Effects of bicuculline-induced epileptiform activity on development of receptive field properties in striate cortex and lateral geniculate nucleus of the rabbit.

Studies have shown that normal development of receptive field properties in striate cortex and lateral geniculate nucleus (LGN) of the rabbit is severely altered in the presence of penicillin-induced disruption of cortical neuronal activity. We wished to replicate these studies using a different convulsant drug in order to rule out possible effects due to the penicillin drug itself. Aqueous bicuculline was injected twice daily into a cannula implanted over the monocular region of one striate cortex. Drug administration was initiated on postnatal day 8-9 and was discontinued either on postnatal day 19-24 or on postnatal day 24-30 for studies of the LGN and striate cortex, respectively. Coincidental with the bicuculline injections, control solutions were similarly applied to the monocular region of the contralateral striate cortex. Single-unit recordings made from LGN ipsilateral to bicuculline-treated cortex revealed normal percentages of receptive field types. However, in single-unit recordings made from bicuculline-treated striate cortex, an abnormal percentage distribution of receptive field types was found. In such cortex there was an unusually high proportion of no-response type cells and a substantially reduced proportion of oriented type cells. These developmental abnormalities are virtually the same as those found in the striate cortex of similarly reared animals treated with penicillin. Our present results lend support to our previous conclusion that in the rabbit, disruption of orderly neuronal activity in the geniculostriate system has a detrimental effect on the development of receptive fields in this system.