Intensive Care Interventions Among Children With Toxicologic Exposures to Cardiovascular Medications

OBJECTIVES

Interventions requiring a PICU are rare in toxicologic exposures, but cardiovascular medications are high-risk exposures due to their hemodynamic effects. This study aimed to describe prevalence of and risk factors for PICU interventions among children exposed to cardiovascular medications.

DESIGN

Secondary analysis of Toxicology Investigators Consortium Core Registry from January 2010 to March 2022.

SETTING

International multicenter research network of 40 sites.

PATIENTS

Patients 18 years old or younger with acute or acute-on-chronic toxicologic exposure to cardiovascular medications. Patients were excluded if exposed to noncardiovascular medications or if symptoms were documented as unlikely related to exposure.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Of 1,091 patients in the final analysis, 195 (17.9%) received PICU intervention. One hundred fifty-seven (14.4%) received intensive hemodynamic interventions and 602 (55.2%) received intervention in general. Children less than 2 years old were less likely to receive PICU intervention (odds ratio [OR], 0.42; 95% CI, 0.20-0.86). Exposures to alpha-2 agonists (OR, 2.0; 95% CI, 1.11-3.72) and antiarrhythmics (OR, 4.26; 95% CI, 1.41-12.90) were associated with PICU intervention. In the sensitivity analysis removing atropine from the composite outcome PICU intervention, only exposures to calcium channel antagonists (OR, 2.12; 95% CI, 1.09-4.11) and antiarrhythmics (OR, 4.82; 95% CI, 1.57-14.81) were independently associated with PICU intervention. No independent association was identified between PICU intervention and gender, polypharmacy, intentionality or acuity of exposure, or the other medication classes studied.

CONCLUSIONS

PICU interventions were uncommon but were associated with exposure to antiarrhythmic medications, calcium channel antagonists, and alpha-2 agonists. As demonstrated via sensitivity analysis, exact associations may depend on institutional definitions of PICU intervention. Children less than 2 years old are less likely to require PICU interventions. In equivocal cases, age and exposure to certain cardiovascular medication classes may be useful to guide appropriate disposition.

Development of a treatment selection algorithm for SGLT2 and DPP-4 inhibitor therapies in people with type 2 diabetes: a retrospective cohort study

BACKGROUND

Current treatment guidelines do not provide recommendations to support the selection of treatment for most people with type 2 diabetes. We aimed to develop and validate an algorithm to allow selection of optimal treatment based on glycaemic response, weight change, and tolerability outcomes when choosing between SGLT2 inhibitor or DPP-4 inhibitor therapies.

METHODS

In this retrospective cohort study, we identified patients initiating SGLT2 and DPP-4 inhibitor therapies after Jan 1, 2013, from the UK Clinical Practice Research Datalink (CPRD). We excluded those who received SGLT2 or DPP-4 inhibitors as first-line treatment or insulin at the same time, had estimated glomerular filtration rate (eGFR) of less than 45 mL/min per 1·73 m², or did not have a valid baseline glycated haemoglobin (HbA_1c) measure (<53 or ≥120 mmol/mol). The primary efficacy outcome was the HbA_1c value reached 6 months after drug initiation, adjusted for baseline HbA_1c. Clinical features associated with differential HbA_1c outcome on the two therapies were identified in CPRD (n=26 877), and replicated in reanalysis of 14 clinical trials (n=10 414). An algorithm to predict individual-level differential HbA_1c outcome on the two therapies was developed in CPRD (derivation; n=14 069) and validated in head-to-head trials (n=2499) and CPRD (independent validation; n=9376). In CPRD, we further explored heterogeneity in 6-month weight change and treatment discontinuation.

FINDINGS

Among 10 253 patients initiating SGLT2 inhibitors and 16 624 patients initiating DPP-4 inhibitors in CPRD, baseline HbA_1c, age, BMI, eGFR, and alanine aminotransferase were associated with differential HbA_1c outcome with SGLT2 inhibitor and DPP-4 inhibitor therapies. The median age of participants was 62·0 years (IQR 55·0-70·0). 10 016 (37·3%) were women and 16 861 (62·7%) were men. An algorithm based on these five features identified a subgroup, representing around four in ten CPRD patients, with a 5 mmol/mol or greater observed benefit with SGLT2 inhibitors in all validation cohorts (CPRD 8·8 mmol/mol [95% CI 7·8-9·8]; CANTATA-D and CANTATA-D2 trials 5·8 mmol/mol [3·9-7·7]; BI1245.20 trial 6·6 mmol/mol [2·2-11·0]). In CPRD, predicted differential HbA_1c response with SGLT2 inhibitor and DPP-4 inhibitor therapies was not associated with weight change. Overall treatment discontinuation within 6 months was similar in patients predicted to have an HbA_1c benefit with SGLT2 inhibitors over DPP-4 inhibitors (median 15·2% [13·2-20·3] vs 14·4% [12·9-16·7]). A smaller subgroup predicted to have greater HbA_1c reduction with DPP-4 inhibitors were twice as likely to discontinue SGLT2 inhibitors than DPP-4 inhibitors (median 26·8% [23·4-31·0] vs 14·8% [12·9-16·8]).

INTERPRETATION

A validated treatment selection algorithm for SGLT2 inhibitor and DPP-4 inhibitor therapies can support decisions on optimal treatment for people with type 2 diabetes.

FUNDING

BHF-Turing Cardiovascular Data Science Award and the UK Medical Research Council.

Warfarin Overdose in an Adolescent Not Dependent on Anticoagulation: Reversal Strategy and Kinetics

INTRODUCTION

Warfarin induces coagulopathy. Guidelines protocolize reversal of supratherapeutic international normalized ratio (INR) in patients dependent on anticoagulation, but practices vary for reversing warfarin-induced coagulopathy after overdose in non-warfarin-dependent patients.

CASE REPORT

This is the report of a 15-year-old female who ingested her father's warfarin (100-200 mg) in a self-harm attempt. At hour 24 post-ingestion, her INR was 2.00 and she was admitted for monitoring. Reversal of coagulopathy was initially deferred pending the INR trend. The INR was 5.10 at hour 60 and 2.5 mg oral vitamin K1 (VK1) was given. At hour 85, the INR peaked at 6.67 and she received a second oral dose of 2.5 mg VK1. On day 8, she was medically cleared with an INR of 1.31. On day 11, she developed lower abdominal pain and diarrhea. Imaging revealed a duodenal hematoma, and symptoms improved spontaneously. She was again medically cleared 13 days post-ingestion. Her serum warfarin concentration peaked at 19 mcg/mL at hour 46. Serial warfarin concentrations were obtained, demonstrating first-order elimination kinetics and a 30-hour half-life.

CONCLUSION

A restrictive approach to coagulopathy reversal in non-warfarin-dependent patients with intentional warfarin overdose may result in worsening coagulopathy, bleeding, and lengthy hospital stay. Given the risk for significant, prolonged coagulopathy, these patients should be treated early with VK1, with subsequent serial INR monitoring and probable additional VK1 dosing. Delayed peak warfarin concentrations support consideration of gastrointestinal decontamination in late presenters.

Genetic variants in transcription factors are associated with the pharmacokinetics and pharmacodynamics of metformin

One-third of type 2 diabetes patients do not respond to metformin. Genetic variants in metformin transporters have been extensively studied as a likely contributor to this high failure rate. Here, we investigate, for the first time, the effect of genetic variants in transcription factors on metformin pharmacokinetics (PK) and response. Overall, 546 patients and healthy volunteers contributed their genome-wide, pharmacokinetic (235 subjects), and HbA1c data (440 patients) for this analysis. Five variants in specificity protein 1 (SP1), a transcription factor that modulates the expression of metformin transporters, were associated with changes in treatment HbA1c (P < 0.01) and metformin secretory clearance (P < 0.05). Population pharmacokinetic modeling further confirmed a 24% reduction in apparent clearance in homozygous carriers of one such variant, rs784888. Genetic variants in other transcription factors, peroxisome proliferator-activated receptor-α and hepatocyte nuclear factor 4-α, were significantly associated with HbA1c change only. Overall, our study highlights the importance of genetic variants in transcription factors as modulators of metformin PK and response.

Personal and professional use of complementary therapies by nurses in NSW, Australia

In this study, we investigate the personal and professional use of complementary therapies by nurses in NSW, Australia. We found that the therapies and products used by respondents were similar to those used by the general population. Seventy-four percent of respondents had used a complementary therapy in the last year and 38% had used them with a patient. In addition, 67% indicated that they would refer to a complementary practitioner. Respondents were also found to have favourable views of complementary therapies with 85% believing they improve quality of life and only 0.8% indicating they serve no purpose. No major differences were seen between respondents residing in the city vs those in regional areas. The data from this study support the view that nurses are high users of complementary therapies and that they may be the health profession most open to the use of complementary therapies as an integral part of normal health care.

