Development of parvalbumin immunoreactivity in the chick Edinger Westphal nucleus

Abstract

To determine when the calcium-binding protein parvalbumin appears during development, neurons in the chick Edinger Westphal nucleus were examined for parvalbumin immunoreactivity at a variety of embryonic stages. Parvalbumin immunoreactivity appeared on embryonic day 14 (E14, Hamburger and Hamilton stage 40) in predominantly lateral Edinger Westphal neurons.Cytochrome oxidase activity within the nucleus was examined throughout development, as an indicator of physiological activity, and expression of cytochrome oxidase was compared with that of parvalbumin. Cytochrome oxidase activity was found to be uniformly high in all parts of the Edinger Westphal nucleus throughout development. Either the Edinger Westphal nucleus in physiologically active quite early in its development or other energy demands mask the correlation of cytochrome oxidase with electrical activity. Cytochrome oxidase was expressed well before parvalbumin immunoreactivity appeared.Voltage-activated calcium currents were characterized in E 12 Edinger Westphal neurons. In both amplitude and composition, E l 2 calcium currents resemble those in E l 6 neurons, excluding the possibility that calcium currents appear de novo during or just prior to the appearance of parvalbumin.Both cytochrome oxidase activity and calcum currents are observed in Edinger Westphal neurons well before the appearance of parvalbumin during development. These findings do not exclude the possibility that physiological activity affects the expression of parvalbumin since other factors such as changing patterns of synaptic activity or the appearance of calcium conducting NMDA receptors have yet to be examined. However, they raise the possibility that additional factors such as an intrinsic developmental program or a change in the neuron's basal intracellular calcium requirements may also be involved.

Immunohistochemical localization of AMPA-type glutamate receptor subunits in the nucleus of the Edinger-Westphal in embryonic chick

“…Developmental studies in embryonic chickens have shown that EW neurons are electrophysiologically active at E12, as revealed by cytochrome oxidase activity, and also at that age develop voltage-activated calcium currents [10]. At E14, an increase in parvalbumin occurs in EW neurons, without any further change in voltage-activated calcium currents [8,9,10].…”

“…At E14, an increase in parvalbumin occurs in EW neurons, without any further change in voltage-activated calcium currents [8,9,10]. These investigators suggested that the expression of parvalbumin at E14 might occur due to, or in association with, the addition of a calcium conducting channel at E14 [10].…”

“…At E14, an increase in parvalbumin occurs in EW neurons, without any further change in voltage-activated calcium currents [8,9,10]. These investigators suggested that the expression of parvalbumin at E14 might occur due to, or in association with, the addition of a calcium conducting channel at E14 [10]. Since the insertion of calcium-permeable AMPA GluR would augment the calcium conductance in developing EW neurons, we sought to characterize the time course of the expression of AMPA-type GluR subunits within EW in chicken embryos from E10-E21, especially those that form calcium permeable channels (lacking GluR2).…”

“…Note that antidromic evoked potentials in response to stimulation of their preganglionic endings in the ciliary ganglion [17], as well as cytochrome oxidase activity [10], can be detected in EW neurons as early as E8, indicating that the EW input to the ciliary ganglion and EW neurons themselves are capable of electrical excitability by E8. Nonetheless, our data indicate that the ability to respond to afferent input via AMPA type glutamate receptors is poorly developed from E8 to E12.…”

“…For all GluR subunits, the percentage of immunoreactive neurons increased markedly at E14. This is noteworthy because at this developmental stage, Fuji and co-workers reported an appearance of parvalbumin immunoreactivity in EW neurons [10], which would potentially buffer the cytosolic calcium increase caused by the calcium permeable channels. After E14, the frequency of GluR1-immunoreactive neurons dramatically declined to about 2%, and that for GluR2/3 declined to a lesser degree.…”