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The serotonergic somatosensory projection to the tectum of normal and eyeless salamanders
Author(s) -
Gruberg Edward R.,
Harris William A.
Publication year - 1981
Publication title -
journal of morphology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.652
H-Index - 74
eISSN - 1097-4687
pISSN - 0362-2525
DOI - 10.1002/jmor.1051700105
Subject(s) - serotonergic , somatosensory system , neuropil , serotonin , biology , tectum , neuroscience , anatomy , superior colliculus , midbrain , central nervous system , genetics , receptor
The spinotectal somatosensory projection was compared in normal, genetically eyeless, and embryonically manipulated salamanders. In normal animals, serotonin fluorescence was restricted to the intermediate tectalneuropil. This same region showed both high levels of serotonin uptake and somatosensory single unit electrical activity. In mutant eyeless salamanders and in normal animals enucleated early in development, serotonin fluorescence, serotonin uptake, and somatosensory activity were present in the superficial tectal neuropil. One‐eyed animals, either genetically normal axolotls with one eye enucleated embryonically or genetically eyeless animals in which a normal eye had been transplanted, showed normal intermediate serotonin fluroescence and somatosensory physiology in the visually innervated half‐tectum. In the visually uninnervated half‐tectum, they showed superficial serotonin fluorescence and somatosensory physiology. In normal animals, 5,7‐dihydroxytryptamine (5,7‐DHT), a specific poison for serotonergic fibers, eliminated physiological responses in the contralateral somatosensory tectal region. The 5,7‐DHT poisoning also abolished U.V.‐induced serotonin fluorescence in the intermediate tectal neuropil. These results are discussed in terms of (1) evidence for serotonin as a central neurotransmitter for somatosensory information in the tectum, (2) the effects of eyelessness on tectal organization, and (3) related results in other animals.