High use of complementary therapies in a New South Wales rural community

In this study a postal questionnaire was used to investigate the use of complementary therapies (CT) in a rural region of New South Wales (NSW). A total of 70.3% of respondents reported using one or more therapies with 62.7% having visited a complementary practitioner. Vitamin/mineral therapy (68.7%), chiropractic (26.1%) and massage therapy (25.1%) were the most frequently used therapies, with the most commonly visited practitioners being chiropractors (55.3%) and those trained in vitamin/mineral therapy (47.9%). Of the vitamins, vitamin C and multivitamins were used most often, with garlic and Echinacea being the most used herbal products. The main source of information were friends (64.5%) with most people indicating that CT could improve quality of life and provide relief of symptoms. Results suggest that CT use in rural communities is high and that, in light of these findings, there is a need for training in CT to be included in the undergraduate and continuing education of health professionals. Furthermore, these professionals should be alert to the potential for increased numbers of herb-drug interactions in rural communities.

Complementary therapy use by nursing, pharmacy and biomedical science students

Attitudes towards the use of complementary therapies by students of undergraduate Bachelor of Nursing, Pharmacy and Biomedical Sciences were determined using a self-administered questionnaire. Overall, 78% of students had used a complementary therapy in the past year and 56% had visited a complementary therapy practitioner. The therapies most used were those involving vitamins, mineral and other supplements. Practitioners specializing in this area were the most visited, followed by chiropractors. Commonly used products included vitamin C, multivitamins, B group vitamins, garlic, iron and echinacea. Most students thought complementary therapies improved quality of life, with friends and family providing the main sources of information. There were few differences attributable to course or gender. The results suggest that these students have favorable attitudes towards complementary therapies and that many choose to use them as part of normal health care.

Comparison of glutamate and gamma-aminobutyric acid uptake binding sites in frontal and temporal lobes in schizophrenia

BACKGROUND

Theories of schizophrenia proposing deficiencies of amino acid [glutamate, gamma-aminobutyric acid (GABA)] neurons are in accord with the observed temporal lobe pathology of the disease rather than with the newer theory of glutamate hyperinnervation and hyperfunction in areas of prefrontal cortex. This study addresses the issue by measuring specific uptake sites as indices of glutamatergic and GABAergic neuron densities in frontal and temporal lobes.

METHODS

Frontal cortex (six areas) and temporal lobe (six areas of cortex, amygdala, and hippocampus) were dissected from 19 control autopsy brains and 12 brains from neuroleptic drug-treated schizophrenic patients. Groups had similar ages, postmortem intervals, and storage times. Membranes, prepared from tissue homogenates, were incubated with D-[3H]aspartate to measure neuronal and glial glutamate uptake site binding in 14 areas and with [3H]nipecotic acid to measure neuronal GABA uptake site binding in 11 areas.

RESULTS

Glutamate and GABA uptake sites were not reduced in prefrontal and temporal areas. Instead, we found small increases in glutamate uptake sites in prefrontal areas. Some tendency toward increased GABA uptake sites were not disease-related.

CONCLUSIONS

Our findings concur with other studies that propose locally overabundant glutamate systems in prefrontal cortex in schizophrenia. Losses of amino acid neurons do not accompany the temporal lobe pathology.

Absence of basal ganglia amino acid neuron deficits in schizophrenia in three collections of brains

Amino acid (glutamatergic, GABAergic) neuron deficiency theories of schizophrenia offer plausible explanations of pathogenesis. However, reports of disease-related reductions in amino acid synthesizing enzymes in post-mortem brains are contradictory. We measured neuronal uptake sites for gamma-aminobutyric acid (GABA; [3H]nipecotic acid binding) and nerve terminal/glial uptake sites for L-glutamate (D-[3H aspartate binding) in three independent groups of post-mortem brains from patients with schizophrenia and control subjects. Measurements were also made of the phencyclidine site of the glutamate N-methyl-D-aspartate (NMDA) receptor. Samples from patients showed no reductions in the binding of [3H]nipecotic acid or D-[3H]aspartate in caudate, putamen or globus pallidus. On the contrary, some increased binding of both ligands was observed in patients in many comparisons with controls. There were no clear-cut changes in NMDA receptor binding. The most consistent change in the brain sets was increased [3H]nipecotic acid binding in caudate-putamen. This could be due to neuroleptic treatment. The findings produce no evidence that schizophrenia involves major loss of GABA neuron terminals in the basal ganglia or losses of corticostriatal glutamatergic projections.

