The cellular strategy leading to formation of neuronal circuits in the rodent barrel cortex is still a matter of controversy. Both selective and constructive mechanisms have been proposed. The selective mechanism invo...The cellular strategy leading to formation of neuronal circuits in the rodent barrel cortex is still a matter of controversy. Both selective and constructive mechanisms have been proposed. The selective mechanism involves an overproduction of neuronal processes and synapses followed by activity dependent pruning. Conversely, a constructive mechanism would increase the number of axons, dendrites, and synapses during development to match functionality. In order to discern the contributions of these two mechanisms in establishing a neuronal circuit in the somatosensory cortex, morphometric analysis of dendritic and axonal arbor growth was performed. Also, the number of synapses was followed by electron microscopy during the first month of life. We observed that axonal and dendritic arbors retracted distal branches, and elongated proximal branches, resulting in increased arbor complexity. This neuronal remodeling was accompanied by the steady increase in the number of synapses within barrel hollows. Similarly, the content of molecular markers for dendrites, axons and synapses also increased during this period. Finally, cytochrome oxidase activity rose with age in barrels indicating that the arbors became more complex while synapse density and metabolic demands increased. Our results support the simultaneous use of both selective and constructive mechanisms in establishing the barrel cortex circuitry.展开更多
Objective To evaluate the effect of electrical stimulation of dorsal raphe nucleus（DRN）on response properties of layer IV barrel cortex neurons following long-term sensory deprivation.Methods Male Wistar rats were d...Objective To evaluate the effect of electrical stimulation of dorsal raphe nucleus（DRN）on response properties of layer IV barrel cortex neurons following long-term sensory deprivation.Methods Male Wistar rats were divided into sensory-deprived（SD）and control（unplucked）groups.In SD group,all vibrissae except the D2 vibrissa were plucked on postnatal day one,and kept plucked for a period of 60 d.After that,whisker regrowth was allowed for 8-10 d.The D2 principal whisker（PW） and the D1 adjacent whisker（AW）were either deflected singly or both deflected in a serial order that the AW was deflected 20 ms before PW deflection for assessing lateral inhibition,and neuronal responses were recorded from layer IV of the D2 barrel cortex.DRN was electrically stimulated at inter-stimulus intervals（ISIs）ranging from 0 to 800 ms before whisker deflection.Results PW-evoked responses increased in the SD group with DRN electrical stimulation at ISIs of 50 ms and 100 ms,whereas AW-evoked responses increased at ISI of 800 ms in both groups.Whisker plucking before DRN stimulation could enhance the responsiveness of barrel cortex neurons to PW deflection and decrease the responsiveness to AW deflection. DRN electrical stimulation significantly reduced this difference only in PW-evoked responses between groups.Besides,no DRN stimulation-related changes in response latency were observed following PW or AW deflection in either group.Moreover, condition test（CT）ratio increased in SD rats,while DRN stimulation did not affect the CT ratio in either group.There was no obvious change in 5-HT2A receptor protein density in barrel cortex between SD and control groups.Conclusion These results suggest that DRN electrical stimulation can modulate information processing in the SD barrel cortex.展开更多
Circuits in barrels of the rodent brain’s primary somatosensory (S1) cortex build up following constructivist rules. Previous evidence in mice supports that the precise addition of barrel neuropil is promoted by insu...Circuits in barrels of the rodent brain’s primary somatosensory (S1) cortex build up following constructivist rules. Previous evidence in mice supports that the precise addition of barrel neuropil is promoted by insulin-like growth factor-1 (IGF-1). The signaling cascades mediating this response remain undetermined. To address whether the effects of IGF-1 upon the growth of S1 circuits are mediated by insulin receptor substrate-1 (IRS-1), we studied barrel size in adult mice having the IRS-1 gene knocked out (IRS-1 ko). Our results reveal that barrel size is similar between wild type and IRS-1 ko mice suggesting that IRS-1 is not essential for barrel circuitry growth. Hence, investigations aimed at exploring other substrates activated by IGF-1, namely IRS-2 and IRS-4, are needed to reveal signaling pathways that mediate the precise addition of S1 neuronal circuitry.展开更多
文摘The cellular strategy leading to formation of neuronal circuits in the rodent barrel cortex is still a matter of controversy. Both selective and constructive mechanisms have been proposed. The selective mechanism involves an overproduction of neuronal processes and synapses followed by activity dependent pruning. Conversely, a constructive mechanism would increase the number of axons, dendrites, and synapses during development to match functionality. In order to discern the contributions of these two mechanisms in establishing a neuronal circuit in the somatosensory cortex, morphometric analysis of dendritic and axonal arbor growth was performed. Also, the number of synapses was followed by electron microscopy during the first month of life. We observed that axonal and dendritic arbors retracted distal branches, and elongated proximal branches, resulting in increased arbor complexity. This neuronal remodeling was accompanied by the steady increase in the number of synapses within barrel hollows. Similarly, the content of molecular markers for dendrites, axons and synapses also increased during this period. Finally, cytochrome oxidase activity rose with age in barrels indicating that the arbors became more complex while synapse density and metabolic demands increased. Our results support the simultaneous use of both selective and constructive mechanisms in establishing the barrel cortex circuitry.
