Fusiform Neurons Research Articles

Development of electrophysiological properties of fusiform neurons from the dorsal cochlear nucleus of mice before and after hearing onset.

The dorsal cochlear nucleus (DCN) in the auditory brainstem integrates auditory and somatosensory information. Mature DCN fusiform neurons fall into two qualitatively distinct types: quiet, with no spontaneous regular action potential firing, or active, with regular spontaneous action potential firing. However, how these firing states and other electrophysiological properties of fusiform neurons develop during early postnatal days to adulthood is not known. Thus, we recorded fusiform neurons from mice from P4 to P21 and analyzed their electrophysiological properties. In the prehearing phase (P4-P13), we found that most fusiform neurons are quiet, with active neurons emerging after hearing onset at P14. Subthreshold properties underwent significant changes before hearing onset, whereas changes to the action potential waveform occurred mainly after P14, with the depolarization and repolarization phases becoming markedly faster and half-width significantly decreased. The activity threshold in posthearing neurons was more negative than in prehearing cells. Persistent sodium current (INaP) was increased after P14, coinciding with the emergence of spontaneous firing. Thus, we suggest that posthearing expression of INaP leads to hyperpolarization of the activity threshold and the active state of the fusiform neuron. At the same time, other changes refine the passive membrane properties and increase the speed of action potential firing of fusiform neurons.NEW & NOTEWORTHY Auditory brainstem neurons express unique electrophysiological properties adapted for their complex physiological functions that develop before hearing onset. Fusiform neurons of the DCN present two firing states, quiet and active, but the origin of these states is not known. Here, we showed that the quiet and active states develop after hearing onset at P14, along with changes in action potentials, suggesting an influence of auditory input on the refining of fusiform neuron's excitability.

Salicylate activates KATP channels and reduces spontaneous firing in glycinergic cartwheel neurons in the dorsal cochlear nucleus of rats

High doses of salicylate induce tinnitus in humans and experimental animals. The Dorsal Cochlear Nucleus is implicated with the genesis of tinnitus, and increased activity in this nucleus is seen in animal models of tinnitus. Incubation of brainstem slices containing the DCN with millimolar salicylate reduces the spontaneous firing of glycinergic cartwheel neurons and glycinergic neurotransmission on fusiform neurons, the principal neuron of this nucleus. However, the mechanism of salicylate mediating this effect is not known. Recently, we have shown that KATP channels strongly modulate the spontaneous firing of cartwheel neurons. We tested if KATP channels could mediate the effects of salicylate on cartwheel neurons. Perfusion of 1.4 mM salicylate hyperpolarizes the membrane of cartwheel neurons and stops firing. Salicylate produces an outward current similar to the KATP current seen in quiet cartwheel neurons. Activation of this current is occluded by the KATP agonist diazoxide, which is produced by the opening of KATP channels. The antagonist of AMP-kinase (AMPK), dorsomorphim, inhibited salicylate effects, suggesting that they could be mediated by activation of this kinase. Still, the AMPK agonist, AICAR, did not reproduce salicylate effects but occluded them. Additionally, inhibiting mitochondrial ATP synthesis with the protonophore CCCP reproduced, albeit with less efficacy, and inhibited the effects of salicylate. We concluded that salicylate in millimolar concentrations opens KATP channels in DCN cartwheel neurons, inhibiting spontaneous firing of these neurons, probably by activating AMPK and reducing mitochondrial ATP synthesis.

Age-Related Hearing Loss: Sensory and Neural Etiology and Their Interdependence.

