-induced sleeping time. The TRH metabolite DKP (5 micrograms) had no effect on the sleeping time following intra-accumbens injection. Intra-septal injection of TRH (1.0-5.0 micrograms), RX 77368 (0.1-1.0 microgram) and CG 3509 (0.1-1.0 microgram) also reversed the pentobarbitone-induced sleeping time. In contrast, TRH (5 micrograms) injected into the striatum had no effect on the pentobarbitone-induced sleeping time, and CG 3509 (0.1 microgram) and RX 77368 (0.1 microgram) had weaker effects following intrastriatal injection compared to injection of these analogues into the nucleus accumbens and septum. Measurements of core temperature and respiration rate in rats following intra-accumbens or septal injection of TRH, CG 3509 and RX 77368 showed these peptides to reverse pentobarbitone-induced hypothermia and stimulate respiration rate. However, while intrastriatal injections of CG 3509 and RX 77368 caused an increase in respiration rate they had no effect on core temperature. These results suggest a close association between peptide-induced respiratory stimulation and reversal of pentobarbitone-induced anaesthesia. Since intra-accumbens and septal injection of dopamine (20-100 micrograms) failed to reverse anaesthesia, it is unlikely that the peptide-induced responses are mediated via dopamine release.

Decrease in levels of thyrotrophin-releasing hormone (TRH) in the n. accumbens and lumbar spinal cord following repeated electroconvulsive shock.

The study investigated the effects of single and repeated electroconvulsive shock on levels and release of TRH in specific brain regions and thoracic and lumbar spinal cord. Whilst single electroconvulsive shock had no effect on TRH in any of the regions of the brain and spinal cord studied, repeated electroshock (5 shocks over 10 days and the rats killed 24 hr after the last shock) caused a significant decrease (-42 and -40% respectively) in levels of TRH in the nucleus accumbens and lumbar spinal cord. In the thoracic cord the level of TRH was also decreased after repeated electroshock but this did not reach significance. In contrast repeated electroshock had no significant effect on the content of TRH of the septal nuclei, hypothalamus, suprachiasmatic nucleus, or dorsal and medial raphe nuclei. Release of TRH was measured from slices prepared from nucleus accumbens and septal nuclei after repeated electroshock. A decrease in release was observed in nucleus accumbens with no effect in the septal nuclei. the results are discussed in relation to the possible interaction between dopaminergic and serotoninergic neurones and TRH in the antidepressant effects of electroconvulsive therapy.

Behavioural and biochemical evidence for the release of noradrenaline in mouse brain by TRH and some of its biologically stable analogues.

Small doses of clonidine probably induce hypoactivity (a distinct form of sedation) by stimulating presynaptic alpha 2-adrenoceptors. This was attenuated by injection of 0.1-10 mg/kg of thyrotropin releasing hormone (TRH) or its biologically stable analogues, CG3509, CG3703 and RX77368, when these were given 10 min before clonidine. This effect was dose-dependent in all cases, but the analogues were more potent than TRH. The TRH metabolites, TRH acid and histidyl-proline diketopiperazine (10 mg/kg) were without effect. This response was still attenuated by the analogues, but not TRH, when these were given 1 hr before clonidine. The results, therefore, suggested that it was the basic tripeptide structure which was active and TRH was less potent than its analogues because of rapid metabolism. Attenuation of hypoactivity by TRH and analogues was not due to increased dopaminergic function because apomorphine (5 mg/kg) was ineffective. Thyrotropin releasing hormone (20 mg/kg), CG3509 (10 mg/kg) and CG3703 (1 mg/kg) also induced locomotor activity and produced various other behavioural changes. This was inhibited by prazosin (3 mg/kg) and haloperidol (0.5 mg/kg) but not by yohimbine (1 mg/kg). Apomorphine (5 mg/kg)-induced activity was inhibited by haloperidol and yohimbine but not by prazosin. This indicated that the activity produced by the TRH compounds, but not apomorphine, was partly mediated by alpha 1-adrenoceptors. Both CG3509 (10(-5) and 10(-4) M) and RX77368 (10(-4) M) evoked the release of endogenous noradrenaline from slices of hypothalamus in vitro. The TRH analogues, however, had no affinity for alpha 1- or alpha 2-adrenoceptors in ligand-receptor binding experiments. Viewed overall, the data showed that TRH and its analogues induced the release of noradrenaline in the brain. In addition, a comparison of the behavioural effects of TRH compounds with dopamine and alpha 1-adrenoceptor agonists suggested that in mice these behavioural responses resulted from stimulation of both noradrenergic and dopaminergic function.

