Neuroscience
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Vestibulospinal reflexes elicited by head displacement become appropriate for body stabilization owing to the integration of neck input by the cerebellar anterior vermis. Due to this integration, the preferred direction of spinal motoneurons' responses to animal tilt rotates by the same angle and by the same direction as the head over the body, which makes it dependent on the direction of body displacement rather than on head displacement. It is known that the cerebellar control of spinal motoneurons involves the reticular formation. ⋯ The modifications of reticular neurons' responses were different from those observed in the P-cells of the cerebellar anterior vermis, which rarely showed gain and activity changes and often exhibited a rotation of their response directions. In conclusion, reticular neurons take part in the neck tuning of vestibulospinal reflexes by transforming a head-driven sensory input into a body-centred postural response. The present findings prompt re-evaluation of the role played by the reticular neurons and the cerebellum in vestibulospinal reflexes.
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In order to better understand and treat neuropathic pain, scientific study must use methods that can assess pain processing at the cortical level where pain is truly perceived. Operant behavior paradigms can accomplish this. We used an operant task to evaluate changes following chronic constriction injury to the trigeminal nerves. ⋯ These behavioral changes were accompanied by an increase in TRPV1 positive cells and an increased intensity of TRPM8 staining at 2 weeks post-injury, when cold allodynia is maximal. These findings suggest that the incorporation of operant behavioral assessment in the study of pain may provide insight into the relationship among peripheral changes, motivational drive, and pain. Understanding this relationship will allow us to better treat and prevent chronic neuropathic pain.
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This work compares the effects on brain stimulation reward (BSR) when combining D2 dopamine receptor and AMPA glutamate receptor manipulations in the sublenticular central extended amygdala (SLEAc) and the nucleus accumbens shell (NAc shell). Thirty-seven male Long Evans rats received medial forebrain bundle (MFB) stimulation electrodes and bilateral injection guide cannulae aimed at either the SLEAc or the NAc shell. The rate-frequency paradigm was used to assess drug-induced changes in stimulation reward effectiveness and in response rate following 0.5 μl infusions of 0.50 μg of 1,2,3,4-tetrahydro-6-nitro-2,3-dioxo-benzo[f]quinoxaline-7-sulfonamide (NBQX) (AMPA receptor antagonist), 10.0 μg of quinpirole (D2 receptor agonist), 0.25 μg of AMPA (AMPA receptor agonist), 3.0 μg of eticlopride (D2 receptor antagonist), 0.50 μg of NBQX with 10.0 μg of quinpirole, and 0.25 μg of AMPA with 3.0 μg of eticlopride. ⋯ When injected into the NAc shell the drugs had only one significant effect on the frequency required to maintain half-maximal responding: injections of NBQX with quinpirole ipsilateral to the stimulation site increased required frequency significantly more than did injections of saline. Contrary to expectations, stimulating AMPA receptors with and without co-blockade of D2 receptors also decreased the stimulation's reward efficacy, although these effects may reflect general behavioral disruption more than effects on reward per se. These results indicate a role for the SLEAc in BSR and also suggest that SLEAc neurons ipsi- and contralateral to the stimulated MFB play their roles in BSR through different mechanisms.
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Drinking alcohol in moderation is often considered a health-conscious behavior, associated with improved cardiovascular and brain health. However, "moderate" amounts of alcohol include drinking 3-4 alcohol beverages in a day, which is closer to binge drinking and may do more harm than good. Here we examined how daily drinking of moderate-high alcohol alters the production of new neurons in the adult hippocampus. ⋯ Therefore, moderate alcohol consumption did not disrupt basic sensory, motor or learning processes. However, the number of cells produced in the dentate gyrus of the hippocampus was reduced by nearly 40%. Thus, even moderate consumption of alcohol for a relatively short period of time can have profound effects on structural plasticity in the adult brain.
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Associative learning can enable cues from the environment to stimulate feeding in the absence of physiological hunger. How learned cues are integrated with the homeostatic regulatory system is unknown. Here we examined whether the underlying mechanism involves the hypothalamic orexigenic neuropeptide regulators orexin/hypocretin (ORX) and melanin-concentrating hormone (MCH). ⋯ In contrast, there were very few MCH neurons with Fos induction in both the Paired and Unpaired conditions. Thus, the food-cue selectively induced Fos in ORX but not in MCH neurons. These results suggest a role for ORX in cue-induced feeding that occurs in the absence of physiological hunger.