Neuroscience
-
Clathrin adaptor protein (AP)180 is a synaptic protein that regulates the assembly of clathrin-coated vesicles. Several endocytic proteins including AP2, CALM, and epsin 1 have functions or molecular structures similar to AP180. We determined if AP180 associates with functional synapses in cultured hippocampal neurons. ⋯ Epsin 1 immunoreactivity was found in both synaptic and extrasynaptic sites, and its synaptic distribution only partially overlapped with that of AP180. These results support roles for AP180 in synaptic function in neurons. The findings also provide information on the distribution of AP2, CALM, and epsin 1 in cells of the nervous system that suggest different roles for these endocytic proteins in the biology of these cells.
-
The inferior colliculus (IC) plays a key role in the processing of auditory information and is thought to be an important site for genesis of wild running seizures that evolve into tonic-clonic seizures. IC neurons are known to have Ca(2+) channels but neither their types nor their pharmacological properties have been as yet characterized. Here, we report on biophysical and pharmacological properties of Ca(2+) channel currents in acutely dissociated neurons of adult rat IC, using electrophysiological and molecular techniques. ⋯ The fraction of current (approximately 12%) resistant to the above blockers, which was blocked by 30 microM nickel and inactivated with tau of 15-50 ms, was considered as R-type Ca(2+) channel current. Consistent with the pharmacological evidences, Western blot analysis using selective Ca(2+) channel antibodies showed that IC neurons express Ca(2+) channel alpha(1A), alpha(1B), alpha(1C), alpha(1D), and alpha(1E) subunits. We conclude that IC neurons express functionally all members of HVA Ca(2+) channels, but only a subset of these neurons appear to have developed functional LVA channels.
-
Immunohistochemistry for the somatostatin sst2A receptor was performed on the rat trigeminal ganglion to know its function in the trigeminal nervous system. The immunoreactivity was detected in 9.4% of primary sensory neurons in the ganglion. These neurons were small to medium-sized (range=106.5-1123.2 microm(2); mean+/-S. ⋯ In the brainstem trigeminal sensory nuclear complex, both the neuronal cell body and the neuropil exhibited sst2A receptor-immunoreactivity in the superficial medullary dorsal horn. The present study indicates that sst2A receptor-immunoreactive trigeminal nociceptors innervate the nasal mucosa. They may project to the superficial laminae of the medullary dorsal horn.
-
We investigated the role of in vivo synaptic activity upon trafficking of the N-methyl-D-aspartate (NMDA) receptor subunit, NR2B, at mature synapses by electron microscopic immunocytochemistry. In vivo blockade of NMDA receptors was achieved by applying the NMDA receptor antagonist, D-2-amino-5-phosphonovalerate (D-APV), onto the cortical surface of one hemisphere of anesthetized adult rats. Inactive L-2-amino-5-phosphonovalerate (L-APV) was applied to the contralateral hemisphere for within-animal control and to assess basal level of NR2B subunits at synapses. ⋯ The data demonstrate that blockade of NMDA receptors induces trafficking of NR2B subunits out of synaptic membranes, spines, and terminals. This is in sharp contrast to a previous observation that NR2A subunits move into spines and axon terminals following in vivo blockade with D-APV. These findings point to yet unknown, NMDA receptor activity-dependent mechanisms that separately regulate the localization of NR2A and NR2B subunits at synapses.
-
Following 2 weeks acclimation to the running wheel in the home cages, an i.p. injection of a synthetic double-stranded RNA, polyriboinosinic:polyribocytidylic acid (poly I:C, 3 mg/kg), was performed to produce the immunologically induced fatigue in rats. The daily amounts of spontaneous running wheel activity decreased to about 40-60% of the preinjection level until day 9 with normal circadian rhythm, then gradually returned to the baseline level by day 14. Rats given a heat exposure (36 degrees C for 1 h) for the consecutive 3 days showed an increase in activity except for the first day. ⋯ Quantitative analysis of mRNA levels using a real-time capillary reverse transcriptase-polymerase chain reaction (RT-PCR) method revealed that interferon-alpha (IFN-alpha) mRNA contents in the cortex, hippocampus, hypothalamic medial preoptic, paraventricular, and ventromedial nuclei were higher in the poly I:C group than those in the saline and heat-exposed groups on day 7, although the amount of interleukin-1 beta mRNA showed no differences. Serum adrenocorticotropic hormone and catecholamine levels were not significantly different between groups. The present results indicate that the prolonged fatigue induced by poly I:C, which is evaluated by the spontaneous running wheel activity, can be used as an animal model for the immunologically induced fatigue associated with viral infection, and suggest that brain IFN-alpha may play a role in this model.