Age-related hearing loss (ARHL) is a common, increasing problem for older adults, affecting about 1 billion people by 2050. We aim to correlate the different reductions of hearing from cochlear hair cells (HCs), spiral ganglion neurons (SGNs), cochlear nuclei (CN), and superior olivary complex (SOC) with the analysis of various reasons for each one on the sensory deficit profiles. Outer HCs show a progressive loss in a basal-to-apical gradient, and inner HCs show a loss in a apex-to-base progression that results in ARHL at high frequencies after 70 years of age. In early neonates, SGNs innervation of cochlear HCs is maintained. Loss of SGNs results in a considerable decrease (~50% or more) of cochlear nuclei in neonates, though the loss is milder in older mice and humans. The dorsal cochlear nuclei (fusiform neurons) project directly to the inferior colliculi while most anterior cochlear nuclei reach the SOC. Reducing the number of neurons in the medial nucleus of the trapezoid body (MNTB) affects the interactions with the lateral superior olive to fine-tune ipsi- and contralateral projections that may remain normal in mice, possibly humans. The inferior colliculi receive direct cochlear fibers and second-order fibers from the superior olivary complex. Loss of the second-order fibers leads to hearing loss in mice and humans. Although ARHL may arise from many complex causes, HC degeneration remains the more significant problem of hearing restoration that would replace the cochlear implant. The review presents recent findings of older humans and mice with hearing loss.

Vestibular Brainstem Dysmorphology in an Animal Model of Autism Spectrum Disorder

Introduction - Prenatal exposure to the antiepileptic drug valproic acid (VPA) is associated with an elevated risk of a diagnosis of autism spectrum disorder (ASD) in humans. Accordingly, in utero exposure to VPA is a clinically relevant and validated animal model of ASD. Previous work from our lab on VPA-exposed animals revealed significant changes in the auditory brainstem and cerebellum. Specifically, we have shown fewer neurons in the auditory brainstem, reduced expression of calcium binding proteins, reduced connectivity and hyperactivation in response to pure tone stimuli. In the cerebellum, we have found smaller Purkinje cells, reduced expression of calbindin (CB) and significant gait ataxia. Based on these findings, we rationalized that brainstem vestibular pathways might similarly be affected in VPA-exposed animals. We therefore hypothesized that in utero VPA exposure will result in fewer neurons in the vestibular nuclei, reduced CB+ immunolabeling, postural instability and poor gait performance after vestibular challenge. Methods - After timed mating, pregnant rats were fed peanut butter meals from embryonic days 7 through 12. Dams in the VPA groups were fed peanut butter with 800mg/kg VPA on E10 and 12. Pups were delivered without interference and were handled by experimenters from postnatal day (P) 15-20. Starting on P21, control and VPA-exposed animals underwent a battery of motor tests and vestibular challenges from P21-28. All morphological studies were done using brain tissue from P28 animals. Results - Compared to control animals, we found significantly fewer neurons in the spinal, lateral and superior vestibular nuclei and larger neuronal cell bodies in the spinal and lateral vestibular nuclei in VPA-exposed animals. In the lateral nucleus we also found significantly more stellate and fusiform neurons but fewer round/oval neurons. Preliminary examination of the number of CB+ terminals in the vestibular nuclei suggests that afferent inputs to these neurons may have reduced CB expression. Behavioral tests suggest that VPA-exposed animals are more severely impacted by vestibular challenge than control animals. Conclusion and Significance - Our results are consistent with both structural and functional changes in animals exposed to VPA in utero. Together, our research provides evidence for significant brainstem dysfunction and we propose these alterations extend to human cases of ASD. This work will clarify the brainstem centers impacted in ASD and may lead to the development of simple, non-invasive tests of vestibular function to screen for ASD.

ATP-sensitive K+ channels control the spontaneous firing of a glycinergic interneuron in the auditory brainstem.

