Lead-induced neurodegenerative events and abnormal behaviors occur via ORXRergic/GABA(A)Rergic mechanisms in a marine teleost.

The hindering effects of metals and in particular lead (Pb) are representing a growing threat to aquatic organisms such as fish. This observation derives from toxic concentrations of Pb accounting for altered neurophysiological activities of some interesting teleost models like Thalassoma pavo, a fish species highly known for its host-cleaning symbiosis. In this study, the nominal PbNO(3) concentration of 1.6 mg/L was capable of reducing feeding and resting bouts as early as 24 h of exposure while hyperactive swimming episodes were also detected. Such abnormal behaviors were tightly correlated to up-regulated orexin receptor (ORXR) mRNA expression levels in some brain areas such as the lateral thalamic nucleus (+213%) and the optic tectum (+90%) with respect to controls. Interestingly, these transcriptional effects seemed to be attenuated when Pb-exposed fish received either 100 ng/g of ORX-A (-70%) or 0.1 µg/g of γ-aminobutyric acid(A) receptor (GABA(A)R) agonist muscimol (MUS; -97%) compared to fish exposed to Pb alone. Moreover, a net neurodegenerative process of the different brain areas was reported after Pb exposure as displayed by their marked amino cupric silver stained cells while these cells were devoid of any staining reaction after treatment with MUS only. Conversely, addition of the GABA(A)R antagonist bicuculline (BIC; 1 µg/g) moderately (p<0.05) enhanced Pb-dependent behavioral and neurodegenerative actions. Overall, these first indications strongly point to altered ORXR/GABA(A)R interactions during neurotoxic events of a metal that by evoking harmful neurobiological dysfunctions may endanger the survival of commercially valuable fish with eventual repercussions on human health.

α GABA(A) subunit-orexin receptor interactions activate learning/motivational pathways in the goldfish.

Orexins (ORXs) cross-talking with γ-aminobutyric acid(A) receptor (GABA(A)R) is beginning to constitute a key neuronal signaling feature responsible for the successful promotion of sleep-wake cycle, feeding and motor behaviors plus reward/motivational activities. In this work, ORX-A and the two α GABA(A)R agonists (zolpidem, ZOL; diazepam, DZP) accounted for very great (p<0.001) increases of feeding while only DZP elicited great (p<0.01) levels of food intake in the goldfish (Carassius auratus). It was, however, T-maze and conditioned place preference (CPP) methods that allowed us to specifically establish learning/reward-related events operating in an ORX-A+GABA(A)R-dependent fashion in our experimental model. T-maze data showed that conditioned ORX-A treated-fish were capable of reaching the red/blue chamber and ingesting their food reward in a very greatly reduced latency time with respect to untreated conditioned fish while DZP and ZOL greatly and moderately (p<0.05) reduced their latency time, respectively. Regarding CPP study, conditioned ORX-A- and DZP-treated animals showed comparably greater preferences for the conditioned compartment that became even greater in ORX-A+DZP-treated fish. Surprisingly, ORX receptor expression of the telencephalon was preferentially activated by ORX-A treatments while diencephalic/mesencephalic structures and namely the tuberculum posterioris (TPp) were more sensitive to DZP especially following treatment with ORX-A+DZP. Overall, behavioral performances along with ORX receptor transcriptional properties tend to point to α GABA(A)R agonists as enhancers of palatability while the ORXergic system constitutes a crucial link between satiety-related and cognitive centers through the activation of TPp thus proposing this ascending dopaminergic system as a key target of learning/reward processes in fish.

Aestivation and hypoxia-related events share common silent neuron trafficking processes.

