[18F]FDG-PET/CT-based risk stratification in women with locally advanced uterine cervical cancer.

BACKGROUND: [18F]FDG-PET/CT is used for staging and treatment planning in patients with locally advanced cervical cancer (LACC). We studied if a PET-based prediction model could provide additional risk stratification beyond International Federation of Gynaecology and Obstetrics (FIGO) staging in our population with LACC to aid treatment decision making. METHODS: In total, 183 patients with LACC treated with chemoradiation between 2013 and 2018 were included. Patients were treated according to FIGO 2009 and retrospectively reclassified according to FIGO 2018 staging system. After validation of an existing PET-based prediction model, the predicted recurrent free survival (RFS), disease specific survival (DSS) and overall survival (OS) at 1, 3, and 5 years, based on metabolic tumor volume (MTV), maximum standardized uptake value (SUVmax) and highest level of [18F]FDG-positive node was calculated. Then the observed survival was compared to the predicted survival. An area under the curve (AUC) close to or higher than 0.7 was considered adequate for accurate prediction. The Youden (J) index defined survival chance cutoff values for low and high risk groups. RESULTS: All AUC values for the comparison between predicted and observed outcomes were > 0.7 except for 5-year RFS and for 5-year OS which were close to 0.7 (0.684 and 0.650 respectively). Cutoff values for low and high risk survival chance were 0.44 for the 3-year RFS and 0.47 for the 5-year OS. The FIGO 2009 system could not differentiate between the risk profiles. After reclassification according to FIGO 2018, all patients with stage IIIC2 and IVB fell in the high risk and almost all patients with stages IB2-IIIB and IVA in the low risk group. In patients with stage IIIC1 disease the FIGO stage cannot discriminate between the risk profiles. CONCLUSIONS: Low and high risk patients with LACC can be identified with the PET-based prediction model. In particular patients with stage IIIC1 need additional risk stratification besides the FIGO 2018 staging. The Kidd model could be a useful tool to aid treatment decision making in these patients. Our results also support the choice of [18F]FDG-PET/CT imaging in patients with LACC.

Choice of gDNA isolation method has a significant impact on average murine Telomere Length estimates.

Telomere Length (TL) and integrity is significantly associated with age-related disease, multiple genetic and environmental factors. We observe mouse genomic DNA (gDNA) isolation methods to have a significant impact on average TL estimates. The canonical qPCR method does not measure TL directly but via the ratio of telomere repeats to a single copy gene (SCG) generating a T/S ratio. We use a monochromatic-multiplex-qPCR (mmqPCR) method which multiplexes the PCR and enables quantification of the target and the single copy gene within the same qPCR reaction. We demonstrate that TL measurements, from murine gDNA, isolated via Spin Columns (SC) and Magnetic Beads (MB), generate significantly smaller T/S ratios compared to gDNA isolated via traditional phenol/chloroform methods. The former methods may impede correct TL estimation by producing non representative fragment sets and reducing qPCR efficacy. This work highlights discrepancies in TL measurements due to different extraction techniques. We recommend the use of gDNA isolation methods that are shown to preserve DNA length and integrity, such as phenol/chloroform isolation. We propose that widely used high throughput DNA isolation methodologies can create spurious associations within a sample set, thus creating misleading data. We suggest that published TL associations should be revisited in the light of these data.

Practising Less is More: An Exploration of What it Means to See "This Patient" Not a "Patient Like This".

In the last decade literature focused on a "less is more" approach has been primarily represented by clinical cases describing the excesses of an aggressive, redundant, non-personalized, and non-respectful medicine. Most of these articles focus on a "more is worse" approach and centre around the downstream negative consequences of medical overuse. Having identified a gap in the literature on the experience and practice of less, rather than the harms of excess, we carried out an exploratory qualitative study into how a "less is more" approach works in practice. A hermeneutic phenomenological approach was adopted to allow us to examine the realm of lived experience as a valid data source and as a path from which to understand a "less is more" approach "from the bedside." A Phenomenology of Practice was chosen as a more specific frame for this research because of its added focus on action and practical application in professional settings. Seventy stories written by physicians, patients, nurses, caregivers, and other health professionals have been received and analysed. These stories were gathered as part of a project called "Slow Stories" which aimed to collect clinical cases that have been positively resolved by adopting a "less is more" approach to patient care. After having conducted an in-depth analysis, separately and as a group, the researchers identified five key phenomenological themes; Time to relate is time to heal; Doing more does not mean doing better; Settings for a slow medicine; Slow care at the end of life; and Personalized vs. standardized treatment. Each of these themes offers insights into how a "less is more" approach can be used in practice and illustrates how a "less is more" strategy can play a significant role in positively resolving certain clinical cases.

