Authors: Antonia MarinBurgin F James Eisenhart William B Kristan Kathleen A French
Publish Date: 2005/10/05
Volume: 192, Issue: 2, Pages: 123-133
Abstract
During development many embryos show electrical coupling among neurons that is spatially and temporally regulated For example in vertebrate embryos extensive dye coupling is seen during the period of circuit formation suggesting that electrical connections could prefigure circuits but it has been difficult to identify which neuronal types are coupled We have used the leech Hirudo medicinalis to follow the development of electrical connections within the circuit that produces local bending This circuit consists of three layers of neurons four mechanosensory neurons P cells 17 identified interneurons and approximately 24 excitatory and inhibitory motor neurons These neurons can be identified in embryos and we followed the spatial and temporal dynamics as specific connections developed Injecting Neurobiotin into identified cells of the circuit revealed that electrical connections were established within this circuit in a precise manner from the beginning Connections first appeared between motor neurons mechanosensory neurons and interneurons started to connect at least a day later This timing correlates with the development of behaviors so the pattern of emerging connectivity could explain the appearance first of spontaneous behaviors driven by a electrically coupled motor network and then of evoked behaviors when sensory neurons and interneurons are added to the circuitThis work was supported by NIH research grant NS35336 to WBK a Fundacion Antorchas grant to AMB and an NIH training grant T32AG00216 to FJE We thank Pablo E Schilman for assistance with statistical analyses and comments on the manuscript The experiments comply with the “Principles of animal care” publication No 86–23 revised 1985 of the National Institute of Health
Keywords: