Neuroscience
-
Exercise reduces ischemia and reperfusion (I/R) injury in the rat stroke model. We investigated whether pre-ischemic exercise ameliorates blood-brain barrier (BBB) dysfunction in stroke by reducing matrix metalloproteinase (MMP)-9 expression and strengthening basal lamina. Adult male Sprague-Dawley rats were subjected to a 30 min exercise program on a treadmill 5 days a week for 3 weeks. ⋯ TIMP-1 protein levels were significantly (P<0.01) increased by exercise. Our results indicate that pre-ischemic exercise reduces brain injury by improving BBB function and enhancing basal lamina integrity in stroke. This study suggests that the neuroprotective effect of physical exercise is associated with an imbalance of MMP-9 and TIMP-1 expression.
-
Plethodontid salamanders display intricate courtship behaviors. Proteinaceous courtship pheromones were recently discovered in the submandibular (mental) gland of the male Plethodon shermani, the red-legged salamander. Behavioral studies showed that these male pheromones are delivered by direct contact to the female snout and modulate her receptivity during courtship. ⋯ Unlike other known vertebrate reproductive pheromones, courtship pheromones in P. shermani were effective only at a high concentration. This could result from the particular mode of pheromone transfer in that species, which involves sustained direct contact between male and female. It is concluded that salamander courtship pheromones exert their influence on behavior through the vomeronasal pathway and its direct projections to the preoptic and hypothalamic regions.
-
mu-Opioid agonists frequently activate output neurons in the brain via disinhibition, that is, by inhibiting "secondary cells," which results in disinhibition of "primary cells," considered to be output neurons. Secondary cells are generally presumed to be inhibitory interneurons that serve only to regulate the activity of the output neurons. However, studies of the opioid-sensitive neurons in the rostral ventromedial medulla, a region with a well-documented role in nociceptive modulation, indicate that the opioid-inhibited neurons in this region (termed "on-cells" when recorded in vivo) have a distinct functional role that parallels and opposes the output of the subset of RVM neurons that are activated following opioid administration, the "off-cells." The aim of the present study was to analyze the relative timing of on- and off-cell reflex-related firing in the rostral ventromedial medulla to help determine whether on-cells are likely to function as inhibitory interneurons in this region. ⋯ Contrary to what would be expected if on-cells were inhibitory interneurons, off-cells typically ceased firing before on-cells began reflex-related firing, with a mean 481 (+/-69) ms lag between the final off-cell spike and the first on-cell spike. This suggests that on-cells do not mediate the off-cell pause, and points instead to presynaptic mechanisms in opioid-mediated disinhibition of medullary output neurons. These data also support an independent role for on-cells in pain modulation.
-
Slack (Slo 2.2), a member of the Slo potassium channel family, is activated by both voltage and cytosolic factors, such as Na(+) ([Na(+)](i)) and Cl(-) ([Cl(-)](i)). Since the Slo family is known to play a role in hypoxia, and since hypoxia/ischemia is associated with an increase in H(+) and CO(2) intracellularly, we hypothesized that the Slack channel may be affected by changes in intracellular concentrations of CO(2) and H(+). To examine this, we expressed the Slack channel in Xenopus oocytes and the Slo 2.2 protein was allowed to be inserted into the plasma membrane. ⋯ In the presence of low [Na(+)](i) (5 mM), the Slack channel open probability decreased when exposed to decreased pH or increased CO(2) in a dose-dependent fashion (from 0.28+/-0.03, n=3, at pH 7.3 to 0.006+/-0.005, n=3, P=0.0004, at pH 6.8; and from 0.65+/-0.17, n=3, at 0.038% CO(2) to 0.22+/-0.07, n=3, P=0.04 at 12% CO(2)). In the presence of high [Na(+)](i) (45 mM), Slack open probability increased (from 0.03+/-0.01 at 5 mM [Na(+)](i), n=3, to 0.11+/-0.01, n=3, P=0.01) even in the presence of decreased pH (6.3). Since Slack activity increases significantly when exposed to increased [Na(+)](i), even in presence of increased H(+), we propose that Slack may play an important role in pathological conditions during which there is an increase in the intracellular concentrations of both acid and Na(+), such as in ischemia/hypoxia.
-
In the mammalian spinal cord, the ventrolateral funiculus (VLF) has been identified as critical to postural control and locomotor function, in part due to the reticulospinal pathways it contains. The primary purpose of this descriptive study was to investigate the distribution of neurons in the medulla labeled retrogradely from the VLF and the intermediate gray matter of specific lumbar and cervical spinal cord segments in the adult rat. We made discrete injections of Fluoro-Ruby (FR) into the intermediate gray matter at the cervical (C) 5/6, 7/8 or lumbar (L) 2 segmental levels followed by a single injection of Fluoro-Gold (FG) into the right VLF at T9. ⋯ These results describe a substantial population of ipsilateral and commissural medullary neurons that project to both cervical and thoracolumbar segments. Two different populations of commissural neurons are described, one with axons that cross the midline rostral to T9, and one with axons that cross the midline caudal to T9. These observations provide strong additional evidence for a pattern of reticulo- and vestibulospinal projections that include substantial numbers of commissural neurons and project to multiple cervical and thoracolumbar levels.