A two-process theory of schizophrenia: evidence from studies in post-mortem brain

Glutamate and GABA are the principle neurotransmitters of the cerebral cortex and are known to modulate dopaminergic function. Evidence of structural abnormalities in the cortex raises the possibility that schizophrenia involves disturbances of cortical amino-acid neurotransmission. The psychotomimetic effects of phencyclidine, a glutamate antagonist, have been taken to suggest that schizophrenia involves reduced brain glutamate function. Direct evidence for diminished glutamate function in schizophrenia is lacking. However, in polar temporal cortex and hippocampus we reported evidence of an asymmetric loss of glutamate terminals, and of reduced GABA function, which may be secondary to the loss of glutamatergic input. Glutamate cell body markers are spared in temporal lobe; the neurones which degenerate may originate in frontal cortex. A number of studies have reported increases in markers of glutamatergic cell bodies and terminals in orbital frontal cortex in schizophrenia. These findings are consistent with the presence of an abnormally abundant glutamatergic innervation, which may be the result of an arrest in the normal process of cellular and synaptic elimination which occurs during development. There is evidence that frontal abnormalities in schizophrenia are genetically determined. We suggest that glutamatergic abnormalities in anterior temporal cortex in schizophrenia are the result of the degeneration of fronto-temporal projections. Orbital frontal projections to polar temporal cortex may be prone to degeneration because they arise from an unstable frontal cortical cytoarchitecture which has not completed the normal process of post-natal remodelling. The structural abnormality of the orbital frontal region may confer vulnerability to some intrinsic or extrinsic mechanism, which brings about a progressive degeneration of projections to polar temporal lobe.

Familial and developmental abnormalities of front lobe function and neurochemistry in schizophrenia

structural abnormalities of the cerebral cortex in schizophrenia have been revealed by magnetic resonance imaging, although it is not clear whether these abnormalities are diffuse or local. We predicted that changes in cortical structure would result in abnormalities in biochemical markers for the glutamate system in post-mortem brain, and that the pattern of neurochemical abnormalities would be a clue to the distribution and extent of pathology. A number of studies have now reported increases in biochemical and other markers of glutamatergic cell bodies and terminals in the frontal cortex in schizophrenia. These findings are consistent with the presence of an abnormally abundant glutamatergic innervation, which may be due to an arrest in the normal developmental process of synaptic elimination. In the anterior temporal cortex and hippocampus there is evidence of an asymmetric loss of glutamate terminals, and of reduced GABA function, which may be secondary to the glutamatergic deficit. Glutamate cell body markers are spared in the temporal lobe; we argue that the loss of glutamate uptake sites may reflect the loss of an extrinsic glutamatergic innervation of the polar temporal cortex which arises from the frontal cortex. These fronto-temporal projections may be vulnerable because they arise from a cytoarchitecture which has not been stabilized by remodelling during early post-natal life. There have been several therapeutic studies of drugs with actions on brain glutamate systems. Based on the glutamate deficiency theories, one approach has been to enhance glutamatergic function using agonists of the N-methyl-D-aspartate-linked glycine site. However, there are no clear therapeutic effects, and some studies report aggravation of positive symptoms. This might be expected if, as part of our post-mortem studies suggested, there is excess glutamatergic innervation in some brain regions in schizophrenia. There is neuropsychological evidence that frontal abnormalities in schizophrenia may be genetically determined. We found that first degree relatives of schizophrenic patients were selectively impaired in tests of frontal lobe function, whereas both frontal and temporal function is impaired in patients We conclude that the genetic predisposition to schizophrenia involves impaired frontal lobe function. Psychotic symptoms develop only when a second process results in a loss of fronto-temporal projections and leads to temporal lobe dysfunction.