BACKGROUND: The availability of oxygen is a limiting factor for neuronal survival since low levels account not only for the impairment of physiological activities such as sleep-wake cycle, but above all for ischemic-like neurodegenerative disorders. In an attempt to improve our knowledge concerning the type of molecular mechanisms operating during stressful states like those of hypoxic conditions, attention was focused on eventual transcriptional alterations of some key AMPAergic silent neuronal receptor subtypes (GluR1 and GluR2) along with HSPs and HIF-1α during either a normoxic or a hypoxic aestivation of a typical aquatic aestivator, i.e. the lungfish (Protopterus annectens). RESULTS: The identification of partial nucleotide fragments codifying for both AMPA receptor subtypes in Protopterus annectens displayed a putative high degree of similarity to that of not only fish but also to those of amphibians, birds and mammals. qPCR and in situ hybridization supplied a very high (p < 0.001) reduction of GluR1 mRNA expression in diencephalic areas after 6 months of aerial normoxic aestivation (6mAE). Concomitantly, high (p < 0.01) levels of HSP70 mRNAs in hypothalamic, mesencephalic and cerebellar areas of both 6mAE and after 6 months of mud hypoxic aestivation (6mMUD) were detected together with evident apoptotic signals. Surprisingly, very high levels of GluR2 mRNAs were instead detected in thalamic along with mesencephalic areas after 6 days of normoxic (6dAE) and hypoxic (6dMUD) aestivation. Moreover, even short- and long-term hypoxic states featured high levels of HIF-1α and HSP27 transcripts in the different brain regions of the lungfish. CONCLUSIONS: The distinct transcriptional variations of silent neurons expressing GluR1/2 and HSPs tend to corroborate these factors as determining elements for the physiological success of normoxic and hypoxic aestivation. A distinct switching among these AMPA receptor subtypes during aestivation highlights new potential adaptive strategies operating in key brain regions of the lungfish in relation to oxygen availability. This functional relationship might have therapeutic bearings for hypoxia-related dysfunctions, above all in view of recently identified silent neuron-dependent motor activity ameliorations in mammals.

Flat and tubular membrane systems for the reconstruction of hippocampal neuronal network.

The selection of appropriate biomaterials that promote cellular adhesion and growth is particularly important for the in vitro reconstruction of neuronal network. This study focused on the development of new polymeric membranes in flat and tubular (hollow-fibre) configurations as novel biomaterials for neuronal outgrowth. Two membrane systems constituted by modified polyetheretherketone (PEEK-WC) and polyacrylonitrile (PAN) membranes were developed and used for the culture of hamster hippocampal neurons. We demonstrated that all investigated membranes supported the adhesion and growth of hippocampal neurons enhancing neuronal differentiation and neurite alignment. The differences in cell behaviours between cells cultured on flat and hollow-fibre (HF) membranes were highlighted by the quantitative analysis of neuronal marker fluorescence intensity, morphometric analysis, RT-PCR analysis and also by metabolic activity measurements. In particular, the PAN HF membranes showed ideal growth culture conditions, guaranteeing adequate levels of metabolic features. Primary hippocampal cells cultured on PAN HF membranes were able to recreate in vitro a 3D neural tissue-like structure that, mimicking the hippocampal tissue, could be used as a tool for the study of natural and pathological neurobiological events.

PAN hollow fiber membranes elicit functional hippocampal neuronal network.

This study focuses on the development of an advanced in vitro biohybrid culture model system based on the use of hollow fibre membranes (HFMs) and hippocampal neurons in order to promote the formation of a high density neuronal network. Polyacrylonitrile (PAN) and modified polyetheretherketone (PEEK-WC) membranes were prepared in hollow fibre configuration. The morphological and metabolic behaviour of hippocampal neurons cultured on PAN HF membranes were compared with those cultured on PEEK-WC HF. The differences of cell behaviour between HFMs were evidenced by the morphometric analysis in terms of axon length and also by the investigation of metabolic activity in terms of neurotrophin secretion. These findings suggested that PAN HFMs induced the in vitro reconstruction of very highly functional and complex neuronal networks. Thus, these biomaterials could potentially be used for the in vitro realization of a functional hippocampal tissue analogue for the study of neurobiological functions and/or neurodegenerative diseases.

Feeding behaviors and ORXR-ß-GABA A R subunit interactions in Carassius auratus.

