Intravenous administration of interleukin-1β induces Fos-like immunoreactivity in corticotropin-releasing hormone neurons in the paraventricular hypothalamic nucleus of the rat

It has been shown that acute administration of recombinant human interleukin 1β (IL-1) to rats elicits an activation of the pituitary-adrenal axis. In the present study we investigated immunohistochemically the expression of Fos-like immunoreactivity (Fos-LI) in the hypothalamus of rats following intravenous injection of IL-1. One, 2 and 4 h after IL-1 or physiological saline injections, rats were killed and perfused, and the brains processed for Fos-immunohistochemistry. Dense populations of neurons containing Fos-LI-positive nuclei were found in the paraventricular hypothalamic nuclei (PVH) of IL-1-treated rats. In particular, the dorsal medial parvocellular part, but also some of the other parvocellular subdivisions contained many Fos-LI neurons. Maximal induction of staining was found at a dose of 5 μ/rat after 1 or 2 h survival, while immunostaining had decreased to almost control levels after 4h. No Fos-LI was found in the PVH of control aminals. Double immunocytochemical staining for Fos and corticotropin-releasing hormone (CRH) revealed that Fos-LI was predominantly present in parvocellular CRH-containing neurons of the PVH. The finding that peripherally injected IL-1 induces Fos-LI in hypothalamic CRH neurons strengthens the hypothesis that these neurons are part of the circuitry mediating IL-1-induced activation of the pituitary-adrenal axis.     

Dynamic changes of striatal dopamine D2 receptor binding at later stages after unilateral lesions of the medial forebrain bundle in Parkinsonian rat models

The dorsal premammillary nucleus (PMd) is one of the most responsive hypothalamic sites during exposure to a predator or its odor, and to a context previously associated with a predatory threat; and lesions or pharmacological inactivation centered therein severely reduced the anti-predatory defensive responses. Previous studies have shown that beta adrenergic transmission in the PMd seems critical to the expression of fear responses to predatory threats. In the present study, we have investigated the putative sources of catecholaminergic inputs to the PMd. To this end, we have first described the general pattern of catecholaminergic innervation of the PMd by examining the distribution and morphology of the tyrosine hydroxylase (TH) immunoreactive fibers in the nucleus; and next, combining Fluoro Gold (FG) tracing experiments and TH immunostaining, we determined the putative sources of catecholaminergic inputs to the nucleus. Our results revealed that the PMd presents a moderately dense plexus of catecholaminergic fibers that seems to encompass the rostral pole and ventral border of the nucleus. Combining the results of the FG tract-tracing and TH immunostaining, we observed that the locus coeruleus was the sole brain site that contained double FG and TH immunostained cells. In summary, the evidence suggests that the locus coeruleus is seemingly a part of the circuit responding to predatory threats, and, as shown by the present results, is the sole source of catecholaminergic inputs to the PMd, providing noradrenergic inputs to the nucleus, which, by acting via beta adrenoceptor, seems to be critical for the expression of anti-predatory responses.     

Influence of ascending noradrenergic fibers on the neurotensin-like immunoreactive neurons in the rat paraventricular nucleus

The topographic organization of cells containing choline-acetyltransferase (CAT) and located within the magnocellular nuclei of the basal forebrain was studied by correlating maximum CAT decrease in one or another cortical region with a given localization of the cell lesions. Lesions were made by using ibotenic acid. Lesions affecting the ventral pallidum decreased CAT activity in the antero-medial prefrontal cortex and lesions of the internal and ventral borders of the pallidum decreased CAT activity in sensori-motor and parieto-temporal cortices. None of these lesions produced a decrease of CAT activity in the hippocampus. These results suggest that it is possible to show the presence of a specific cholinergic projection from the basal forebrain to the medial-associative prefrontal cortex of the rat.     

SOCS3通过抑制STAT3抑制受损伤大鼠初级感觉神经元生长

目的通过慢病毒转导SOCS3和作用相反的突变型SOCS3(mSOCS3),体外研究SOCS3在成年鼠的初级感觉神经元再生中的作用。方法将慢病毒载体质粒pRRL-SOCS3-IRES-GFP,pRRL-mSOCS3-IRES-GFP和pRRL-STAT3ER-IRES-GFP分别转染293T细胞,包装慢病毒载体并测定滴度。完全切断大鼠左侧坐骨神经,术后饲养8-128h,在不同时间点摘取双侧L5背根神经节。通过实时PCR和原位杂交检测DRGs中SOCS3 mRNA的存在;通过背根神经节分离神经元培养,分别将三种慢病毒载体感染神经元细胞,采用免疫荧光染色法观察神经元细胞核质反应和突起的长度。结果大鼠左侧坐骨神经损伤后,SOCS3 mRNA的表达在背根神经节神经元中明显增加,外源性SOCS3能阻止神经元中STAT3的磷酸化及核移位,mSOCS3增强了突起生长。结论 SOCS3可通过抑制STAT3抑制轴突生长。     

