The morphology and topographic distribution of substance-P-like immunoreactive amacrine cells in the cat retina.
In cat retinal wholemounts, substance-P-like immunoreactivity (SP-IR) was localized in a distinct population of amacrines whose cell bodies were normally placed in the ganglion cell layer. Although displaced amacrines accounted for 80-95% of the SP-IR amacrines in peripheral retina, this proportion decreased considerably within the area centralis, accounting for 50-80% of the labelled cells at maximum density. The SP-IR cells in both the inner nuclear and ganglion cell layers gave rise to well-defined varicose dendrites of uniform appearance that stratified around 60% depth (S3/S4) of the inner plexiform layer. In addition, sparse fine dendrites in stratum 1 (S1) could sometimes be traced to inner nuclear cells and occasionally to displaced amacrines. The combined SP-IR cell density ranged from less than 50 cells mm-2 in the far periphery to more than 500 cells mm-2 in the area centralis; the maximum density showed little individual variation despite wide differences in the proportion of displaced cells. The 39,000 SP-IR amacrines in a mapped retina had a triangular topographic distribution, with intermediate isodensity lines extending vertically in superior retina and horizontally along both arms of the visual streak. Colocalization experiments established that all SP-IR cells in cat retina showed GABA-like immunoreactivity, and that the SP-IR amacrines were quite distinct from the cholinergic amacrines identified by choline acetyltransferase immunohistochemistry.
Vaney
D I
DI
National Vision Research Institute of Australia, Carlton, Victoria.
Whitington
G E
GE
Young
H M
HM
D000818:Animals; D002415:Cats; D002795:Choline O-Acetyltransferase / Q000276:immunology; D005260:Female; D007106:Immune Sera / Q000276:immunology; D008297:Male; D009474:Neurons / Q000276:immunology*; D012160:Retina / Q000166:cytology*; D013373:Substance P / Q000276:immunology*; D005680:gamma-Aminobutyric Acid / Q000276:immunology
D007106:Immune Sera; D013373:Substance P; D005680:gamma-Aminobutyric Acid; D002795:Choline O-Acetyltransferase