A comparison of the motor behaviours produced by the intrathecal administration of thyrotrophin-releasing hormone and thyrotrophin-releasing hormone analogues in the conscious rat.

The behaviours evoked by the intrathecal injection of thyrotrophin-releasing hormone and a variety of analogues (RX77368, CG3509 and CG3703) were examined in conscious rats and the spread of injectate at the peak of the behavioural response was determined using 14C-labelled RX77368. The number of wet-dog shakes observed following intrathecal injection of thyrotrophin-releasing hormone, RX77368, CG3509 and CG3703 was linearly related to log10 dose (0.01-200 micrograms) in the first 6 min with the relative potencies being 1:7:10:60 respectively. The thyrotrophin-releasing hormone analogues also produced a marked forepaw-licking behaviour, but this did not increase with dose. Intrathecal or intraperitoneal pretreatment with prazosin (0.5 microgram and 1 or 2 mg/kg, respectively) attenuated both the wet-dog shake and forepaw-licking behaviours normally produced by the thyrotrophin-releasing hormone peptides. Following intrathecal [14C]RX77368 the radioactivity was principally restricted to the spinal cord with only limited amounts rostral to the rhombencephalon. These results imply that a tonically active bulbospinal noradrenergic pathway facilitates both thyrotrophin-releasing hormone-induced behaviours via alpha 1-adrenoceptors.

The effects of monoamine neurotoxins on peptides in the rat spinal cord.

The coexistence of two neuronally-localised peptides, substance P and thyrotropin-releasing hormone (TRH), in descending serotoninergic nerve fibres to the spinal cord was investigated using immunocytochemical and biochemical methods. Substance P-like material in the spinal cord was shown to be identical to the undecapeptide substance P by the criteria of gel filtration, high performance liquid chromatography and behaviour in substance P specific radioimmunoassays. Immunocytochemical staining for 5-hydroxytryptamine, substance P, and TRH showed that all three substances had a similar distribution in nerve fibres and terminals in the ventral and lateral grey matter of the spinal cord. After treatment with the serotonin neurotoxin 5,7-dihydroxytryptamine, neuronal elements containing 5-hydroxytryptamine, substance P and TRH degenerated and disappeared from these parts of the spinal cord in parallel with one another. Biochemical measurements of 5-hydroxytryptamine, substance P and TRH in the spinal cord after treatment with 5,7-dihydroxytryptamine confirmed that these three substances were all depleted from the ventral horn and, in addition, showed that there was a small depletion of substance P from the dorsal horn. Two other neuropeptides, somatostatin and methionine-enkephalin were not depleted from the spinal cord by treatment with 5,7-dihydroxytryptamine nor was substance P in other parts of the brain. Substance P in the spinal cord was unaffected by 6-hydroxydopamine, a drug known to destroy catecholamine-containing neurones. These results are consistent with coexistence of substance P and TRH together with 5-hydroxytryptamine in the descending axons and terminals of bulbospinal neurones.

Changes in monoamine metabolites measured by simultaneous in vivo differential pulse voltammetry and intracerebral dialysis.

