Intraocular fibre growth of grafted locus coeruleus neurons: sensory denervation counteracts alterations induced by thyroid hormone deficiency.

Immature central noradrenaline neurons from the nucleus locus coeruleus were grafted to surgically thyroidectomized adult rats. As previously reported, fibre production from locus coeruleus in the host iris is hampered by thyroid hormone deficiency. We wanted to investigate if sensory denervation of the target iris tissue, a procedure known to enhance fibre production from locus coeruleus neurons, would interact with and possibly reverse the morphological signs of thyroid hormone deficiency.

Prenatal ontogeny of neurons with enkephalin-like immunoreactivity in the rat central nervous system: an immunohistochemical mapping investigation.

Immunohistochemical techniques were used to describe the presence of endogenous levels of enkephalin-like immunoreactivity (ELI) in the developing central nervous system of the rat up until birth. The appearance and prenatal ontogeny of nerve cell bodies, nerve fiber pathways and varicose terminal plexuses expressing ELI were thus mapped using the indirect fluorescence immunohistochemical technique and fluorescein- and rhodamine-conjugated second antisera. ELI was first observed in beaded fibers along the midline from ventral pons to cervical spinal cord by prenatal day 15.

Intraocular development and adrenergic innervation of cortical and subcortical brain areas: influence of thyroid hormone deficiency.

Various immature brain regions have been isolated by grafting to the anterior chamber of the eye of adult recipients. The role of thyroid hormones for the growth of these isolated brain areas as well as their morphological maturation and adrenergic innervation in the eye have been investigated by surgical thyroidectomy of adult recipients prior to the intraocular brain grafting. Cortex cerebri showed a donor stage correlated thyroid hormone dependency so that 18-day donor fetuses gave rise to larger cortex grafts, whereas full-term donor fetuses resulted in smaller cortex grafts in thyroidectomized hosts.

Thyroid hormone dependency in immature but not mature grafted locus coeruleus neurons. Evidence from intraocular innervation of iris transplants.

Fetal brain tissue pieces containing locus coeruleus noradrenaline neurons were combined with sequentially or simultaneously grafted irides in the anterior eye chamber of thyroidectomized or normal host rats. The aim was to reveal possible morphological alterations in the adrenergic fibres innervating the iris grafts, induced by thyroid hormone deficiency, and to compare that possible hormone dependency with what has been found before in host irides innervated by locus coeruleus neurons. Nerve fibre outgrowth was evaluated in iris whole mounts, using Falck Hillarp fluorescence histochemistry.

Thyroxin dependency of the developing locus coeruleus. Evidence from intraocular grafting experiments.

Surgical thyroidectomies were used as means of altering the thyroid state of adult recipients to study the possible influence of thyroid hormones on fibre formation in irides by immature noradrenaline neurons of the locus coeruleus grafted to the eye. Whole-mount preparations of irides were analysed using fluorescence histochemistry according to Falck-Hillarp, subjectively estimating on a 'blind' basis the number of fibres, their pattern of distribution and individual morphology in the iris dilator plate. Neurones of the locus coeruleus formed nerve fibres in irides of thyroidectomized recipients to the same extent as in controls.

Restoration of dopaminergic function by grafting of fetal rat substantia nigra to the caudate nucleus: long-term behavioral, biochemical, and histochemical studies.

Motor deficits produced in rats by unilateral substantia nigra lesions have been found to be reduced by grafts of fetal rat substantia nigra to the dopamine denervated caudate nucleus. In the present study these grafts were examined behaviorally, histochemically, and biochemically over six to 10-month periods. The grafts were found to survive in a healthy condition and contain catecholaminergic cells and fibers after eight to ten months.

Nerve growth factors in the rat iris.

Nerve growth factor (NGF) activity was not detected by bioassay in irides killed immediately after excision but NGF appeared within 24 h in living irides placed in culture or grafted to a host eye. Furthermore, sensory and, although less effective, sympathetic denervation of irides in situ led within 10 days to the appearance of NGF activity. In addition, freezing and thawing released a parasympathetic neuronotrophic factor activity from irides.

Growth interaction between locus coeruleus and trigeminal ganglion after intraocular double grafting.

Fetal trigeminal ganglia were combined in the anterior chamber of eyes of rat recipients with sequentially grafted fetal locus coeruleus transplants. After maturation of both grafts in oculo the growth pattern of locus coeruleus derived noradrenaline fibres in the iris was examined with Falck-Hillarp fluorescence histochemistry. Contrary to what was expected from earlier studies, which revealed a radiating halo of fibres around the CNS tissue on the iris, the locus coeruleus-derived fibres radiated to a large extent from the adjacent trigeminal ganglion attachment.

A system of atypical catecholamine-containing nerve fibres in the rat iris present after total superior cervical ganglionectomy.

A system of hitherto unknown weakly fluorescent fibres was detected in the rat iris by Falck-Hillarp fluorescence histochemistry after superior cervical ganglionectomy. These long smooth winding (SW)-fibres had a scarce and unusual distribution, forming loops and meandering for long distances with limited branching. Pharmacological tests suggest that they store a catecholamine but differ from adrenergic nerves in lacking an efficient uptake mechanism for amines.

Conditions for adrenergic hyperinnervation in hippocampus: II. Electrophysiological evidence from intraocular double grafts.

