Neuroscience
-
The intrinsic cardiac nervous system modulates cardiac function by acting as an integration site for regulating autonomic efferent cardiac output. This intrinsic system is proposed to be composed of a short cardio-cardiac feedback control loop within the cardiac innervation hierarchy. For example, electrophysiological studies have postulated the presence of sensory neurons in intrinsic cardiac ganglia (ICG) for regional cardiac control. ⋯ Sequential labeling of VGLUT1 and VGLUT2 in adjacent tissue sections was used to evaluate the co-localization of VGLUT1 and VGLUT2 in ICG neurons. Our studies yielded the following results: (1) ICG contain glutamatergic neurons with GLS for glutamate production and VGLUT1 and 2 for transport of glutamate into synaptic vesicles; (2) atrial ICG contain neurons that project to ventricle walls and these neurons are glutamatergic; (3) many glutamatergic ICG neurons also were cholinergic, expressing VAChT; (4) VGLUT1 and VGLUT2 co-localization occurred in ICG neurons with variation of their protein expression level. Investigation of both glutamatergic and cholinergic ICG neurons could help in better understanding the function of the intrinsic cardiac nervous system.
-
Principles of negative reinforcement learning may play a critical role in the etiology and treatment of depression. We examined the integrity of positive reinforcement learning in congenitally helpless (cH) rats, an animal model of depression, using a random ratio schedule and a devaluation-extinction procedure. Furthermore, we tested whether an antidepressant dose of the monoamine oxidase (MAO)-B inhibitor deprenyl would reverse any deficits in positive reinforcement learning. ⋯ Reinforcer motivation as assessed by lever pressing across sessions with progressively decreasing reward probabilities was highest in congenitally non-helpless (cNH, n=10) rats as long as the reward probabilities remained relatively high. cNH compared to wild-type (n=10) rats were also more resistant to extinction across sessions. Compared to saline (n=5), deprenyl (n=5) reduced the duration of immobility of cH rats in the forced swimming test, indicative of antidepressant effects, but did not restore any deficits in the acquisition of a FI 20 schedule. We conclude that positive reinforcement learning was impaired in rats bred for helplessness, possibly due to motivational impairments but not deficits in reward sensitivity, and that deprenyl exerted antidepressant effects but did not reverse the deficits in positive reinforcement learning.
-
The capacity to flexibly switch between different task rules has been previously associated with distributed fronto-parietal networks, predominantly in the left hemisphere for phasic switching sub-processes, and in the right hemisphere for more tonic aspects of task-switching, such as rule maintenance and management. It is thus likely that the white matter (WM) connectivity between these regions is critical in sustaining the flexibility required by task-switching. This study examined the relationship between WM microstructure in young adults and task-switching performance in different paradigms: classical shape-color, spatial and grammatical tasks. ⋯ No association was found with behavioral measures obtained in the grammatical task-switching paradigm. The switch costs, a measure of phasic switching processes, were not correlated with WM microstructure in any task. This study shows that a more efficient inter-hemispheric connectivity within the frontal lobes favors sustained task-switching processes, especially with task contexts embedding non-verbal components.
-
Autophagy plays an essential role in neurodevelopment, axonal guidance, neuropathic pain remission, and neuronal survival. Inhibiting the mammalian target of rapamycin (mTOR) signaling pathway can induce the occurrence of autophagy. In this study, we initially detected the effect of probucol on autophagy after spinal cord injury (SCI) by intraperitoneally injecting spinal cord-injured rats with probucol for 7days. ⋯ Immunofluorescence results indicated that the expression of Caspase-3 protein was evidently decreased and that of Beclin-1 protein was increased by probucol. Nissl staining and Basso, Beattie, and Bresnahan scores showed that the quantity and function of motor neurons were visibly preserved by probucol after SCI. This study showed that probucol inhibited the mTOR signaling pathway to induce autophagy, reduce neural cell apoptosis and promote recovery of neurological function after SCI.
-
Kynurenine pathway metabolites (KPM) are thought to be synthesized mainly by non-neuronal cells in the mammalian brain. KPM are of particular interest because several studies demonstrated their implication in various disorders of the nervous system. Among KPM is xanthurenic acid (XA) deriving from the catabolism of 3-hydroxykynurenine. ⋯ Our results also reveal that XA-like immunoreactivity is not expressed by glial cells. To double-check our findings, we have also used another XA antibody obtained from a commercial source to confirm the neuronal expression of XA. Together, our results suggest that, differently to several other KPM produced by glial cells, XA exhibits a neuronal distribution in the mouse brain.