Diagnostic delay and prognosis in primary central nervous system lymphoma compared with glioblastoma multiforme.

Glioblastoma multiforme (GBM) and primary central nervous system lymphoma (PCNSL) are malignant cerebral neoplasms associated with poor prognosis. Early diagnosis and subsequent planning of adequate treatment strategy are relevant to improve survival and reduce neurological deficit. Two groups of patients affected by GBM and PCNSL were compared to identify: (1) factors influencing the time necessary to obtain a correct diagnosis; (2) the influence of the interval time from clinical onset to diagnosis on the prognosis. Fifty-six patients (28 PCNSL and 28 GBM, 23 females and 33 males) referred to the same hospital setting were retrospectively evaluated. The mean age at diagnosis was 61 years. The two groups were comparable in terms of age, sex, clinical symptoms at onset and performance status. There was no relevant difference in time span from clinical onset to first neuroimaging examination, while time span from first neuroimaging to final morphological diagnosis was much longer in PCNSL patients (p = 0.008). Multivariate Cox regression analysis, including both PCNSL and GBM cases, showed a significant association of the overall survival with: time to diagnosis (HR 0.06), age at onset (HR 1.04). Our results show a significant diagnostic delay in PCNSL cases. Age at onset of disease and time to diagnosis emerge as clinical factors affecting overall survival in both groups. Stereotactic-guided biopsy should be chosen as routine method to early diagnose PCNSL. The clinical relevance of early diagnosis in GBM and PCNSL needs to be emphasized to maximize the overall survival in both neoplasms.

The neural correlates of road sign knowledge and route learning in semantic dementia and Alzheimer's disease.

BACKGROUND: Although there is a growing body of research on driving and Alzheimer's disease (AD), focal dementias have been understudied. Moreover, driving has never been explored in semantic dementia (SD). METHODS: An experimental battery exploring road sign knowledge and route learning was applied to patients with SD and AD selected in the early-moderate stage of disease and to a group of healthy participants. Neuropsychological data were correlated to cerebral hypometabolism distribution, investigated by means of positron emission tomography. RESULTS: The two dementias showed opposite profiles. Patients with SD showed poor road sign knowledge and normal performance in route learning. By contrast, patients with AD showed low performance in route learning test with preservation of semantic knowledge of road signs. In SD, there was a correlation of semantic knowledge impairment with hypometabolism in the left temporolateral cortex. No correlation between the AD region of interests (ROIs) and the relevant behavioural indices was found, while in the whole-brain analysis there was a significant correlation between route learning and the superior frontal gyrus. DISCUSSION AND CONCLUSIONS: For the first time, driving skills were explored in SD, and it is showed a differential profile from the one detected in AD. We demonstrate that the left anterior temporal cortex is implicated in road sign knowledge, while a distributed cortical network, including the frontal cortex, is likely to process route learning.

Emergency room access for recurring seizures: when and why.

BACKGROUND AND PURPOSE: To develop a hypothetical model identifying potentially modifiable predictive factors of Emergency Room (ER) visits by patients suffering from drug resistant epilepsy. METHODS: During a 1-year period, all adult drug resistant patients followed by the same epileptologist were recruited after the occurrence of one or more epileptic attacks. They were divided into two groups based on whether they went to the ER after seizures. A prospective comparative analysis of the clinical and social characteristics of the two groups was performed in order to identify independent predictors of ER visits. Logistic regression analysis was used to confirm the potential predictive role of the evaluated variables. RESULTS: Logistic regression analysis confirmed the potential role in predicting ER visits for these variables: foreign nationality, current psychiatric therapy, current antiepileptic drug polytherapy, comorbidities, more than one episode in the same day and changes in usual seizure pattern. A relevant association was also found between the frequency of ER neuroimaging use and the following variables: occurrence of episodes on holidays or weekends, current antiepileptic drug monotherapy, multiple comorbidities and brain injury after seizure. CONCLUSIONS: The present study evaluated factors, some potentially amenable to change, related to drug resistant epileptic patients' ER visits following a seizure. This information may serve to improve the clinical and therapeutic management of patients, decrease the need for urgent care and reduce subsequent patient stress and related costs.

