Neuroendocrine secretory protein 55 (NESP55) in the spinal cord of rat: an immunocytochemical study

The immunohistochemical expression of a novel chromogranin-like protein, neuroendocrine secretory protein 55 (NESP55), in the rat spinal cord was investigated. NESP55-immunoreactive cells were detected in the ventral horn, intermediate laminae, and deep dorsal horn, comprising motoneurons, autonomic neurons, and interneurons throughout all spinal segments. Within laminae I-II of the dorsal horn, one or two NESP55-positive cells were often seen. Nerve fibers also contained NESP55 immunoreactivity (IR) and were particularly prominent in the ventral horn. No nerve terminals/varicosities appeared to contain NESP55 in any spinal lamina. Double-staining experiments revealed that a high proportion of the NESP55-positive neurons were cholinergic. Moreover, NESP55-IR in the motoneurons was evenly distributed in the whole cytoplasm with a finely granular appearance. In contrast, the fluorescent material in the preganglionic neurons was concentrated in the perinuclear region and largely overlapped with the trans-Golgi network marker TGN38. Our data provide detailed morphological information on the distribution of NESP55-IR in the rat spinal cord. Also, the differential intracellular expression of NESP55-IR in the spinal motoneurons and autonomic neurons suggests that NESP55 may be processed into different secretory granules and may be involved in both constitutive and regulated pathways in these neurons.     

Intra-lateral septal infusions of folic acid alone or combined with various antidepressant drugs produce antidepressant-like actions in male Wistar rats forced to swim

Intra-cerebral administrations of folic acid produce antidepressant-like effects; either alone or combined with several antidepressant drugs. However, the specific limbic structures implied in the antidepressant-like actions of folic acid are un-known. Thus, intra-lateral septal infusions of folic acid (5.0 nmol, P < 0.05; 10.0 nmol, P < 0.05) or oral administrations of folic acid (50 mg/kg, P < 0.05, p.o.; 75.0; mg/kg, P < 0.05, p.o.) or systemic administrations of fluoxetine (20.0 mg/kg, P < 0.05; 25.0 mg/kg, P < 0.05) reduced immobility by increasing swimming behavior in the forced swimming test (FST) of male Wistar rats. Conversely, desipramine (10.0 mg/kg, P < 0.05; 15.0 mg/kg, P < 0.05) reduced immobility by increasing climbing behavior. Subthreshold doses of folic acid (2.5 nmol/intra-LSN) combined with subthreshold doses of folic acid (25.0 mg/kg, p.o., P < 0.05) or with subthreshold doses of fluoxetine (15.0 mg/kg, P < 0.05) and they produced antidepressant-like effects which were canceled by ketanserin. In conclusion, intra-lateral septal infusions of folic acid alone or combined with systemic doses of folic acid or fluoxetine reduced immobility in the FST. These antidepressant-like actions, probably, were due to modifications of the serotonergic system since swimming behavior was increased and these effects were canceled by ketanserin.     

Splanchnic and pelvic mechanosensory afferents signal different qualities of colonic stimuli in mice

BACKGROUND&AIMS: Mechanosensory information from the colon is conducted via lumbar splanchnic nerves (LSN) and sacral pelvic nerves (PN) to the spinal cord. The precise nature of mechanosensory information encoded by each pathway has remained elusive. Here, we characterize and directly compare the properties of mechanosensitive primary afferents from these 2 pathways. METHODS: Using a novel in vitro mouse colon preparation, mechanosensitive primary afferents were recorded from the LSN and PN and distinguished based on their response to receptive field stimulation with 3 distinct mechanical stimuli: probing (70 mg-4 g), circular stretch (1-5 g), and mucosal stroking (10-1000 mg). RESULTS: Five different classes of afferent were recorded from the LSN and PN. Three of these classes of afferent (serosal, muscular, and mucosal) were conserved between both pathways; however, their respective proportions, receptive field distributions, and response properties differed greatly. In general, these 3 classes of afferent recorded from the PN responded to lower stimulation intensities, displayed greater response magnitudes, and adapted less completely to mechanical stimulation compared with their LSN counterparts. In addition, the LSN and PN each contain a specialized class of afferent (mesenteric and muscular/mucosal), which is unique to their respective pathway. CONCLUSIONS: The splanchnic and pelvic pathways contain distinct populations of mechanosensitive afferents. These afferents are capable of detecting an array of mechanical stimuli and are individually tuned to detect the type, magnitude, and duration of the stimulus. This knowledge contributes to our understanding of the role that these 2 pathways play in conveying mechanical information from the colon.     

