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At least 307 records · Page 17Linked to original sources
PubMed1989

Synaptogenesis in the rat suprachiasmatic nucleus demonstrated by electron microscopy and synapsin I immunoreactivity.

Synaptogenesis was studied in the rat suprachiasmatic nucleus (SCN) using quantitative ultrastructural analysis and synapsin I immunohistochemistry. SCN neurons are formed between embryonic days 13 and 17 (E13-E17), and the SCN is a distinct hypothalamic nucleus by E18. At E19 the nucleus is very immature and there are few synapses. Synaptogenesis proceeds slowly until P4 but increases rapidly between P4 and P10. At P10 the number of synapses per unit area is the same as in the adult SCN and all synaptic types present in the adult are evident. However, the SCN continues to increase in volume to the adult with approximately 30% of total synaptic number added between P10 and a young adult age. The appearance of synapsin I immunoreactivity correlates very precisely with the development of synapses in the SCN as shown by ultrastructural analysis between E19 and P6. The pattern of appearance of synapsin I immunoreactivity demonstrates that synaptogenesis in the SCN is significantly delayed in comparison to adjacent hypothalamic nuclei. Synapsin I immunohistochemistry is a reliable marker of synapse formation in the developing SCN. A correlation of these anatomical data with prior functional studies suggests that SCN neurons are born as individual circadian oscillators that undergo a rapid development in the first 10 days after birth to form a functional neural network subserving circadian rhythm generation and regulation.

Animals↗
PubMed1988

Human gut neuroanatomy: methodology for a quantitative analysis of nerve elements and neurotransmitter diversity in the human "enteric nervous system".

After a few decad of neglect, the "enteric nervous system" has recently regained the attention of investigators. Indeed, various studies, such as those which led to the isolation from the gut of a number of neuropeptides, subsequently demonstrated throughout the nervous system, have prompted major advancements of modern neuroscience. In spite of a wealth of animal investigations and a number of human studies, however, available information concerning the human "enteric nervous system" is comparatively sparse. In the opinion that such lack of information was largely due to unavailability of appropriate techniques, we have initiated and developed a new comprehensive methodology. This way, a quantitative analysis was made possible of both nerve structure and transmitter status, point-to-point along the gut, as well as within the various, functionally heterogeneous components of the gastrointestinal wall itself. After a general introduction, the present review is intended to summarize such methodology, with the addition of a few illustrative examples of application and a practically-oriented guideline to its use, in the form of technical appendix.

Autonomic Nervous System↗
PubMed1994

[Experimental techniques for developing new drugs acting on dementia (5)--Screening method in drug evaluation on neurite regeneration in primary cultured neurons].

Neurite regeneration is one of the important processes in the reconstruction of neuronal networks. We observed neurite elongation and branching of an individual neuron cultured at a comparatively low cell density. We also observed neurite re-elongation and branching of neurites amputated by a laser beam. Screening method in drug evaluation on neurite regeneration in primary cultured neurons and effects of basic fibroblast growth factor (bFGF) and astrocyte-derived conditioned medium (ACM) are explained in this report.

Animals↗
PubMed1996

[Synaptic reorganization in early childhood experience and learning processes: relevance for the development of psychological diseases].

This article presents a neurobiological hypothesis of experience- and learning dependent synaptic reorganization processes in the juvenile brain and their influence on the normal development of intellectual, emotional and social abilities. Based on experimental data we offer the theory that during early learning events (also termed as imprinting) the initially relatively unspecifically organized synaptic network in the higher associative brain areas undergoes an experience- and learning-dependent reorganization. This process involves synaptic sprouting as well as synaptic pruning of redundant synaptic connections and results in a more specific and efficient neuronal network, which provide the basis for learning processes during later life. Sensory or social deprivation during early childhood impairs this synaptic reorganization of the brain and thereby prevents the normal development of intellectual, emotional and social abilities. Under adverse environmental and familial circumstances these deficits may eventually lead to mental disorders such as neuroses. Since early learning and the underlying synaptic reorganization processes are restricted to specific sensitive phases during brain development the resulting mental and social deficits are remarkably stable, which may be one explanation of the resistance of certain mental disorders to psychotherapy. The intention of this provocative hypothesis is to stimulate future research initiatives using an interactive neurobiological and neuropsychological approach to gain more insight into these cellular mechanisms and to develop innovative therapeutical strategies.

Adolescent↗
PubMed1997

Expression of brain lipid binding protein in the brain of the adult canary and its implications for adult neurogenesis.

Brain lipid binding protein (BLBP), a member of the fatty acid binding protein family, is expressed at high levels in the mammalian central nervous system during development, but not in adulthood. Because the brain of adult birds continues to show significant levels of neurogenesis, we thought it likely that BLBP expression would also be present. We used a polyclonal antibody against BLBP to study the presence of this protein in the adult canary brain. This antibody stained 1) fibers and perikarya of radial cells in the telencephalon; 2) Bergmann glia in the cerebellum; 3) astrocytes; 4) tanicytes in the walls of the third ventricle; 5) the neuropil of certain forebrain and brainstem regions, including nuclei of the song system; and 6) some migrating cells in the telencephalon. This anatomical distribution suggests that BLBP plays a role in the neuronal migration and synaptic reorganization of adult avian brain.

Aging↗
PubMed1998

Substance P modulates NMDA responses and causes long-term protein synthesis-dependent modulation of the lamprey locomotor network.