Cartwheel neurons provide potent inhibition to fusiform neurons in the dorsal cochlear nucleus (DCN). Most cartwheel neurons fire action potentials spontaneously, but the ion channels responsible for this intrinsic activity are unknown. We investigated the ion channels responsible for the intrinsic firing of cartwheel neurons and the stable resting membrane potential found in a fraction of these neurons (quiet neurons). Among the ion channels controlling membrane potential of cartwheel neurons, the presence of open ATP-sensitive potassium channels (KATP ) is responsible for the existence of quiet neurons. Our results pinpoint KATP channel modulation as a critical factor controlling the firing of cartwheel neurons. Hence, it is a crucial channel influencing the balance of excitation and inhibition in the DCN. Cartwheel neurons from the dorsal cochlear nucleus (DCN) are glycinergic interneurons and the primary source of inhibition on the fusiform neurons, the DCN's principal excitatory neuron. Most cartwheel neurons present spontaneous firing (active neurons), producing a steady inhibitory tone on fusiform neurons. In contrast, a small fraction of these neurons do not fire spontaneously (quiet neurons). Hyperactivity of fusiform neurons is seen in animals with behavioural evidence of tinnitus. Because of its relevance in controlling the excitability of fusiform neurons, we investigated the ion channels responsible for the spontaneous firing of cartwheel neurons in DCN slices from rats. We found that quiet neurons presented an outward conductance not seen in active neurons, which generates a stable resting potential. This current was sensitive to tolbutamide, an ATP-sensitive potassium channel (KATP ) antagonist. After inhibition with tolbutamide, quiet neurons start to fire spontaneously, while the active neurons were not affected. On the other hand, in active neurons, KATP agonist diazoxide activated a conductance similar to quiet neurons' KATP conductance and stopped spontaneous firing. According to the effect of KATP channels on cartwheel neuron firing, glycinergic neurotransmission in DCN was increased by tolbutamide and decreased by diazoxide. Our results reveal a role of KATP channels in controlling the spontaneous firing of neurons not involved in fuel homeostasis.

Aberrant expression of Nav1.6 in the cochlear nucleus correlates with salicylate-induced tinnitus in rats

Hyperactivity in cochlear nucleus (CN) is one of the major neural correlates for tinnitus induction, yet the molecular factors that participate in the neuronal hyperexcitability remain unclear. The present study showed that acute and chronic administrations of salicylate were both capable of inducing reversible tinnitus in rats. The number of GAD 65/67-immunoreactive neurons in the AVCN and DCN was decreased, while the number of VGLUT 1/2-immunoreactive neurons in the AVCN and DCN was increased when rats were experiencing tinnitus, providing evidence for excitatory-inhibitory imbalance in CN is correlated with tinnitus. Interestingly, the expression level of Nav1.6, an important subtype of voltage-gated sodium channels was significantly increased in the DCN and AVCN of rats experiencing tinnitus, the up-regulation of Nav1.6 was returned to normal level following the disappearance of tinnitus. Double-labeling experiments revealed that Nav1.6 expression was down-regulated in the GAD 65/67-positive neurons in the DCN and AVCN of rats experiencing tinnitus. Notably, the percentage of co-localization of Nav1.6 and NeuN-labeling fusiform neurons was markedly increased in the DCN during tinnitus. These findings uncover the tinnitus-associated alteration in Nav1.6, a potential key contributor that can lead to hyperexcitability in CN and contribute to salicylate-induced tinnitus.

Somato-dendritic morphology and axon origin site specify von Economo neurons as a subclass of modified pyramidal neurons in the human anterior cingulate cortex.

Von Economo neurons (VENs) are modified pyramidal neurons characterized by an extremely elongated rod-shaped soma. They are abundant in layer V of the anterior cingulate cortex (ACC) and fronto-insular cortex (FI) of the human brain, and have long been described as a human-specific neuron type. Recently, VENs have been reported in the ACC of apes and the FI of macaque monkeys. The first description of the somato-dendritic morphology of VENs in the FI by Cajal in 1899 (Textura del Sistema Nervioso del Hombre y de los Vertebrados, Tomo II. Madrid: Nicolas Moya) strongly suggested that they were a unique neuron subtype with specific morphological features. It is surprising that a clarification of this extremely important observation has not yet been attempted, especially as possible misidentification of other oval or fusiform cells as VENs has become relevant in many recently published studies. Here, we analyzed sections of Brodmann area 24 (ACC) stained with rapid Golgi and Golgi-Cox in five adult human specimens, and confirmed Cajal's observations. In addition, we established a comprehensive morphological description of VENs. VENs have a distinct somato-dendritic morphology that allows their clear distinction from other modified pyramidal neurons. We established that VENs have a perpendicularly oriented, stick-shaped core part consisting of the cell body and two thick extensions - an apical and basal stem. The perpendicular length of the core part was 150-250μm and the thickness was 10-21μm. The core part was characterized by a lack of clear demarcation between the cell body and the two extensions. Numerous thin, spiny and horizontally oriented side dendrites arose from the cell body. The basal extension of the core part typically ended by giving numerous smaller dendrites with a brush-like branching pattern. The apical extension had a topology typical for apical dendrites of pyramidal neurons. The dendrites arising from the core parthad a high dendritic spine density. The most distinct feature of VENs was the distant origin site of the axon, which arose from the ending of the basal extension, often having a common origin with a dendrite. Quantitative analysis found that VENs could be divided into two groups based on total dendritic length - small VENs with a peak total dendritic length of 1500-2500μm and large VENs with a peak total dendritic length of 5000-6000μm. Comparative morphological analysis of VENs and other oval and fusiform modified pyramidal neurons showed that on Nissl sections small VENs might be difficult to identify, and that oval and fusiform neurons could be misidentified as VENs. Our analysis of Golgi slides of Brodmann area 9 from a total of 32 adult human subjects revealed only one cell resembling VEN morphology. Thus, our data show that the numerous recent reports on the presence of VENs in non-primates in other layers and regions of the cortex need further confirmation by showing the dendritic and axonal morphology of these cells. In conclusion, our study provides a foundation for further comprehensive morphological and functional studies on VENs between different species.

A New Neural Pathway from the Ventral Striatum to the Nucleus Basalis of Meynert with Functional Implication to Learning and Memory

The cholinergic neurons in the nucleus basalis of Meynert (NBM) are among the first group of neurons known to become degenerated in Alzheimer’s disease, and thus the NBM is proposed to be involved in learning and memory. The marginal division (MrD) of the striatum is a newly discovered subdivision at the ventromedial border of the mammalian striatum and is considered to be one part of the ventral striatum involved in learning and memory. The present study provided evidence to support the hypothesis that the MrD and the NBM were structurally connected at cellular and subcellular levels with functional implications in learning and memory. First, when wheat germ agglutinin-conjugated horseradish peroxidase (WGA-HRP) was stereotaxically injected into the NBM, fusiform neurons in the MrD were retrogradely labeled with WGA-HRP gray-blue particles and some of them were double stained in brown color by AchE staining method. Thus, cholinergic neurons of the MrD were shown to project to the neurons in the NBM. Second, in anterograde tract-tracing experiments where WGA-HRP was injected to the MrD, the labeled WGA-HRP was found to be anterogradely transported in axons from the MrD to the synaptic terminals with dendrites, axons, and perikaryons of the cholinergic neurons in the NBM when observed under an electronic microscope, indicating reciprocal structural connections between the MrD and the NBM. Third, when bilateral lesions of the MrD were injured with kainic acid in rats, degenerative terminals were observed in synapses of the NBM by an electronic microscope and severe learning and memory deficiency was found in these rats by the Y-maze behavioral test. Our results suggest reciprocal cholinergic connections between the MrD of the ventral striatum and the NBM, and implicate a role of the MrD-NBM pathway in learning and memory. The efferent fibers of cholinergic neurons in the NBM mainly project to the cortex, and severe reduction of the cholinergic innervation in the cortex is the common feature of Alzheimer’s patients. The newly discovered cholinergic neural pathway between the MrD of the ventral striatum and the NBM is supposed involved in the memory circuitries of the brain and probably might play a role in the pathogenesis of the Alzheimer’s disease.

