Microtubule-associated protein 1B (MAP1B)-deficient neurons show structural presynaptic deficiencies in vitro and altered presynaptic physiology.

Microtubule-associated protein 1B (MAP1B) is expressed predominantly during the early stages of development of the nervous system, where it regulates processes such as axonal guidance and elongation. Nevertheless, MAP1B expression in the brain persists in adult stages, where it participates in the regulation of the structure and physiology of dendritic spines in glutamatergic synapses. Moreover, MAP1B expression is also found in presynaptic synaptosomal preparations. In this work, we describe a presynaptic phenotype in mature neurons derived from MAP1B knockout (MAP1B KO) mice. Mature neurons express MAP1B, and its deficiency does not alter the expression levels of a subgroup of other synaptic proteins. MAP1B KO neurons display a decrease in the density of presynaptic and postsynaptic terminals, which involves a reduction in the density of synaptic contacts, and an increased proportion of orphan presynaptic terminals. Accordingly, MAP1B KO neurons present altered synaptic vesicle fusion events, as shown by FM4-64 release assay, and a decrease in the density of both synaptic vesicles and dense core vesicles at presynaptic terminals. Finally, an increased proportion of excitatory immature symmetrical synaptic contacts in MAP1B KO neurons was detected. Altogether these results suggest a novel role for MAP1B in presynaptic structure and physiology regulation in vitro.

Coupling of glutamate and glucose uptake in cultured Bergmann glial cells.

Glutamate, the main excitatory neurotransmitter in the vertebrate brain, exerts its actions through specific membrane receptors present in neurons and glial cells. Over-stimulation of glutamate receptors results in neuronal death, phenomena known as excitotoxicity. A family of sodium-dependent, glutamate uptake transporters mainly expressed in glial cells, removes the amino acid from the synaptic cleft preventing neuronal death. The sustained sodium influx associated to glutamate removal in glial cells, activates the sodium/potassium ATPase restoring the ionic balance, additionally, glutamate entrance activates glutamine synthetase, both events are energy demanding, therefore glia cells increase their ATP expenditure favouring glucose uptake, and triggering several signal transduction pathways linked to proper neuronal glutamate availability, via the glutamate/glutamine shuttle. To further characterize these complex transporters interactions, we used the well-established model system of cultured chick cerebellum Bergmann glia cells. A time and dose-dependent increase in the activity, plasma membrane localization and protein levels of glucose transporters was detected upon d-aspartate exposure. Interestingly, this increase is the result of a protein kinase C-dependent signaling cascade. Furthermore, a glutamate-dependent glucose and glutamate transporters co-immunoprecipitation was detected. These results favour the notion that glial cells are involved in glutamatergic neuronal physiology.

A novel multi-target ligand (JM-20) protects mitochondrial integrity, inhibits brain excitatory amino acid release and reduces cerebral ischemia injury in vitro and in vivo.

We previously showed that JM-20, a novel 1,5-benzodiazepine fused to a dihydropyridine moiety, possessed an anxiolytic profile similar to diazepam and strong neuroprotective activity in different cell models relevant to cerebral ischemia. Here, we investigated whether JM-20 protects against ischemic neuronal damage in vitro and in vivo. The effects of JM-20 were evaluated on hippocampal slices subjected to oxygen and glucose deprivation (OGD). For in vivo studies, Wistar rats were subjected 90 min of middle cerebral artery occlusion (MCAo) and oral administration of JM-20 at 2, 4 and 8 mg/kg 1 h following reperfusion. Twenty-four hours after cerebral blood flow restoration, neurological deficits were scored, and the infarct volume, histopathological changes in cortex, number of hippocampal and striatal neurons, and glutamate/aspartate concentrations in the cerebrospinal fluid were measured. Susceptibility to brain mitochondrial swelling, membrane potential dissipation, H2O2 generation, cytochrome c release, Ca2+ accumulation, and morphological changes in the organelles were assessed 24 h post-ischemia. In vitro, JM-20 (1 and 10 µM) administered during reperfusion significantly reduced cell death in hippocampal slices subjected to OGD. In vivo, JM-20 treatment (4 and 8 mg/kg) significantly decreased neurological deficit scores, edema formation, total infarct volumes and histological alterations in different brain regions. JM-20 treatment also protected brain mitochondria from ischemic damage, most likely by preventing Ca2+ accumulation in organelles. Moreover, an 8-mg/kg JM-20 dose reduced glutamate and aspartate concentrations in cerebrospinal fluid and the deleterious effects of MCAo even when delivered 8 h after blood flow restoration. These results suggest that in rats, JM-20 is a robust neuroprotective agent against ischemia/reperfusion injury with a wide therapeutic window. Our findings support the further examination of potential clinical JM-20 use to treat acute ischemic stroke.

