Identification and characterisation of angiotensin II receptor subtypes in human brain

Autoradiographic and homogenate binding studies using the radioligand, [125I]angiotensin II, identified a heterogeneous distribution of specific binding sites (defined by angiotensin II, 1.0 microM) throughout the human forebrain. Highest AT receptor densities were detected in the paraventricular nucleus, median eminence, substantia nigra, putamen and caudate nucleus (2.4, 1.2, 1.0, 0.30 and 0.24 fmol/mg tissue equivalent, respectively). The AT1 receptor antagonist, losartan (1.0 microM) competed for the majority of the specific binding. [125I]Angiotensin II-specific binding (although not consistently above non-specific binding levels) was also detected in various other brain regions (e.g. amygdala, entorhinal cortex, frontal cortex, hippocampus, inferior colliculus, nucleus accumbens, parietal cortex, periaquaductal grey, superior colliculus, striate cortex, temporal cortex, thalamus). In the presence of losartan (1.0 microM), angiotensin II, saralasin, losartan and PD123177 competed for [125I]angiotensin II binding to membranes prepared from the cerebellum or substantia nigra with a rank order of affinity; angiotensin II = saralasin > PD123177 > losartan. In the presence of PD123177 (1.0 microM), the rank order of affinity of losartan and PD123177 was reversed. These studies indicate the presence of both AT1 and AT2 receptor subtypes within various regions of the human forebrain.

Scombroid poisoning. Case series of 10 incidents involving 22 patients

Scombroid poisoning is a form of ichthyosarcotoxism caused by the consumption of 'spoiled' fish of the dark meat varieties. It can be considered a mild-to-moderate form of 'food poisoning' and it occurs world-wide. Ten incidents, involving 22 patients, were reported to Tygerberg Hospital Pharmacology and Toxicology Consultation Centre in the first quarter of 1990. Cape yellowtail (Seriola lalandii) was involved in all the cases. The presenting symptoms and signs (in order of frequency) were: skin rash, diarrhoea, palpitations, headache, nausea and abdominal cramps, paraesthesia, an unusual taste sensation and breathing difficulties. The patients responded well to anti-histamines and, in most, the condition resolved within 12-24 hours. Although histamine plays an important role in the pathogenesis of scombroid poisoning, the exact mechanism is still unresolved. The condition should be recognised and not confused with a true seafood allergy. Health workers are urged to alert the authorities when outbreaks of suspected cases of scombroid poisoning are encountered in order to establish the possible cause and to prevent further cases.

Pharmacological comparison of the rat and guinea-pig cortical high affinity 5-hydroxytryptamine uptake system

The pharmacological characteristics of the high affinity [3H]5-hydroxytryptamine ([3H]5-HT) uptake system were investigated in the cerebral cortex of the rat and guinea-pig. In crude cortical synaptosomal preparations from the rat and guinea-pig, [3H]5-HT accumulated with high affinity (Km, 72 +/- 12 and 57 +/- 14 nM for rat and guinea-pig cortical synaptosomal preparation, respectively, mean +/- SEM, N = 5) and with a comparable maximum activity (Vmax, 1.22 +/- 0.21 and 0.90 +/- 0.19 pmol/min/mg protein for rat and guinea-pig cortical synaptosomal preparation, respectively, mean +/- SEM, N = 5). Competition studies employing a range of structurally diverse competing compounds showed that the [3H]5-HT uptake was pharmacologically similar in both preparations. However, citalopram possessed approximately 10-fold weaker affinity to prevent [3H]5-HT uptake in the guinea-pig preparation when compared to the rat and all of the tricyclic antidepressants assessed in the present studies (amitriptyline, nortriptyline, desipramine and imipramine) displayed higher affinity in the guinea-pig preparation when compared to the rat. It is concluded that the high affinity 5-HT uptake systems in the rat and guinea-pig cortex are similar but may not be identical.