Enhancement of Endocannabinoid-dependent Depolarization-induced Suppression of Excitation in Glycinergic Neurons by Prolonged Exposure to High Doses of Salicylate

The Dorsal Cochlear Nucleus (DCN) is a region which has been traditionally linked to the genesis of tinnitus, the constant perception of a phantom sound. Sodium salicylate, a COX-2 inhibitor, can induce tinnitus in high doses. Hyperactivity of DCN neurons is observed in several animal models of tinnitus, including salicylate-induced tinnitus. The DCN presents several forms of endocannabinoid (EC)-dependent synaptic plasticity and COX-2 can also participate in the oxidative degradation of ECs. We recently demonstrated that short-term perfusion of sodium salicylate and other inhibitors of both oxidative and hydrolytic EC degradation did not affect depolarization-induced suppression of excitation (DSE), a form of EC-dependent short-term synaptic plasticity. Here, we show that prolonged incubation with high doses of sodium salicylate (1.4 mM) enhances DSE of synapses onto glycinergic DCN interneurons but not those innervating glutamatergic DCN fusiform neurons. This effect was not reproduced with lower doses of salicylate (140 µM) or with ibuprofen, another inhibitor of COX-2. This effect was not observed in the presence of AM251, an antagonist/inverse agonist of cannabinoid CB1 receptors, showing that it was dependent on EC release. Finally we demonstrated that incubation with salicylate potentiated the increase in intracellular calcium during the depolarization. Our results point to an increased inhibition of DCN inhibitory CW neuron during depolarizations, probably by an enhanced EC release during the depolarizations, which is potentially significant for DCN hyperactivity and tinnitus generation.

Audiogenic seizure activity following HSV-1 GAD65 sense or antisense injection into inferior colliculus of Long-Evans rat.

Herpes virus technology involving manipulation of GAD65 was used to study effects on audiogenic seizures (AGS). Audiogenic seizure behaviors were examined following injections of replication-defective herpes simplex virus (HSV-1) vectors incorporating sense or antisense toward GAD65 along with 10% lac-Z into the central nucleus of inferior colliculus (CNIC) of Long-Evans rats. In seizure-sensitive animals developmentally primed by intense sound exposure, injection of GAD65 in the sense orientation increased wild running latencies and reduced incidence of clonus compared with lac-Z only, unoperated, and vehicle seizure groups. In contrast, infection of CNIC with GAD65 antisense virus resulted in 100% incidence of wild running and clonus behaviors in AGS animals. Unprimed animals not operated continued to show uniform absence of seizure activity. Administration of GAD65 antisense virus into CNIC produced novel wild running and clonus behaviors in some unprimed animals. Staining for β-galactosidase in all vector animals revealed no differences in pattern or numbers of immunoreactive cells at injection sites. Qualitatively, typical small and medium multipolar/stellate and medium fusiform neurons appeared in the CNIC of vector animals. These results demonstrate that HSV-1 vector constructs implanted into the CNIC can predictably influence incidence and severity of AGS and suggest that viral vectors can be useful in studying GABA mechanisms with potential for therapeutic application in epilepsy. This article is part of a Special Issue entitled "Genetic and Reflex Epilepsies, Audiogenic Seizures and Strains: From Experimental Models to the Clinic".

Morphology of Human Nucleus Accumbens Neurons Based on the Immunohistochemical Expression of Gad67

Abstract The nucleus accumbens is a part of the ventral striatum along with the caudate nucleus and putamen. The role of the human nucleus accumbens in drug addiction and other psychiatric disorders is of great importance. The aim of this study was to characterize medium spiny neurons in the nucleus accumbens according to the immunohistochemical expression of GAD67. This study was conducted on twenty human brains of both sexes between the ages of 20 and 75. The expression of GAD67 was assessed immunohistochemically, and the characterization of the neurons was based on the shape and size of the soma and the number of impregnated primary dendrites. We showed that neurons of the human nucleus accumbens expressed GAD67 in the neuron soma and in the primary dendrites. An analysis of the cell body morphology revealed the following four different types of neurons: fusiform neurons, fusiform neurons with lateral dendrites, pyramidal neurons and multipolar neurons. An immunohistochemical analysis showed a strong GAD67 expression in GABAergic medium spiny neurons, which could be classifi ed into four different types, and these neurons morphologically correlated with those described by the Golgi study.