Autoradiography with [3H]8-OH-DPAT reveals increases in 5-HT(1A) receptors in ventral prefrontal cortex in schizophrenia

We previously reported increased glutamatergic innervation in orbital frontal cortex in schizophrenia. In view of the evidence that one serotonin (5-HT) receptor, the 5-HT(1A) subtype, is associated with cortical glutamatergic neurons, we have used quantitative receptor autoradiography to measure the specific binding of the 5-HT(1A) receptor ligand [3H]8-OH-DPAT (2 nM) in sections of orbital frontal cortex taken from 18 control and 12 schizophrenic postmortem brains. Schizophrenic patients, as compared with controls, had increased 5-HT(1A) receptor binding in the three orbital frontal regions examined. These effects were pronounced in the male subgroup, and were most apparent in the outer cortical laminae. These data are consistent with the hypothesis that schizophrenia is associated with an abnormal glutamatergic afferent innervation of orbital frontal cortex.

Use of MRI for measuring structures in frozen postmortem brain

A method was developed for magnetic resonance imaging (MRI) of human autopsy brains stored long-term at -70 degrees C. Scanning brains at temperatures between -70 and -8 degrees C gave minimal MRI signals consistent with protons having limited freedom of movement at low temperature. Raising brain temperature improved the signal such that scanning at -1 degree C generated images with good in-plane resolution, grey/white matter contrast, and fine detail of cortical sulcal/gyral patterns. To validate the method, volume and area measurements were made using computerized image analysis on stored digital images of 14 brains from adult subjects of both genders and various ages. The data confirmed that brain volume was inversely correlated with age, and female subjects had smaller brains. This is a valuable new method for acquiring morphometric data from previously unscanned pathologic brains that are to be used for neurochemical and molecular investigations.

Effect of smear layer removal on the diffusion permeability of human roots

Ten human maxillary incisors, extracted because of periodontal disease or nonrestorable caries, were obtained and instrumented to a size #70 K-Flex file at the working length using a standard stepback technique. Tritiated water (3H2O) was placed in the root canals and allowed to diffuse to the external surface of the roots until it reached a constant rate. The smear layer in each of the experimental roots was then removed using 0.5 M EDTA followed by 5.25% sodium hypochlorite (NaOCI). The constant rate diffusion of 3H2O was remeasured. The roots were then stored in deionized H2O for 2 months and the constant rate diffusion of 3H2O was remeasured. A statistically significant difference was noted between all three groups. A decrease in the diffusion permeability of the root to 3H2O was noted immediately after smear layer removal and the highest permeability was recorded after storage in the deionized water for 2 months.

The effect of dentin depth on the permeability and ultrastructure of primary molars

The purpose of this study was to measure the permeability of primary molar and permanent premolar dentin at various thicknesses from the pulp and to correlate permeability with the tubule density and diameter of dentin using SEM. The data were examined for statistically significant differences using two-way analysis of variance, multiple comparison Scheffe, and regression analysis. The permeability of all teeth increased with decreasing dentin thickness. The removal of the smear layer resulted in a significant increase in the permeability. However, the permeability of the dentin in premolars was significantly higher than that in the primary molars. The density and diameter of the dentinal tubular in primary molars were lower than the values reported for permanent teeth and may account for the lower permeability of the primary molars.

Effects of aluminum oxalate/glycine pretreatment solutions on dentin permeability

Aluminum oxalate buffered with glycine to pH 0.5-2.5 has been proposed as a dentin pretreatment for the Gluma bonding system. In this experiment, the effects of 1-minute treatments of smear layers with these aluminum oxalates on the permeability of human dentin were determined in vitro. The aluminum oxalate solutions at pH 0.5-1.5 removed most of the original smear layer but occluded the tubules with crystalline deposits which decreased dentin permeability. Those solutions used at pH 2.0 and 2.5 increased dentin permeability. All dentin pretreatments increased dentin permeability when measured after a 24-hour storage period, especially the solutions at pH 2.0 and 2.5. The SEM correlates of these permeability changes indicated that these solutions remove the smear layer but reocclude the tubules with precipitates which are probably different forms of calcium oxalate, aluminum phosphate and calcium phosphates.