Following sequential intraocular transplantations of areas containing NE cell bodies (locus coeruleus or superior cervical ganglion) and of NE fiber target areas (hippocampus), both pieces mature in a manner analogous to that observed for individual transplants. NE-containing nerve fibers, derived from either LC or SCG transplants, can be seen to invade the hippocampal formation. When LC is used, the invading fibers markedly hyperinnervate the hippocampus while SCG-derived fiber densities approximate those seen with innervation from the adrenergic ground plexus of the iris.

Conditions for adrenergic hyperinnervation in hippocampus: I. Histochemical evidence from intraocular double grafts.

The developing hippocampal anlage of rats was homologously grafted to the anterior chamber of the eye of adult recipients. After intraocular maturation of the hippocampal graft and removal of the sympathetic innervation of the eye by ipsilateral superior cervical ganglionectomy, four types of monoamine neurons were transplanted to the eye chamber: Peripheral sympathetic neurons, central adrenergic neurons of locus coeruleus, central dopaminergic neurons of substantia nigra, and central 5-hydroxytryptamine neurons of the lower raphe nuclei. All four classes of monoamine neurons were able to reinnervate the hippocampal graft, but the fiber ingrowth differed markedly.

Opioid peptides excite pyramidal neurons and evoke epileptiform activity in hippocampal transplants in oculo.

The effect of opiate peptide administration on the electrical activity of intraocular hippocampal transplants was studied. Similar to observations in situ, the administration of beta-endorphin or methionine enkephalin produces a concentration-dependent increase in the firing rate of identified pyramidal neurons within hippocampal formation transplants. In addition, these peptides elicit a profound increase in 'EEG' amplitude, which ultimately develops into epileptiform activity.

Seizures and related epileptiform activity in hippocampus transplanted to the anterior chamber of the eye: modulation by cholinergic and adrenergic input.

Transplants of rat hippocampus into the anterior chamber of the eye of a host animal were used to assess the effects of cholinergic and adrenergic neuronal inputs on the generation and duration of seizure activity. Cholinomimetics initiated both seizures and hypersynchronous neuronal activity in the transplants. Cyclic guanosine monophosphate (GMP) derivatives and isobutyl methylxanthine elicited similar changes.

Brain grafts reduce motor abnormalities produced by destruction of nigrostriatal dopamine system.

In order to determine if brain tissue grafts can provide functional input to recipient central nervous system tissue, fetal rat dopamine-containg neurons were implanted adjacent to the caudate nucleus of adult recipients whose endogenous dopaminergic input had been destroyed. The grafts showed good survival and axonal outgrowth. Motor abnormalities, which had been induced by the destruction of the endogenous dopaminergic input to the caudate, were significantly reduced after grafting of the fetal brain tissue.

Isolated catecholaminergic projections from substantia nigra and locus coeruleus to caudate, hippocampus and cerebral cortex formed by intraocular sequential double brain grafts.

Sequential intraocular grafting of defined areas from fetal rat brain to adult host rats was used to explore the possibility that such double grafts would become interconnected. Norepinephrine- containing neurons of the locus coeruleus were grafted together with either parietal cerebral cortex, hippocampus, or the caudate nucleus. Dopamine-containing neurons of the substantia nigra were transplanted together with either parietal cerebral cortex or the caudate nucleus.

NGF and anti-NGF: evidence against effects on fiber growth in locus coeruleus from cultures of perinatal CNS tissues.

The present study examines whether the developing noradrenergic neurons of locus coeruleus depend on endogenous nerve growth factor (NGF) for nerve fiber production and if exogenous NGF stimulates fiber growth in this nucleus, using a collagen gel tissue culture technique. Lucus coeruleus from perinatal rat brain was used in three culture experiments: (1) lucus coeruleus, parietal cerebral cortex, and the superior cervical ganglion, prepared from newborn rats and cultured in different sectors of the same dishes; (2) locus coeruleus and parietal cerebral cortex from 17-day-old rat fetuses cultured in the same manner, and (3) locus coeruleus from 17-day-old rat fetuses co-cultured with spinal, sympathetic and ciliary ganglia from 8-day chick embryos. Experiments 1 and 2 were run with and without addition of NGF and anti-NGF, experiment 3 with and without anti-NGF.

Lead blockade of norepinephrine-induced inhibition of cerebellar Purkinje neurons.

Biochemical studies showing that lead (Pb++) inhibits cerebellar adenylate cyclase (IC50 = 2 micrometer) prompted us to test the effects of this cation on the depression of spontaneous discharge of Purkinje (P) cells produced by iontophoresis of norepinephrine (NE). Previous studies have suggested that the effects of NE on P cell discharge may be mediated by activation of a NE-sensitive adenylate cyclase. Iontophoresis of Pb++ in situ, and in cerebellar transplants in oculo, reliably antagonized NE responses in over 80% of the P cells studied in both preparations.

Locus coeruleus fibre growth in oculo induced by trigeminotomy.

Locus coeruleus from fetal donors was homologously grafted to the anterior eye chambers of adult rats whose eyes were sympathetically denervated. After intraocular maturation, outgrowth of noradrenaline-containing fibres from the locus coeruleus neurons on the host iris was studied by Falck--Hillarp fluorescence histochemistry. In control animals locus coeruleus grafts produce a halo of noradrenaline-containing nerve fibres around the graft, covering approximately one third of the surface of the host iris.