Evidence for the presence of serotonergic nerves and receptors in the iris-ciliary body complex of the rabbit.
The rabbit iris-ciliary body contains 78 +/- 6 ng/gm serotonin (5-HT) while the amine content in the aqueous humor is less than 0.01 ng/100 microliter. The low levels of endogenous 5-HT in the iris-ciliary body could not be directly detected by immunocytochemistry. However, pretreatment in vivo and in vitro with L-tryptophan and pargyline resulted in the localization of a sparse population of 5-HT fibers. These fibers could not be studied by exposing the tissue to exogenous 5-HT since the amine was taken up by noradrenergic fibers as well. This was confirmed in studies involving superior cervical ganglionectomy. It is concluded that 5-HT is taken up by both serotonergic and adrenergic fibers of the iris-ciliary body. In the presence of lithium, 5-HT stimulated an increase in the 3H-inositol phosphate accumulation in a dose-dependent manner in tissue where the phosphoinositide pool was labeled with 3H-inositol. A variety of agonists and antagonists were used to show that the 5-HT response is mediated, at least partly, by 5-HT2 receptors. The 5-HT-mediated effect on inositol phosphates is unaffected by superior cervical ganglionectomy. The effect of noradrenaline, which also stimulates inositol phosphate accumulation (but via alpha 1-adrenergic receptors in the iris-ciliary body), was elevated following superior cervical ganglionectomy.
Tobin
A B
AB
Nuffield Laboratory of Ophthalmology, Oxford University, United Kingdom.
Unger
W
W
Osborne
N N
NN
D000818:Animals; D002851:Chromatography, High Pressure Liquid; D002924:Ciliary Body / Q000294:innervation*; D015171:Ganglionectomy; D007150:Immunohistochemistry; D007295:Inositol Phosphates / Q000378:metabolism; D007498:Iris / Q000294:innervation*; D008094:Lithium / Q000494:pharmacology; D009412:Nerve Fibers / Q000187:drug effects / Q000378:metabolism; D010293:Pargyline / Q000494:pharmacology; D011817:Rabbits; D011985:Receptors, Serotonin / Q000032:analysis*; D012701:Serotonin / Q000378:metabolism / Q000502:physiology*; D014364:Tryptophan / Q000494:pharmacology
D007295:Inositol Phosphates; D011985:Receptors, Serotonin; D012701:Serotonin; D014364:Tryptophan; D008094:Lithium; D010293:Pargyline