Aloysia gratissima prevents cellular damage induced by glutamatergic excitotoxicity.

OBJECTIVES: Aloysia gratissima aqueous extract (AE) was investigated as a putative protective agent against quinolinic acid (QA)-induced seizures in mice and hippocampal cell damage. Additionally, AE and ferulic acid (FA), the major compound of AE, were tested against neurotoxicity evoked by glutamate or its N-methyl-D-aspartate receptor (NMDAR) agonist, QA on hippocampal slices, in vitro. METHODS: Mice were treated with AE before QA infusion (36.8 nmol/site) and seizures were analysed. Cellular viability and modulation of excitatory amino acid transport were verified in hippocampal slices. In-vitro AE or FA was tested against neurotoxicity induced by glutamate or QA. KEY FINDINGS: AE did not prevent QA-induced seizures; however, it prevented cellular death and disruption of excitatory amino acid transport. In-vitro AE (0.1 or 1.0 mg/ml) or FA (1 or 10 µm), improved cell viability against citotoxicity exerted by glutamate or QA, respectively. Both AE and FA have protective effects depending on activation of the phosphatidylinositol-3 kinase (PI3K) signalling pathway. CONCLUSIONS: AE attenuated QA-induced cell damage possibly involving the glutamate transport modulation through NMDAR interaction. FA shows a similar profile of neuroprotection promoted by AE. Therefore, AE treatment might be a useful strategy in preventing brain damage caused by exacerbation of glutamatergic toxicity in nervous system disorders.

Cortical spreading depression in traumatic brain injuries: is there a role for astrocytes?

Cortical spreading depression (CSD) is a presumably pathophysiological phenomenon that interrupts local cortical function for periods of minutes to hours. This phenomenon is important due to its association with different neurological disorders such as migraine, malignant stroke and traumatic brain injury (TBI). Glial cells, especially astrocytes, play an important role in the regulation of CSD and in the protection of neurons under brain trauma. The correlation of TBI with CSD and the astrocytic function under these conditions remain unclear. This review discusses the possible link of TBI and CSD and its implication for neuronal survival. Additionally, we highlight the importance of astrocytic function for brain protection, and suggest possible therapeutic strategies targeting astrocytes to improve the outcome following TBI-associated CSD.

Stimulation of the Po-shen and Shen-hun scalp-acupuncture bands modifies levels of inhibitory and excitatory amino acids in the immature rat brain.

OBJECTIVE: In the present study, the effect of stimulation of the Po-shen and Shen-hun scalp-acupuncture bands on tissue amino acid concentrations in several brain regions in awake and pentobarbital-sedated immature rats was evaluated. MATERIALS AND METHODS: Sprague-Dawley rats (aged 15 days) were organized in four groups of at least eight animals: control groups received saline solution 0.9% or sodium pentobarbital at 30mg/kg dosage via intraperitoneal. Experimental groups received saline solution or sodium pentobarbital plus stimulation in Po-shen and Shen-hun scalp-acupuncture bands for one continuous hour during 10 sessions by using scalp-acupuncture. RESULTS: As compared to rats receiving saline solution, scalp-acupuncture produced significant changes in amino acid concentrations, depending on the analyzed region, as follows: in inhibitory amino acids, a GABA increase was observed in amygdala and hippocampus (491 and 184%, respectively), but a decrease in the substantia nigra (80%); glycine showed decrease in all the analyzed regions, except for an increase in brainstem(78%); glutamine presented an increase in hippocampus and cortex (42 and 149%, respectively). In the case of excitatory amino acids, glutamate decreased in all the analyzed regions; whereas aspartate decreased in substantia nigra and brainstem (77.08 and 35%, correspondingly) but increased in hippocampus and cortex (32 and 54%, respectively). The combined treatment of scalp-acupuncture and a GABAergic depressant drug like pentobarbital resulted in almost all changes induced in amino acids for scalp-acupuncture alone being significantly reverted. CONCLUSION: Stimulation of the Po-shen and Shen-hun scalp-acupuncture bands by using scalp-acupuncture alone might produce depressant activity by changes in amino acids, but the combination with a GABAergic tranquilizer like sodium pentobarbital can interfere with this response.

