Brain research
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Comparative Study
Intra-amygdalar injection of DAMGO: effects on c-Fos levels in brain sites associated with feeding behavior.
It is well known that the mu opioid agonist, Tyr-D-Ala-Gly-(me) Phe-Gly-ol (DAMGO), increases food intake in rats when injected into a variety of brain sites including the central nucleus of the amygdala (CeA). Immunohistochemical studies measuring c-Fos immunoreactivity (IR) suggest that the CeA contributes to opioid-related feeding. In the current study, we injected 2 nmol of DAMGO and measured food intake, c-Fos IR levels in various brain sites involved in feeding behavior, and mu opioid receptor internalization. ⋯ Administration of DAMGO into the CeA increased c-Fos IR levels in the shell of the nucleus accumbens (NAcc), but not in 17 other brain sites that were studied. We also found that intra-CeA injection of DAMGO, prior to LiCl injection, decreased c-Fos IR levels in the CeA compared to vehicle-injected rats. Thus, intra-CeA administration of DAMGO may increase feeding, in part, by activating neurons in the shell of the nucleus accumbens and by inhibiting activity of selected neurons in the CeA.
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Comparative Study Clinical Trial
The effects of muscle vibration on anticipatory postural adjustments.
The current study investigated the influence of changes in sensory information related to postural stability on anticipatory postural adjustments (APAs) in standing subjects. Subjects performed fast arm movements and a load release task while standing on a stable force platform or on an unstable board. We manipulated sensory information through vibration of the Achilles tendons and additional finger touch (contact forces under 1 N). ⋯ Small changes in the other index related to reciprocal activation (R-index) were found only in trunk muscles. Light touch and vibration induced opposing changes in the C-index, suggesting their opposite effects on the stabilization of a reference point or vertical. We conclude that the central nervous system deploys patterns of adjustments in which increased co-contraction of distal muscles and reciprocal adjustments in trunk muscles are modified to ensure equilibrium under postural instability.
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In the view of importance of intergeniculate leaflet in circadian rhythms processes and lack of information about electrophysiological properties of isolated intergeniculate leaflet (IGL) neurons, we carried out extracellular recordings of the spontaneous activity of rat IGL cells in vitro. Unlike other structures of visual thalamus, IGL neurons have the ability to generate a robust spontaneous neuronal activity when maintained in vitro. We have observed that in a standard incubation fluid IGL neurons display at least three distinct firing patterns: continuously irregular-with a wide variety of firing rates, tonic-with a very stable level of activity, and phasic (slow bursts)-with intermittent silent periods. Our study is the first electrophysiological demonstration of IGL neuronal activity in vitro.
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Morphine analgesic potency following systemic administration was assessed in male and female mice undergoing prior and repeated intrathecal morphine injections. Although morphine ED50 values were significantly increased in both sexes relative to their respective saline-injected controls, the magnitude of tolerance was greater in females. Intrathecal injection alone had no effect on morphine analgesia. The data suggest that spinal mechanisms contribute to sex differences in analgesic tolerance following systemic morphine administration.