Ih Equalizes Membrane Input Resistance in a Heterogeneous Population of Fusiform Neurons in the Dorsal Cochlear Nucleus.

In a neuronal population, several combinations of its ionic conductances are used to attain a specific firing phenotype. Some neurons present heterogeneity in their firing, generally produced by expression of a specific conductance, but how additional conductances vary along in order to homeostatically regulate membrane excitability is less known. Dorsal cochlear nucleus principal neurons, fusiform neurons, display heterogeneous spontaneous action potential activity and thus represent an appropriate model to study the role of different conductances in establishing firing heterogeneity. Particularly, fusiform neurons are divided into quiet, with no spontaneous firing, or active neurons, presenting spontaneous, regular firing. These modes are determined by the expression levels of an intrinsic membrane conductance, an inwardly rectifying potassium current (IKir). In this work, we tested whether other subthreshold conductances vary homeostatically to maintain membrane excitability constant across the two subtypes. We found that Ih expression covaries specifically with IKir in order to maintain membrane resistance constant. The impact of Ih on membrane resistance is dependent on the level of IKir expression, being much smaller in quiet neurons with bigger IKir, but Ih variations are not relevant for creating the quiet and active phenotypes. Finally, we demonstrate that the individual proportion of each conductance, and not their absolute conductance, is relevant for determining the neuronal firing mode. We conclude that in fusiform neurons the variations of their different subthreshold conductances are limited to specific conductances in order to create firing heterogeneity and maintain membrane homeostasis.

High doses of salicylate reduces glycinergic inhibition in the dorsal cochlear nucleus of the rat

High doses of salicylate induce reversible tinnitus in experimental animals and humans, and is a common tinnitus model. Salicylate probably acts centrally and induces hyperactivity in specific auditory brainstem areas like the dorsal cochlear nucleus (DCN). However, little is known about the effect of high doses of salicylate in synapses and neurons of the DCN. Here we investigated the effects of salicylate on the excitability and evoked and spontaneous neurotransmission in the main neurons (fusiform, cartwheel and tuberculoventral) and synapses of the DCN using whole cell recordings in slices containing the DCN. For this, we incubate the slices for at least 1 h in solution with 1.4 mM salicylate, and recorded action potentials and evoked and spontaneous synaptic currents in fusiform, cartwheel (CW) and putative tuberculoventral (TBV) neurons. We found that incubation with salicylate did not affect the firing of fusiform and TBV neurons, but decreased the spontaneous firing of cartwheel neurons, without affecting AP threshold or complex spikes. Evoked and spontaneous glutamatergic neurotransmission on the fusiform and CW neurons cells was unaffected by salicylate and evoked glycinergic neurotransmission on fusiform neurons was also unchanged by salicylate. On the other hand spontaneous glycinergic transmission on fusiform neurons was reduced in the presence of salicylate. We conclude that high doses of salicylate produces a decreased inhibitor drive on DCN fusiform neurons by reducing the spontaneous firing of cartwheel neurons, but this effect is not able to increase the excitability of fusiform neurons. So, the mechanisms of salicylate-induced tinnitus are probably more complex than simple changes in the neuronal firing and basal synaptic transmission in the DCN.

How can development and plasticity contribute to understanding evolution of the human brain?

How can development and plasticity contribute to understanding evolution of the human brain?

Central pupillary light reflex circuits in the cat: II. Morphology, ultrastructure, and inputs of preganglionic motoneurons.