Glutamatergic mechanisms of the dorsal periaqueductal gray matter modulate the expression of conditioned freezing and fear-potentiated startle.

It is well known that excitatory amino acids induce unconditioned fear responses when locally injected into the dorsal periaqueductal gray matter (dPAG). However, there are only few studies about the involvement of excitatory amino acids mediation in dPAG in the expression of conditioned fear. The present series of experiments evaluates the participation of AMPA/Kainate and NMDA glutamatergic receptors of dPAG in the expression of conditioned fear, assessed by the fear-potentiated startle (FPS) and conditioned freezing responses. Wistar rats were subjected to fear conditioning to light. Twenty-four hours later, they received intra-dPAG injections of kainic acid or NMDA (AMPA/Kainate and NMDA agonists) and 1,2,3,4-Tetrahydro-6-nitro-2,3-dioxo-benzo[f]quinoxaline-7-sulfonamide disodium salt hydrate (NBQX) or D(-)-2-Amino-7-phosphonoheptanoic acid (AP7) (AMPA/Kainate and NMDA antagonists) and were submitted to the FPS test. Conditioned freezing response was simultaneously measured. Effects of drug treatment on motor activity were evaluated in the open-field test. Intra-dPAG injections of glutamatergic agonists enhanced conditioned freezing and promoted pro-aversive effects in the FPS. Lower doses of the agonists had no effect or enhanced FPS whereas higher doses disrupted FPS, indicating a non-monotonic relationship between fear and FPS. The antagonist NBQX had no significant effects while AP7 decreased conditioned freezing but did not affect FPS. Both antagonists reduced the effects of the agonists. The obtained results cannot be attributed to motor deficits. The results suggest an important role of the AMPA/Kainate and NMDA mechanisms of the dPAG in the expression of conditioned freezing and FPS.

Antinociceptive and anti-hypernociceptive effects of Se-phenyl thiazolidine-4-carboselenoate in mice.

In this study, the antinociceptive, anti-hypernociceptive and toxic effects of orally administered (R)-Se-phenyl thiazolidine-4-carboselenoate (Se-PTC, 1-50 mg/kg) were evaluated in mice. Se-PTC did not change plasma aspartate (AST) and alanine aminotransferase (ALT) activities or urea and creatinine levels. Furthermore, in an open field test, Se-PTC did not alter the number of crossings and rearing. Se-PTC significantly reduced the amount of writhing when assessed by acetic acid-induced visceral nociception and attenuated the licking time of the injected paw in the early and late phases of a formalin test. In addition, Se-PTC reduced nociception produced by intra-plantar (i.pl.) injection of glutamate, capsaicin, cinnalmaldehyde, bradykinin, phorbol myristate acetate and 8-Bromo-cAMP. Se-PTC caused a significant increase in hot plate and tail-immersion response latencies, but the antinociceptive effect of Se-PTC in the tail immersion was not abolished by pretreatment with the non-selective opioid receptor antagonist, naloxone. Se-PTC (25 mg/kg) significantly inhibited nociceptive behavior induced by intrathecal (i.t.) injection of glutamate, N-methyl-D-aspartate (NMDA) and (±)-1-aminocyclopentane-trans-1,3-dicarboxylic acid (trans-ACPD), but failed to affect nociception induced by kainate and α-amino-3-hydroxy-5-mehtyl-4-isoxazolepropionic acid (AMPA). Mechanical hypernociception induced by carrageenan and Complete Freund's Adjuvant was attenuated by Se-PTC administration. These results indicate that Se-PTC produces antinociception in several models of nociception.

Octyl-methoxycinnamate (OMC), an ultraviolet (UV) filter, alters LHRH and amino acid neurotransmitters release from hypothalamus of immature rats.

OMC (octyl-methoxycinnamate), is an endocrine disruptor with estrogenic activity, which is used in sunscreen creams as a UV filter. We studied its " IN VITRO" effects on the hypothalamic release of LHRH as well as on the amino acid neurotransmitter system in immature rats of 15 (prepubertal) and 30 (peripubertal) days of age. OMC decreased the LH-RH release significantly in male and female rats of both age. In male rats OMC increased the release of GABA while in the female ones It diminished the excitatory amino acid aspartate (ASP) and Glutamate (GLU) without modifications in the hypothalamic GABA release. These results suggest that during sexual maturation the inhibitory effect of OMC on LH-RH release appears to be related to its action on the inhibitory and excitatory amino acid neurotransmitters in male and female rats.