Behavioural pharmacology of 5-HT3 receptor ligands

Extensive studies have ascribed a role for the central 5-HT3 receptor in the modulation of behaviour. Much of the work stems from the actions of potent and selective 5-HT3 receptor antagonists; these agents reduce mesolimbic dopamine initiated hyperactivity, release suppressed behaviour, reduce the reinforcing properties and withdrawal symptoms of drugs of abuse, enhance cognitive performance and modulate appetite. This article reviews the preclinical and clinical evidence implicating the 5-HT3 receptor in these indications and discusses the potential neurochemical mechanisms underlying the behavioural changes.

Pharmacological comparison of the sigma recognition site labelled by [3H]haloperidol in human and rat cerebellum

The radioligand binding characteristics of [3H]haloperidol (in the presence of spiperone, 25 nmolL-1) were investigated in rat and human cerebellar membranes. In both rat and human cerebellar membrane preparations saturation studies with [3H]haloperidol (non-specific binding defined by pentazocine, 10 mumolsL-1) demonstrated high affinity saturable specific binding to a homogenous population of binding sites (rat, Bmax 6693 +/- 1242 fmol mg-1 protein, pKD 8.33 +/- 0.08; human, Bmax 2550 +/- 437 fmol mg-1 protein, pKD 8.59 +/- 0.11; mean +/- SEM, n = 3-6). Competition studies employing a wide range of structurally diverse competing compounds displayed that the [3H]haloperidol binding site was pharmacologically similar in both preparations and comparable to sigma recognition sites previously identified in various tissues originating from different species. In addition, with reference to the potential subtypes of sigma recognition sites, the labelling of these sites by low nanomolar concentrations of [3H]haloperidol provides evidence that they belong to the sigma-1 recognition site subtype. The present findings suggest that the pharmacology of the rat and human cerebellar sigma recognition site are directly comparable and provides further supporting evidence towards the use of [3H]haloperidol radioligand binding studies in the rat to detect sigma receptor ligands with potential therapeutic activity.

Agonist interactions with 5-HT3 receptor recognition sites in the rat entorhinal cortex labelled by structurally diverse radioligands

1. The pharmacological properties of 5-HT3 receptor recognition sites labelled with [3H]-(S)-zacopride, [3H]-LY278,584, [3H]-granisetron and [3H]-GR67330 in membranes prepared from the rat entorhinal cortex were investigated to assess the presence of cooperativity within the 5-HT3 receptor complex. 2. In rat entorhinal cortex homogenates, [3H]-(S)-zacopride, [3H]-LY278,584, [3H]-granisetron and [3H]-GR67330 labelled homogeneous densities of recognition sites (defined by granisetron, 10 microM) with high affinity (Bmax = 75 +/- 5, 53 +/- 5, 92 +/- 6 and 79 +/- 6 fmol mg-1 protein, respectively; pKd = 9.41 +/- 0.04, 8.69 +/- 0.14, 8.81 +/- 0.06 and 10.14 +/- 0.04 for [3H]-(S)-zacopride, [3H]-LY278,584, [3H]-granisetron and [3H]-GR67330, respectively, n = 3-8). 3. Quipazine and granisetron competed for the binding of each of the radioligands in the rat entorhinal cortex preparation at low nanomolar concentrations (pIC50; quipazine 9.38-8.51, granisetron 8.62-8.03), whilst the agonists, 5-hydroxytryptamine (5-HT), phenylbiguanide (PBG) and 2-methyl-5-HT competed at sub-micromolar concentrations (pIC50; 5-HT 7.16-6.42, PBG 7.52-6.40, 2-methyl-5-HT 7.38-6.09). 4. Competition curves generated with increasing concentrations of quipazine, PBG, 5-HT and 2-methyl-5-HT displayed Hill coefficients greater than unity when the 5-HT3 receptor recognition sites in the entorhinal cortex preparation were labelled with [3H]-LY278,584, [3H]-granisetron and [3H]-GR67330. These competing compounds displayed Hill coefficients of around unity when the sites were labelled with [3H]-(S)-zacopride. Competition for the binding of [3H]-(S)-zacopride, [3H]-LY278,584, [3H]-granisetron and [3H]-GR67330 by granisetron generated Hill coefficients around unity.5. The nature of the interaction of competing compounds (quipazine, granisetron, PBG, 5-HT, 2-methyl-5-HT) for the [3H]-(S)-zacopride binding site in the rat entorhinal cortex preparation was not altered by the removal of the Krebs ions or the addition of the monoamine oxidase inhibitor, pargyline, to the HEPES/Krebs buffer.6. In conclusion, the present studies provide further evidence towards the presence of cooperativity within the 5-HT3 receptor macromolecule and indicate that either [3H]-(S)-zacopride labels a different site on the receptor complex from [3H]-LY278,584, [3H]-granisetron or [3H]-GR67330, or it binds in such a manner as to prevent the conformatory change in the receptor protein responsible for the cooperative binding of agonists (and quipazine).