Orexins are one of the most potent orexigenic factors in fish that through their interaction with the GABA(A) receptor system assures the successful execution of feeding, motor and sleep-wake activities. In the present study, the effects of ORX-A (10ng/g BW) very greatly enhanced (p<0.001) the time spent in feeding behaviors while at the same time moderately increased (p<0.05) food intake of the goldfish. It is worthy to note that the great variations of time spent in feeding behaviors induced by ß GABA(A)R agonist (muscimol, MUS) and antagonist (bicuculline, BIC) did not result to be correlated to any significant variations of food intake. It was, however, a T-maze study allowing us to establish that learning and mnemonic events very likely also operated in an ORX-A+GABA(A)R-dependent fashion in our fish model. Indeed, animals conditioned by red/blue lights greatly reduced latency time in the presence of ORX-A while neither MUS nor BIC alone modified such a parameter, with the exception of ORX-A+MUS being responsible for a moderate decrease of latency time with respect to conditioned fish treated with a saline solution. Conversely, ORX-A+MUS/BIC seemed to interfere with ORX-A actions as shown by their very great increase in latency time. Moreover, T-maze results appeared to be strengthened by evident ORXR transcriptional variations especially by the very great mRNA densities detected in some telencephalic regions of animals treated with ORX-A. Of all telencephalic regions Dl, considered homologous to the mammalian hippocampus, proved to be a major target for ORX-A effects. Overall, these data suggest that it is mainly the ORXergic system that promotes feeding behaviors via reward pathways in teleost fish as in mammals. Surprisingly, ß GABA(A)R drugs did not modify such behaviors when given alone while the inhibitory effect on cognitive/reward processes was evoked when given together with ORX-A, suggesting that more than ß subunits other GABA(A)R subunits could be promoting mnemonically guided motor behaviors.

Distinct α GABA(A)R subunits influence structural and transcriptional properties of CA1 hippocampal neurons.

The hippocampus is recognized as a major telencephalic area modulating learning and episodic memory through the activation of its different subregions. The various functional properties of Ammon's horn 1 (Cornu Amonis 1; CA1) area have been shown to rely on GABAergic and Glutamat- (Glu)-ergic neuronal signals during both postnatal and adult stages. For this purpose, it was the aim of the present study to establish whether certain alpha GABA(A)R subunits (alpha(2,5)) were capable of modifying CA1 structural and functional features via their interaction with specific NMDA receptor subunits such as NR1 during early development stages of the hibernating hamster (Mesocricetus auratus). Indeed, in vitro addition of the selective alpha(2,5) GABA(A)R agonist diazepam (DZP; alpha(2,5)) accounted for early neuronal formations that were blocked by its antagonist flumazenil (FLM). In particular, the former drug caused very great (p<0.001) increases of dendritic sprouting and branching processes mainly at day in vitro (DIV) 3, while its effects still continued to be responsible for moderate (p<0.05) increases of axonal length during the entire culture period. Contextually, DZP was also responsible for a very great up-regulated expression of neuritic NR1 and MAP2 together with a great (p<0.01) increase of synaptophysin at DIV7. Overall, this first study suggests a specifically tight cross-talking relationship of GABAergic/Gluergic mechanisms operating during CA1 neuronal development, which may bring us closer to the identification of more selective therapeutic targets for hippocampal-linked neurological disorders.

Lungfish aestivating activities are locked in distinct encephalic γ-aminobutyric acid type A receptor α subunits.

Ammonia in dipnoans plays a crucial role on neuronal homeostasis, especially for those brain areas that maintain torpor and awakening states in equilibrium. In the present study, specific α subunits of the major neuroreceptor inhibitory complex (GABA(A) R), which predominated during some phases of aestivation of the lungfish Protopterus annectens, turned out to be key adaptive factors of this species. From the isolation, for the first time, of the encoding sequence for GABA(A) R α1, α4 , and α5 subunits in Protopterus annectens, qPCR and in situ hybridization levels of α4 transcript in thalamic (P < 0.001) and mesencephalic (P < 0.01) areas proved to be significantly higher during long aestivating maintenance states. Very evident α5 mRNA levels were detected in diencephalon during short inductive aestivating states, whereas an α4 /α1 turnover characterized the arousal state. Contextually, the recovery of physiological activities appeared to be tightly related to an evident up-regulation of α1 transcripts in telencephalic and cerebellar sites. Surprisingly, TUNEL and amino cupric silver methods corroborated apoptotic and neurodegenerative cellular events, respectively, above all in telencephalon and cerebellum of lungfish exposed to long maintenance aestivating conditions. Overall, these results tend to underlie a novel GABAergic-related ON/OFF molecular switch operating during aestivation of the lungfish, which might have a bearing on sleeping disorders.

Influence of micro-patterned PLLA membranes on outgrowth and orientation of hippocampal neurites.