Integrative hypothesis for Huntington's disease: a brief review of experimental evidence.

Huntington's disease (HD) is a demential, neurodegenerative inheritable disease affecting middle-aged patients. HD is characterized by uncontrolled choreiform movements, psychiatric symptoms and cognitive decline. Histopathological changes in HD brains reveal a considerable damage to basal ganglia, particularly affecting middle-sized spiny neurons from the caudate-putamen region. Neurochemical changes are specifically oriented to deplete GABAergic and cholinergic systems, while molecular alterations include an increased expression of CAG trinucleotide at exon 1 from the huntingtin (htt) gene, as well as aggregation of mutant htt. Although several hypotheses regarding the mechanisms by which neurotoxicity is triggered in HD brains have been suggested on the basis of experimental evidence, so far it remains not clear which of them are predominant or whether they are complementary. Recent experimental evidence through transgenic mice models reveal an interesting interaction between expanded CAG triplets, mutant htt, and the increase in toxic metabolites from the kynurenine pathway. Further evidence supports the assumption that different toxic mechanisms (i.e. excitotoxicity, energy metabolism impairment, inflammatory events, oxidative stress, etc.) are confluent and depend on each other. In this review we will briefly summarize some of those findings and propose a final integrative hypothesis for HD.

The anion channel blocker, 4,4'-dinitrostilbene-2,2'-disulfonic acid prevents neuronal death and excitatory amino acid release during glycolysis inhibition in the hippocampus in vivo.

Neuronal death associated with cerebral ischemia and hypoglycemia is related to increased release of excitatory amino acids (EAA) and energy failure. The intrahippocampal administration of the glycolysis inhibitor, iodoacetate (IOA), induces the accumulation of EAA and neuronal death. We have investigated by microdialysis the role of exocytosis, glutamate transporters and volume-sensitive organic anion channel (VSOAC) on IOA-induced EAA release. Results show that the early component of EAA release is inhibited by riluzole, a voltage-dependent sodium channel blocker, and by the VSOAC blocker, tamoxifen, while the early and late components are blocked by the glutamate transport inhibitors, L-trans-pyrrolidine 2,4-dicarboxylate (PDC) and DL-threo-beta-benzyloxyaspartate (DL-TBOA); and by the VSOAC blocker 4,4'-dinitrostilbene-2,2'-disulfonic acid (DNDS). Riluzole, DL-TBOA and tamoxifen did not prevent IOA-induced neuronal death, while PDC and DNDS did. The VSOAC blockers 5-nitro-2-(3-phenylpropyl-amino) benzoic acid (NPPB) and phloretin had no effect either on EAA efflux or neuronal damage. Results suggest that acute inhibition of glycolytic metabolism promotes the accumulation of EAA by exocytosis, impairment or reverse action of glutamate transporters and activation of a DNDS-sensitive mechanism. The latest is substantially involved in the triggering of neuronal death. To our knowledge, this is the first study to show protection of neuronal death by DNDS in an in vivo model of neuronal damage, associated with deficient energy metabolism and EAA release, two conditions involved in some pathological states such as ischemia and hypoglycemia.

Local differences in GABA release induced by excitatory amino acids during retina development: selective activation of NMDA receptors by aspartate in the inner retina.

Glutamate and GABA are the major excitatory and inhibitory neurotransmitters in the CNS. In the retina, it has been shown that glutamate and aspartate and their agonists kainate and NMDA promote the release of GABA. In the chick retina, at embryonic day 14 (E14), glutamate and kainate were able to induce the release of GABA from amacrine and horizontal cells as detected by GABA-immunoreactivity. NMDA also induced GABA release restricted to amacrine cell population and its projections to the inner plexiform layer (E14 and E18). Although aspartate reduced GABA immunoreactivity, specifically in amacrine cells of E18 retinas, it was not efficient to promote GABA release from retinas at E14. As observed in differentiated retinas, dopamine inhibited the GABA release promoted by NMDA and aspartate but not by kainate. Our data show that different retinal sites respond to distinct EAAs via different receptor systems.