Angiotensin-converting enzyme inhibition, angiotensin, and cognition

In these studies, we have investigated possible cognition-enhancing effects of angiotensin-converting enzyme (ACE) inhibition, and putative neurochemical correlates for these actions. In a mouse habituation model, ACE inhibitors improved basal performance and antagonized scopolamine-induced deficits. The performance of aged mice and those with lesions of the nucleus basalis was also improved. ACE inhibition also improved scopolamine-impaired performance of rats in a swim-maze model. Neurochemical studies showed that a low dose (10 micrograms/kg i.p.) of ceranapril caused significant alterations in ex vivo rat brain catecholamine levels in the nucleus accumbens, amygdala, and septum. In further studies, angiotensin II (Ang II) was shown to decrease potassium-stimulated [3H] acetylcholine release from slices of rat entorhinal and human temporal cortex, an effect that could be antagonized by the angiotensin receptor antagonist [1-sar,8-thr]Ang II. It is concluded that ACE inhibition can improve both basal and impaired performance in animal models of learning, and that this improvement may be in part a consequence of the removal by ACE inhibition of an inhibitory tone on central acetylcholine release, and/or an effect on central catecholaminergic function.

Identification of angiotensin II receptor subtypes in human brain

The present study assessed the binding characteristics of [125I]angiotensin II to slices of human cerebellum adhered to glass slides using quantitative receptor autoradiography. Specific [125I]angiotensin II binding, defined by the inclusion of unlabelled angiotensin II (1.0 microM), was detected in the molecular layer of the cerebellum (0.09 +/- 0.02 fmol/mg tissue equivalent, mean +/- s.e.m., n = 3). The angiotensin II-2 receptor subtype selective ligand, PD123177, competed for approximately 65% of the specific binding in the molecular layer whilst the remainder of the specific binding was displaced by the angiotensin II-1 receptor subtype selective ligand, DuP753. It is concluded that angiotensin II receptor subtypes exist in human brain tissue and provide potential therapeutic sites of action.

The 1989 revision of the U.S. Standard Certificates and Reports

This report examines the procedures followed in the 1989 revision of the U.S. Standard Certificates of Live Birth and Death; License and Certificate of Marriage; Certificate of Divorce, Dissolution of Marriage, or Annulment; and Reports of Fetal Death and Induced Termination of Pregnancy. It outlines the history and basic principles of the standard certificates and reports and describes the principal additions, modifications, and deletions of items. In addition, it discusses changes in the format of the standard certificates and reports as well as the implementation of the new certificates and reporting forms.

Neurochemical consequences following injection of the substance P analogue, DiMe-C7, into the rat ventral tegmental area

The effect on forebrain catecholamine- and indoleamine-related neurochemical levels was investigated following stimulation of the rat ventral tegmental area with the substance P analogue, DiMe-C7. DiMe-C7 (6.0 micrograms) induced a marked hyperactivity in rats with maximal response between 15 and 30 min following the injection. Fifteen min following the DiMe-C7 injection levels of dopamine and/or its metabolites (3,4-dihydroxyphenylacetic acid, homovanillic acid) were significantly increased in the nucleus accumbens, amygdala, entorhinal cortex and striatum relative to vehicle-injected animals. Although the increase in dopamine metabolism in the nucleus accumbens is consistent with the behavioural hyperactivity, it is concluded that other forebrain nuclei may also be involved in the mediation of the hyperactivity response.