A direct comparison has been made of the drug-induced changes in extracellular levels of 3,4-dihydroxyphenylacetic acid and 5-hydroxyindoleacetic acid measured using intracerebral dialysis and differential pulse voltammetry with carbon fibre electrodes. The comparison was carried out in chloral hydrate anaesthetized rats with a pretreated carbon fibre electrode implanted in one striatum and an intracerebral dialysis loop in the contralateral striatum. 3,4-Dihydroxyphenylacetic acid and 5-hydroxyindoleacetic acid in the dialysis perfusates were assayed by high pressure liquid chromatography with electrochemical detection. d-Amphetamine (2 mg/kg) decreased extracellular 3,4-dihydroxyphenylacetic acid and the height of the 3,4-dihydroxyphenylacetic acid oxidation peak, while haloperidol (0.5 mg/kg) increased 3,4-dihydroxyphenylacetic acid levels measured in the perfusates and the height of the 3,4-dihydroxyphenylacetic acid oxidation peak. In these experiments there were parallel changes in 3,4-dihydroxyphenylacetic acid levels and peak height and a close correlation between these changes. Tranylcypromine (10 mg/kg) produced an almost parallel decrease in extracellular 5-hydroxyindoleacetic acid (dialysis) and the height of the 5-hydroxyindoleacetic acid oxidation peak, with similar percentage changes and good correlation values being obtained. However, while 5-hydroxy-L-tryptophan (25 mg/kg) increased both the 5-hydroxyindoleacetic acid levels and the height of the 5-hydroxyindoleacetic acid oxidation peak, 5-hydroxyindoleacetic acid in the dialysis perfusates showed a greater increase than the oxidation peak. The results show a close correlation between changes in extracellular 3,4-dihydroxyphenylacetic acid and its respective voltammetric peak and strongly support the use of in vivo differential pulse voltammetry for monitoring dopamine metabolism.(ABSTRACT TRUNCATED AT 250 WORDS)

Quantitative autoradiography with radiopharmaceuticals, Part 1: Digital film-analysis system by videodensitometry: concise communication.

A simple low-cost digital film-analysis system using videodensitometry was developed to quantitate autoradiograms. It is based on a TV-film analysis system coupled to a minicomputer. Digital sampling of transmitted light intensities through the autoradiogram is performed with 8-bit gray levels according to the selected array size (128 X 128 to 1024 X 1024). The performance characteristics of the system provide sufficient stability, uniformity, linearity, and intensity response for use in quantitative analysis. Digital images of the autoradiograms are converted to radioactivity content, pixel by pixel, using step-wedge standards. This type of low-cost system can be installed on conventional mini-computers commonly used in modern nuclear medical facilities. Quantitative digital autoradiography can play an important role, with applications stretching from dosimetry calculations of radiopharmaceuticals to metabolic studies in conjunction with positron-emission tomography.

Biphasic effects of intra-accumbens histamine administration on spontaneous motor activity in the rat; a role for central histamine receptors.

1. The effect of intra-accumbens injection of histamine and related compounds on the spontaneous motor activity of the rat has been investigated. 2. Microinjections of histamine (1-200 micrograms) induced dose-dependent, biphasic changes in rat activity consisting of an initial brief hypoactivity response followed by a marked hyperactivity phase. The histamine metabolite, n-tele-methylhistamine was without effect. 3. Pretreatment with the H1-receptor antagonist mepyramine (10 micrograms) blocked the hypoactivity response and markedly attenuated histamine-induced hyperactivity. In contrast, pretreatment with the H2-receptor antagonist SKF93479 had no effect on histamine-induced behaviour. 4. Microinjection of the H1-receptor agonist 2-thiazolylethylamine induced a marked hyperactivity response, but unlike the response to histamine, there was no initial hypoactivity. The H2-receptor agonist dimaprit had no apparent behavioural effects following intra-accumbens injection. 5. Intra-accumbens injection of the non-selective histamine agonists n alpha-methylhistamine or n alpha, n alpha-dimethylhistamine induced both marked hypoactivity and hyperactivity responses which were comparable with the effects of histamine. 6. The present results demonstrate a histamine, H1-receptor-mediated arousal in the nucleus accumbens which follows transitory hypoactivity, possibly due to activation of presynaptic H3-receptors.