基金supported by the grant from Kerman Neuroscience Research Centre of KermanUniversity of Medical Sciences(86-44/4/k)
文摘Objective To evaluate the effect of electrical stimulation of dorsal raphe nucleus（DRN）on response properties of layer IV barrel cortex neurons following long-term sensory deprivation.Methods Male Wistar rats were divided into sensory-deprived（SD）and control（unplucked）groups.In SD group,all vibrissae except the D2 vibrissa were plucked on postnatal day one,and kept plucked for a period of 60 d.After that,whisker regrowth was allowed for 8-10 d.The D2 principal whisker（PW） and the D1 adjacent whisker（AW）were either deflected singly or both deflected in a serial order that the AW was deflected 20 ms before PW deflection for assessing lateral inhibition,and neuronal responses were recorded from layer IV of the D2 barrel cortex.DRN was electrically stimulated at inter-stimulus intervals（ISIs）ranging from 0 to 800 ms before whisker deflection.Results PW-evoked responses increased in the SD group with DRN electrical stimulation at ISIs of 50 ms and 100 ms,whereas AW-evoked responses increased at ISI of 800 ms in both groups.Whisker plucking before DRN stimulation could enhance the responsiveness of barrel cortex neurons to PW deflection and decrease the responsiveness to AW deflection. DRN electrical stimulation significantly reduced this difference only in PW-evoked responses between groups.Besides,no DRN stimulation-related changes in response latency were observed following PW or AW deflection in either group.Moreover, condition test（CT）ratio increased in SD rats,while DRN stimulation did not affect the CT ratio in either group.There was no obvious change in 5-HT2A receptor protein density in barrel cortex between SD and control groups.Conclusion These results suggest that DRN electrical stimulation can modulate information processing in the SD barrel cortex.
基金supported in part by CONACyT(Grant No.82879 to G.G.O.)PAPIIT-UNAM(Grants Nos.IN203912-3 to G.G.O.and IA202013-2 to E.U.Q.)CIC-UMSNH(Grant No.8.37 to A.L.F.F.).
文摘Circuits in barrels of the rodent brain’s primary somatosensory (S1) cortex build up following constructivist rules. Previous evidence in mice supports that the precise addition of barrel neuropil is promoted by insulin-like growth factor-1 (IGF-1). The signaling cascades mediating this response remain undetermined. To address whether the effects of IGF-1 upon the growth of S1 circuits are mediated by insulin receptor substrate-1 (IRS-1), we studied barrel size in adult mice having the IRS-1 gene knocked out (IRS-1 ko). Our results reveal that barrel size is similar between wild type and IRS-1 ko mice suggesting that IRS-1 is not essential for barrel circuitry growth. Hence, investigations aimed at exploring other substrates activated by IGF-1, namely IRS-2 and IRS-4, are needed to reveal signaling pathways that mediate the precise addition of S1 neuronal circuitry.