Developmental changes in brain activation during novel grammar learning in 8-25-year-olds.

While it is well established that grammar learning success varies with age, the cause of this developmental change is largely unknown. This study examined functional MRI activation across a broad developmental sample of 165 Dutch-speaking individuals (8-25 years) as they were implicitly learning a new grammatical system. This approach allowed us to assess the direct effects of age on grammar learning ability while exploring its neural correlates. In contrast to the alleged advantage of children language learners over adults, we found that adults outperformed children. Moreover, our behavioral data showed a sharp discontinuity in the relationship between age and grammar learning performance: there was a strong positive linear correlation between 8 and 15.4 years of age, after which age had no further effect. Neurally, our data indicate two important findings: (i) during grammar learning, adults and children activate similar brain regions, suggesting continuity in the neural networks that support initial grammar learning; and (ii) activation level is age-dependent, with children showing less activation than older participants. We suggest that these age-dependent processes may constrain developmental effects in grammar learning. The present study provides new insights into the neural basis of age-related differences in grammar learning in second language acquisition.

Study protocol: a comprehensive multi-method neuroimaging approach to disentangle developmental effects and individual differences in second language learning.

BACKGROUND: While it is well established that second language (L2) learning success changes with age and across individuals, the underlying neural mechanisms responsible for this developmental shift and these individual differences are largely unknown. We will study the behavioral and neural factors that subserve new grammar and word learning in a large cross-sectional developmental sample. This study falls under the NWO (Nederlandse Organisatie voor Wetenschappelijk Onderzoek [Dutch Research Council]) Language in Interaction consortium (website: https://www.languageininteraction.nl/ ). METHODS: We will sample 360 healthy individuals across a broad age range between 8 and 25 years. In this paper, we describe the study design and protocol, which involves multiple study visits covering a comprehensive behavioral battery and extensive magnetic resonance imaging (MRI) protocols. On the basis of these measures, we will create behavioral and neural fingerprints that capture age-based and individual variability in new language learning. The behavioral fingerprint will be based on first and second language proficiency, memory systems, and executive functioning. We will map the neural fingerprint for each participant using the following MRI modalities: T1-weighted, diffusion-weighted, resting-state functional MRI, and multiple functional-MRI paradigms. With respect to the functional MRI measures, half of the sample will learn grammatical features and half will learn words of a new language. Combining all individual fingerprints allows us to explore the neural maturation effects on grammar and word learning. DISCUSSION: This will be one of the largest neuroimaging studies to date that investigates the developmental shift in L2 learning covering preadolescence to adulthood. Our comprehensive approach of combining behavioral and neuroimaging data will contribute to the understanding of the mechanisms influencing this developmental shift and individual differences in new language learning. We aim to answer: (I) do these fingerprints differ according to age and can these explain the age-related differences observed in new language learning? And (II) which aspects of the behavioral and neural fingerprints explain individual differences (across and within ages) in grammar and word learning? The results of this study provide a unique opportunity to understand how the development of brain structure and function influence new language learning success.

Exploring feature-based approaches in PET images for predicting cancer treatment outcomes.

Accumulating evidence suggests that characteristics of pre-treatment FDG-PET could be used as prognostic factors to predict outcomes in different cancer sites. Current risk analyses are limited to visual assessment or direct uptake value measurements. We are investigating intensity-volume histogram metrics and shape and texture features extracted from PET images to predict patient's response to treatment. These approaches were demonstrated using datasets from cervix and head and neck cancers, where AUC of 0.76 and 1.0 were achieved, respectively. The preliminary results suggest that the proposed approaches could potentially provide better tools and discriminant power for utilizing functional imaging in clinical prognosis.

Dietary trace amine-dependent vasoconstriction in porcine coronary artery.