Regionally selective deficits in uptake sites for glutamate and gamma-aminobutyric acid in the basal ganglia in schizophrenia

In a post-mortem study of schizophrenic and control subjects, the sodium-dependent binding of D-[3H]aspartate and [3H]nipecotic acid were used to investigate uptake sites of glutamate and gamma-aminobutyric acid (GABA), respectively, in subcortical brain regions. Binding to the glutamate uptake site was substantially reduced in both the putamen and lateral pallidum of the schizophrenic subjects. Binding to the GABA uptake site was substantially reduced in the putamen; smaller reductions were apparent in the caudate nucleus and lateral pallidum. The results suggest that glutamatergic and GABAergic mechanisms in the basal ganglia are abnormal in schizophrenia. These abnormalities could be relevant to the development of psychosis but could also relate to the spectrum of mild motor disturbances often described in the disease.

Age-related changes in binding to excitatory amino acid uptake site in temporal cortex of human brain

The binding of D-[3H]aspartate to the specific uptake site for the excitatory amino acids glutamate and aspartate was measured in homogenates of temporal lobe cortex taken at postmortem from 76 human infant and adult brains. Binding levels were very low in brains of preterm and term infants but increased rapidly during the first 20 postnatal weeks to reach levels which exceeded those in adult brains. Linear regression analysis which compared the amount of D-[3H]aspartate binding with the age of the infant, showed a positive correlation up to 25 postnatal weeks. Saturation analysis showed that the maximum number of D-[3H]aspartate binding sites (Bmax) in temporal cortex from infants aged 20 postnatal weeks was 3 times greater than the number of sites in adult brain. The findings show that the number of excitatory amino acid uptake sites, which may be associated in part with presynaptic terminals, increase in number rapidly after birth. Furthermore, the data may indicate that a slow regression of excitatory amino acid terminals occurs during the later stages of brain development.

Dentin permeability: sealing the dentin in crown preparations

Provisional restorations of full crown preparations may permit more microleakage of bacteria and their products than the final castings do. However, most investigations of the sealing qualities of cemented castings have reported that they too permit dye leakage. One approach to the problem is to seal the dentin with dentin bonding agents at the completion of the crown preparation. This study evaluated the ability of six different dentin bonding agents to seal the dentin of crown preparations of human teeth in vitro using two independent techniques. The first technique quantitated fluid filtration across dentin before and after treatment with dentin bonding agents at one hour, one day, one week, and one month and after thermocycling. The second method measured silver nitrate penetration of the thin veneers of dentin bonding agents into the dentin. Both methods correlated well with each other. The best seals were obtained with Prisma Universal Bond 2 or Superbond powder plus liquid. The worst seals were found using Gluma and Superbond liquid only. Clearfil PhotoBond, Amalgambond, and Scotchbond 2 gave intermediate results. Although the dentin bonding agents tend to accumulate on chamfers, thereby increasing their thickness to 200-300 microns, the method looks promising as a simple way to protect the pulp from the consequences of microleakage.

Alterations in phencyclidine and sigma binding sites in schizophrenic brains. Effects of disease process and neuroleptic medication

The specific binding of [3H]TCP and [3H](+)3-PPP, radioligands which respectively label PCP-NMDA and sigma binding sites was measured in tissue homogenates prepared from dissected areas of control and schizophrenic postmortem brains. [3H]TCP binding was bilaterally increased in orbital frontal cortex (Brodmann area 11) of schizophrenic brains. This finding may be due to an increased glutamatergic innervation of orbital frontal cortex since it parallels our findings of increased [3H]kainate and [3H]D-aspartate binding in this area. In contrast, [3H](+)3-PPP binding was reduced in each of the four brain regions examined. The reductions were greatest in brains from the schizophrenic subjects receiving neuroleptics at the time of death. Neuroleptics remaining in the brains of these subjects may compete in vitro with [3H](+)3-PPP for binding to the sigma site.

Analysis of laminar distribution of kappa opiate receptor in human cortex: comparison between schizophrenia and normal

Quantitative receptor autoradiography using the ligand [3H]U 69593 and tritium sensitive film was used to visualize the kappa subtype of opiate receptor in sections from 4 normal human postmortem brains. Data obtained from cortical scans, which measured receptor densities across the left and right parahippocampal gyri, were subject to Fourier analysis. This revealed that the kappa receptor distribution was described by a curve having significant first and second component harmonics. This analysis method can be used to describe a binding pattern mathematically, thus enabling a comparison to be made between normal and diseased brains. The same analysis was applied to [3H]U 69593 autoradiograms prepared from sections of 4 schizophrenic postmortem brains. The kappa receptor distribution in the schizophrenic group not only failed to produce the same pattern as the controls, but also showed no consistent pattern within the group. The method described can be used to investigate alterations in receptor distribution which occur in neuropsychiatric diseases involving neuronal dysplasia or atrophy.

