Signal clipping by the rod output synapse

The properties of synapses between retinal neurons make an essential contribution to early visual processing. Light produces a graded hyperpolarization in photoreceptors, up to 25 mV in amplitude, and it is conventionally assumed that all of this response range is available for coding visual information. We report here, however, that the rod output synapse rectifies strongly, so that only potential changes within 5 mV of the rod dark potential are transmitted effectively to postsynaptic horizontal cells. This finding is consistent with the voltage-dependence of the calcium current presumed to control neurotransmitter release from rods. It suggests functional roles for the strong electrical coupling of adjacent rods and the weak electrical coupling of adjacent rods and cones. The existence of photoreceptor coupling resolves the apparent paradox that rods have a 25 mV response range, while signals greater than 5 mV in amplitude are clipped during synaptic transmission. We predict that the strengths of rod-rod and rod-cone coupling are quantitatively linked to the relationship between the rod response range and the synapse operating range.     

An electrophoretic study of proteins secreted by the rat submandibular gland in response to autonomic agonists

Summary Proteins secreted by the rat submandibular gland after administration of autonomic agonists have been fractionated by sodium dodecyl sulphate (SDS) — polyacrylamide gel electrophoresis. α-adrenoceptor, β-adrenoceptor and muscarinic agonists were all found to cause the secretion of different protein populations. This work is supported by a grant from the Cystic Fibrosis Research Trust, made to Dr C.J. Jones, whose help and supervision is gratefully acknowledged.     

Reduction of the quantum content of endplate potentials by atropine

Zusammenfassung Postsynaptische Potentiale der Muskelfasern (EPP) des isolierten Rattenzwerchfells wurden intrazellulär abgeleitet. Die statistische Analyse zeigt, dass der Mengenanteil von EPP bei Anwesenheit von Atropin vermindert ist und zwar simultan mit der postsynaptischen Blockade. Die Erholung des presynaptischen Effektes ist viel langsamer als diejenige des postsynaptischen.

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This work was supported by a grant (to J.I.H.) from the US. National Science Foundation. D.F.W. was a postdoctoral fellow of the US Public Health Service.