ABSTRACT
Objective Aδ and C fiber nociceptors can be excited when people received contact heat stimulation(CHS) and this excitation may be reflected by functional magnetic resonance imaging(fMRI).The aim of this study was to observe the different fMRI characteristics in CHS with distinct temperatures in healthy people and to explore the pain related functional network.Depending on the fMRI results,we can evaluate the values of CHS-fMRI during the research of brain functional connectivity.Methods Twenty-two healthy volunteers were recruited to this study.During the acquisition of fMRI,the right dorsal forearm received two different CHS in 41 and 51 degree respectively(41 ℃ CHS-fMRI group and 51 ℃ CHS-fMRI group),and two series of fMRI data were obtained for each subject.The brain activation was obtained by using one sample t test for the 41 ℃CHS-fMRI group and 51 ℃CHS-fMRI group separately.The difference between 41 ℃ CHS-fMRI group and 51 ℃ CHS-fMRI group was analyzed by paired-sample t-test.Result These activated brain areas in 41 ℃ CHS-fMRI group included bilateral superior temporal gyrus (STG),contralateral transverse temporal gyrus,contralateral amygdala,bilateral insula,bilateral inferior frontal gyrus (IFG),contralateral hippocampus,bilateral putamen,contralateral supramarginal,ipsilateral postcentral,ipsilateral inferior parietal lobule,ipsilateral middle temporal gyrus (MTG),bilateral cerebelum,bilateral middle cingulate cortex and bilateral posterior cingulate cortex.These activated brain areas in 51 ℃ CHS-fMRI group included bilateral STG,bilateral amygdala,contralateral hippocampus,bilateral thalamus,contralateral putamen,bilateral insula,bilateral IFG,bilateral cerebellum,contralateral postcentral,contralateral superior parietal lobule,bilateral MTG,bilateral precuneus,and contralateral cuneus.Compared with 41 ℃ CHS-fMRI group,the 51 ℃ CHS-fMRI group showed higher brain activation in bilateral cerebellum (right:4.455,left:3.891),ipsilateral precuneus (4.150),contralateral insula (3.530),contralateral IFG (3.530),and contralateral postcentral (3.530; t =2.83,P ＜ 0.01).Conclusions There are common brain activated areas and specific areas for each group,which suggested that existence of two central pathways activated by Aδ and C fiber which have different effects in perception of pain and have their brain network responsively.It may become one of the ideal pain stimulation methods with CHS-fMRI,which warrant worth further research.
ABSTRACT
PURPOSE: Pelvic organ neural cross-talk is mediated by central and peripheral pathways. We investigated the effects of colorectal distention at the peripheral level on mechanosensitive bladder single unit afferent activity. MATERIALS AND METHODS: We used 16 female Sprague-Dawley® rats in this study. The single unit afferent activity of nerves originating from the bladder were identified by electrical stimulation of the pelvic nerve and by bladder distention. They were classified by conduction velocity as C or Aδ fibers. After measuring single unit afferent activity during constant bladder filling without colorectal distention, measurements during bladder filling were repeated with colorectal distention at 20, 40 and 60 mm Hg. To evaluate the convergence of bladder and colorectal afferent fibers, rapid colorectal distention was performed with an empty bladder. Bladder afferent fibers with an increased response to rapid colorectal distention were defined as convergent fibers and the others were defined as nonconvergent fibers. RESULTS: A total of 30 single units (19 C and 11 Aδ fibers) were isolated. Continuous colorectal distention increased the bladder single unit afferent activity of C and Aδ fibers in a pressure dependent manner. C fibers could be divided into convergent (12) and nonconvergent (7) fibers but all Aδ fibers were nonconvergent. The facilitatory effect of continuous colorectal distention on bladder single unit afferent activity was absent in nonconvergent C fibers. CONCLUSIONS: In rats the convergence of bladder and colorectal peripheral nerves was electrophysiologically identified only in mechanosensitive C fibers and not in Aδ fibers. Continuous colorectal distention probably increased the bladder single unit afferent activity of C fibers through direct convergence at the peripheral level between the bladder and sensory ganglia. It probably increased the bladder single unit afferent activity of Aδ fibers through an alternative pathway.