Fluid and protein flux across the pulpodentine complex of the dog in vivo

Dentinal fluid volume and protein concentrations were measured from cavities prepared in the dentine of dog molars. Fluid was collected under spontaneous conditions, during the application of negative pressures, and during a recovery period. The data allowed the calculation of dentine permeability as hydraulic conductances, fluid flux, protein flux, reflection coefficients and pulpal tissue pressures. In general, the protein concentration of dentinal fluid was about one-fifth that of plasma during spontaneous conditions and it fell when fluid flux was increased by the application of external negative pressures. The collection and analysis of dentinal fluid looks promising as a non-invasive method of assessing the state of the underlying pulp.

Identification and distribution of 5-HT3 recognition sites within the human brainstem

The present studies demonstrate the presence of specific [3H]GR65630 binding sites within the human brainstem using the techniques of in vitro receptor autoradiography and ligand binding to homogenates. Autoradiography revealed the greatest accumulation of specific binding in the area postrema and subpostrema (AP/ASP). A lower level of specific binding was identified in the nucleus tractus solitarius (excluding area subpostrema). No specific binding was evident in the remainder of the hindbrain at this level. Discrete dissection followed by ligand binding to homogenates revealed that the specific binding of [3H]GR65630 (defined by the presence of 30 microM metoclopramide) was differentially distributed with highest levels in the AP/ASP (112.1 fmol/mg protein) and lower levels in the dorsal vagal complex (nucleus tractus solitarius--excluding the area subpostrema--dorsal motor nucleus of the vagus and hypoglossal nucleus) (DVC) and olivary nucleus (ON) (22.9 and 3.9 fmol/mg, respectively). No specific binding was detectable in the reticular formation (RF) located ventral to the dorsal vagal complex. The specific [3H]GR65630 binding site was pharmacologically similar to the 5-HT3 receptor since the potent and selective 5-HT3 receptor antagonists ICS 205-930 and zacopride (100 nM) and the agonist 5-HT (10 microM) inhibited binding to the same extent as metoclopramide in each of the individual areas (90, 60 and 20% in the AP/ASP, DVC and ON, respectively). The 5-HT1-like and 5-HT2 receptor antagonist methysergide (10 microM) failed to compete for the binding site. 5-HT3 receptor recognition sites within the AP/ASP and the DVC may be functionally involved in the ability of 5-HT3 receptor antagonists to control emesis.

Reduced GABA uptake sites in the temporal lobe in schizophrenia

The binding of [3H]nipecotic acid, a ligand for labelling GABA uptake sites in brain, was measured in left and right frontal cortex, polar temporal cortex, hippocampus and amygdala from control and schizophrenic postmortem brains. In schizophrenic brains, single concentration [3H]nipecotic acid binding was reduced bilaterally in amygdala and hippocampus and on the left side only in polar temporal cortex. These data suggest that GABA neurones are involved in the cerebral atrophy of schizophrenia and, in agreement with other studies, that this process is most pronounced in left temporal cortex.

Frontal cortical and left temporal glutamatergic dysfunction in schizophrenia

Glutamatergic mechanisms have been investigated in postmortem brain samples from schizophrenics and controls. D-[3H]Aspartate binding to glutamate uptake sites was used as a marker for glutamatergic neurones, and [3H]kainate binding for a subclass of postsynaptic glutamate receptors. There were highly significant increases in the binding of both ligands to membranes from orbital frontal cortex on both the left and right sides of schizophrenic brains. The changes are unlikely to be due to antemortem neuroleptic drug treatment, because no similar changes were recorded in other areas. A predicted left-sided reduction in D-[3H]aspartate binding was refuted at 5% probability, but not at 10%. Previously reported high concentrations of dopamine in left amygdala were strongly associated with low concentrations of D-[3H]aspartate binding in left polar temporal cortex in the schizophrenics. The findings are compatible with an overabundant glutamatergic innervation of orbital frontal cortex in schizophrenia. The results also suggest that schizophrenia may involve left-sided abnormalities in the relationship between temporal glutamatergic and dopaminergic projections to amygdala.

