Proximal negative response and retinal sensitivity in the mudpuppy, Necturus maculosus.

Centre and surround influences on the proximal negative response of the pigeon retina

“…First, the negative response transients to a small light spot centred in the neighbourhood of the electrode is comparable to the PNR of the inner plexiform layer as reported in other species (Ogden, 1973;Proenza & Burkhardt, 1973;Burkhardt, 1970) and confirms earlier observations in this laboratory, including a lack of polarity inversion with electrode depth (Holden, 1972). We have not, however, been able to substantiate a polarity inversion accompanying annular stimulation as recently reported in the mudpuppy (Proenza & Burkhardt, 1973) and therefore cannot offer evidence that the generators of the centre-based PNR are tangentially oriented in the retina. Secondly, and in contrast to the mudpuppy findings, the response wate form which we measure to an annulus has a prominent negative component.…”

Interactions of rod and cone signals in the mudpuppy retina.

“…This increased sensitivity was probably produced by cone input coming from the rod-cone and cone bipolars. This notion is substantiated by spectral measurements of the mudpuppy proximal negative response (Proenza & Burkhardt, 1973), an extracellular field potential arising predominantly from amacrine cells (Burkhardt, 1970). The dark-adapted spectral curve of the proximal negative response in the mudpuppy shows predominantly rod sensitivity but, like the amacrine cells, is somewhat more sensitive than the rods to long wave-lengths.…”

Sensitization and centre‐surround antagonism in Necturus retina

“…Most aspects of the preparation and recording have been described in detail elsewhere (Proenza & Burkhardt, 1973). A mudpuppy (Necturus maculous) was decapitated, pithed, and the head hemisected.…”

“…A micropipette of 1-2 /zm tip o.d. was filled with Ringer solution and used to record the proximal negative response by operationally adjusting the electrode depth to obtain a response of maximum amplitude (see Proenza & Burkhardt, 1973). Fine micropipettes filled with 1-5 M-KCl were used for intracellular recording and had DC resistances of 200-400 MC when measured in a saline bath.…”

“…Potentials were monitored on an oscilloscope and fed to an FM converter (0-1000 Hz band width) whose output was recorded on magnetic tape along with stimulus signals. Permanent records were made later by photography or with an x-y plotter (Proenza & Burkhardt, 1973). This report is based on observations drawn from a total of fifty-five preparations.…”