Sensitization of the gill withdrawal reflex in Aplysia californica is an elementary form of learning, in part resulting from presynaptic facilitation of the LE mechanoreceptor neurons of the abdominal ganglion. It has previously been established that either application of serotonin or direct stimulation of a group of facilitatory neurons, the L29 cells of the abdominal ganglion, can simulate the effect of physiological stimulation in producing presynaptic facilitation. Because the evidence that serotonin serves as a facilitatory transmitter was indirect, we examined the distribution of serotonin-immunoreactive fibers and cell bodies in the abdominal ganglion in order to answer two questions: (1) do the sensory neurons receive serotonergic innervation and (2) are the L29 cells serotonergic? We observed two distinctive patterns of serotonergic innervation within the ganglion, sparse and dense. The sparse pattern is correlated with a serotonin-stimulated increase in cAMP in identified target cells, while the dense innervation is not. We found a sparse distribution of serotonin-immunoreactive fibers with varicosities close to both cell bodies and processes of identified LE sensory cells. It therefore is likely that the sensory neurons do receive serotonergic innervation. We also mapped the population of serotonergic neuronal cell bodies in the ganglion, and found five clusters of neurons. Cells in one of these clusters, the identified RB neurons, had previously been shown to synthesize serotonin from tryptophan and to contain the neurotransmitter in high concentration. Identified L29 facilitator cells marked by injection with Lucifer Yellow do not contain serotonin immunoreactivity and therefore evidently are not a source of serotonergic input onto sensory cells.

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The uptake and anterograde axonal transport of ' 25 1-wheat germ agglutinin (WGA) has been investigated in the visual system of the chick . In order to obtain a marker with specific and homogeneous binding properties, the iodinated lectin was affinity purified by passage over an Nacetylglucosamine (NAcGlu)-Sepharose column after iodination . 22 h after vitreal injection of the purified ' 25 1-WGA, radioactive label was found accumulated in the retinoreceptive layers of the contralateral optic tectum. Gel electrophoresis of tectal homogenates revealed that > 80% of the retrieved label ran in a band which comigrated with native WGA . In chicks injected with the fraction of the iodinated preparation that failed to bind to the affinity column, there was no evidence of tectal labeling . These findings support the hypothesis that WGA is selectively taken up by chick retinal ganglion cells and transported intact in an anterograde direction to their axon terminals in the contralateral optic tectum. This raises the possibility that constituents of perikaryal membrane, i .e ., lectin receptors, are transported in an anterograde direction by chick retinal ganglion cells .

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A 92-year-old man presented with months of progressive blurry vision, worsening acutely in his right eye. He denied pain, diplopia, or photopsias. His history was significant for multiple myeloma, prostate cancer, and malignant melanoma of his right shoulder treated with local excision. He had local recurrence with hepatic metastasis of the melanoma treated with radiation and chemotherapy. On examination, his visual acuity was counting fingers in the right eye and 20/60 in the left eye. Amsler grid testing demonstrated metamorphopsia in the right eye. Fundus exam of the right and left eyes revealed multiple, elevated, pigmented choroidal lesions, with associated subretinal fluid in the right macula. This appearance is consistent with hematogenous metastasis of cutaneous malignant melanoma to the choroid and associated serous fluid-causing metamorphopsia. The patient was enrolled in a clinical trial combining plasmid IL-12 with pembrolizumab (Keytruda; Merck, Whitehouse Station, NJ). He passed away 2 months after initial presentation to our clinic. [Ophthalmic Surg Lasers Imaging Retina. 2016;47:497.].