Correlation of the electrical and intrinsic optical signals in the chicken spreading depression phenomenon.

This paper presents some results on the correlation between the electrophysiological and intrinsic optical signals (IOS) of spreading depression waves in chicken retinae. We first show that the peak of the time derivative of the electrophysiological wave occurs precisely when the optical signal reaches the electrode tip. Second, by comparing bath applications of propranolol and glycerol it can be shown that the slow potential shift is not directly correlated to the intrinsic optical signal. Propranolol depresses the amplitude of the electrical wave, although the intrinsic optical signal continues being visible. On the other hand, we observe total absence of the IOS under glycerol, while the electrical wave is always present. Correlations of this kind are relevant for a deeper understanding of the underlying mechanisms of the spreading depression phenomenon.

A depressäo alastrante sob o efeito de bário / Spreading depression under the effect of barium

Apresentamos aqui os resultados de medidas ópticas e eletro-fisiológicas obtidas durante a ocorrência de ondas de depressão alastrante (DA) na retina de galinha in vitro. Adquirindo simultaneamente os sinais supracitados foi possível analisar a sua relaçäo temporal e espacial durante a DA. As ondas foram elicitadas sob condiçöes de controle e com a aplicaçäo de cloreto de bário à soluçäao de perfusäo. Algumas das características mais afetadas foram a variaçäo lenta do potencial extra-celular, a velocidade e o valor absoluto do pico da derivada do sinal de tensäo. A onda óptica intrínseca (IOS) também foi afetada. Apesar disso, o pico da derivada (do potencial) ocorreu senpre no momento da chegada da onda óptica à ponta da micropipeta. Como o bário é um bloqueador de células gliais, os resultados dos experimentos evidenciam a relaçäo entre a despolarizaçäo glial e outros fenômenos comcomitantes tais como a onda de tensäo e o IOS, o que deverá ser objeto de investigaçöes futuras

Abstract - ln this paper we present the results of optical and electro-physiological measurements carried out during the occurrence of spreading depression waves in the in vitro chicken retina. Simultaneously acquiring the optical and electrical signals, we could verify the temporal and spatial relationship between them. The waves have been elicited under control conditions and with the application of barium chloride to the perfusing solution. Some of the most affected features of the waves were the negative slow potential shift, the velocity and the peak absolute value of the derivative of the potential wave. The intrinsic optical signal (IOS) was also affected. Nevertheless, the peak value ofthe derivative occurred always when the !OS was exactly on the tip ofthe micropipette. As longas bariurn is a K-channel blocker specific for glial cells, the results of these experiments pennit to conclude that the relationship between the glial depolarization and the concornitant phenomena such as the potential wave and the !OS exists and should be the subject offurther investigation