The differential activities of R (+)- and S(-)-zacopride as 5-HT3 receptor antagonists

R(+)- and S(-)-zacopride were assessed as potential 5-HT3 receptor antagonists in behavioural and biochemical tests. The S(-)isomer was more potent than the R(+)isomer to antagonise the hyperactivity induced by the injection of amphetamine or the infusion of dopamine into the nucleus accumbens in the rat. In contrast, the R(+)isomer was more potent to reduce the aversive behaviour of mice to a brightly illuminated environment and in a marmoset human threat test, to facilitate social interaction in rats, to increase performance in a mouse habituation test and prevent a scopolamine-induced impairment, and to antagonise the inhibitory effect of 2-methyl-5-hydroxytryptamine to reduce [3H]acetylcholine release in slices of the rat entorhinal cortex. In binding assays, [3H]S(-)-zacopride and [3H]R(+)-zacopride labelled homogenous populations of high-affinity binding sites in the rat entorhinal cortex, R(+)-zacopride compete for a further 10 to 20% of the binding of [3H]R(+)/S(-)-zacopride or [3H]R(+)-zacopride in excess of that competed for by (S)(-)-zacopride. It is concluded that both isomers of zacopride have potent but different pharmacological activities, with the possibility of different recognition sites to mediate their effects.

Aspects of work of women medical doctors in the Cape Province. A preliminary investigation

Women form an increasingly important part of the medically trained workforce in South Africa. However, little is known about the professional issues and work-related problems affecting them. A survey was undertaken of all registered female medical practitioners practising in the Cape Province in order: (i) to ascertain their current pattern of work; (ii) to identify factors that influence this work pattern; and (iii) to identify factors that would help these women stay in the profession or re-enter it more easily after an absence. A questionnaire on biographical information, qualifications, employment (full-time/part-time), capacity in which employed, ease of keeping up to date, information about those participants not at present practising medicine, and changes in working conditions that would make it easier for those not practising to return to medical practice was posted to all eligible doctors. Of 774 copies posted, 480 were returned (62%). At the time of the survey, 90% of the respondents under 65 years of age were employed. The reason most often cited as to why respondents stopped practising was family commitments. The availability of part-time posts was most often mentioned as a working condition that would make return to work easier. Twice as many respondents found it difficult or very difficult to keep up with current practices than those who found it easy or very easy. There were 196 women (41%) who had been unemployed for more than 6 months; 44 ascribed this to the unavailability of posts. Women doctors need more flexible training schedules and conditions of employment. Part-time training and part-time career options should be extended.(ABSTRACT TRUNCATED AT 250 WORDS)

Characterisation and autoradiographic localisation of 5-HT3 receptor recognition sites identified with [3H]-(S)-zacopride in the forebrain of the rat

The pharmacological characterisation and topographical distribution of [3H]-(S)-zacopride recognition sites in the forebrain of the rat was studied using homogenate and autoradiographic radioligand binding techniques. [3H]-(S)-Zacopride labelled a single, saturable, specific binding site (defined by 10.0 microM granisetron) in homogenates prepared from the entorhinal cortex of the rat (pKD = 9.51 +/- 0.08; Bmax = 104 +/- 7 fmol mg-1 protein; mean +/- SEM, n = 8). Pharmacological characterisation of the recognition site, within the entorhinal cortex, suggested that [3H]-(S)-zacopride selectively labelled the recognition site of the 5-HT3 receptor. Specific binding of [3H]-(S)-zacopride (defined by 1.0 microM granisetron) was differentially distributed throughout the forebrain of the rat; highest densities were located within sub-nuclei of the amygdala (cortical amygdaloid nucleus, amygdalohippocampal area, posterior medial cortical amygdaloid nucleus, posterior lateral amygdaloid nucleus), cortical areas (primary olfactory cortex, entorhinal cortex) and hippocampus. Non-specific binding was distributed homogeneously, although lower in myelinated structures. It is concluded that [3H]-(S)-zacopride selectively labels 5-HT3 receptor recognition sites within the forebrain of the rat; the topographical distribution of these sites, within the limbic nuclei, is consistent with the behavioural actions in animal models of the selective 5-HT3 receptor antagonists.