In neuronal tissue engineering many efforts are focused on creating biomaterials with physical and chemical pathways for controlling cellular proliferation and orientation. Neurons have the ability to respond to topographical features in their microenvironment causing among others, axons to proliferate along surface features such as substrate grooves in micro-and nanoscales. As a consequence these neuronal elements are able to correctly adhere, migrate and orient within their new environment during growth. Here we explored the polarization and orientation of hippocampal neuronal cells on nonpatterned and micro-patterned biodegradable poly(l-lactic acid) (PLLA) membranes with highly selective permeable properties. Dense and porous nonpatterned and micro-patterned membranes were prepared from PLLA by Phase Separation Micromolding. The micro-patterned membranes have a three-dimensional structure consisting of channels and ridges and of bricks of different widths. Nonpatterned and patterned membranes were used for hippocampal neuronal cultures isolated from postnatal days 1-3 hamsters and the neurite length, orientation and specific functions of cells were investigated up to 12 days of culture. Neurite outgrowth, length plus orientation tightly overlapped the pattern of the membrane surface. Cell distribution occurred only in correspondence to membrane grooves characterized by continuous channels whereas on membranes with interconnected channels, cells not only adhered to and elongated their cellular processes in the grooves but also in the breaking points. High orientation degrees of cells were determined particularly on the patterned porous membranes with channel width of 20 mum and ridges of 17 mum whereas on dense nonpatterned membranes as well as on polystyrene culture dish (PSCD) controls, a larger number of primary developed neurites were distributed. Based on these results, PLLA patterned membranes may directly improve the guidance of neurite extension and thereby enhancing their orientation with a consequently highly ordered neuronal cell matrix, which may have strong bearings on the elucidation of regeneration mechanisms.

Environmental stressors and neurobiological features of marine teleosts: histamine receptors as targets.

The excessive levels of aquatic endocrine disruptors (EDs) and namely heavy metals plus xenoestrogens account for irregular gas exchange processes, reduced reproductive success, as well as abnormal social interactions of marine teleost fish. These effects at the encephalic level appear to derive from the interference of major signaling factors such as histamine (HA) neuroreceptor subtypes (H(1-4)R). HA is one of the main biogenic amine neuronal system responsible for regulatory homeostatic functions, including sleep-wake rhythms and motor activities. Recently, interests have begun to focus attention on toxic effects of some heavy metals, i.e., cadmium (Cd) and lead (Pb), and how they are capable of eliciting motor dysfunctions via HAergic receptor subtypes. Interestingly, subtype 2 (H(2)R) proved to be a preferential target of heavy metal-dependent altered locomotor maneuvers, as displayed by its specific antagonist (cimetidine)-inducing non-synchronous swimming activities (Santos et al., 2003, Pharmacol Biochem Behav 75:25-33). Conversely, although the preferential H(3)R antagonist (thioperamide) did not interfere with normal swimming behaviors, it surprisingly did ameliorate heavy metal-dependent hyperactive states (Giusi et al., 2008, Toxicol Appl Pharmacol 227:248-256). In the case of the xenoestrogens atrazine and endosulfan, their actions tend to mostly account for feeding alterations through hypothalamic H(3)R-dependent mechanisms. The aim of this review is to highlight the type of ED-HAergic neuroreceptor variations that are involved in stressor-dependent neurobehavioral responses of commercially valuable marine teleosts.

GABAergic influences on ORX receptor-dependent abnormal motor behaviors and neurodegenerative events in fish.

At date the major neuroreceptors i.e. gamma-aminobutyric acid(A) (GABA(A)R) and orexin (ORXR) systems are beginning to be linked to homeostasis, neuroendocrine and emotional states. In this study, intraperitoneal treatment of the marine teleost Thalassoma pavo with the highly selective GABA(A)R agonist (muscimol, MUS; 0.1 microg/g body weight) and/or its antagonist bicuculline (BIC; 1 microg/g body weight) have corroborated a GABA(A)ergic role on motor behaviors. In particular, MUS induced moderate (p<0.05) and great (p<0.01) increases of swimming towards food sources and resting states after 24 (1 dose) and 96 (4 doses) h treatment sessions, respectively, when compared to controls. Conversely, BIC caused a very strong (p<0.001) reduction of the former behavior and in some cases convulsive swimming. From the correlation of BIC-dependent behavioral changes to neuronal morphological and ORXR transcriptional variations, it appeared that the disinhibitory action of GABA(A)R was very likely responsible for very strong and strong ORXR mRNA reductions in cerebellum valvula and torus longitudinalis, respectively. Moreover these effects were linked to evident ultra-structural changes such as shrunken cell membranes and loss of cytoplasmic architecture. In contrast, MUS supplied a very low, if any, argyrophilic reaction in hypothalamic and mesencephalic regions plus a scarce level of ultra-structural damages. Interestingly, combined administrations of MUS+BIC were not related to consistent damages, aside mild neuronal alterations in motor-related areas such as optic tectum. Overall it is tempting to suggest, for the first time, a neuroprotective role of GABA(A)R inhibitory actions against the overexcitatory ORXR-dependent neurodegeneration and consequently abnormal swimming events in fish.

