ISSN:
1432-1351
Keywords:
Key words Lamina
;
Neuronal plasticity
;
5-HT receptors
;
Photoreceptor
;
Electroretinogram
;
AbbreviationsERG electroretinogram
;
PDH pigment-dispersing hormone
;
PDF pigment-dispersing factor
;
5-HT 5-hydroxytryptamine
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Medicine
Notes:
Abstract Two sets of wide-field neurons extend neurites into the fly's optic lamina, where monopolar cells receive photoreceptor input. They exhibit immunoreactivity to antibodies raised against either 5-hydroxytryptamine or the crustacean peptide PDH, respectively. Both are proposed whole-field neuromodulators of vision, apparently regulating a circadian rhythm of monopolar cell size. Seeking functional correlates, we have re-examined the electroretinogram for circadian rhythmicity, and for responses to locally injected 5-hydroxytryptamine and peptide. Long-term electroretinogram recordings from Calliphora entrained to a light/dark cycle and then transferred to constant darkness, uncovered a gradual, modest increase during the subjective night in the electroretinogram's ON- and OFF-transients, from the lamina's monopolar cells. Five to twenty nl of 5-hydroxytryptamine (10−3 mol · 1−1) injected into the head haemolymph strongly enhanced the electroretinogram transients, an action reversed by 5-hydroxytryptamine antagonists. Injected into the eye, 5-hydroxytryptamine (10−4 mol · 1−1) had the opposite effect; the rapid onset there suggests direct action, whilst the opposing effect from haemolymph injection suggests a different receptor site. Pigment-dispersing hormone (2.2 × 10−5 mol · 1−1) injected into the haemolymph increased the electroretinogram transients along a biphasic course, with a slow partial recovery; injected into the eye, it lacked effect.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/s003590050400
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