Neuroscience
-
Comparative Study
Modulation of forelimb and hindlimb muscle activity during quadrupedal tied-belt and split-belt locomotion in intact cats.
The modulation of the neural output to forelimb and hindlimb muscles when the left and right sides step at different speeds from one another in quadrupeds was assessed by obtaining electromyography (EMG) in seven intact adult cats during split-belt locomotion. To determine if changes in EMG during split-belt locomotion were modulated according to the speed of the belt the limb was stepping on, values were compared to those obtained during tied-belt locomotion (equal left-right speeds) at matched speeds. Cats were chronically implanted for EMG, which was obtained from six muscles: biceps brachii, triceps brachii, flexor carpi ulnaris, sartorius, vastus lateralis and medial gastrocnemius. ⋯ During split-belt locomotion, there was a clear differential modulation of the EMG patterns between flexors and extensors and between the slow and fast sides. Changes in the EMG pattern of some muscles could be explained by the speed of the belt the limb was stepping on, while in other muscles there were clear dissociations from tied-belt values at matched speeds. Therefore, results show that EMG patterns during split-belt locomotion are modulated to meet task requirements partly via signals related to the stepping speed of the homonymous limb and from the other limbs.
-
Comparative Study
Reelin influences the expression and function of dopamine D2 and serotonin 5-HT2A receptors: a comparative study.
Reelin is an extracellular matrix protein that plays a critical role in neuronal guidance during brain neurodevelopment and in synaptic plasticity in adults and has been associated with schizophrenia. Reelin mRNA and protein levels are reduced in various structures of post-mortem schizophrenic brains, in a similar way to those found in heterozygous reeler mice (HRM). Reelin is involved in protein expression in dendritic spines that are the major location where synaptic connections are established. ⋯ We observed increased expression (p<0.05) in striatum membranes and decreased expression (p<0.05) in frontal cortex membranes for both dopamine D2 and serotonin 5-HT2A receptors from HRM compared to WTM. Our results show parallel alterations of D2 and 5-HT2A receptors that are compatible with a possible hetero-oligomeric nature of these receptors. These changes are similar to changes described in schizophrenic patients and provide further support for the suitability of using HRM as a model for studying this disease and the effects of antipsychotic drugs.
-
Comparative Study
Deciphering the spatio-temporal expression and stress regulation of Fam107B, the paralog of the resilience-promoting protein DRR1 in the mouse brain.
Understanding the molecular mechanisms that promote stress resilience might open up new therapeutic avenues to prevent stress-related disorders. We recently characterized a stress and glucocorticoid-regulated gene, down-regulated in renal cell carcinoma - DRR1 (Fam107A). DRR1 is expressed in the mouse brain; it is up-regulated by stress and glucocorticoids and modulates neuronal actin dynamics. ⋯ In the adult mouse, expression was restricted to neurogenic niches, like the dentate gyrus. In contrast to DRR1, Fam107B mRNA expression failed to be modulated by glucocorticoids and social stress in the adult mouse. In summary, Fam107B and DRR1 show different spatio-temporal expression patterns in the central nervous system, suggesting at least partially different functional roles in the brain, and where the glucocorticoid receptor (GR)-induced regulation appears to be a unique property of DRR1.
-
Ontogenetic life and stress can have different effects on the nerve growth factor (NGF) and its tyrosine kinase receptor A (TrkA) in the structures of the limbic system. This study aimed to explore the influence of two different stressors, acute and chronic exposure to forced swim (FS) stress or high-light open-field (HL-OF) stress, on cells containing NGF and TrkA. Immunofluorescence staining was used to reveal the density of NGF and TrkA immunoreactive (ir) cells in the paraventricular nucleus (PVN) of the hypothalamus or hippocampal subfields CA1, CA3 and dentate gyrus (DG) in adult (postnatal day 90; P90) and aged (P720) rats. ⋯ Despite lack of change in the density of NGF-ir and TrkA-ir cells between P90 and P720 non-stressed rats, a significant age-related decrease in NGF-ir and TrkA-ir cells in the PVN of FS- and HL-OF-stressed rats was noted. However, in the hippocampus, an age-related decrease in NGF-ir or TrkA-ir cells was observed in all rats except acute FS-stressed rats. The changes are possibly associated with involutional aging processes caused by insufficient control of hypothalamic-pituitary-adrenal (HPA) axis functioning in P720 rats and may contribute to disturbances in NGF signaling.
-
The opioid system is involved in infant-mother bonds and adult-adult bonds in many species. We have previously shown that μ opioid receptors (MORs) and κ opioid receptors (KORs) are involved in regulating the adult attachment of the monogamous titi monkey. The present study sought to determine the distribution of MOR and KOR in the titi monkey brain using receptor autoradiography. ⋯ Relative MOR binding in the titi monkey hypothalamus was much greater than that found in rodents. This study was the first to examine MOR and KOR binding in a monogamous primate. The location of these receptors gives insight into where ligands may be acting to regulate social behavior and endocrine function.