Distinct alpha subunits of the GABAA receptor are responsible for early hippocampal silent neuron-related activities.

The modulatory actions of GABA(A) receptor subunits are crucial for morphological and transcriptional neuronal activities. In this study, growth of hamster hippocampal neurons on biohybrid membrane substrates allowed us to show for the first time that the two major GABA(A) alpha receptor subunits (alpha(2,5)) are capable of early neuronal shaping plus expression differences of some of the main neuronal cytoskeletal factors (GAP-43, the neurotrophin--BDNF) and of Gluergic subtypes. In a first case the inverse alpha(5) agonist (RY-080) seemed to account for the reduction of dendritic length at DIV7, very likely via lower BDNF levels. Conversely, the effects of the preferentially specific agonist for hippocampal alpha(2) subunit (flunitrazepam) were, instead, directed at the formation of growth cones at DIV3 in the presence of greatly (P < 0.01) diminished GAP-43 levels as displayed by strongly reduced axonal sprouting. It is interesting to note that concomitantly to these morphological variations, the transcription of some Gluergic receptor subtypes resulted to be altered. In particular, flunitrazepam was responsible for a distinctly rising expression of axonal NR1 mRNA levels from DIV3 (P < 0.01) until DIV7 (P < 0.001), whereas RY-080 evoked a very great (P < 0.001) downregulation of dendritic GluR2 at only DIV7. Together, our results demonstrate that GABA(A) alpha(2,5) receptor-containing subunits by regulating the precise synchronization of cytoskeletal factors are considered key modulating neuronal elements of hippocampal morphological growth features. Moreover, the notable NR1 and GluR2 transcription differences promoted by these GABA(A) alpha subunits tend to favorably corroborate the early role of alpha(2) + alpha(5) on hippocampal neuronal networks in hibernating rodents through the recruitment and activation of silent neurons, and this may provide useful insights regarding molecular neurodegenerative events.

Light- and dark-dependent orexinergic neuronal signals promote neurodegenerative phenomena accounting for distinct behavioral responses in the teleost Thalassoma pavo.

The neuropeptides hypocretins/orexins (ORX) are known to control state-dependent activities such as sleep-wakefulness, energy homeostasis, thermoregulation, and maternal behaviors. To date, interests regarding environmental-related ORX-ergic neuronal functions have dealt with mammals; only recently is attention beginning to be directed toward aquatic vertebrates. Here, photoperiod-dependent effects of ORX-A on behavioral, neurodegenerative and transcriptional activities were evaluated in some forebrain areas of a teleost Labridae (ornate wrasse, Thalassoma pavo). The ornate wrasse, when treated intraperitoneally with a high physiological dose (100 ng/g) of ORX-A and exposed to a natural photoperiod (12L:12D), exhibited very high (P < 0.001) locomotion and feeding behaviors. ORX-A in the presence of a constant light photoperiod accounted for numerically even greater (>500%) feeding frequencies. Conversely, constant dark conditions very strongly reduced feeding habits and moderately (P < 0.05) increased resting states. In this case, the same ORX-A and photoperiodic conditions responsible for altered behaviors also induced neurodegenerative processes in the different hypothalamic, mesencephalic, and telencephalic neuronal fields. Interestingly, this ORX-A treatment seemed to be correlated to greater up-regulatory patterns of ORX receptor mRNA in these same brain areas, above all under constant light conditions rather than natural photoperiod. On the other hand, telencephalic sites provided a very active expression capacity during the dark phase. Overall, these results suggest for the first time that at least in the ornate wrasse, light- and dark-dependent ORX-ergic neuronal activities are able to cause short- and long-term abnormal motor behaviors, likely through neurodegenerative and transcriptional events in a brain regional manner.

A sexually dimorphic distribution pattern of the novel estrogen receptor G-protein-coupled receptor 30 in some brain areas of the hamster.