BACKGROUND AND PURPOSE: The dietary trace amines tyramine and beta-phenylethylamine (beta-PEA) can increase blood pressure. However, the mechanisms involved in the vascular effect of trace amines have not been fully established. The purpose of this study was to evaluate whether trace amine-dependent vasoconstriction was brought about by tyramine and beta-PEA acting as indirect sympathomimetic agents, as previously assumed, or whether trace amine-dependent vasoconstriction could be mediated by recently discovered trace amine-associated (TAA) receptors. EXPERIMENTAL APPROACH: The responses to p-tyramine and beta-PEA were investigated in vitro in rings of the left anterior descending coronary arteries of pigs. KEY RESULTS: p-Tyramine induced a concentration-dependent (0.1-3 mM) vasoconstriction. The maximum response and pD(2) value for p-tyramine was unaffected by endothelium removal or pre-treatment with antagonists for adrenoceptors, histamine, dopamine or 5-HT receptors. beta-PEA also produced a concentration-dependent (0.3-10 mM) vasoconstriction which was unaffected by endothelium removal, beta-adrenoceptor or 5-HT receptor antagonists. A substantial, but reduced, response to beta-PEA was obtained in the presence of prazosin (alpha(1)-adrenoceptor antagonist), haloperidol (D(2)/D(3) dopamine receptor antagonist) or mepyramine (H(1) histamine receptor antagonist). The pD(2) value for beta-PEA was unaffected by any of the antagonists tested. CONCLUSIONS AND IMPLICATIONS: Vasoconstriction induced by p-tyramine does not involve an indirect sympathomimetic effect, although vasoconstriction caused by beta-PEA may occur, in part, by this mechanism. We therefore propose that trace amine-dependent vasoconstriction is mediated by phenylethylamine-specific receptors, which are closely related to or identical to TAA receptors. These receptors could provide a target for new antihypertensive therapies.

Complete or ultraconservative removal of decayed tissue in unfilled teeth.

BACKGROUND: The treatment of deep dental decay has traditionally involved removal of all the soft demineralised dentine before a filling is placed. However this has been challenged in three groups of studies which involve sealing soft caries into the tooth. The three main groups either remove no caries and seal the decay into the tooth, remove minimal (ultraconservative) caries at the entrance to a cavity and seal the remaining caries in, or remove caries in stages over two visits some months apart to allow the pulp time to lay down reparative dentine (the stepwise excavation technique). OBJECTIVES: To test the null hypothesis of no difference in the incidence of damage or disease of the nerve of the tooth (pulp), progression of decay and longevity of restorations irrespective of whether the removal of decay had been minimal (ultraconservative) or complete. SEARCH STRATEGY: The Cochrane Oral Health Group Trials Register, Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, PubMed and EMBASE databases were searched. The reference lists in relevant papers were checked. SELECTION CRITERIA: Randomised controlled trials and controlled clinical trials comparing minimal (ultraconservative) caries removal with complete caries removal in unrestored permanent and deciduous teeth. DATA COLLECTION AND ANALYSIS: Outcome measures recorded were exposure of the nerve of the tooth (pulp) during caries removal, patient experience of symptoms of pulpal inflammation or necrosis, progression of caries under the filling, time until the filling was lost or replaced. Due to the heterogeneity of the included studies the overall estimate of effect was calculated using a random-effects model. MAIN RESULTS: Four studies met the inclusion criteria; two stepwise excavation studies and two ultraconservative caries removal studies. Partial caries removal in symptomless, primary or permanent teeth reduces the risk of pulp exposure. We found no detriment to the patient in terms of pulpal symptoms in this procedure and no reported premature loss or deterioration of the restoration. AUTHORS' CONCLUSIONS: The results of this systematic review reject the null hypothesis of no difference in the incidence of damage or disease of the nerve of the tooth (pulp) irrespective of whether the removal of decay had been minimal (ultraconservative) or complete and accepts the null hypothesis of no difference in the progression of decay and longevity of restorations. However, the number of included studies is small and differ considerably. Partial caries removal is therefore preferable to complete caries removal in the deep lesion, in order to reduce the risk of carious exposure. However, there is insufficient evidence to know whether it is necessary to re-enter and excavate further but studies that have not re-entered do not report adverse consequences.

Radioligand binding and functional responses of ligands for human recombinant adenosine A(3) receptors.

