Brain research
-
Comparative Study
Psychophysical 'perceptual maps' of heat and pain sensations by direct localization of CO2 laser stimuli on the skin.
Brain activation patterns derived from neurofunctional methods are often implicitly regarded as being directly related to subjective perceptual experience in an iso- or at least homomorph manner, neglecting the operational differences between these two dimensions. This paper (a) introduces a method for assessing 'perceptual maps' of stimulation patterns presented to the body surface, providing a means to parametrically relate neural representation and subjective percept, and (b) applies this method to demonstrate the existence of 'somatotopic maps' of hot and painful stimulus patterns independent from mechanoceptive co-activation. Brief (90 ms) CO2 laser pulses were presented in an array of multiple stimulation sites on the dorsal forearms (N. radialis area, C7 dermatome) of healthy subjects. ⋯ R2>0.80 in 10 out of 12 subjects). Nonlinear models were advantageous in some subjects only. Our method can be useful in assessing inter-individual differences or experimentally induced shifts in somatotopic processing.
-
Comparative Study
Biphasic cytoarchitecture and functional changes in the BBB induced by chronic inflammatory pain.
The blood-brain barrier (BBB) is a dynamic system which maintains brain homeostasis and limits CNS penetration via interactions of transmembrane and intracellular proteins. Inflammatory pain (IP) is a condition underlying several diseases with known BBB perturbations, including stroke, Parkinson's, multiple sclerosis and Alzheimer's. Exploring the underlying pathology of chronic IP, we demonstrated alterations in BBB paracellular permeability with correlating changes in tight junction (TJ) proteins: occludin and claudin-5. ⋯ Confocal microscopy demonstrated continuous expression of both occludin and JAM-1, each co-localizing with ZO-1. The increased claudin-5 expression was not limited to the junction. These results provide evidence that chronic IP causes dramatic alterations in specific cytoarchitectural proteins and demonstrate alterations in molecular properties during CFA, resulting in significant changes in BBB paracellular permeability.
-
Afferent pathways innervating the urinary bladder consist of myelinated Adelta- and unmyelinated C-fibers, the neuronal cell bodies of which correspond to medium and small-sized cell populations of dorsal root ganglion (DRG) neurons, respectively. Since hyperpolarization-activated cyclic nucleotide-gated cation (HCN) channel currents have been identified in various peripheral sensory neurons, we examined the expression of isoforms of HCN channels in the L6-S1 spinal cord and bladder afferent neurons from L6-S1 DRG in rats. ⋯ In dye-labeled bladder afferent neurons, HCN-2-positive cells were found in approximately 60% of neurons, and HCN-2 was expressed in both small- and medium-sized neurons with a higher ratio (expression ratio: 61% and 50% of neurons, respectively) compared with unidentified DRG neurons, in which the HCN expression ratio was 47% and 21% of small- and medium-sized cells, respectively. These results suggest that HCN-2 is the predominant subtype of HCN channels, which can control neuronal excitability, in small-sized C-fiber and medium-sized Adelta fiber DRG neurons including bladder afferent neurons, and might modulate activity of bladder afferent pathways controlling the micturition reflex.
-
Previous studies have demonstrated that either transplantation of bone marrow stromal cells (MSC) or physical exercise regimens can elicit limited functional recovery following spinal cord injury, presumably through different mechanisms. The present study examined whether transplantation of MSC derived from transgenic Fischer alkaline phosphatase (AP) rats, in combination with exercise, would have synergistic effects leading to recovery of function that is greater than either alone. Adult female Sprague-Dawley rats received a moderate thoracic contusion injury and were divided into three groups: operated controls (Op-Control), MSC transplant recipients (MSC), and MSC transplant recipients plus exercise (MSC+Ex). ⋯ Immunocytochemical analysis provided no evidence that MSC differentiated into neurons, astrocytes or oligodendrocytes. Muscle mass of the medial gastrocnemius was diminished in the Op-Control group indicating significant atrophy, but was partially preserved in both the MSC and MSC+Ex groups. Our results indicate that combining the beneficial effects of rat MSC and this exercise protocol was not sufficient to enhance behavioral recovery.
-
The retrograde tracer cholera toxin beta-subunit (CTB) was used to trace long ascending propriospinal projections from neurons in the lumbosacral spinal cord to the upper cervical (C3) gray matter in adult male Sprague-Dawley rats. Following large 0.5 microl CTB injections restricted mainly to the upper cervical ventral horn (n=5), there were many lumbosacral CTB-positive neurons (14-17/section) in the intermediate gray and ventral horn (dorsal lamina VIII, medial VII extending into X) contralaterally, with fewer at corresponding ipsilateral locations. Labeled cells (4-8/section) were also observed in contralateral laminae IV-VI and the lateral spinal nucleus, with fewer ipsilaterally. ⋯ These results suggest direct projections from ventromedially located neurons of lumbar and sacral segments to the contralateral ventral gray matter of upper cervical segments, as well as from neurons in the intermediate but not superficial dorsal horn. They further suggest that some lumbosacral superficial dorsal horn neurons project to the upper cervical dorsal horn. These propriospinal projections may be involved in coordinating head and neck movements during locomotion or stimulus-evoked motor responses.