The isolation of the G-protein-coupled receptor 30 (GPR30), an orphan membrane receptor unrelated to nuclear estrogen receptors (ERs), has become a key factor towards the unraveling of rapid estrogen action. This membrane receptor together with cellular signaling intermediaries, i.e., extracellular signal-dependent kinases 1 and 2, may promote neuronal proliferation and differentiation activities. In the present study, an evident gene expression pattern of GPR30 characterized postnatal 7 (young) and 60 (adult) days of age hamsters as shown by its heterogeneous mRNA distribution in hypothalamic, amygdalar and cerebellar areas of both sexes. In particular, most of the brain areas considered in the adult hamster plus only the amygdala and cerebellum of young animals behaved in a sexually dimorphic fashion. This similar pattern was also detected for the ERalpha and beta, as shown by the latter receptor prevailing in young and adult females, while the former predominated in young females. Even for the two kinases, a sexually dimorphic distribution was featured above all for young hamsters. Overall, the findings of the present study established a distinct expression pattern of the novel ER (GPR30) that may operate differently in some brain areas of the hamster and this may provide interesting insights regarding its probable neuroprotective role during the execution of some hibernating states, which are typical of our rodent model.

Specific cerebral heat shock proteins and histamine receptor cross-talking mechanisms promote distinct lead-dependent neurotoxic responses in teleosts.

Recent interests are beginning to be directed towards toxic neurobiological dysfunctions caused by lead (Pb) in aquatic vertebrates. In the present work, treatment with a maximum acceptable toxic concentration of this heavy metal was responsible for highly significant (p<0.01) abnormal motor behaviors such as hyperactive movements in the teleost Thalassoma pavo and the same treatment accounted for significantly (p<0.05) enhanced hyperventilating states. On the other hand, greater abnormal motor behaviors were detected in the presence of the histamine (HA) receptor subtype 2 (H(2)R) antagonist cimetidine (Cim), as shown by the very robust (p<0.001) increases of the two behavioral states. Interestingly, elevated expression levels of stress-related factors, i.e. heat shock protein70/90 (HSP90/70) orthologs were reported for the first time in hypothalamic and mesencephalic areas of Pb-treated teleosts. In particular, an up-regulation of HSP70 was readily detected when this heavy metal was given concomitantly with Cim, while the histamine subtype 3 antagonist (H(3)R) thioperamide (Thio), instead, blocked Pb-dependent up-regulatory trends of both chaperones in mostly hypothalamic areas. Moreover, intense neuronal damages of the above brain regions coincided with altered expressions of HSP70 and HSP90 when treated only with Cim. Overall these first results show that distinct H(n)R are able to exert a net neuroprotective role arising from their interaction with chaperones in fish exposed to Pb-dependent stressful conditions making this a potentially key interaction especially for T. pavo, aquatic species which plays an important ecological role towards the survival of other commercially vital fishes.

Some environmental contaminants influence motor and feeding behaviors in the ornate wrasse (Thalassoma pavo) via distinct cerebral histamine receptor subtypes.

Common environmental contaminants such as heavy metals and pesticides pose serious risks to behavioral and neuroendocrine functions of many aquatic organisms. In the present study, we show that the heavy metal cadmium and the pesticide endosulfan produce such effects through an interaction of specific cerebral histamine receptor subtypes in the teleost ornate wrasse (Thalassoma pavo). Treatment of this teleost with toxic cadmium levels for 1 week was sufficient to induce abnormal swimming movements, whereas reduced feeding behaviors were provoked predominantly by elevated endosulfan concentrations. In the brain, these environmental contaminants caused neuronal degeneration in cerebral targets such as the mesencephalon and hypothalamus, damage that appeared to correlate with altered binding levels of the three major histamine receptors (subtypes 1, 2, and 3). Although cadmium accounted for reduced binding activity of all three subtypes in most brain regions, it was subtype 2 that seemed to be its main target, as shown by a very great (p < 0.001) down-regulation in mesencephalic areas such as the stratum griseum central layer. Conversely, endosulfan provided very great and great (p < 0.01) up-regulating effects of subtype 3 and 1 levels, respectively, in preoptic-hypothalamic areas such as the medial part of the lateral tuberal nucleus, and in the suprachiasmatic nucleus. These results suggest that the neurotoxicant-dependent abnormal motor and feeding behaviors may well be tightly linked to binding activities of distinct histamine subtypes in localized brain regions of the Thalassoma pavo.

The histaminergic signaling system exerts a neuroprotective role against neurodegenerative-induced processes in the hamster.

