Journal of Neuroscience, Vol 5, 2719-2725, Copyright © 1985 by Society for Neuroscience
Parasympathetic, sympathetic, and sensory interactions in the iris: nerve growth factor regulates cholinergic ciliary ganglion innervation in vivo
JA Kessler
Interactions between peptidergic sensory nerves, noradrenergic sympathetic
nerves, and cholinergic parasympathetic fibers were examined in the rat
iris. The putative peptide neurotransmitter, substance P (SP), was used as
an index of the trigeminal sensory innervation, tyrosine hydroxylase (TH)
activity served to monitor the sympathetic fibers, and choline
acetyltransferase (CAT) activity was used as an index of the
parasympathetic innervation. Destruction of the sympathetic innervation by
neonatal administration of 6-hydroxydopamine resulted in increased SP
development and a smaller increase in CAT activity in the iris. Moreover,
trigeminal ablation resulted in an increase in both TH and CAT activities.
Finally, ciliary ganglionectomy resulted in increased SP and a smaller
increase in TH activity in the iris. Administration of nerve growth factor
(NGF) into the anterior chamber substantially increased both SP and TH
activity in the iris and also increased CAT activity to a lesser extent.
Moreover, administration of anti-NGF into the anterior chamber prevented
both the sympathectomy-induced increases in SP and CAT, and the increases
in TH and CAT activities after trigeminal ablation, suggesting that NGF
mediated these increases. These observations suggest that the sympathetic,
sensory, and parasympathetic innervations of the iris interact by altering
availability of NGF elaborated by the iris. Regulation of iris CAT activity
was examined in greater detail. Injection of the cholinergic toxin, AF64A,
into the anterior chamber concurrently with ablation of the sympathetic and
sensory innervations paradoxically increased CAT activity, whereas AF64A
alone decreased CAT activity.(ABSTRACT TRUNCATED AT 250 WORDS)