Diagnostic delay in migraine with aura.

Migraine with aura (MWA) is a common headache, characterized by short-lasting neurological signs preceding an headache attack with migraine characteristics. We have recently performed several investigations about time-delay for migraine without aura diagnosis (MWoA). Aim of this study was to compare the time necessary to obtain a correct diagnosis in MWA and MWoA patients. We enrolled 31 consecutive patients affected by MWA and 62 age- and sex-matched patients affected by MWoA. All subjects were submitted to a face-to-face interview about the time-delay from symptoms' onset and a correct migraine typology diagnosis, the number of specialists consulted and the instrumental examinations performed. Independent samples and repeated measures t test, Mann-Whitney U were performed to compare the variables of the cases with the matched controls. No significant differences were found among the collected variables. Diagnostic delay was significantly different (p < 0.05), resulting lower in patients affected by MWA than in those with MWoA. In fact, subjects affected by MWA had a mean diagnostic delay of 6.70 years (SE ± 1.5), while patients affected by MWoA had a mean interval of 10.7 years (SE ± 1.20). Patients affected by MWA present a significant lower delay for the formulation of a correct diagnosis with respect to subjects with MWoA. This could be probably due to the fact that MWA patients develop major alarm reactions related to visual symptoms and look for an earlier appointment with a specialist medical center.

The real usefulness and indication for migraine diagnosis of neurophysiologic evaluation.

According to IHS criteria, a correct clinical history is fully adequate for a diagnosis of migraine. Patients usually perform many useless instrumental and laboratoristic exams and specialistic evaluations. In particular, electroencephalogram (EEG) is often prescribed as a first-line study in migraine patients. The objective is to analyze the indications of EEG in migraine and to evaluate whether its performance may negatively influence the time necessary to obtain a correct diagnosis. In particular, we compared the effects of EEG performance with those related to neuroradiological examinations in terms of time necessary to obtain a migraine diagnosis. 400 consecutive patients affected by migraine without aura were enrolled. Demographic and clinical data were collected. We used an ordinal regression model considering diagnostic delay as the main outcome and EEG and radiological examinations (in particular brain CT) as predictors. Delay was defined as a time to diagnosis greater than 1-year. Age, sex, number of specialists and examinations were included in the model as covariates. EEG represented the most often performed non-radiologic examination in our sample (20 %). It was associated with a significant risk of diagnostic delay [OR 1.66 (95 % CI 1.65-1.66, p < 0.001)]. An appropriate workup, including CT scan and early referral to a headache center was the most time-saving approach, being associated to the lowest probability of diagnostic delay [OR 0.72 (95 % CI 0.63-0.82, p < 0.001)]. EEG is a frequently prescribed exam in migraine. Our data show that it can contribute to diagnostic delay, highlighting only uncertain and unspecific elements. These data confirm the usefulness of a wide application of IHS guidelines, not recommending this exam for migraine detection.

Applause sign: is it really specific for Parkinsonian disorders? Evidence from cortical dementias.

OBJECTIVE: The applause sign, originally reported as a specific sign of progressive supranuclear palsy (PSP), has recently been found in several parkinsonian disorders. Its nature is still uncertain. It has been interpreted as a motor perseveration or a form of apraxia. The present study aims to: (a) verify the specificity of the applause sign for parkinsonian disorders, examining the presence of the applause sign in cortical dementias which should be error free and (b) clarify the nature of the applause sign (resulting or not from apraxia). METHODS: 77 subjects were included: 10 PSP, 15 frontotemporal dementia (FTD), 29 Alzheimer's disease (AD) and 23 normal controls. The presence of apraxia was an exclusion criterion. All patients underwent a detailed neuropsychological examination, and cognitive performance was correlated to the applause sign. RESULTS: All patient groups showed the applause sign and differed significantly from normal subjects who were error free. No difference was found when comparing PSP with FTD and FTD with AD. AD differed significantly from PSP but they were not error free (31% of patients with AD showed the applause sign). The only correlation with background neuropsychology was found for measures of executive functions. CONCLUSIONS: The presence of the applause sign in cortical dementia does not confirm the specificity of the applause sign for parkinsonian disorders. The applause sign should be interpreted as a sign of frontal lobe dysfunction rather than a form of apraxia, and can likely be detected in any kind of disease which involves frontal lobe structures to some extent.

