Abstract
Field potentials (FPs) were recorded from the dorsal surface of the toad's ( Bufo marinus) optic tectum (OT) in response to onset (ON) and offset (OFF) of diffuse illumination. FPs showed initial positive deflections P1 ∗ due to presynaptic axonal inputs; subsequent negative N1 and N2 waves and positive P2 and P3 waves reflected summated excitatory and inhibitory postsynaptic processes, respectively, in superficial tectal laminae. The influence of neuropharmaca on the visually evoked FPs was investigated. Acetylcholine led to an initial increase and a subsequent decrease of the N1 and P2 waves, e.g., suggesting a cholinergic retinotectal transmission and a delayed ACh-receptor desensitization. The effects on N1, N2, and P2, P3 waves were differently strong in response to ON- and OFF-stimulation. After administration of alpha-tubocurarine, the N1 and P2 waves were reduced, while in the first OFF response the N2 and P3 waves were remarkably enlarged, particularly the former. GABA led to an unexpected increase of all waves, whereas picrotoxine showed opposite effects, suggesting a special GABAergic excitatory mechanism. Dopamine, L-dopa, or apomorphine did not influence the visually evoked FPs.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callMore From: Comparative Biochemistry and Physiology -- Part A: Physiology
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