Tachykinin immunoreactivity is found in a ventromedial spinal plexus in the lamprey. Neurons in this plexus project bilaterally and are thus in a position to modulate locomotor networks on both sides of the spinal cord. We have examined the effects of the tachykinin substance P on NMDA-evoked locomotor activity. Brief (10 min) application of tachykinin neuropeptides results in a prolonged concentration-dependent (>24 hr) modulation of locomotor activity, shown by the increased burst frequency and more regular burst activity. These effects are blocked by the tachykinin antagonist spantide II. There are at least two phases to the burst frequency modulation. An initial phase (approximately 2 hr) is associated with the protein kinase C-dependent potentiation of cellular responses to NMDA. The long-lasting phase (>2 hr) appears to be protein synthesis-dependent, with protein synthesis inhibitors causing the increased burst frequency to recover after washing for 2-3 hr. The modulation of the burst regularity is caused by a separate effect of tachykinins, because unlike the burst frequency modulation it does not require the modulation of NMDA receptors for its induction and is blocked by H8, an inhibitor of cAMP- and cGMP-dependent protein kinases. The effects of substance P were mimicked by the dopamine D2 receptor antagonist eticlopride. The effects of eticlopride were blocked by the tachykinin antagonist spantide II, suggesting that eticlopride may endogenously release tachykinins. Because locomotor activity in vitro corresponds to that during swimming in intact animals, we suggest that endogenously released tachykinins will result in prolonged modulation of locomotor behavior.

Animals↗
PubMed1976

Effect of sympathetic nerve stimulation on net transvascular movement of fluid in canine adipose tissue.

Net transvascular movement of fluid has been studied in the isolated, autoperfused subcutaneous adipose tissue of the dog, during and after sympathetic nerve stimulation (1-15 Hz) and during infusion of 50% glucose i.a. Net fluid movement was calculated as the difference between change in tissue volume and change in blood volume. Tissue volume was measured by plethysmography and blood volume by external monitoring of circulating 131I-albumin. No net fluid movement of statistical significance was found during or after nerve stimulation except during the first minute of stimulation at 15 Hz when a small net absorption (p less than 0.05) was obtained. In contrast, infusion of glucose at 25-75 mOsm/kg H2O produced a dose-dependent net absorption lasting several minutes, amounting maximally to 0.30 ml x min-1 x 100 g-1. The absence of prolonged net absorption in subcutaneous adipose tissue during nerve stimulation as well as the absence of net filtration after stimulation may be explained by an essentially unaltered mean hydrostatic capillary pressure. The results indicate that adipose tissue does not contribute to the fluid homeostasis of the body via sympathetic resetting of the pre-postcapillary resistance ratio. Thus, mobilisation of fluid from the interstitial space in adipose tissue into the blood does not seem to occur by nerve activity.

Adipose Tissue↗
PubMed1979

The effect of vasodilatation and sympathetic nerve activation on net water absorption in the cat's small intestine.

The rate of net water uptake from the feline small intestine has been investigated during control conditions, during graded infusions of the vasodilator drug isopropylnoradrenaline, and during electrical stimulation of the regional sympathetic nerve fibres to the gut. Net water absorption rate was largely unaffected by intestinal vasodilatation. The fraction of the absorbate transported via the lymphatics remained also constrant at 20-40% of the total absorption regardless of blood flow rate. Stimulating the sympathetic nerve fibres to the small intestine increased, however, net water absorption rate. The increase was particularly pronounced when blood pressure was kept constant during the period of stimulation. The absorption rate was on an average almost doubled at a stimulation frequency of 8 Hz during constant pressure conditions. The mechanism(s) explaining this nervous control of water absorption are tentatively discussed.

Adrenergic Fibers↗
PubMed1994

Brainstem network controlling descending drive to phrenic motoneurons in rat.

Contraction of the diaphragm is controlled by phrenic motoneurons that receive input from sources that are not fully established. Bulbospinal (second-order) neurons projecting to phrenic motoneurons and propriobulbar (third-order) neurons projecting to these bulbspinal neurons were investigated in rat by transsynaptic transport of the neuroinvasive pseudorabies virus. Bulbospinal neurons were located predominantly in the medullary lateral tegmental field in two functionally described regions, the ventral respiratory group and Bötzinger complex. An intervening region, the pre-Bötzinger complex, contained essentially no phrenic premotoneurons. Bulbospinal neurons were also located in ventral, interstitial, and ventrolateral subnuclei of the solitary tract, and gigantocellular, Kölliker-Fuse, parabrachial, and medullary raphe nuclei. A monosynaptic pathway to phrenic motoneurons from the nucleus of the solitary tract was confirmed; monosynaptic pathways from upper cervical spinal cord, spinal trigeminal nucleus, medical and lateral vestibular nuclei, and medial pontine tegmentum were not verified. Locations of third-order neurons were consistent with described projections to the ventral respiratory group, from contralateral ventral respiratory group, Bötzinger complex, A5 noradrenergic cell group, and the following nuclei; solitary, raphe, Kölliker-Fuse, parabrachial, retrotrapezoid, and paragigantocellular. Novel findings included a projection from locus coeruleus to respiratory premotoneurons and the lack of previously described pathways from area postrema and spinal trigeminal nucleus. These second- and third-order neurons from the output network for diphragm motor control which includes numerous behaviors (e.g., respiration, phonation, defecation). Of the premotoneurons, the rostral ventral respiratory group is the primary population controlling phrenic motoneurons.

Animals↗