Platelet amyloid precursor protein isoform expression in Alzheimer's disease: evidence for peripheral marker.

Alzheimer's disease (AD) is a chronic neurodegenerative disorder characterized by a progressive cognitive and memory decline. Among peripheral markers of AD, great interest has been focused on the amyloid precursor protein (APP). In this regard, platelets represent an important peripheral source of APP since it has been demonstrated that the three major isoforms, that are constituted of 770, 751 and 695 aa residues, are inserted in the membrane of resting platelets. APP 751 and APP 770 contain a Kunitz-type serine protease inhibitor domain (APP KPI) and APP 695 lacks this domain. To address this issue, we first examined the platelet APP isoform mRNAs prospectively as biomarker for the diagnosis of AD by means of real-time quantitative PCR, and then evaluated the correlation between APP mRNA expression levels and cognitive impairment of enrolled subjects. Differential gene expression measurements in the AD patient group (n=18) revealed a significant up-regulation of APP TOT (1.52-fold), APP KPI (1.32-fold), APP 770 (1.33-fold) and APP 751 (1.26-fold) compared to controls (n=22). Moreover, a statistically significant positive correlation was found between APP mRNA levels (TOT, KPI, 770 and 751) and cognitive impairment. Since AD definitive diagnosis still relies on pathological evaluation at autopsy, the present results are consistent with the hypothesis that platelet APP could be considered a potential reliable peripheral marker for studying AD and could contribute to define a signature for the presence of AD pathology.

The role of instrumental examinations in delayed migraine diagnosis.

Patients affected by migraine without aura very often consult different specialists who, misunderstanding the correct diagnosis, submit them to different instrumental examinations. The objective of the study was to assess if each instrumental examination was really useful for a faster migraine definition, or on the contrary, it increased the time delay for a correct diagnosis. We enrolled 300 consecutive patients referring to our Headache Center with a first diagnosis of migraine without aura and submitted them to a face-to-face interview about time from disease's onset to a correct diagnosis. In each patient, the first instrumental examination performed to specifically investigate migraine-related symptoms was defined. Brain MRI, brain CT, sinus CT, sinus X-rays, cervical spine X-rays and EEG were the most often performed examinations. All the exams, with the exception of brain CT, determined a significant increase of time delay in migraine diagnosis (p < 0.05). Brain CT was significantly associated with a higher probability to obtain a correct diagnosis in less than 1 year. Migraine without aura patients are usually addressed to perform radiological and other instrumental examinations. This attitude may increase the risk of time delay to obtain a correct diagnosis. The performance of a careful clinical history evaluation and neurological examination, with the addition of a brain CT when appropriate, is the best approach for a rapid and correct diagnosis of migraine without aura.

Taste preference of Chlorella sp. algae from dairy wastewater by weaned dairy calves.

The objective of this study was to evaluate the taste preference of calves fed Chlorella sp. microalgae produced from dairy lagoon wastewater. Six Holstein dairy heifer calves that were 12 to 14 wk of age (107 ± 3.8 kg of body weight) were fed 0 (control), 30, or 60 g of Chlorella sp. daily, and all calves were fed all treatments in a sequential elimination study. For the 7-d experiment, d 1 to 2 were for diet adaptation and d 3 to 4 were for data collection. During the final 3 d, the primary consumed treatment was removed to determine the second preferred treatment. Calves were ranked for total intake from the consumption of all treatments. The microalgae product used in this study was isolated from dairy wastewater lagoon, and microalgae biomass was produced using outdoor hanging bag bioreactors with Chlorella sp. to recycle the wastewater. The biomass was sterilized and kept frozen at -4°C until fed to calves. Calves were housed individually in hutches with outdoor access under solar panels, with free-choice water. Calves consumed more dry matter from control calf starter (3.4 kg/d) than from the starter with 30 g (2.42 kg/d) or 60 g (1.56 kg/d) of microalgae during the first 2-d period. During the second 2-d period (d 3 and 4), dry matter intake was reduced for the 60 g/d microalgae starter compared with the control and 30 g/d microalgae starters. Five of 6 calves in this study always ranked the control treatment first when given a choice and ranked the 30 g of microalgae starter second choice. Results indicated that microalgae may be added to calf starter; however, calves preferred calf starter without microalgae.