Reduced D-[3H]aspartate binding in Down's syndrome brains

The binding of D-[3H]aspartate to glutamate uptake sites was measured in post-mortem brains from subjects with Down's syndrome (DS) and age-matched controls. DS brains had substantially reduced D-[3H]aspartate binding in the frontal and temporal cortex, hippocampus and caudate nucleus. There was no correlation between the numbers of Alzheimer-like plaques and tangles or clinically-assessed dementia and D-[3H]aspartate binding in DS brains. The binding of [3H]N-(1-[2-thienyl]cyclohexyl)piperidine ([3H]TCP) to postsynaptic N-methyl-D-aspartate sites was normal in DS brains. This study suggests that the reduction in glutamate uptake sites in DS is more substantial and widespread than in Alzheimer's disease.

Regional changes in [3H]D-aspartate and [3H]TCP binding sites in Alzheimer's disease brains

The specific binding of [3H]D-aspartate, a marker for the presynaptic glutamate uptake site, and [3H]N-(1-[2-Thienyl]cyclohexyl)-piperidine [( 3H]TCP), a high affinity ligand for the N-methyl-D-aspartate (NMDA)-associated phencyclidine binding site, was measured in homogenates of brain from normal subjects and from subjects with neuropathologically confirmed Alzheimer's disease. Alzheimer's disease was associated with a reduction in [3H]D-aspartate binding density in temporal cortex and caudate nucleus. By contrast, a reduction in the receptor density for [3H]TCP binding was only recorded in the frontal cortex. Thus, glutamate-containing nerve terminals are severely reduced in Alzheimer's disease, whilst the postsynaptic NMDA-phencyclidine receptor complex is much less affected. These findings have implications for theories of glutamate neurotoxicity in Alzheimer's disease.

Loss of cortical GABA uptake sites in Alzheimer's disease

[3H]Nipecotic acid bound to membranes of human brain in a saturable, reversible manner which was totally dependent on the presence of sodium ions. The potencies of compounds in inhibiting the specific binding of [3H]nipecotic acid were closely correlated with their potencies in inhibiting the neuronal uptake of [3H]GABA. Compounds selective for GABA receptors were inactive. [3H]Nipecotic acid appears to label neuronal high affinity GABA uptake sites. The binding of [3H]nipecotic acid was substantially reduced in the temporal cortex of brains from subjects with Alzheimer-type dementia, but not in other brain regions. It is concluded that some loss of GABA terminals occurs in this disease.

Hypophysectomy may non-selectively alter pharmacokinetic parameters to enhance the ability of haloperidol to increase striatal dopamine receptor density in the rat

We have investigated the effect of a range of doses of haloperidol (0.625-5.0 mg/kg/day) or saline, administered for 14 days, followed by a 3 day drug washout period, to sham operated or hypophysectomized rats. Haloperidol increased the number of specific striatal 3H-spiperone binding sites (Bmax) in sham-operated animals at doses of 2.5 and 5.0 mg/kg/day, and in hypophysectomized animals at all doses used (0.625-5.0 mg/kg/day). The inhibition of locomotor activity produced by haloperidol was greater in hypophysectomized than sham-operated animals. Plasma and striatal haloperidol levels after equivalent doses were greater in hypophysectomized than in sham-operated animals. We conclude that hypophysectomy may enhance the ability of haloperidol to induce striatal dopamine receptor supersensitivity in the rat, and that this may be due to differences in the pharmacokinetic handling of haloperidol between sham-operated and hypophysectomized animals.

Hyperprolactinaemia does not alter specific striatal 3H-spiperone binding in the rat

We have investigated the effect of single injections (1 mg/animal i.v.) of prolactin or vehicle, and repeated depot (0.125-1.0 mg/animal/day) or bolus (1.0 mg/animal/day) administration of prolactin or vehicle for 6 days to adult male rats. The density (Bmax) and affinity (Kd) of specific striatal [3H]spiperone binding was not changed by any of the prolactin treatment schedules used. Allogeneic transplants of anterior pituitary glands resulted in an increased concentration of circulating prolactin but did not alter the density or affinity of specific striatal [3H]spiperone binding in male rats, measured 2 weeks following the operation. Prolactin did not displace specific striatal [3H]spiperone binding when incorporated in vitro. Any effect of prolactin on striatal dopamine receptor function appears to be exerted only by high, non-physiological concentrations, and such effects are difficult to reproduce.