Catalogo Articoli (Spogli Riviste)

OPAC HELP

Titolo:
FAST AND SLOW PHOTORECEPTORS - A COMPARATIVE-STUDY OF THE FUNCTIONAL DIVERSITY OF CODING AND CONDUCTANCES IN THE DIPTERA
Autore:
LAUGHLIN SB; WECKSTROM M;
Indirizzi:
UNIV CAMBRIDGE,DEPT ZOOL,DOWNING ST CAMBRIDGE CB2 3EJ ENGLAND UNIV OULU,DEPT PHYSIOL SF-90220 OULU 22 FINLAND
Titolo Testata:
Journal of comparative physiology. A, Sensory, neural, and behavioral physiology
fascicolo: 5, volume: 172, anno: 1993,
pagine: 593 - 609
SICI:
0340-7594(1993)172:5<593:FASP-A>2.0.ZU;2-M
Fonte:
ISI
Lingua:
ENG
Soggetto:
POTASSIUM CHANNELS; DROSOPHILA PHOTORECEPTORS; BLOWFLY PHOTORECEPTORS; VENTRAL PHOTORECEPTORS; BIBIONIDAE DIPTERA; SEXUAL DIMORPHISM; VISUAL-SYSTEM; SODIUM-PUMP; LIMULUS; RETINA;
Keywords:
PHOTORECEPTOR; RESPONSE DYNAMICS; VISUAL ECOLOGY; POTASSIUM CHANNELS; DIVERSITY;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Citazioni:
47
Recensione:
Indirizzi per estratti:
Citazione:
S.B. Laughlin e M. Weckstrom, "FAST AND SLOW PHOTORECEPTORS - A COMPARATIVE-STUDY OF THE FUNCTIONAL DIVERSITY OF CODING AND CONDUCTANCES IN THE DIPTERA", Journal of comparative physiology. A, Sensory, neural, and behavioral physiology, 172(5), 1993, pp. 593-609

Abstract

1. From a comparison of the photoresponses and membrane properties ofphotoreceptors from 20 species of Diptera, we conclude that coding inthe time domain is matched to the dictates of visual ecology. This matching involves the dynamics of phototransduction and the use of an appropriate mix of potassium conductances to tune the photoreceptor membrane. 2. Rapidly flying, manoeuvrable diurnal Diptera from several families have fast photoreceptors, with comer frequencies (the frequency at which signal power falls by a half) of between 50 and 107 Hz. The ponderous and predominantly nocturnal tipulids have slow photoreceptorswith fully light adapted corner frequencies of 16 to 19 Hz. 3. Dark adapted fast photoreceptors, have a lower gain (as indicated by lower noise levels), a lower sensitivity, and light adapt more rapidly than dark adapted slow photoreceptors. Fast cells also have much lower inputresistances and shorter time constants. 4. Fast photoreceptors rectify more strongly in the steady state because of a weakly inactivating delayed rectifier potassium conductance with fast and slow components of activation. Slow photoreceptors rectify less strongly in the steady state because their membrane properties are dominated by strongly inactivating outward currents with reversal potentials in the range - 80 to - 90 mV. 5. The differences between potassium conductances match thediffering functional requirements of fast and slow photoreceptors. The non-inactivating delayed rectifier promotes the rapid response of fast cells by reducing the membrane time constant. This is an expensive strategy, involving large conductances and currents. Slowly flying nocturnal insects do not require a high speed of response. The potassium conductances in their slow photoreceptors inactivate to avoid costly and unnecessary ion fluxes. 8. Both the dynamics of the photoresponse and photoreceptor membrane properties exhibit sexual dimorphism. Light adapted photoreceptors in the enlarged male dorsal eye of Bibio markiihave a corner frequency of 42 Hz, compared with 27 Hz for cells in the smaller female eye. This difference in frequency response correlateswith the male's higher spatial acuity and is accompanied by consistent differences in potassium conductance activation rate. We conclude that the divison between fast and slow cells is the product of cellular constraints, metabolic costs and the requirements of coding efficiencyat different light levels and retinal image velocities.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 04/12/20 alle ore 09:52:37