Preganglionic motoneurons supplying the ciliary ganglion control lens accommodation and pupil diameter. In cats, these motoneurons make up the preganglionic Edinger-Westphal population, which lies rostral, dorsal, and ventral to the oculomotor nucleus. A recent cat study suggested that caudal motoneurons control the lens and rostral motoneurons control the pupil. This led us to examine the morphology, ultrastructure, and pretectal inputs of these populations. Preganglionic motoneurons retrogradely labeled by introducing tracer into the cat ciliary ganglion generally fell into two morphologic categories. Fusiform neurons were located rostrally, in the anteromedian nucleus and between the oculomotor nuclei. Multipolar neurons were found caudally, dorsal and ventral to the oculomotor nucleus. The dendrites of preganglionic motoneurons within the anteromedian nucleus crossed the midline, providing a possible basis for consensual responses. Ultrastructurally, several different classes of synaptic profiles contact preganglionic motoneurons, suggesting that their activity may be modified by a variety of inputs. Furthermore, there were differences in the synaptic populations contacting the rostral vs. caudal populations, supporting the contention that these populations display functional differences. Anterogradely labeled pretectal terminals were observed in close association with labeled preganglionic motoneurons, particularly in the rostral population. Ultrastructural analysis revealed that these terminals, packed with clear, spherical vesicles, made asymmetric synaptic contacts onto motoneurons in the rostral population, indicating that these cells serve the pupillary light reflex. Thus, the preganglionic motoneurons found in the cat display morphologic, ultrastructural, and connectional differences suggesting that this rostral preganglionic population is specialized for pupil control, whereas more caudal elements control the lens.

Immunolocalization of different neuropeptides in human interthalamic adhaesion indicates its functionality.

The interthalamic adhaesion (IA), gray matter connecting both thalami, is absent in about a quarter of human brains. Controversies are present about the nature and functional significance of the human IA. In six adult human brains we investigated the expression of different neuropeptides: somatosatin (SOM), neuropeptide Y (NPY), ghrelin, neurotensin (NT), adrenocorticotropic hormone (ACTH), substance P (SP) and L-enkephalin (L-Enk) in neurons and/or neuropil of the IA, using immunohistochemistry (streptavidin-biotin technique). In neurons, as well as in fibers, we found immunoreactivity for ghrelin, SOM, L-Enk and NT. However, reactivity for NPY, SP and ACTH was present only in fibers within the IA. Fusiform neurons were immunoreactive for SOM, Ghrelin, L-Enk, and NT, neurons with oval perikaryon for SOM, and L-Enk, triangular neurons showed immunoreactivity mainly for NT and multipolar neurons for NT and L-Enk. These findings can contribute to the understanding of the function of interthalamic adhaesion, and to resolving the question whether it is a vestigial structure. No mather if the interthalamic adhaesion is vestigial structure or not, its presence or absence could be a marker for other, genetic or functional differences between human brains. Our findings indicate the presence of certain neuronal organization in the human interthalamic adhaesion which could have functional significance, and do not support its vestigial nature.

Nitrergic Neurons in the Spinal Cord of the Bottlenose Dolphin (Tursiops truncatus)

Nitric oxide (NO) is a freely diffusible gaseous neurotransmitter generated by a selected population of neurons and acts as a paracrine molecule in the nervous system. NO is synthesized from l-arginine by means of the neuronal nitric oxide synthase (nNOS), an enzyme requiring nicotine adenine dinucleotide phosphate (NADPH) as cofactor. In this study, we used histochemical and immunohistochemical techniques to investigate the distribution of NADPH-diaphorase (NADPH-d) and nNOS in the spinal cord of the bottlenose dolphin (Tursiops truncatus). Cells with a fusiform-shaped somata were numerous in the laminae I and II. The intermediolateral horn showed darkly-stained cells with a multipolar morphology. Neurons with a multipolar or fusiform morphology were observed in the ventral horn. Multipolar and fusiform neurons were the most common cell types in lamina X. Nitrergic fibers were numerous especially in the dorsal and intermediolateral horns. The presence of nitrergic cells and fibers in different laminae of the spinal cord suggests that NO may be involved in spinal sensory and visceral circuitries, and potentially contribute to the regulation of the complex retia mirabilia.