Angiotensin II inhibits cortical cholinergic function: implications for cognition

In the present studies we have shown that angiotensin II (AT II), in a concentration-dependent manner in rat tissue (10(-9)-10(-5) M) or at a single concentration in human tissue (10(-6) M), can inhibit potassium-stimulated release of [3H]acetylcholine ( [3H]Ach) from slices of rat entorhinal cortex and human temporal cortex preloaded with [3H]choline for the biochemical analyses. The inhibitory effects of AT II (10(-6) M) were antagonised by the specific AT II receptor antagonist [1-sarcosine, 8-threonine]AT II in a concentration-dependent manner in rat tissue (10(-11)-10(-8) M) and at the single concentration employed in the human studies (10(-7) M). Also demonstrated were other components of the angiotensin system in the human temporal cortex; ACE activity was present (1.03 nmol min-1 mg-1 protein), as were AT II recognition sites (Bmax = 8.6 fmol mg-1 protein). It is hypothesised that the potential cognitive enhancing properties of ACE inhibitors may reflect their action to prevent the formation of AT II and so remove an inhibitory modulator of cholinergic function.

Topographical distribution of 5-HT3 receptor recognition sites in the ferret brain stem

The distribution of [3H]zacopride (1.0 nM) to putative 5-HT3 receptor recognition sites in the ferret hindbrain was assessed using autoradiography. Specific binding (defined by the inclusion of granisetron, 1.0 microM) was heterogeneously distributed with highest density within the dorsal vagal complex (area postrema, nucleus tractus solitarius and dorsal motor nucleus of the vagus nerve). Lower densities were detected in the spinal trigeminal nerve complex whilst no other significant specific binding was detected ventral to the dorsal vagal complex. The location of 5-HT3 receptor recognition sites within the dorsal vagal complex may provide sites of action for zacopride and other 5-HT3 receptor antagonists to inhibit the emesis induced by cancer chemotherapeutic agents and x-radiation.

The UK Children's Cancer Study Group: testicular malignant germ cell tumours 1979-1988

The United Kingdom Children's Cancer Study Group (UKCCSG) malignant germ cell tumour (MGCT) studies were undertaken to establish standard protocols of investigation, staging, and treatment. The efficacy of new drug combinations and the value of serial measurements of serum alphafetoprotein (AFP) and human chorionic gonadotrophin (HCG) were evaluated. Following the initial surgery, staging of the tumour was performed using a variety of investigative approaches. In stage 1 testicular tumours, orchidectomy was performed. In more advanced tumours, and in stage 1 tumours that failed to show the expected decline in AFP or recurred, chemotherapy was used after appropriate surgery. Seventy-three boys, under 14 years of age, with testicular MGCTs have been entered into the UKCCSG studies since 1979. Serum AFP was measured preoperatively, or within 2 weeks of operation, in 70 boys. It was unequivocally elevated in 69. Monitoring by serial AFP measurement proved valuable in assessing response and in early detection of recurrence. HCG was measured in 46 boys, and was raised in three. Sixty-seven (91%) of the tumours were yolk sac (Teilum) tumours, four were immature teratoma, and two were mixed MGCTs. The only non-AFP producing tumour was an immature polydermal teratoma in a 1-year-old boy. Serum HCG was raised in three boys with yolk sac tumours, one with a mixed teratoma, and one 14-year-old boy who had a mixed MGCT. The results of treatment were assessed on April 1, 1989 (median time from diagnosis, 3 years 4 months). Seventy-one boys were alive, 48 of whom had been cured by orchidectomy alone. The remaining 25 patients received chemotherapy.(ABSTRACT TRUNCATED AT 250 WORDS)