The neurotoxic 3-nitropropionic acid (3-NP), a freckled milk vetch-derived inhibitor of mitochondrial enzymatic processes that is capable of mimicking the typical pathological features of neurodegenerative disorders, behaved in a differentiated manner in a hibernating rodent (hamster) with respect to a nonhibernating rodent (rat). Treatment of the two rodents with both an acute and chronic 3-NP dose supplied deleterious neuronal effects due to distinct histamine receptor (H(n)R) transcriptional activities, especially in the case of the rat. In hamsters, these treatment modalities accounted for overall reduced global activity in a freely moving environment and overt motor symptoms such as hindlimb dystonia and clasping with respect to the greater abnormal motor behaviors in rats. This behavioral difference appeared to be strongly related to qualitative fewer neuronal alterations and, namely, lesser crenated cell membranes, swollen mitochondria, and darkened nuclei in hamster brain areas. Moreover, a mixed H(1,3)R mRNA expression pattern was reported for both rodents treated with a chronic 3-NP dose as demonstrated by predominantly low H1R mRNA levels (>50%) in rat striatum and cortex, whereas extremely high H3R levels (>80%) characterized the lateral and central amygdala nuclei plus the striatum of hamsters. Interestingly, the H3R antagonist (thioperamide) blocked 3-NP-dependent behaviors plus induced an up-regulation of H1R levels in mainly the above-reported hamster amygdalar nuclei. Overall, these results show, for the first time, that a major protective role against neurodegenerative events appears to be strongly related to the expression activity of H(1,3)R subtypes of amygdalar neurons in this hibernating model.

Effects of the xenoestrogen bisphenol A in diencephalic regions of the teleost fish Coris julis occur preferentially via distinct somatostatin receptor subtypes.

The xenoestrogen bisphenol A, a contaminant used in the manufacturing of polymers for many consumer products, has been shown to mimic estrogenic actions. This xenoestrogen regulates secretion and expression of pituitary lactotrophs plus morphological and structural features of estrogen target tissues in rodents. Recently, ecological hazards produced by bisphenol A have drawn interests towards the effects of this environmental chemical on neurobiological functions of aquatic vertebrates of which little is known. In this study, the effects of bisphenol A on the distribution of the biologically more active somatostatin receptor subtypes in diencephalic regions of the teleost fish Coris julis were assessed using nonpeptide agonists (L-779, 976 and L-817, 818) that are highly selective for subtype(2) and subtype(5), respectively. Bisphenol A proved to be responsible for highly significant increased binding levels of subtype(2) in hypothalamic areas, while markedly decreased levels of subtype(5) were found in these diencephalic areas, as well as in the medial preglomerular nucleus. The extensive distribution of somatostatin receptor subtype(2) and subtype(5) in the teleost diencephalic areas suggests that, like in mammals, this receptor system may not only be involved in enhanced hypophysiotropic neurohormonal functions but might also promote neuroplasticity events.

Different somatostatin receptor subtypes are operating in the brain of the teleost fish, Coris julis.

Characterization of somatostatinergic (sst) neuronal activity through the application of nonpeptidyl agonists L-779,976 and L-817,818 which are highly specific for the sst receptors (sstr) sstr(2) and sstr(5), respectively, shows for the first time that sstr2, 5-like subtypes are the two major sstr subtypes operating in the brain of the teleost sea wrasse, Coris julis. A somewhat high but heterogeneous distribution pattern (> 30 < 180 fmol/mg wet tissue weight) of neurons expressing sstr2, 5 was reported in the different diencephalic regions plus in mesencephalon and telencephalon while low values were obtained in the cerebellum. Application of the above nonpeptidyl agonists permitted us to identify sstr2-like as the predominant subtype in telencephalic areas such as the entopeduncular nucleus (E) and postcommissural nucleus of the ventral telencephalon (Vp) as well as in hypothalamic and thalamic areas. At the same time high levels of neurons expressing sstr5-like, that greatly overlap those of sstr2-like in the diencephalic areas such as the anteroventral part of the preoptic nucleus (NPOav), the dorsal habenular nucleus (NHd) and the ventrolateral thalamic nucleus (VL), indicate that sstr2-like is very likely not the only sstr subtype acting in this fish brain. The predominance of sstr5-like in other brain areas is confirmed by the high quantities of this subtype in mesencephalic areas such as the torus longitudinalis (TLo). Overall, the discriminately differing densities of neurons expressing both subtypes seem to point to this system as a key molecular basis accounting for the distinct neurophysiological and behavioral sst-dependent activities in Coris julis.