The binding and functional properties of adenosine receptor ligands were compared in Chinese hamster ovary cells transfected with human adenosine A(3) receptors. Inhibition of [(125)I]-aminobenzyl-5'-N-methylcarboamidoadenosine ([(125)I]-AB-MECA) binding by adenosine receptor ligands was examined in membrane preparations. Inhibition of forskolin-induced cAMP accumulation by agonists was measured using a cAMP enzyme immunoassay. The rank order of agonist potency for both assays was N(6)-(3-iodobenzyl)-adenosine-5'-N-methyluronamide (IB-MECA) > 5'-N-ethylcarboxamidoadenosine (NECA) > (-)-N(6)-[(R)-phenylisopropyl] adenosine (R-PIA) > 4-aminobenzyl-5'-N-methylcarboxamidoadenosine (AB-MECA) > N(6)-cyclopentyl adenosine (CPA) > adenosine. The radioligand binding rank order of antagonist potency was N-[9-chloro-2-(2-furanyl)[1,2,4]-triazolo[1,5-c]quinazolin-5-benzeneacetamide (MRS1220) > 1,3-dipropyl-8-cyclopentylxanthine (DPCPX) > 8-phenyltheophylline (8-PT) > 8-(p-sulfophenyl)-theophylline (8-SPT). MRS1220 competitively inhibited the effect of IB-MECA on cAMP production, with a K(B) value of 0.35 nm. These data are characteristic of adenosine A(3) receptors. The absence of Mg(2+) and presence of guanosine 5'-(gamma-thio)triphosphate (GTPgammaS) significantly reduced agonist binding inhibition potency, indicating binding to high- and low-affinity states. The IB-MECA, NECA and R-PIA IC(50) values were greater for the cAMP assay than for radioligand binding, suggesting an efficient stimulus-response transduction pathway.

LPS exacerbates functional and inflammatory responses to ovalbumin and decreases sensitivity to inhaled fluticasone propionate in a guinea pig model of asthma.

BACKGROUND AND PURPOSE: Asthma exacerbations contribute to corticosteroid insensitivity. LPS is ubiquitous in the environment. It causes bronchoconstriction and airway inflammation and may therefore exacerbate allergen responses. This study examined whether LPS and ovalbumin co-administration could exacerbate the airway inflammatory and functional responses to ovalbumin in conscious guinea pigs and whether these exacerbated responses were insensitive to inhaled corticosteroid treatment with fluticasone propionate (FP). EXPERIMENTAL APPROACH: Guinea pigs were sensitized and challenged with ovalbumin and airway function recorded as specific airway conductance by whole body plethysmography. Airway inflammation was measured from lung histology and bronchoalveolar lavage. Airway hyper-reactivity (AHR) to inhaled histamine was examined 24 h after ovalbumin. LPS was inhaled alone or 24 or 48 h before ovalbumin and combined with ovalbumin. FP (0.05-1 mg·mL(-1) ) or vehicle was nebulized for 15 min twice daily for 6 days before ovalbumin or LPS exposure. KEY RESULTS: Ovalbumin inhalation caused early (EAR) and late asthmatic response (LAR), airway hyper-reactivity to histamine and influx of inflammatory cells into the lungs. LPS 48 h before and co-administered with ovalbumin exacerbated the response with increased length of the EAR, prolonged response to histamine and elevated inflammatory cells. FP 0.5 and 1 mg·mL(-1) reduced the LAR, AHR and cell influx with ovalbumin alone, but was ineffective when guinea pigs were exposed to LPS before and with ovalbumin. CONCLUSIONS AND IMPLICATIONS: LPS exposure exacerbates airway inflammatory and functional responses to allergen inhalation and decreases corticosteroid sensitivity. Its widespread presence in the environment could contribute to asthma exacerbations and corticosteroid insensitivity in humans.

A quantitative autoradiographical study on the distribution of somatostatin sst2 receptors in the rat central nervous system using [125I]-BIM-23027.