Extracranial aneurysms of the posterior inferior cerebellar artery. Literature review and report of a new case.

Aneurysms arising from the extracranial portion of the posterior-inferior cerebellar artery (PICA) are considered extremely rare. To date, only ten cases have been reported in the literature. The authors report a case of a 29 year-old male patient admitted comatose in Hunt-Hess grade IV because of an subarachnoid haemorrhage predominantly involving the left cranio-vertebral junction up to C2 rather than the posterior fossa and the fourth ventricle. Angiography showed an extracranial aneurysm at left vertebral artery-PICA junction a few millimetres superior to the dural entry point of the vertebral artery (VA). A left extreme-lateral approach was performed and the aneurysm was successfully clipped. On first year follow-up the patient had completely recovered with no neurological deficits. This paper analyzes the literature review about these rare aneurysms and the technical notes regarding the cranio-vertebral junction approach to these lesions. Factors affecting the neurological outcome of these aneurysms are also reported.

Simple schwannomatosis or an incomplete Coffin-Siris? Report of a particular case.

BACKGROUND: Schwannomatosis is a genetic disorder that belongs to NF family. The mutation of SMARCB1 gene has been related to this entity and Coffin-Siris syndrome, as well. We reported a case of a female patient with SMARCB1 mutation who has developed a spontaneuous spleen rupture. CASE DESCRIPTION: A 28 years old female patient with a story of a Sjogren syndrome, celiac disease and a surgically treated schwannoma, presented to our observation in July 2013 for a pain on the left elbow, where a tumefation was present. After neuroradiological evaluations, a surgical resection was performed and a schwannoma was diagnosed. Genetic exams revealed a puntiform SMARCB1 gene mutation. During 2015, she was subdued to the removal of an another schwannoma located into the cervical medullary canal. Few months later, she was operated in an another hospital for a spontaneous spleen rupture in a possible context of wandering spleen. CONCLUSION: We think that the patient could suffer from a partially expressed Coffin-Siris syndrome. No cases of spontaneous rupture in a context of wandering spleen have been ever described as for as schwannomatosis or Coffin-Siris syndrome are concerned. More cases are necessary to establish a direct relationship.

Foreign accent syndrome as the initial sign of primary progressive aphasia.

Foreign accent syndrome (FAS) is a rare speech disorder characterised by the emergence of a new accent, perceived by listeners as foreign. FAS has usually been described following focal brain insults, such as stroke. We describe the unusual case of a woman presenting with FAS as the earliest symptom of progressive degenerative brain disease. At presentation, she showed no language or other cognitive impairment, and functional and structural brain imaging were normal. Follow-up 1 year later revealed the emergence of mild expressive language problems. Repeat functional neuroimaging showed mild hypoperfusion of the perisylvian speech area of the left hemisphere, and structural imaging showed mild left perisylvian atrophy. We interpret the case as an unusual presentation of primary progressive non-fluent aphasia. The case provides further evidence of the variable and circumscribed nature of the clinical presentation of focal cerebral degeneration.

Evolution of a prolactin-secreting pituitary microadenoma into a fatal carcinoma: a case report.