Genetic Basis and Neural Mechanism of Autism Spectrum Disorder*

Autism spectrum disorder (ASD) is a defective mental disease and its core impairments are social function defect, communication defect, restrictive and stereotyped behavior pattern. The paper introduces the genetic basis and neural mechanism of ASD. ASD has high genetic rate, and 5-HT and testosterone of ASD individual are both higher. Neuroimaging studies find that there are some differences between ASD and normal individuals in the structure and function of amygdala, cingulate gyrus, the fusiform gyrus, mirror neurons, prefrontal lobe and other brain areas, but it is inconsistent in the discrepancy direction of some areas' activation patterns. In addition, the results of functional connectivity studies also confirm the hypothesis that the ASD individuals are under-connection. Future research should focus more on how to use the basic research outcomes to put forward effective treatment and training for clinical research.

Synaptic relationship between somatostatin‐ and neurokinin‐1 receptor‐immunoreactive neurons in the pre‐Bötzinger complex of rats

The pre-Bötzinger complex (pre-BötC) in the ventrolateral medulla oblongata is critical for the generation of respiratory rhythm in mammals. Somatostatin (SST) and neurokinin 1 receptor (NK1R) immunoreactivity have been used as markers of the pre-BötC. SST immunoreactivity almost completely overlaps with small fusiform NK1R-immunoreactive (ir) neurons, the presumed rhythmogenic neurons, but not with large multipolar NK1R-ir neurons. Understanding the neurochemical characteristics, especially the synaptic relationship of SST/NK1R-ir neurons within the pre-BötC network is essential in providing cellular and structural bases for understanding their physiological significance. This work has not been documented so far. We found that SST immunoreactivity was highly expressed in terminals, somas, and primary dendrites in the pre-BötC. Besides the small fusiform neurons, a small population of medium-sized NK1R-ir neurons also colocalized with SST. Large NK1R-ir neurons were not SST-ir, but received somatostatinergic inputs. SST-ir terminals were glutamatergic or GABAergic, and synapsed with NK1R-ir neurons. Most of synapses between them were of the symmetric type, indicating their inhibitory nature. Asymmetric synapses were evident between SST-ir terminals and NK1R-ir dendrites, strongly suggesting an excitatory innervation from the presumed rhythmogenic neurons as these neurons are glutamatergic. We speculate that SST-mediated excitatory and inhibitory synaptic transmission onto NK1R-ir rhythmogenic and follower neurons synchronizes their activity to contribute to respiratory rhythmogenesis and control.

Histological Structure of The Optic Tectum in The Fresh Water Turtle in The Clemmys caspica caspica (Gmelin, 1774)

A histological study was conducted to examine the structure of optic tectum in Clemmys caspica caspica. The results showed that the optic tectum consist of seven strata and the third stratum consists of three substrata, as follows: The stratum zonula (SZ), the stratum opticum (SO), the stratum griseum et fibrosum superficiale (SGFS) which consist of three substrata are a, b, c, the stratum griseum centrale (SGC), the stratum album centrale (SAC), the stratum griseum periventriculare (SGP), and the stratum album periventriculare (SAP). The stratum zonula (SZ) was the thinnest stratum in the optic tectum and its main thickness was (17-19) μm, while the stratum griseum et fibrosum superficiale (SGFS) was the thickest and its main thickness was (234-243) μm.The stratum opticum (SO), which represents the second stratum called the optic fibers tract, it was found that the optic fibers enter the optic tectum through this stratum while these fibers goout from optic tectum through the (SGP) which is the sixth stratum.The stratum griseum et fibrosum superficiale (SGFS) which represents the third stratum contain a large number of stallete and piriform multipolar neurons and fusiform neurons.