Neuroscience
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In a previous study, it was shown that populations of climbing fibers, derived from the inferior olivary complex (IOC) contain the peptide corticotropin releasing factor (CRF) and that the expression of this peptide in climbing fibers could be modulated by the level of activity in olivary afferents. The intent of this study was to determine if there was comparable plasticity in the distribution of the type 1 CRF receptor (CRF-R1) in the cerebellum of the rat. Our results indicate that CRF-R1 was localized primarily to Purkinje cell somata and their primary dendrites and granule cells. ⋯ Further, interneurons responded with a decrease in receptor expression following more intense levels of stimulation suggesting the possibility of internalization of the receptor. In contrast, Bergmann glial cells showed an increased expression in receptor expression. These data suggest that CRF released from climbing fibers may modulate the physiological properties of basket and stellate cells as well as having a heretofore unidentified and potentially unique effect on Bergmann glia.
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The mesolimbic dopaminergic system, originating from the ventral tegmental area (VTA) is implicated in the rewarding properties of ethanol. VTA dopaminergic neurons are under the tonic control of GABAergic innervations. Application of GABAergic agents changes ethanol consumption. ⋯ Thus, ethanol dually modulates GABAergic transmission to dopaminergic neurons in the VTA. Ethanol modulation depends on the activity of VTA GABAergic neurons, which were inhibited by the activation of mu-opioid receptors. This dual modulation of GABAergic transmission by ethanol may be an important mechanism underlying alcohol addiction.
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Comparative Study
Noradrenergic, but not cholinergic, deafferentation of prefrontal cortex impairs attentional set-shifting.
Both norepinephrine and acetylcholine have been shown to be critically involved in mediating attention but there remains debate about whether they serve similar or unique functions. Much of what is known about the role of these neurochemicals in cognition is based on manipulations done at the level of the cell body but these findings are difficult to reconcile with data regarding the unique contribution of cortical subregions, e.g. the dorsolateral prefrontal cortex, to attention. ⋯ We also clarified the nature of the attentional deficits by assessing the ability of rats to disregard irrelevant stimuli. Noradrenergic lesions did not alter the ability of rats to ignore irrelevant stimuli, suggesting that the attentional deficit results from an overly focused attentional state that retards learning that a new stimulus dimension predicts reward.
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A wide variety of human and animal experiments suggest that the anterior cingulate cortex (ACC) is one of the key brain substrates subserving higher order processing of noxious information. However, no sufficient data are now available regarding the mediation by ACC of different levels of pain processing as well as its potential descending modulation of spinal nociception. Using the well-developed rat bee venom (BV) model, the present study evaluated the effect of lesions of bilateral ACC on two levels of spontaneous nociceptive behaviors (spinally-processed persistent paw flinching reflex and supraspinally-processed paw lifting/licking) and heat or mechanical hypersensitivity under the inflammatory pain state. ⋯ Motor coordination, as measured by Rota-Rod treadmill test, was not impaired by bilateral ACC lesions. These results implicate that the ACC area of the brain plays differential roles in the mediation of different levels of spontaneous pain-related behaviors. The present study also provides additional evidence for the ACC-mediated descending facilitation of primary hyperalgesia (pain hypersensitivity) identified in the injured area under inflammatory pain state.
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Onset of auditory brainstem responses in chickens takes place at about embryonic day 11/12 (E11/12). We investigated early development of neuronal properties of chicken nucleus laminaris neurons, the third-order auditory neurons critically involved in sound localization. Whole-cell patch recordings were performed in brainstem slices obtained at E10, E11, E12, E14, E16, and E18. ⋯ Excitatory postsynaptic potentials (EPSPs) were first recorded at E10, prior to and independent of the cochlear afferent inputs from the auditory nerve to the cochlear nucleus. EPSPs became markedly briefer in duration during the period studied. We conclude that the basic features of the key neuronal properties of NL neurons are well constructed during early development from E10 to E18.