O sistema glutamatérgico e desordens neuropsiquiátricas: aspectos básicos / The glutamatergic system and neuropsychiatric disorders: basic aspects

O sistema glutamatérgico, um dos mais extensos do sistema nervoso central, é formado por neurônios, vias e receptores específicos. O agonista natural corresponde a um aminoácido excitador de constituição relativamente simples, o glutamato. Este atua em uma ampla gama de subtipos de receptores, ionotrópicos e metabotrópicos, que oferecem a possibilidade de uma variada atividade sináptica, desde a neurotransmissão rápida até às respostas lentas que induzem modificações sinápticas de longa duração. Essa ampla distribuição dos receptores influencia neurônios que transmitem com o mesmo ou com outros neurotransmissores. Os receptores ionotrópicos, os mais bem estudados, apresentam funções diferenciadas, sendo que o do tipo AMPA é responsável pela maior parte das transmissões sinápticas excitadoras rápidas, a do tipo KA contribui nas respostas pós-sinápticas nas sinapses excitadoras, podendo ainda modular a liberação pré-sináptica do transmissor em determinadas sinapses, enquanto o receptor NMDA é fundamental na indução de formas específicas de plasticidade sináptica. Os variados receptores metabotrópicos também contribuem de modo importante em diversas dessas atividades. Dessa maneira, o sistema glutamatérgico encontra-se relacionado a diversas funções normais, como a plasticidade neural, subjacente a processos cognitivos, assim como a situações patológicas, responsáveis por diversas desordens neuropsiquiátricas agudas e crônicas. O conhecimento detalhado do sistema glutamatérgico, portanto, é essencial para a compreensão de variados processos normais e patológicos, assim como das possibilidades de intervenção farmacológica com objetivos terapêuticas

Ontogenic modifications in the effect of the GABAergic system on the hypothalamic excitatory amino acids: its relationship with GABAergic control of gonadotrophin secretion during sexual maturation in female rats.

Aminooxyacetic acid (AOAA), an inhibitor of gamma-aminobutyric transaminase, stimulates the in vitro GABA release by medial and anterior preoptic hypothalamic areas in prepubertal female rats (6, 15 and 30 days of age). This increase of GABA release at 15 days of age, was accompanied by a significant increase (P<0.01) in the hypothalamic release of glutamate (GLU) and aspartate (ASP), the excitatory amino acids involved in N-methyl-D-aspartate neurotransmission and a decrease in the release of these excitatory amino acids at 6 and 30 days of age (P<0.01). The increase in the hypothalamic release of GLU and ASP at 15 days of age was accompanied by a significant increase of the plasmatic LH and FSH concentration, while the hypothalamic decrease of excitatory amino acids release induced by AOAA also decreased LH and FSH plasmatic levels at 6 and 30 days of age. In summary, the present results show that in female rats there are differences in the effect of GABAergic system the hypothalamic release of GLU and ASP and on gonadotrophin secretion at different ages of prepubertal period, i.e. an inhibitory effect at 6 and 30 days of age and a stimulatory one at 15 days of age. It is proposed that the different effects of GABA on gonadotrophin secretion in prepubertal rats previously described are connected with ontogenic changes in the interrelationships between GABAergic and NMDA neurotransmission systems during sexual maturation of the hypothalamus in female rats. It is probable that these ontogenic modifications are connected with the maturation of interneuronal connection and/or new receptors activity.

In vivo potentiation of glutamate-mediated neuronal damage after chronic administration of the glycolysis inhibitor iodoacetate.

Neuronal damage associated with cerebral ischemia and hypoglycemia might be the consequence of the extracellular accumulation of excitatory amino acids. In previous studies we showed that elevation of glutamate and aspartate extracellular levels by inhibition of its uptake in vivo is not sufficient to induce neuronal damage unless mitochondrial energy metabolism is compromised. In the present study we show that chronic systemic administration of the glycolysis inhibitor iodoacetate (25 mg/kg) induces no damage to the brain per se but enhances neuronal vulnerability to glutamate-mediated neurotoxicity in the hippocampus. Tissue injury is well protected either by antagonizing NMDA glutamate receptors with MK-801 or by administration of pyruvate, a substrate of the tricarboxylic acid cycle. In contrast to systemic treatment, local infusions through a dialysis probe of 5 mM iodoacetate into the hippocampus induced acute lesions not sensitive to MK-801. Iodoacetate intrahippocampal perfusion induced substantial increases in the extracellular levels of glutamate (3.5-fold), taurine (8.8-fold), and particularly aspartate (35-fold). Neuronal damage under this conditions occurs very rapidly as revealed by the histological analysis of animals transcardially perfused immediately after iodoacetate perfusion. Aspartate might contribute to neuronal damage since intrahippocampal administration of this amino acid (600 nmol/microl) induces extensive lesions. The present study might suggest that impairment of glucose oxidation through the glycolytic pathway in vivo facilitates glutamate neurotoxicity. Additionally, the results indicate that pyruvate might prevent as efficiently as glutamate receptor antagonists glutamate-mediated neuronal damage associated with ischemia/hypoglycemia.