The actions of (-)N-n-propylnorapomorphine and selective dopamine D1 and D2 receptor agonists to modify the release of [3H]dopamine from the rat nucleus accumbens

The ability of (-)N-n-propylnorapomorphine and selective D1 and D2 dopamine receptor agonists and antagonists to modify the release of [3H]dopamine, induced by potassium from the nucleus accumbens, was studied using an in vitro superfusion technique. (-)N-n-Propylnorapomorphine, in picomolar concentrations, inhibited the release of [3H]dopamine, the inhibition being antagonised by fluphenazine and the selective D2 receptor antagonist sulpiride; the selective D1 receptor antagonist SCH 23390 was ineffective. The selective D1 receptor agonist SKF 38393 and the selective D2 agonist quinpirole, both inhibited the potassium-induced release of [3H]dopamine; no synergistic effect was observed to a combined treatment with SKF 38393 and quinpirole. The effects of SKF 38393 and quinpirole were selectively antagonised by SCH 23390 and sulpiride, respectively, although both antagonists failed to modify the release of [3H]dopamine when administered alone. Receptor antagonists for other transmitter sites, e.g. noradrenaline, 5-hydroxytryptamine and acetylcholine, failed to modify potassium-induced release of [3H]dopamine, when administered alone or to prevent the inhibition of the release caused by (-)N-n-propylnorapomorphine. It is concluded that the action of dopamine agonists on both dopamine D1 and D2 receptors in the nucleus accumbens can reduce the release of [3H]dopamine in the in vitro system. Comparable actions in vivo may contribute to the ability of dopamine agonists to moderate locomotor responding.

The effects of ondansetron, a 5-HT3 receptor antagonist, on cognition in rodents and primates

The selective 5-HT3 receptor antagonist, onansetron, has been assessed in three tests of cognition in the mouse, rat and marmoset. In a habituation test in the mouse, ondansetron facilitated performance in young adult and aged animals, and inhibited an impairment in habituation induced by scopolamine, electrolesions or ibotenic acid lesions of the nucleus basalis magnocellularis. Arecoline failed to improve basal performance in young adult mice but inhibited the impairment caused by scopolamine and lesions of the nucleus basalis magnocellularis. In the T-maze reinforced alternation task in rats, ondansetron and arecoline antagonised a scopolamine-induced impairment. In an object discrimination and reversal learning task in the marmoset, assessed using a Wisconsin General Test Apparatus, ondansetron improved performance in a reversal learning task. We conclude that ondansetron potently improves basal performance in rodent and primate tests of cognition and inhibits the impairments in performance caused by cholinergic deficits.

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.

Biochemical models for cognition enhancers

Although the etiology of Alzheimer's disease includes a wide range of dysfunction, the most essential dysfunction is probably in the mesolimbic acetylcholine (ACh) system. Three novel approaches to modulating ACh function were considered, somatostatin, serotonin (5-HT) and modulation of cortical ACh tone through angiotension II. Concerning somatostatin there is no correlation between the decrease in somatostatin binding sites in brain and choline-acetyl-transferase activity suggesting that modulating somatostatin is not a promising therapeutic approach to Alzheimer's disease. With 5-HT, evidence suggests that 5-HT receptors (in particular 5HT1A) are located on cholinergic projections and behavioral evidence suggests 5-HT modulation of memory function. This area could therefore develop rapidly, particularly in view of the recent discovery of numerous subtypes of 5-HT receptor. Concerning the third approach, recent evidence has shown that angiotensin converting enzyme (ACE) inhibitors can facilitate ACh release and also possess cognition enhancing activity. The possibility was also evoked that drugs such as piracetam might prevent age-related decreases in ACh receptor density. Concerning trophic factors (e.g. glutamate-induced neuronal sprouting) most approaches have induced amnesia but the search for partial glutamate agonists may have potential. Finally, a neuronal transplant approach was considered but was thought to be very difficult in view of the global brain shrinkage associated with aging and Alzheimer's disease.