Study of the efferent connections of the enkephalinergic magnocellular dorsal nucleus in the guinea-pig hypothalamus using lesions, retrograde tracing and immunohistochemistry: evidence for a projection to the lateral septum

The efferents of enkephalin-immunoreactive neurons in the magnocellular dorsal nucleus of the guinea-pig were studied using different neuroanatomical methods and indirect immunocytochemical technique. Following unilateral implantation of the fluorescent dye 4',6-diamidino-2-phenylindole in the lateral septal nucleus, retrogradely-labeled perikarya were found in the magnocellular dorsal nucleus. These labeled perikarya reacted with antiserum against enkephalin, demonstrating that enkephalin-immunoreactive neurons in the magnocellular dorsal nucleus project to the lateral septal nucleus. In other experiments, complete bilateral lesions were produced in the magnocellular dorsal nucleus by electrocoagulation. Enkephalin-immunoreactive nerve fibers and terminals were totally depleted in the lateral septal nucleus. This confirms that septal enkephalin-immunoreactive terminals originate in the magnocellular dorsal nucleus and further suggests that this nucleus is the source of all the enkephalin-immunoreactive material found in the septum. Experiments utilizing two different fluorescent dyes, 4',6-diamidino-2-phenylindole and propidium iodide, injected in each side of the lateral septal nucleus, respectively, demonstrated that the magnocellular dorsal nucleus gives off axon collaterals to both sides of the septum, since double-labeling of individual cell bodies was detected in the nucleus. By relating this finding to the results obtained after unilateral destruction of the nucleus, which caused an incomplete loss of enkephalin- immunoreactive material in the lateral septal nucleus ipsilaterally, it is suggested that the enkephalinergic hypothalamo-septal pathway contains unbranching neurons projecting ipsilaterally and branching neurons distributing fibers ipsilaterally and contralaterally. Lesion experiments, and experiments based on the retrograde axonal transport of horseradish peroxidase after intravenous injections, demonstrated that the magnocellular dorsal nucleus contributes neither to the tubero-infundibular nor to the hypothalamo-neurohypophyseal tracts. The lateral septal nucleus receives numerous aminergic and peptidergic projections, indicating the potential importance of this region in physiological and behavioral events. In the guinea-pig, the well-demarcated enkephalinergic pathway demonstrated in this study provides a convenient model for the experimental study of the enkephalinergic innervation of the lateral septal nucleus.     

Validity of multi-fiber muscle velocity recovery cycles recorded at a single site using submaximal stimuli

Objective

To examine the validity of multi-fiber muscle velocity recovery cycles (VRCs) recorded by direct muscle stimulation with submaximal stimuli.

Methods

VRCs were recorded from tibialis anterior muscle in normal volunteers with 1, 2 and 5 conditioning stimuli. Recordings were made with 6 different amplitudes of conditioning stimuli. Recordings were also made with two recording electrodes, at least 15 mm apart.

Results

Muscle VRCs in 6 subjects were not significantly different for conditioning stimuli between 80% and 150% of test stimulus amplitude. When recorded at two sites in 9 subjects, VRCs were similar when estimated over the shorter distance, the longer distance, and from the conduction time between the two electrodes.

Conclusions

Multi-fiber muscle VRCs can be reliably recorded with a single recording electrode and with equal amplitude conditioning and test stimuli.

Significance

Clinical neurophysiologists can be assured that this new method of testing muscle membrane properties provides valid and robust measurements on normal muscles.