Neuroscience
-
Schizophrenia is a severe condition that has been associated with functional abnormalities in dopaminergic (DA) neurons of the ventral tegmental area (VTA). Neurokinin-3 receptors (NK3Rs) of the tachykinin family of neuropeptides modulate the activity of VTA DA neurons and might be involved in DA abnormalities relevant to schizophrenia. Recent work from our lab showed that systemic injection of the dopamine D1/D2 receptor agonist apomorphine in rats, which mimics schizophrenia-like behaviors in humans, also evoked a redistribution of NK3Rs in DA neurons of the rat VTA. ⋯ In non-TH, presumably GABAergic neurons of the VTA, the NK3R densities in somata and dendrites were not significantly changed by apomorphine with or without SB222200. The results suggest that the NK3R antagonist SB222200 is effective against the apomorphine-evoked NK3R internalization in VTA DA dendrites, but does not prevent nuclear NK3R trafficking in VTA DA neurons. These results might have important implications in targeting NK3R antagonists in basic or clinical studies.
-
The olfactory bulb (OB) has been recently identified as a circadian oscillator capable of operating independently of the master circadian pacemaker, the suprachiasmatic nuclei of the hypothalamus. OB oscillations manifest as rhythms in clock genes, electrical activity, and odor sensitivity. Dopamine, norepinephrine, and serotonin have been shown to modulate olfactory information processing by the OB and may be part of the mechanism that underlies diurnal changes in olfactory sensitivity. ⋯ Serotonin and its metabolite hydroxyindoleacetic acid appear to rhythmically fluctuate. Each of these monoamines has been shown to alter OB circuit behavior and influence odor processing. Rhythmic release of serotonin may be a mechanism by which the suprachiasmatic nuclei communicate, indirectly, with the OB.
-
Immediate early transcription is an integral part of the neuronal response to environmental stimulation and serves many brain processes including development, learning, triggers of programmed cell death, and reaction to injury and drugs. Following a stimulus, neurons express a select few genes within a short period of time without undergoing de novo protein translation. Referred to as the 'gateway to genetic response', these immediate early genes (IEGs) are either expressed within a few minutes of stimulation or later within the hour. ⋯ IEGs expressed later in the hour do not depend on this mechanism. On the basis of this Polymerase II poising, we propose that the immediate early genes can be grouped in two distinct classes: the rapid and the delayed IEGs. The possible biological relevance of these classes in neurons is discussed.
-
Over the years it has become crystal clear that a variety of processes encode time-of-day information, ranging from gene expression, protein stability, or subcellular localization of key proteins, to the fine tuning of network properties and modulation of input signals, ultimately ensuring that physiology and behavior are properly synchronized to a changing environment. The purpose of this review is to put forward examples (as opposed to generate a comprehensive revision of all the available literature) in which the circadian system displays a remarkable degree of plasticity, from cell autonomous to circuit-based levels. In the literature, the term circadian plasticity has been used to refer to different concepts. ⋯ The discovery of daily remodeling of neuronal structures will be referred herein as structural circadian plasticity, and represents an additional and novel phenomenon modified daily. Finally, any plasticity that has to do with a circadian parameter would represent a type of circadian plasticity; as an example, adjustments that allow organisms to adapt their daily behavior to the annual changes in photoperiod is a form of circadian plasticity at a higher organizational level, which is an emergent property of the whole circadian system. Throughout this work we will revisit these types of changes by reviewing recent literature delving around circadian control of clock outputs, from the most immediate ones within pacemaker neurons to the circadian modulation of rest-activity cycles.
-
The article reviews evidence for sensitive periods in the sensory systems and considers their neuronal mechanisms from the viewpoint of the system's neuroscience. It reviews the essential cortical developmental steps and shows its dependence on experience. It differentiates feature representation and object representation and their neuronal mechanisms. ⋯ Additional to developmental molecular effects on synaptic plasticity, a combination of several integrative effects of deprivation on brain functions, including feature representation (affecting the starting point for learning), categorization function, top-down interactions and cross-modal reorganization close the sensitive periods and may contribute to their critical nature. Further, non-auditory effects of auditory deprivation are discussed. To reopen critical periods, removal of molecular breaks in synaptic plasticity and focused training therapy on the integrative effects are required.