Psychostimulant Drugs and Neuroplasticity

Role of microRNA-132 in Opioid Addiction through Modification of Neural Stem Cell Differentiation

In this editorial, we focused on the article, "MicroRNA-132 in the Adult Dentate Gyrus is Involved in Opioid Addiction Via Modifying the Differentiation of Neural Stem Cells" by Jia and colleagues [...].

Visuo-Acoustic Stimulation's Role in Synaptic Plasticity: A Review of the Literature

Brain plasticity is the capacity of cerebral neurons to change, structurally and functionally, in response to experiences. This is an essential property underlying the maturation of sensory functions, learning and memory processes, and brain repair in response to the occurrence of diseases and trauma. In this field, the visual system emerges as a paradigmatic research model, both for basic research studies and for translational investigations. The auditory system remains capable of reorganizing itself in response to different auditory stimulations or sensory organ modification. Acoustic biofeedback training can be an effective way to train patients with the central scotoma, who have poor fixation stability and poor visual acuity, in order to bring fixation on an eccentrical and healthy area of the retina: a pseudofovea. This review article is focused on the cellular and molecular mechanisms underlying retinal sensitivity changes and visual and auditory system plasticity.

Plasticity in the human visual cortex: an ophthalmology-based perspective

Neuroplasticity refers to the ability of the brain to reorganize the function and structure of its connections in response to changes in the environment. Adult human visual cortex shows several manifestations of plasticity, such as perceptual learning and adaptation, working under the top-down influence of attention. Plasticity results from the interplay of several mechanisms, including the GABAergic system, epigenetic factors, mitochondrial activity, and structural remodeling of synaptic connectivity. There is also a downside of plasticity, that is, maladaptive plasticity, in which there are behavioral losses resulting from plasticity changes in the human brain. Understanding plasticity mechanisms could have major implications in the diagnosis and treatment of ocular diseases, such as retinal disorders, cataract and refractive surgery, amblyopia, and in the evaluation of surgical materials and techniques. Furthermore, eliciting plasticity could open new perspectives in the development of strategies that trigger plasticity for better medical and surgical outcomes.

Behavioral and dorsal raphe neuronal activity following acute and chronic methylphenidate in freely behaving rats

Concomitant behavioral and dorsal raphe (DR) neuronal activity were recorded following acute and chronic dose response of methylphenidate (MPD) in freely moving rats previously implanted with permanent semi-microelectrodes using telemetric (wireless) technology. On experimental day (ED) 1, the neuronal and locomotor activity were recorded after saline (baseline) and MPD (0.6, 2.5 or 10.0mg/kg) injection (i.p.). Animals were injected daily with a single dose of MPD for five consecutive days (ED 2-6) to elicit behavioral sensitization or tolerance. After three washout days, the neuronal and locomotor activity recording was resumed on ED 10 followed by saline and MPD rechallenge injection. The main findings were: (1) the same dose of chronic MPD administration elicited behavioral sensitization in some animals and behavioral tolerance in others. (2) 46%, 56% and 73% of DR units responded to acute 0.6, 2.5 and 10.0mg/kg MPD respectively. (3) 89%, 70% and 86% of DR units changed their baseline activity on ED 10 compared to that on ED 1 in the 0.6, 2.5 and 10.0mg/kg MPD groups respectively. (4) A significant difference in ED 10 baseline activity was observed in the DR neuronal population recording from animals expressing behavioral sensitization compared to that of animals expressing behavioral tolerance. (5) 89%, 78% and 88% of DR units responded to chronic 0.6, 2.5 and 10.0mg/kg MPD respectively. (6) The DR neuronal population recording following acute MPD on ED 1 and rechallenge MPD on ED 10 from animals expressing behavioral sensitization was significantly different from the neuronal population recorded from animals exhibited behavioral tolerance. The correlation between the DR neuronal activity and animal's behavior following chronic MPD exposure suggested that the DR neuronal activity may play an important role in the expression of behavioral sensitization and tolerance induced by chronic MPD administration.

Dorsal raphe neuronal activities are modulated by methylphenidate

This study investigated the electrophysiological properties of the dorsal raphe nucleus (DR) neurons in response to the acute and repetitive administration of methylphenidate (MPH). Activities of DR neurons were recorded from non-anesthetized, freely behaving rats previously implanted bilaterally with permanent semi microelectrodes. The main findings were: (1) after initial (acute) administration of MPH (2.5 mg/kg i.p.) on experimental day one (ED1), 56 % of DR units significantly changed their firing rates. The majority of the responsive units (88 %) exhibited increased firing rate; (2) daily MPH injections were given on ED2 through ED6 followed by 3 washout days. On ED10, 83 % of the DR units significantly changed their baseline activity compared to the baseline activity on ED1; (3) after rechallenge MPH administration on ED10, 63 % of DR units exhibited significant change in their firing rate; the majority of the responsive units (76 %) exhibited a significant increase in their firing rate; (4) The effect of rechallenge MPH administration on ED10 was compared to the effect of initial MPH on ED1, 47 % DR units exhibited a further significant increase in their firing rate while 53 % DR units exhibited decrease or non-change in their firing rate which can be interpreted as electrophysiological sensitization or tolerance. In conclusion, this study demonstrated that acute MPH administration modulated the DR neuronal activities. Repetitive MPH administration modulated the baseline activities of DR units and elicited neurophysiological sensitization or tolerance. The results indicated that MPH affects DR neuronal activity.

Methylphenidate modulates the locus ceruleus neuronal activity in freely behaving rat

The electrophysiological properties of the locus coeruleus (LC) neurons in response to acute and chronic administration of methylphenidate (MPD) were investigated. The extracellular LC neuronal activities were recorded from non-anesthetized, freely behaving rats previously implanted bilaterally with permanent semi microelectrodes. The main findings were: (1) On experimental day 1 (ED1), 87% (94/108) of LC units significantly changed their firing rate after initial (acute) MPD (2.5mg/kg, i.p.) administration. The majority of the responsive units (80%, 75/94) increased their firing rate; (2) Daily MPD (2.5mg/kg) injection was given on ED2 through ED6 followed by 3 washout days (ED7 to 9). On ED10, all LC units exhibited a significant change of their baseline activity compared to their baseline activity on ED1; (3) MPD rechallenge on ED10 elicits 94% (101/108) of LC units significantly changed their firing rate; the majority of them (78%, 79/101) increased their firing rate; (4) The effect of rechallenge MPD administration on ED10 were compared to the effect of initial MPD on ED1, 98% of the LC units exhibited a significant change in their firing rate. 41% (43/106) of them exhibited a significant increase in their firing rate while 59% (63/106) units significantly decreased their firing rate which can be interpreted as electrophysiological sensitization or tolerance respectively. In conclusion, the majority of LC neurons significantly increased their firing rate after acute and chronic MPD administration. This data demonstrated that enhanced LC neuronal activities play important role in the effect of MPD.