Blunted Vagal Cocaine- and Amphetamine-Regulated Transcript Promotes Hyperphagia and Weight Gain

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Increased Number of Dorsal Root Ganglion Neurons in Vitamin-E-Deficient Rats

Quantitative and morphometric observations were carried out on neurons of L₃-L₆ dorsal root ganglia (DRGs) in control and vitamin-E-deficient rats at different ages. Controls were fed a standard diet and sacrificed at 1 or at 5 months of age; deficient rats were fed a diet without vitamin E from 1 to 5 months of age and then sacrificed. No significant difference in total number of neurons was found, but an increase in neuron sizes, a decrease in nucleus-cytoplasm ratio, and a more circular neuron shape were found in controls with increasing age (from 1 to 5 months). In L₃-L₆ DRGs of vitamin-E-deficient rats (5 months of age), a higher number of neurons was found than in those of either young or adult controls. Moreover, some morphometric characteristics of neurons in the deficient rats were similar to those of neurons in 1-month-old controls. The findings suggest that vitamin E deficiency can trigger events resulting in appearance of new neurons, possibly anticipating phenomena that normally occur in aging.     

Quantitative autoradiographic light- and electron microscopic studies on the retinohypothalamic connections in the rat

Summary Light microscopic autoradiography performed subsequent to intraocular injection of ³H-leucine revealed silver grains (SG) above axons of the optic tract which could be followed into the ventral and caudal portion of the suprachiasmatic nuclei (SCN) and above the contralateral anterior hypothalamic nucleus (AHN). By high resolution photometric measurement and computer processing the labelled areas were analysed, thus yielding statistical data of the relative grain distribution. The highest SG density was found in the ventrolateral part of both SCN (SCvl), confirming earlier reports concerning retinohypothalamic connections. That area exhibiting a cytoarchitecture different from the remaining nucleus was traversed, however, by numerous labelled axons. In the caudal part of both SCN a specific projection field of retinal fibres could be located. Here, almost no traversing fibres contribute to the rather circumscribed marked area. In the ventral part of the contralateral AHN, diffuse labelling well above background levels could be observed. Distinction between bypassing and terminating fibres within the SCvl could not be made using light microscopy. Analysis of SG distribution of the SCvl with electron microscopic autoradiography revealed a specific localization of SG within presynaptic terminals containing clear vesicles and pale mitochondria.     

Anatomical substrates of oculomotor control

It is convenient to describe oculomotor neuroanatomy in terms in five to six different eye movement types, each with relatively independent neural circuitry: saccades, vestibulo-ocular reflex, optokinetic response, smooth pursuit, vergence and, most recently added to the list, gaze-holding. Current research indicates that many structures participate in several eye movement types, such as the nucleus reticularis tegmenti pontis, frontal eye fields and pretectum. However, the circuits appear to run in parallel rather than being integrated.     

Ultrastructural localization of immunolabeled substance P and methionine-enkephalin-octapeptide in the surface layer of the dorsal horn of rat spinal cord

Summary A preembedding dual immunolabeling technique and electron microscopy were utilized to demonstrate the localization of immunoreactive substance P and methionine-enkephalin-octapeptide (Enk-8) in ultrathin sections of the surface layer (laminae I and II) of rat spinal dorsal horn. The immunoreaction of Enk-8 was visualized as goldtoned silver particles and that of substance P as diaminobenzidine reaction products. Axonal terminals with immunoreactive substance P, and also unlabeled axonal terminals, formed synaptic junctions with the perikarya and dendritic processes of Enk-8-containing neurons. Dendritic profiles immunolabeled for substance P were synaptically linked with unlabeled axons but not with Enk-8-positive ones. Furthermore, it was found that Enk-8 axons and substance P axons terminated synaptically in juxtaposition to one another on the same immunonegative dendrites. Among the Enk-8-containing neurons axonal profiles also appeared to be synaptically associated with immunoreactive Enk-8 dendritic processes.     

The change in the nucleus pattern during chromatin condensation in Eurygaster integriceps spermatids

When spermiogenesis of Eurygaster integriceps occurs, the pattern of the round nucleus of the spermaiid changes under the influence of a manchette consisting of two large groups of microtubules (up to 130–140 in each). The pericentriolar matter was found to be involved in the changes in the nuclear pattern; it takes part in the formation of the asymmetric intranuclear channel, open at one side. Two zones appear in the nucleus that differ greatly in their rates of chromatin condensation. The two main parts of the future nucleus are thereby established: the apical one with a greater rate of chromatin condensation, which gives origin to the two-walled cylinder, and the outer part, which grows for a long time and extends caudally to the middle piece. At the later stages of nucleus formation, when its larger part is separated from the surface of the middle piece, the vesicles of the endoplasmic reticulum that penetrate between the Nebenkern and the larger part of the nucleus, play a certain role.     

Influence of Opioids in Hypothalamic Nuclei on Cold Thermogenesis of Lean and Obese LA/N-cp Rats

An overactive endogenous opioid peptide system (EOP) in the hypothalamus of the obese rats could contribute to a subnormal metabolic response to cold stress. Specific mu, delta, kappa opioid receptor antagonists and naloxone were infused into cannulaes aimed at the paraventricular nucleus (PVN) of awake freely moving obese (LA/N-cp corpulent) and lean littermate rats. Metabolic responses were measured by indirect calorimetry during thermoneutrality (30°C) and at 10°C for 60 minutes each. When expressed relative to metabolic body size (kg^?.75) obese rats had lower values (obese = 21.1 ± 1.9 vs. lean = 27.9 ± 2.7 ml·kg^?.75.min, mean ± s.d., p<0.05) at 10°C during saline infusion. EOP antagonist infusions at 30°C had no effect on metabolic rate for either lean or obese animals. Mu (23.5 ± 3.4 ml·kg^.-75· min) and delta (23.0 ± 2.0) antagonism and naloxone (25.0 ± 2.3) significantly increased the metabolic response to cold in obese but not lean rats. These data suggest that certain subtypes of EOP receptors in or near PVN are overactive in obese rats. This overactive state may inappropriately inhibit the thermogenic response to cold stress in obesity.     

The GABAergic network in the suprachiasmatic nucleus as a key regulator of the biological clock: does it change during senescence?

GABA is the main neurotransmitter of the hypothalamic suprachiasmatic nucleus (SCN) and plays a key role in the function of this master circadian pacemaker. Despite the evidence that disturbances of biological rhythms are common during aging, little is known about the GABAergic network in the SCN of the aging brain. We here provide a brief overview of the GABAergic structures and the role of GABA in the SCN. We also review some age‐related changes of the GABAergic system occurring in the brain outside the SCN. Finally, we present preliminary data on the GABAergic system within the SCN comparing young and aging mice. In particular, our study on age‐related changes in the SCN focused on the daily expression of the α3 subunit of the GABA_A receptor and on the density of GABAergic axon terminals. Interestingly, our preliminary findings point to alterations of the GABAergic network in the biological clock during senescence.     

Presynaptic Dopamine Dynamics in Striatal Brain Slices with Fast-scan Cyclic Voltammetry

Extensive research has focused on the neurotransmitter dopamine because of its importance in the mechanism of action of drugs of abuse (e.g. cocaine and amphetamine), the role it plays in psychiatric illnesses (e.g. schizophrenia and Attention Deficit Hyperactivity Disorder), and its involvement in degenerative disorders like Parkinson''s and Huntington''s disease. Under normal physiological conditions, dopamine is known to regulate locomotor activity, cognition, learning, emotional affect, and neuroendocrine hormone secretion. One of the largest densities of dopamine neurons is within the striatum, which can be divided in two distinct neuroanatomical regions known as the nucleus accumbens and the caudate-putamen. The objective is to illustrate a general protocol for slice fast-scan cyclic voltammetry (FSCV) within the mouse striatum. FSCV is a well-defined electrochemical technique providing the opportunity to measure dopamine release and uptake in real time in discrete brain regions. Carbon fiber microelectrodes (diameter of ~ 7 μm) are used in FSCV to detect dopamine oxidation. The analytical advantage of using FSCV to detect dopamine is its enhanced temporal resolution of 100 milliseconds and spatial resolution of less than ten microns, providing complementary information to in vivo microdialysis.