Pituitary carcinomas are very rare tumors, nearly always presenting as widely invasive masses, although the hallmark of these lesions is the finding of distant metastases. One third of reported cases are prolactin (PRL)-secreting tumors. We report the case of a fatal pituitary carcinoma evolving within 4 years from a PRL-secreting microadenoma. A 22-year-old woman presented because of galactorrhea. Evaluation of the patient disclosed slight hyperprolactinemia and magnetic resonance imaging (MRI) showed a 7-mm intrapituitary lesion, which responded to treatment with cabergoline. About 4 years after the first evaluation she developed sudden headache, ptosis, and diplopia in the right eye. MRI disclosed the growth of a large pituitary mass, invading the right cavernous sinus. Despite two trans-sphenoidal surgical procedures followed by gamma-knife radiosurgery, the patient showed rapid local progression of the tumor and the occurrence of new lung lesions, probably of metastatic nature. The patient died 7 months after the development of her first neurological symptoms because of tumor apoplexy and subsequent subarachnoid hemorrhage. This case represents the first documented rapid evolution from a microprolactinoma initially responding to dopamine agonists to a fatal pituitary carcinoma.

Peroxynitrite production and NOS expression in astrocytes U373MG incubated with lipoproteins from Alzheimer patients.

Apolipoprotein E (apo E), a plasma protein involved both in the metabolism of cholesterol and triglycerides, particularly in nervous tissue, has been associated with a higher risk of Alzheimer's disease. It has been shown that apo E increased the production of nitric oxide (NO) from human monocyte-derived macrophages (MDM); this effect could represent an important link between tissue redox balance and inflammation, since inflammation and oxidative stress are involved in chronic neurodegenerative disorders. Moreover, it has been evidenced that an overproduction of NO in the central nervous system (CNS) may play a key role in aging and that the glial cells (microglials cells and probably astrocytes) are able to form consistent amounts of NO through the induction of a nitric oxide synthase (iNOS) isoform so-called inducible or inflammatory. This report was performed in order to elucidate the effects produced by lipoproteins from control subjects, AD patients and first degree relatives (offspring) on human astrocyte cells after a short incubation. Peroxynitrite and NO production and NOS expression in cultured astrocytes were measured. We observed a decreased NO production after incubation with both LDL and HDL and an increased peroxynitrite production. As it concerns NOS expression, densitometric analysis of bands indicated that iNOS protein levels were significantly higher in the cells incubated with both AD lipoproteins and offspring lipoproteins compared to cells incubated with control lipoproteins. These findings suggest the possibility to identify in NO pathway a precocious marker of AD.

Glycine-related amino acids stereoselectively affect N-methyl-D-aspartate receptor-mediated contractions of guinea pig ileum: comparison with the inhibition of strychnine-insensitive [3H]glycine binding to rat cortical membranes.

Ten microM glycine, D-serine and D-alanine potentiated L-glutamate (30 microM)-induced contractions of the guinea pig ileum by an average of 35, 53 and 24%, respectively. On the contrary, D-cysteine, at the same concentration, caused a 21% inhibition of the contractile response to L-glutamate. This inhibitory effect of D-cysteine was abolished by 10 microM glycine. The corresponding L-isomers of these amino acids, namely L-serine, L-alanine and L-cysteine and the other amino acids tested, possessed negligible activity or were inactive in this test. The IC50 values of the same compounds for strychnine-insensitive binding of [3H]glycine (20 nM) to cortical membranes from the brain of the rat were: 0.26 microM, glycine; 1.2 microM, D-serine; 2.1 microM, D-alanine; 8.6 microM, D-cysteine; 51 microM, L-serine; 90 microM, L-alanine; greater than 1000 microM, L-cysteine. On the whole, these results point out a strict requirement for stereoselectivity for both of the effects examined. In addition, the results obtained in the ileum preparation suggest that D-cysteine may act as an antagonist, rather than as an agonist at the glycine site which regulates the responses of N-methyl-D-aspartate receptors.

Homotaurine: a GABAB antagonist in guinea-pig ileum.

