The emergence of inhibition in the chick embryo spinal cord

A Neurophysiological Analysis of the Effects of Hypercapnia on the Embryonic Spinal Cord

“…This final frequency is also the same at all ages examined. As discussed below, stable frequencies of burst activity have been fre quently recorded for up to 5 h under normal conditions in this preparation [26]. …”

“…to prevent movement. This dose was previously shown not to affect the fre quency of polyneuronal activity in the spinal cord [26].…”

“…1,2). Recent independ ent evidence from this laboratory has con firmed that blood gases do recover over such short times, but significant alterations have been seen during the final recording segments [27], Studies in normal embryos [26] have also shown that the frequency of burst activity is a good indicator of embryonic age and changes little over relatively long time periods (3-5 h). In addition, since only those embryos that continuously maintained vigorous heart rates were used in this study, a decline in physio logical status could not account for the main tained inhibition.…”

“…12-65), while simultaneous data analysis yielded burst frequency and burst content on teletype printouts [see ref. 26 for a detailed expla nation of computer burst analysis).…”

“…Among these, descending neural systems have been shown to influence the neurally induced motility of chick embryos after 15 days of development [18,24,31]. The functional maturation of inhibitory circuitry also corresponds to the decline in burst fre quency seen after day 13 [19,26], thus provid ing another mechanism for polyneuronal dis charge modification.…”