The kinetic properties, steady state binding characteristics and autoradiographic distribution of the somatostatin (SRIF) sst2 receptor-selective ligand, [125I]-BIM-23027, have been investigated in the rat central nervous system. Analysis of kinetic, saturation and competition binding data in rat hippocampal membranes was consistent with [125I]-BIM-23207 binding to a single population of non-interacting binding sites. Competition studies, using different SRIF ligands suggested that [125I]-BIM-23027 was binding to sites similar to that of the recombinant sst2 receptor. The rank order of affinity for displacing specific binding was BIM-23027 = SRIF > L-362855 > > BIM-23056. There was a widespread distribution of [125I]-BIM-23027 binding sites in the rat central nervous system. The highest density of binding was observed in the dentate gyrus, medial habenular, amygdala, claustrum and lateral septum as well as in the piriform, cingulate and parietal cortex. The cervical and lumbar spinal cord also displayed moderate levels of binding localized to the substantia gelatinosa. The cellular localization of [125I]-BIM-23027 binding was found to be associated with dendritic terminal fields. In contrast, the cellular signal for sst2 receptor mRNA was restricted to cell somata. The widespread distribution of [125I]-BIM-23027 binding sites within the brain suggests that receptors similar to the recombinant sst2 receptor may mediate a variety of different physiological effects within the central nervous system.

Autoradiographic distribution of [3H]L-NG-nitro-arginine binding in rat brain.

The distribution of nitric oxide synthase (NOS), the enzyme which produces nitric oxide, has previously been studied in the rat central nervous system (CNS) using the NADPH-diaphorase technique and anti-NOS antibodies. However, the former method may not always be selective for NOS while the latter is not quantitative. Therefore a selective, quantifiable method would be desirable. L-NG-Nitro-arginine, an inhibitor of NOS, is available in a tritiated form which we have shown to bind to NOS. We have now examined the regional distribution of [3H]L-NG-nitro-arginine binding in the rat CNS using autoradiography. [3H]L-NG-nitro-arginine specific binding was seen in a number of brain regions with the highest levels in the accessory olfactory bulb, the amygdaloid complex, the Islands of Calleja and the cerebellum. This regional distribution of [3H]L-NG-nitro-arginine binding sites in the rat CNS was, in general, similar to that seen with the NADPH-diaphorase method and anti-NOS antibodies, consistent with the view that all three methods identify NOS in the CNS. Thus, [3H]L-NG-nitro-arginine appears to be a useful radioligand for studying the distribution of NOS in the CNS as its binding is quantifiable and apparently selective for NOS.

Evidence for P2X3 receptors in the developing rat brain.

P2X receptor-mediated responses to the ATP analogue, alpha,beta-methylene ATP, in rat brain cannot be accounted for by the receptor proteins known to be present. Such experiments are often performed on cells from neonates and, since differential developmental regulation of P2X1 and P2X2 receptor messenger RNAs has already been demonstrated, this is likely to be the case for other P2X receptors. This study was designed to address the possible existence of alpha,beta-methylene ATP-sensitive P2X3 receptors in rat brains of various ages using a P2X3 receptor-selective antibody. P2X3 receptor protein was found in discrete regions of the embryonic (E16) and neonatal rat brain (P7 and P14) but was not detectable in adult animals. This is the first demonstration of the presence of these receptors in brains from various ages of rat and the differential expression of these receptors in neonates may account for some reported electrophysiological responses to alpha,beta-methylene ATP.

Apparent species differences in the kinetic properties of P2X(7) receptors.

1. Apparent species differences in the responses of recombinant P2X(7) receptors to repeated application of 2'- and 3'-O-(4-benzoylbenzoyl)-ATP (BzATP) have been investigated. 2. Repeated application of 100 microM BzATP resulted in a progressive increase in current magnitude (current growth) at mouse and human, but not rat P2X(7) receptors. 3. Current growth was thought to reflect progressive dilation of the P2X(7) ion-channel to a pore permeable to large molecules (MW<900), suggesting that channel dilation was not occurring at the rat P2X(7) receptor. However, 100 microM BzATP produced a rapid influx of YO-PRO-1 (MW375) in cells expressing rat or human P2X(7) receptors. 4. There were, however, species differences in agonist potency such that 100 microM BzATP was a supra-maximal concentration at rat, but not human or mouse, P2X(7) receptors. Importantly, when sub-maximal concentrations of BzATP or ATP were examined, current growth occurred at rat P2X(7) receptors. 5. The rate of current growth and YO-PRO-1 accumulation increased with agonist concentration and appeared more rapid at rat and human, than at mouse P2X(7) receptors. 6. The potency of BzATP and ATP was 1.5 - 10 fold lower in naïve cells than in cells repeatedly exposed to ATP. 7. This study demonstrates that current growth occurs at mouse, rat and human P2X(7) receptors but only when using sub-maximal concentrations of agonist. Previously, current growth was thought to reflect the progressive increase in pore diameter of the P2X(7) receptor ion channel, however, the results of this study suggest a progressive increase in agonist potency may also contribute.

Molecular cloning and functional characterization of a rat somatostatin sst2(b) receptor splice variant.

1. The mouse somatostatin (SRIF) sst2 receptor exists in two splice variants, sst2(a) and sst2(b), which differ in their intracellular carboxy-termini only. The murine sst2(b) receptor was reported to be less prone to agonist-induced desensitization as compared with the sst2(a) receptor. To determine whether a sst2(b) splice variant with similar functional characteristics exists in the rat, we have isolated a cDNA fragment from rat gastric mucosa encoding a sst2(b) receptor and expressed the full-length protein in CHO-K1 cells for functional characterization. 2. This study provides the first evidence for the occurrence in the rat of the sst2(b) receptor, which has a 15 amino acid carboxy-terminus differing in composition to the 38 amino acid C-terminus of the rat sst2(a) receptor. 3. In CHO-K1 cells expressing rat recombinant sst2(a) or sst2(b) receptors, SRIF caused concentration-dependent increases in extracellular acidification rates (EAR) with pEC50 values of 9.0 and 9.9, respectively. Pre-treatment with pertussis toxin (Ptx) caused a rightward displacement of the SRIF concentration-effect curves with pEC50 values of 8.3 (sst2(a) and 8.4 (sst2(b)). 4. SRIF (3 pM-3 nM) also caused concentration-dependent inhibition of forskolin-stimulated cyclic AMP formation in CHO-sst2(a) cells (pIC50 10.5) and CHO-sst2(b) cells (pIC50 10.4). The degree of inhibition was less with higher concentrations of SRIF resulting in bell-shaped concentration-effect curves. Following pre-treatment with Ptx, the inhibitory effect of SRIF was abolished and SRIF caused only increases in cyclic AMP formation. 5. Both the SRIF-induced increases in EAR and inhibition of cyclic AMP formation were susceptible to agonist-induced desensitization, but this was less apparent following pre-treatment with Ptx. 6. This demonstrates that the operational characteristics of the recombinant rat sst2(a) and sst2(b) receptors are broadly similar. Both isoforms couple to Ptx-sensitive as well as -insensitive G proteins and are equally prone to agonist-induced desensitization.

Chronic 5-HT2 receptor antagonist treatment alters 5-HT1A autoregulatory control of 5-HT release in rat brain in vivo.

Rats treated chronically (14 days) with the 5-HT2 receptor antagonist ritanserin, show decreased 5-HT2 receptor numbers in the frontal cortex. The present experiments were designed to investigate the effects of acute and chronic ritanserin treatment on the autoregulatory control of the release of 5-HT and its metabolite 5-HIAA in vivo in rats using intracerebral dialysis. Neither acute nor chronic ritanserin treatment altered basal extracellular levels of 5-HT or 5-HIAA, suggesting that 5-HT2 receptors do not directly influence 5-HT release. In the control animals, systemic stimulation of somatodendritic 5-HT1A receptors with the 5-HT1A receptor agonist 8-OH-DPAT, inhibited the release of 5-HT presumably via inhibitory feedback autoregulation; an effect also seen in animals treated acutely with ritanserin. However, in the animals treated chronically with ritanserin, administration of 8-OH-DPAT produced an initial increase in extracellular 5-HT which declined gradually to the end of the experiment. These results suggest that chronic, but not acute, 5-HT2 receptor antagonist treatment attenuates the 5-HT1A receptor-mediated autoregulation of 5-HT release. The underlying mechanisms have yet to be ascertained.

5-HT3 receptors in the rat central nervous system are mainly located on nerve fibres and terminals.

