Electrical Activity in the Spinal Cord of the Chick Embryo, in situ

Abstract

Abstract. Unit electrical activity was recorded from single neurons in the lumbo-sacral spinal cord of 15-, 17-, and l9-day chick embryos, in situ. The dorsal columns showed relatively continuous single-unit activity. Below this lies an area of relative quiet 100-200,t deep. The ventral two thirds of the cord was the most active region, being characterized by polyneuronal bursts and intermittently active single units.The origin of motility of the chick embryo has been the subject of considerable conjecture. Kuo,l Schneirla,2 and others have proposed that behavior of the embryo is caused by stimulation. Hamburger,3 in contrast, has hypothesized that embryonic motility results from endogenous activity within the spinal cord. The available evidence supports the hypothesis of spontaneous (nonreflexogenic) motility. Motility, from its onset at 31/2-4 days up to 7 days of incubation, is nonreflexogenic because no adequate external stimulus is effective in evoking a response.4 The nonreflexogenic nature of motility in embryos older than 7 days has been demonstrated by experiments utilizing spinal embryos which were deafferented by the removal of the dorsal half of the spinal cord at two days. These embryos showed normal patterns of leg motility at least up to 15 to 17 days.5 Although the brain influences normal embryonic behavior,6 and sensory input may influence it, these recent experiments imply that autonomous activity of interneurons or motor neurons in the ventral half of the cord is sufficient to sustain motility up to about 15 to 17 days. On the 17th day, the spontaneous, uncoordinated motility of early stages declines and is superseded by a series of coordinated movements which lead to hatching of the chick on day 21.7 Sensory and brain inputs may be necessary for the execution of these late appearing, well organized movements.8The behavioral experiments discussed provide only indirect evidence concerning the neural substrate of embryonic behavior. The neurophysiological basis of motility can be revealed by direct examination of the activity of the spinal cord of the embryo. Given an adequate description of the patterns and distributions of single-unit activity in the normal embryonic spinal cord, it should be possible through experimental intervention to show the relative contributions to behavior of sensory, brain, and local cord inputs. The purpose of this preliminary paper is to provide the required description of the normal activity of single neurons in 508

Sonic hedgehog signaling is decoded by calcium spike activity in the developing spinal cord

“…This profile appears to be rooted in early development through an orderly addition of neurons to the developing network (47). In chicken embryos, neuronal activity is higher in the ventral two thirds of the spinal cord than in the dorsal region (48). Taken together these studies suggest that the patterning of excitability along the dorsoventral axis of the developing spinal cord is highly conserved and relevant for proper spinal cord development.…”

Artificial CSF Motion Ensures Rhythmic Activity in the Developing CNS Ex Vivo: A Mechanical Source of Rhythmogenesis?

“…To address this question, we focused on two distinct structures of the mouse CNS expressing immature rhythmic activity at different developmental times, namely the embryonic hindbrain-spinal cord and the postnatal cortex. Indeed, immature rhythmic activity in the former structures is largely expressed at embryonic stages (Provine et al, 1970;O'Donovan, 1989;Nishimaru et al, 1996;Hanson and Landmesser, 2003;Yvert et al, 2004;Hunt et al, 2005;Thoby-Brisson et al, 2005;MomoseSato et al, 2007), while cortical networks express major rhythms during the first postnatal week (Yuste et al, 1992;Khazipov et al, 2004;Allène et al, 2008). In both cases, we found that the emergence of activity was strictly dependent upon the movement of artificial CSF (aCSF) around the tissue.…”

An experimental investigation of the possible role of tactile and proprioceptive stimulation in certain aspects of embryonic behavior in the chick

“…Yet, until the sophistication of our current analytical techniques is improved, such questions will remain unanswered for the chick embryo. That such sophistication may not be long in coming is suggested by the recent reports that electrophysiological recordings can now be made from the spinal cord of young chick embryos (Provine, Sharma, Sandel & Hamburger, 1970).…”