Branched output neurons of the rat subthalamic nucleus: electrophysiological study of the synaptic effects on identified cells in the two main target nuclei, the entopeduncular nucleus and the substantia nigra

The synaptic responses of entopeduncular and nigral cells to subthalamic stimulation were studied with extracellular recording techniques in rats with and without chronic lesions. Entopeduncular output cells were identified by antidromic activation from the lateral habenula, ventral anterior thalamic nucleus and tegmenti pedunculopontine nucleus. Nigral cells projecting to superior colliculus were identified by antidromic discharge. Stimulation of the subthalamic nucleus produced a short latency suppression of spontaneous activity (10-60 ms duration) of 89% of the entopeduncular cells tested in chronically lesioned rats. Of these cells, 50% were identified as projecting to lateral habenula. On the other hand, subthalamic nucleus stimulation produced a short latency excitation of 73% of the nigral cells tested (4.16 +/- 0.07 ms). Forty-eight percent of these cells projected to superior colliculus. The subthalamic fibres which terminate in entopeduncular nucleus and substantia nigra, come from the same neuronal population since the majority, if not all, rat subthalamic neurones send branched projections to both these nuclei. Therefore, the two different types of responses recorded in these nuclei are elicited by the activation of a single neuronal population. This dual effect could be easily explained if one of the responses is mediated by local interneurones. If not, the same transmitter induces the two responses. The entopeduncular nucleus and substantia nigra which are the main target nuclei of the subthalamic nucleus, are also the only known outputs of the striatum. The subthalamic efferent cells could thus modulate the activity of the entire striatal descending output. It is noteworthy that this subthalamic control is different in entopeduncular nucleus than in substantia nigra.     

Ultrastructural distribution of glycinergic and GABAergic neurons and axon terminals in the rat dorsal cochlear nucleus,with emphasis on granule cell areas

A knowledge of neurotransmitters in the neurons of the rat cochlear nuclear complex is of importance in understanding the function of auditory circuits. Using post-embedding ultrastructural immunogold labelling, the distribution of glycinergic and GABAergic neurons and axonal terminals has been studied in the molecular, fusiform and polymorphic layers of the rat dorsal cochlear nucleus (DCN). This technique is not limited by the penetration of antibodies into the nervous tissue as in pre-embedding methods, and allows a fine neurochemical mapping of the nervous tissue. Numerous glycinergic and GABAergic axon terminals contain pleomorphic and flat synaptic vesicles, and are present in all layers (1, 2, 3) of the dorsal cochlear nucleus. Glycine and GABA-negative large terminals (mossy fibres) are mainly seen in granule cell areas of layer 2 (fusiform layer). Mossy fibres contact the dendrites of GABA- and glycine-negative granule cells and of the few unipolar brush cells (excitatory neurons). The least common cells in the granule cell areas are GABAergic and glycinergic Golgi-stellate neurons. In unipolar brush cells, aggregations of vesicles seem to be the origin of their characteristic ringlet-bodies. Golgi-stellate cells send their inhibitory terminals to the dendrites of granule and unipolar brush cells, occasionally directly to mossy fibres. Small or (less frequently) large GABAergic terminals contact the soma or the main dendrite of unipolar brush cells. The circuit of a hypothetical functional unit of neurons in the DCN is proposed. The inputs from auditory tonotopic or non-auditory non-tonotopic mossy fibres eventually reach pyramidal cells through axons from the granule cells or unipolar brush cells. Pyramidal cells convey an excitatory signal from the DCN to higher mesencephalic nuclei for further elaboration of the acoustic signal.     

Vesicular glutamate transporter 1 and vesicular glutamate transporter 2 synapses on cholinergic neurons in the sublenticular gray of the rat basal forebrain: a double-label electron microscopic study