Homotaurine (3-aminopropane sulphonic acid) did not inhibit the twitch response in guinea-pig ileum longitudinal muscle whilst gamma-aminobutyric acid (GABA) and (-)-baclofen evoked dose-dependent inhibitions. The inhibitory effects of GABA and (-)-baclofen were prevented in the presence of homotaurine 2 X 10(-4) and 10(-3) M. The log dose-effect curves of GABA and (-)-baclofen were shifted in a parallel manner compatible with competitive antagonism. The pA2 of homotaurine with GABA (4.22 +/- 0.05) and (-)-baclofen (4.26 +/- 0.1) were the same. Homotaurine did not antagonize the inhibitory effects of morphine (ED50 4 X 10(-7) M), noradrenaline (ED50 10(-6) M) or ATP (ED50 1.5 X 10(-5) M). The inferior homologue of homotaurine, taurine 10(-3) M, did not modify the inhibitory effects of GABA and (-)-baclofen. Picrotoxin 5 X 10(-5) M antagonized GABAA receptor-mediated contraction but did not affect GABAB receptor-mediated inhibition. At the same concentration the drug did not influence the antagonistic action of homotaurine, thus showing no GABAA receptor-mediated interference. It may be concluded that homotaurine is a competitive antagonist of GABAB mediated effects in the guinea-pig ileum.

GABAA and GABAB receptor-mediated effects in guinea-pig ileum.

1 The effects of gamma-aminobutyric acid (GABA) and related substances were examined in guinea-pig ileum longitudinal muscle.2 GABA at doses ranging from 10(-7) M to 3 x 10(-6) M elicited a relaxation while at higher doses (3 x 10(-6) M - 10(-4) M), as previously described, it caused a contraction followed by relaxation.3 GABA-induced relaxation was bicuculline-insensitive, was mimicked by (-)-baclofen but not by homotaurine and muscimol. The effect of baclofen was stereospecific. GABA- and (-)-baclofen-induced relaxations were dose-dependent and their ED(50) values were similar. A specific cross-desensitization occurred between GABA and (-)-baclofen.4 The bicuculline-insensitive relaxation induced by GABA and (-)-baclofen was prevented by tetrodotoxin and hyoscine but not by phentolamine plus propranolol, naloxone or theophylline.5 In preparations in which the muscle tone was raised by histamine or prostaglandin F(2alpha), GABA and (-)-baclofen induced relaxation to the same extent as before increasing the tone. If the tone was raised by DMPP, a greater bicuculline-insensitive relaxation occurred.6 Contraction caused by GABA was bicuculline-sensitive and was mimicked by homotaurine and muscimol. Contraction was dose-dependent and muscimol was about three times more potent than GABA or homotaurine. A specific cross-desensitization occurred between the contractile effects of GABA and those of homotaurine or muscimol.7 Bicuculline competitively antagonized the contractile effects of GABA, homotaurine and muscimol and gave closely similar pA(2) values. The slope of the Schild plot for the above drugs was near 1, confirming the competitive nature of the antagonism.8 The bicuculline-sensitive contraction induced by GABA, homotaurine and muscimol was abolished by tetrodotoxin and was non-competitively antagonized by hyoscine, while it was unaffected by hexamethonium, mepyramine and methysergide.9 It is concluded that two receptors mediate the GABA effects in guinea-pig ileum: a bicuculline-sensitive GABA(A) receptor, which elicits contraction through an excitatory action on cholinergic post-ganglionic neurones; and a bicuculline-insensitive GABA(B) receptor which causes relaxation through an inhibitory presynaptic action on cholinergic post-ganglionic neurones. We confirm that GABA, homotaurine and muscimol are GABA(A) agonists, while GABA and (-)-baclofen are GABA(B) agonists.

Modulatory activity of GABAB receptors on cholinergic tone in guinea-pig distal colon.