[Factors that lead to death of neurons in neurodegenerative diseases]. / Factores que desencadenan la muerte neuronal en enfermedades neurodegenerativas.

OBJECTIVE: The objective of this paper was to review information related to the various factors which may trigger the mechanisms of cell death, induced or programmed, which take place in the nervous system and their relationship with the aetiopathogenesis of the neurodegenerative diseases. DEVELOPMENT: In recent years it has been recognized that cell death may be not only the consequence of accidental damage but also a sign of a suicide programme. This form of death is currently known as apoptosis. It is a process which is morphologically distinct from accidental cell death or necrosis. It does not cause an inflammatory response. This type of death is not only involved in the development and haemostasis of tissues, but also in setting off neuronal degeneration in experimental models of Parkinson's disease, Huntington's chorea, etc. CONCLUSIONS: In the cell death occurring in neurodegenerative diseases there is more than one induction mechanisms. Understanding the factors which trigger cell death, and the chain of events leading to this, gives grounds for the design of new pharmacological strategies for the treatment of these diseases.

Pentylenetetrazol-induced kindling: early involvement of excitatory and inhibitory systems.

Alterations in the brain of rats receiving a single non-convulsive administration pentylenetetrazol (PTZ), 30 mig/kg, i.p. (single PTZ group) were investigated and compared with those detected in fully PTZ kindled rats (chronic PTZ group). In vitro receptor autoradiography experiments showed that both single and chronic PTZ groups presented mu opioid and benzodiazepine (BDZ) receptor binding in specific brain areas. Using an antibody generated against the delta opioid receptor (DOR-1), it was found that DOR-1 like immunoreactivity was reduced in cortex and amygdala in mice following single and chronic PTZ administration. Microdialysis experiments revealed that the administration of PTZ 30 mg/kg, i.p. in freely moving rats without previous experience with the drug, induces a rise in glutamate release, detected in the first and second 10 min dialysates collected from amygdala (138% and 50%, respectively) and frontal cortex (70% and 45%, respectively) as well as aspartate in frontal cortex in the first and second PTZ-dialysates (143% and 80%, respectively). Subsequently, values returned to basal conditions. It may be speculated that decreased BDZ receptor binding results from enhanced release of GABA. On the other hand, the decrease of mu receptor binding and DOR-1 immunoreactivity observed after PTZ administration may be the result of enhanced levels of opioid peptides probably released over the kindling procedure. In conclusion, the present study indicates that PTZ-kindling is associated with an imbalance between excitatory and inhibitory systems which is apparent early in the epileptogenic process.

Effect of ovarian hormones on the hypothalamic excitatory amino acids system during sexual maturation in female rats.

The present experiments were designed to study in female rats during sexual maturation: (1) the hypothalamic release of aspartate (Asp), glutamate (Glu) and glycine (Gly) which are the excitatory amino acids (EAAs) involved in NMDA neurotransmission and of taurine (Tau), a putative inhibitory amino acid of GnRH secretion; (2) the relationships between the effect of estrogen-progesterone (EP) on the release of these EAAs and the secretion of gonadotropins, and (3) the effect of hypothalamic NMDA receptor stimulation on EAAs release by the hypothalamus as well as the effect of EP on this release. The release of EAAs by the anterior preoptic and medial-basal hypothalamic areas (APOA-MBH) is significantly higher in peripubertal than in prepubertal rats (p < 0.01). EP treatment in prepubertal rats (16 days of age) decreased LH and FSH plasmatic levels and also the in vitro release of Asp, Glu, Gly and Tau. Contrary to the observations in prepubertal rats, in 30-day-old peripubertal rats the ovarian hormones significantly (p < 0.01) increased the levels of LH and FSH as well as the release to the medium of these amino acids.(ABSTRACT TRUNCATED AT 250 WORDS)