The basal forebrain (BF) comprises morphologically and functionally heterogeneous cell populations, including cholinergic and non-cholinergic corticopetal neurons that are implicated in sleep–wake modulation, learning, memory and attention. Several studies suggest that glutamate may be among inputs affecting cholinergic corticopetal neurons but such inputs have not been demonstrated unequivocally. We examined glutamatergic axon terminals in the sublenticular substantia innominata in rats using double-immunolabeling for vesicular glutamate transporters (Vglut1 and Vglut2) and choline acetyltransferase (ChAT) at the electron microscopic level. In a total surface area of 30,000 μm², we classified the pre- and postsynaptic elements of 813 synaptic boutons. Vglut1 and Vglut2 boutons synapsed with cholinergic dendrites, and occasionally Vglut2 axon terminals also synapsed with cholinergic cell bodies. Vglut1 terminals formed synapses with unlabeled dendrites and spines with equal frequency, while Vglut2 boutons were mainly in synaptic contact with unlabeled dendritic shafts and occasionally with unlabeled spines. In general, Vglut1 boutons contacted more distal dendritic compartments than Vglut2 boutons. About 21% of all synaptic boutons (n=347) detected in tissue that was stained for Vglut1 and ChAT were positive for Vglut1, and 14% of the Vglut1 synapses were made on cholinergic profiles. From separate cases stained for Vglut2 and ChAT, 35% of all synaptic boutons (n=466) were positive for Vglut2, and 23% of the Vglut2 synapses were made on cholinergic profiles. On average, Vglut1 boutons were significantly smaller than Vglut2 synaptic boutons. The Vglut2 boutons that synapsed cholinergic profiles tended to be larger than the Vglut2 boutons that contacted unlabeled, non-cholinergic postsynaptic profiles. The presence of two different subtypes of Vgluts, the size differences of the Vglut synaptic boutons, and their preference for different postsynaptic targets suggest that the action of glutamate on BF neurons is complex and may arise from multiple afferent sources.     

The effect of phencyclidine on [3H]GABA and [3H]fulnitrazepam binding in the brain of naive and handling-habituated rats

The effects of handling and handling combined with phencyclidine (PCP) treatment on GABAergic neurotransmission were studied in Sprague-Dawley rats. The animal material consisted of handling-habituated (HH, for 11 d), acutely handled (naive, N), handling-habituated and PCP-treated (10 mg kg^-1 i. p., HH+PCP) and acutely handled (naive) PCP-treated (N+PCP) and unhandled ‘control’ rats. The binding of [³]GANA and [³H]flunitrazepam (FLU) was studied with membrances and the release of [³H]GABA with slices prepared from the striatum and frontal cortex. In the striatum the maximal binding capacity (B_max) and the binding constant (K_D was lower in N rats. K_D constants of [³H]FLU were significantly lower in both brain areas in N rats than in HH rats. After PCP treatment both B_max and K_D for [³H]GAGA diminished. Neither handlign nor PCP had any effect on [³H]GABA release from striatal and frontal cortical slices. Handling prior to killing thus affects differently the GABAergic parameters studied and modulates the PCP-induced effects     

Synaptic inputs of tachykinin-containing nerve terminals to target tyrosine-hydroxylase-, β-endorphin- and neuropeptide Y-producing neurons of the arcuate nucleus. Double pre-embedding immunocytochemical study in the rat

Anatomical connections between tachykinin-containing terminals and three neuronal populations of the arcuate nucleus, chemically defined respectively by β-endorphin (β-END), tyrosine-hydroxylase or neuropeptide Y (NPY) and well represented in the arcuate nucleus, were studied using electron microscope double pre-embedding immunocytochemistry involving a combination of two sensitive chromogens: diaminobenzidine and tetramethylbenzidine.

Following tachykinin immunodetection by diaminobenzidine, and tyrosine-hydroxylase, β-END or NPY immunolabelling by tetramethylbenzidine, tachykinin-immunoreactive terminals were seen presynaptic to tyrosine-hydroxylase immunopositive cells and dendrites principally in the dorsomedial portion of the arcuate nucleus. Tachykinin-immunoreactive processes were also seen in synaptic contact with ventrolaterally located β-END immunopositive perikarya. Tachykinin-immunopositive terminals also contacted NPY- immunoreactive cells and dendritic processes ventromedially.

These results demonstrate the existence of a direct tachykinergic input onto three neuronal populations expected to play a role in the control of reproductive events. Consequently, they suggest, at least, an indirect action for tachykinins in the regulation of reproduction. Especially, tachykinins may indirectly control the luteinizing hormone-releasing hormone neurons via dopamine, β-END and NPY cells and thereby influence luteinizing hormone secretion.     

Immunocytochemical detection of the neurokinin B receptor (NK3) on melanin-concentrating hormone (MCH) neurons in rat brain

The presence of the neurokinin B receptor (NK3 receptor) in the rat lateral hypothalamus and the zona incerta was previously reported. The aim of the present study was to define its cellular localization in these areas. Investigations, coupling immunocytochemical and in situ hybridization techniques, focussed on two neuron populations: the melanin-concentrating hormone (MCH) neurons and a population of neurons recognized by an ovine prolactin antiserum (PRL-ir neurons). While PRL-ir neurons did not exhibit NK3 immunoreactivity, 57%±6% of MCH neurons were strongly stained by the NK3 antiserum. These results suggest that neurokinin B is involved in the regulation of MCH neuron activity via the NK3 receptor; they provide new bases for further investigations on MCH role in the control of food and water intake.