Angiotensin II inhibits acetylcholine release from human temporal cortex: implications for cognition

Angiotensin II was shown to inhibit potassium-stimulated release of [3H]acetylcholine from slices of fresh human temporal cortex, obtained at surgery, and subsequently loaded with [3H]choline for the biochemical analyses. The inhibitory effect of angiotensin II was antagonised by the specific angiotensin II receptor antagonist [1-sarcosine, 8-threonine]-angiotensin II. High affinity binding sites were identified in the human temporal cortex using [125I]angiotensin II, and may provide the functional site of action of angiotensin II to modify [3H]acetylcholine release.

Identification and characterisation of 5-hydroxytryptamine 3 recognition sites in human brain tissue

[3H]Zacopride displayed regional saturable specific binding to homogenates of human brain tissues, as defined by the inclusion of BRL43694 [endo-N-(9-methyl-9-azabicyclo[3.3.1]non-3-yl)-1-methylindazole-3- carboxamide] in the incubation media. Scatchard analysis of the saturation data obtained from amygdaloid and hippocampal tissues identified the binding as being of high affinity and to a homogeneous population of binding sites (KD = 2.64 +/- 0.75 and 2.93 +/- 0.41 nmol/L and Bmax = 55 +/- 7 and 44 +/- 9 fmol/mg of protein in the amygdala and hippocampus, respectively). 5-Hydroxytryptamine 3 (5-HT3) receptor agonists and antagonists competed for the [3H]zacopride binding site, competing with up to 40% of total binding with a similar rank order of affinity in both tissues; agents acting on various other neurotransmitter receptors failed to inhibit binding. Kinetic data revealed a fast association that was fully reversible (k+1 = 6.61 X 10(5) and 7.65 X 10(5)/mol/L/s and k-1 = 3.68 X 10(-3) and 3.45 X 10(-3)/s in the amygdala and hippocampus, respectively). It is concluded that [3H]zacopride selectively labels with high affinity 5-HT3 recognition sites in human amygdala and hippocampus and, if these binding domains represent 5-HT3 receptors, may provide the opportunity for 5-HT3 receptor antagonists to modify 5-HT function in the human brain.

Angiotensin II inhibits the release of [3H]acetylcholine from rat entorhinal cortex in vitro

The effects of angiotensin I and II on basal potassium-induced release of [3H]acetylcholine were investigated in slices of rat entorhinal cortex. Potassium (10-25 mM) produced a concentration-dependent increase in the release of [3H]acetylcholine in the presence of extracellular calcium. Angiotensin II (10(-9)-10(-5) M) (but not angiotensin I) reduced the potassium-induced release of [3H]acetylcholine in a concentration-related manner to 60% of control levels, but did not effect basal tritium release. The effect of angiotensin II was antagonised by [1-sarcosine, 8-threonine] angiotensin II, an angiotensin II receptor antagonist, but not by agents acting on alpha- and beta-adrenoceptors, muscarinic, nicotinic, histamine or 5-hydroxytryptamine receptors nor by the angiotensin converting enzyme (ACE) inhibitor SQ 29852. The results indicate that angiotensin II acting via an angiotensin II receptor can inhibit the release of [3H]acetylcholine in slices of the rat entorhinal cortex. It is hypothesised that the ability of ACE inhibitors to facilitate cognitive processes may be related to a reduced availability of angiotensin II.

Histomorphometry of fresh frozen iliac crest bone biopsies

Although methods are well established for the rapid histological preparation of fresh frozen soft tissues, they remain inadequate for the preservation of hard tissues. A recent technique for sectioning fresh frozen bone, in which sections can be prepared within an hour, has been applied to undecalcified human iliac crest bone biopsies. Quantitative analysis has shown that the static remodeling variables deduced from frozen sections closely resemble those derived from plastic-embedded sections prepared for routine use by established laboratory procedures. It is concluded that the rapid method is reliable for immediate diagnostic and histomorphometric purposes.