Autoradiographic and membrane binding studies with [3H](R,S)- or [3H](S)-zacopride were performed in combination with lesions using various neurotoxins in an attempt to identify which neuronal cell types are endowed with 5-HT3 receptors in the rat central nervous system. Lesions of noradrenergic (by DSP-4), dopaminergic (by 6-hydroxydopamine) and serotonergic (by 5,7-dihydroxytryptamine) systems had little effect generally on the density of 5-HT3 receptors labelled with [3H](R,S)- or [3H](S)-zacopride in various regions of the brain and the spinal cord. The only exception was the amygdala where a significant loss (approximately -20%) of 5-HT3 receptors labelled by [3H](R,S)-zacopride was associated with the selective lesion of serotonergic fibres by 5,7-dihydroxytryptamine. Microinjection of kainic or ibotenic acid into the dorsal and ventral hippocampus reduced the density of 5-HT1A receptors labelled with [3H]8-OH-DPAT (approximately -45%) as expected from their known location on intrinsic neuronal cell bodies and/or dendrites. In contrast, the same lesion did not affect 5-HT3 receptors, suggesting their location on fibres 'en passage'. At the spinal level, 5-HT3 receptors were found to exist on primary afferent fibres terminating within the superficial layers of the dorsal horn, as shown by the marked reduction in the local autoradiographic labelling by [3H](S)-zacopride after either dorsal rhizotomy (-81%) or neonatal capsaicin treatment (-72%). These data suggest that 5-HT3 receptors in the central nervous system are generally located presynaptically on nerve terminals or fibres of non-monoaminergic neurones.

Mediation of the discriminative stimulus properties of 8-hydroxy-2-(di-n-propylamino) tetralin (8-OH-DPAT) by the putative 5-HT1A receptor.

Male Sprague-Dawley rats were trained to discriminate the putative 5-HT1A receptor agonist, 8-hydroxy-2-(di-n-propylamino) tetralin (8-OH-DPAT) from saline in a 2-lever operant drug discrimination paradigm. The 8-OH-DPAT cue was found to be highly selective; neither the 5-HT receptor agonists, quipazine, LSD, MK 212 and RU 24969, the 5-HT releasing agent, p-chloroamphetamine, nor the alpha 2-adrenoceptor agonist, clonidine, were able to substitute for 8-OH-DPAT in tests of generalization. In contrast, both buspirone and TVX Q 7821, which like 8-OH-DPAT have high affinity and selectivity for the 5-HT1A recognition site, generalized to the 8-OH-DPAT cue in a dose-dependent manner. The discriminative stimulus properties of 8-OH-DPAT were not antagonized by the 5-HT2 receptor antagonist, ketanserin, or the selective beta 1- and beta 2-adrenoceptor antagonists, betaxolol and ICI 118.551, indicating that neither 5-HT2 receptors, nor beta-adrenoceptors play a significant role in the behaviour. However, the 8-OH-DPAT cue was antagonized stereoselectively by pindolol and alprenolol, which have relatively high affinity and stereoselectivity for 5-HT1, but not 5-HT2, recognition sites. Similarly, the capacity of TVX Q 7821 to generalize to the 8-OH-DPAT cue could be blocked by pindolol. In view of the fact that 8-OH-DPAT has negligible affinity for the 5-HT1B site, the above results are consistent with its discriminative stimulus properties being mediated by the putative 5-HT1A receptor. Moreover, agonist activity at central 5-HT1A receptors may be an important mechanism contributing to the anxiolytic properties of buspirone and TVX Q 7821.

Effects of repeated treatment with 1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane (DOI) on the autoregulatory control of dorsal raphe 5-HT neuronal firing and cortical 5-HT release.

These experiments were designed to examine the effects of repeated 1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane (DOI) treatment on the autoregulatory control of cortical 5-HT release and dorsal raphe nucleus (DRN) 5-HT neuronal cell firing. Repeated DOI treatment decreased the behavioural responsiveness (wet-dog shakes) of 5-HT2 receptors and attenuated the inhibitory effects of the 5-HT1A receptor agonist, 8-OH-DPAT (8-hydroxy-2-(di-n-propylamino)tetralin), on both cortical 5-HT release and DRN 5-HT neuronal firing. In contrast, the inhibitory effect of acute DOI on cortical 5-HT release and DRN 5-HT neuronal firing was unaffected by repeated DOI treatment. The results demonstrate that changes in the responsiveness of 5-HT2 receptor function may influence the responsiveness of presynaptic 5-HT1A receptors regulating 5-HT neuronal function. The results also provide further evidence that the inhibition of cortical 5-HT release and DRN 5-HT neuronal firing produced by DOI is not mediated by 5-HT2 receptor activation.