The effect of gamma-aminobutyric acid (GABA) administration was studied in both in vitro and in vivo preparations of the guinea-pig distal colon. In in vitro preparations GABA (10(-7) - 10(-3) M) elicited a dose-dependent relaxation; a decrease in the spontaneous contractions was sometimes observed. The effect of GABA was mimicked by (-)-baclofen, which gave a dose-response curve overlapping that of GABA, while (+)-baclofen was about one hundred times less potent. The relaxation responses induced by the above drugs were antagonized by 5-aminovaleric acid (5 X 10(-4) M), which did not affect adenosine-induced relaxation, but they were insensitive to bicuculline (10(-5) M) and picrotoxin (10(-5) M). Moreover, they were prevented by tetrodotoxin (6 X 10(-7) M). In hyoscine (10(-7) M)-pretreated preparations, GABA still evoked a small relaxation response (approx. 10% of the maximum) that was bicuculline-sensitive. Desensitization to GABA (10(-5) M) was observed. A specific cross-desensitization occurred between GABA (10(-5) M) and (-)-baclofen (10(-5) M). In in vivo preparations, GABA (10 mumol kg-1) and (-)-baclofen (5 mumol kg-1) produced a dose-related inhibition of basal tone, while (+)-baclofen (5 mumol kg-1) had much less effect (about 25%). A decrease in the spontaneous contractions was sometimes observed. The relaxant effect of GABA and (-)-baclofen persisted in guinea-pigs pretreated (1-2 min) with picrotoxin (1.6 mumol kg-1), whereas it was significantly reduced in animals injected 1 min beforehand with 5-aminovaleric acid (0.2 mmol). The maximal relaxant effect induced by GABA and (-)-baclofen did not differ from that of atropine (0.9 mumol kg-1) and after atropine administration GABA had no further inhibitory effect. Relaxation responses induced by GABA and (-)-baclofen still occurred after blockade of nicotinic receptors by hexamethonium (0.17 mmol kg-1), which itself caused an increase in the basal tone. When the tone was increased by topical application of physostigmine (40 micrograms), GABA and (-)-baclofen induced a greater relaxation than that obtained in basal conditions. It is concluded that GABA, both in vitro and in vivo administration, inhibits cholinergic tone in guinea-pig distal colon and that this effect is mediated mainly by activation of GABAB receptors. Further experiments are required to ascertain the possible physiological role of a GABA-releasing neuronal system in the colon in vivo.

Agonists, antagonists and modulators of excitatory amino acid receptors in the guinea-pig myenteric plexus.

1. The receptors for glutamic acid (L-Glu) present in the guinea-pig myenteric plexus-ileal longitudinal muscle preparation have been studied by measuring the muscle contraction induced by numerous putative endogenous agonists acting at these receptors. Furthermore, the actions of different concentrations of antagonists, glycine, Mg2+ and Ca2+ on the ileal contractions induced by L-Glu have been evaluated. 2. The EC50 values of the most common putative endogenous agonists of these receptors were: L-Glu 1.9 X 10(-5) M; L-aspartate 8 X 10(-5) M; quinolinate 5 X 10(-4) M; L-homocysteate 1.4 X 10(-4) M; the dipeptide aspartyl-glutamate 8 X 10(-5) M, while N-acetyl-aspartyl-glutamate was inactive. Among the molecules used to classify excitatory amino acid receptors, N-methyl-D-aspartate (NMDA) was the most potent (EC50 5 X 10(-4) M). Kainic and quisqualic acids were almost completely inactive. 3. The responses to L-Glu were competitively antagonized by 2-amino-5-phosphonovaleric acid. They were, also, prevented by hyoscine (10(-7) M) and by tetrodotoxin (3 X 10(-7) M), suggesting that the L-Glu-induced ileal contraction was in some way dependent upon an action on the myenteric cholinergic neurones. Kynurenic acid was a non-competitive antagonist, gamma-D-glutamyl-taurine (10(-4) M) and aminophosphonobutyric acid (10(-4) M) did not modify the L-Glu-induced contractions. 4. Glycine (10(-5) M) significantly potentiated the effects of glutamate especially when the ionic composition of the superfusion medium contained concentrations of Ca2+ in the range of 0.6-1.2 mM. Strychnine 3 X 10(-5) M did not modify the actions of glycine. 5. The data presented here confirm the presence of NMDA receptors in the guinea-pig myenteric plexus, and show that these receptors, similar to those present in primary neuronal cultures may be modulated by glycine.