Biomedical subjects
R L Faull
Publications and source records attributed to R L Faull.
The regional, cellular and subcellular localization of GABAA/benzodiazepine receptors in the substantia nigra of the rat.
The regional, cellular and subcellular distribution of GABAA/benzodiazepine receptors was investigated by light and electron microscopy in the rat substantia nigra. The regional distribution and density of GABAA/benzodiazepine receptor subtypes (Type I and II) was studied using quantitative receptor autoradiography following in vitro labelling of cryostat sections with tritiated ligands. This was followed by a detailed study of the cellular and subcellular distribution and localization of GABAA/benzodiazepine receptors by light and electron microscopy using immunohistochemical techniques with a monoclonal antibody (bd-17) to the beta 2,3 subunits of the GABAA/benzodiazepine receptor complex. Finally, in situ hybridization histochemistry using 35S-labelled oligonucleotide probes was used to demonstrate the cellular distribution of mRNA for the alpha 1 and alpha 2 GABAA receptor subunits in the substantia nigra. The results of the autoradiographic and immunohistochemical studies showed a close correspondence in the regional distribution of GABAA/benzodiazepine receptors in the substantia nigra. A moderate-to-high density of receptors was present throughout the full extent of the substantia nigra pars reticulata with a very low density of receptors in the substantia nigra pars compacta. Quantitative autoradiographic studies showed that: (i) the pars reticulata contained mainly central Type I receptors; (ii) the highest density of receptors was present in the caudal pars reticulata (200 +/- 38 fmol/mg) with successively lower densities of receptors in the middle (176 +/- 31 fmol/mg) and rostral (150 +/- 26 fmol/mg) levels of the pars reticulata; and (iii) the density of receptors in the pars reticulata was reduced by 34% following 6-hydroxydopamine-induced degeneration of dopaminergic pars compacta neurons. At the cellular level, GABAA/benzodiazepine receptor immunoreactivity was localized in a punctate fashion on dendrites and neuronal cell bodies in the pars reticulata. At the subcellular level, GABAA/benzodiazepine receptor immunoreactivity was associated with the pre- and postsynaptic membranes of axodendritic synaptic complexes along the length of small-to-large sized smooth dendrites in the pars reticulata. Two types of immunoreactive axodendritic synaptic complexes were identified: most (about 80%) immunopositive synapses showed equal staining of the pre- and postsynaptic membranes and were associated with small (less than 1.0 micron) axon terminals containing few mitochondria and small, round-to-pleomorphic vesicles in synaptic contact with small, peripheral dendrites; less frequently (about 20%) immunopositive synapses showed a marked immunoreactive thickening of the postsynaptic membrane and were associated with large (greater than 1.0 micron) axon terminals containing numerous mitochondria and mainly pleomorphic vesicles in synaptic contact with large mainstem dendrites.(ABSTRACT TRUNCATED AT 400 WORDS)
Distribution of excitatory and inhibitory amino acid, sigma, monoamine, catecholamine, acetylcholine, opioid, neurotensin, substance P, adenosine and neuropeptide Y receptors in human motor and somatosensory cortex.
Autoradiography was used to visualise N-methyl-D-aspartate, phencyclidine, strychnine-insensitive glycine, alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid, kainic acid, benzodiazepine, gamma-aminobutyric acid type A, sigma, serotonergic, dopaminergic, alpha 2-adrenergic, beta-adrenergic, muscarinic cholinergic, nicotinic, opioid, neurotensin, substance P, adenosine A1 and neuropeptide Y receptors in the human primary motor (Brodmann's area 4) and somatosensory cortex (Brodmann's areas 3, 2 and 1). With the exception of serotonin type 2 receptors, all receptor types examined had a similar distribution in area 4 which showed little dependence on the underlying distribution of cell somata, often continuing unaltered through the somatosensory cortex despite marked cytoarchitectural changes. The highest densities occurred in the outer (most superficial) 30-40% of the cortical grey matter, followed by a band of relatively low binding and then moderate levels in the inner (deeper) region. In many instances, an additional band of dense binding could be discerned in the region of laminae IV/Va running unbroken through both gyri. The distribution of most receptor types in the somatosensory cortex also followed this pattern, except for opioid and kainic acid receptors which showed higher levels in the inner rather than the outer third of this region. At the edge of area 4, a change occurred such that a high density outer band appeared, giving these receptor types the same pattern in area 4 as the majority. Serotonin type 2 receptor levels were quite low in the outermost region of area 4, although the pattern was otherwise similar to that of the other receptors. Thus, with the exception of serotonin receptors, the similarity in many binding site distributions recently noted in area 4 of the rhesus monkey also tends to occur in the human area 4, to the extent that 2 ligands will reverse their usual cortical binding pattern to conform with the common area 4 pattern.
Autoradiographic distribution of sigma receptors in human neocortex, hippocampus, basal ganglia, cerebellum, pineal and pituitary glands.
Autoradiographic distributions of [3H]1,3-di-O-tolylguanidine, [3H]DTG, binding to sigma (sigma) receptors were studied in key human brain regions. High densities occurred in the substantia nigra pars compacta and cerebellum. Pineal and pituitary levels were moderate. In neocortex, binding was high in laminae II-IVA and much lower in the midzone. Moderate binding occurred over hippocampal dentate granular cells and in the striatum. These results differ from those reported for the rodent.
Elevated expression of jun and fos-related proteins in transplanted striatal neurons.
The basal expression of the immediate-early gene protein products fos, fos-related antigens (FRA's), jun and krox-24 was examined using immunocytochemical methods in intrastriatal grafts derived from fetal striatal primordia. Whereas very few, if any, normal adult striatal neurons expressed jun, many neurons in the striatal graft expressed jun at high levels. FRA's, but not fos, were also occasionally induced in some grafted striata. krox-24 was expressed in normal adult striatal neurons, and to a lesser extent in transplanted striatal neurons. These results show that neurons of intrastriatal grafts express jun at substantially higher levels than host striatal neurons, and this may be related to the previously reported increased transcription of neuropeptides in striatal grafts, and/or to the possible failure of transplanted neurons to fully establish normal connections with the host tissue.
Autoradiographic visualisation of [3H]DTG binding to sigma receptors, [3H]TCP binding sites, and L-[3H]glutamate binding to NMDA receptors in human cerebellum.
The autoradiographic distributions of [3H]1,3-di-ortho-tolyguanidine ([3H]DTG), [3H]1-[1-(2-thienyl) cyclohexyl] piperidine ([3H]TCP) and L-[3H]glutamate were studied in the human cerebellum. [3H]DTG is a selective label for the sigma receptor, while L-[3H]glutamate binding was carried out under conditions selective for the N-methyl-D-aspartate (NMDA) receptor. [3H]TCP binding sites and sigma receptors showed marked enrichment in the Purkinje cell layer, while L-[3H]glutamate-labelled NMDA receptors showed virtually no binding in the Purkinje cell layer. The results confirm the existence of [3H]TCP binding sites which are not linked to NMDA receptors in the human cerebellum, having a distribution which is more similar to that of the haloperidol-sensitive sigma receptor.
Differential sensitivity of calbindin and parvalbumin immunoreactive cells in the striatum to excitotoxins.
The neurotoxic effects of ibotenic acid, quinolinic acid and kainic acid on cells in the rat striatum were investigated using immunocytochemistry with antibodies to the calcium binding proteins, calbindin and parvalbumin. The results showed that both ibotenic acid and quinolinic acid affected calbindin and parvalbumin cells to the same extent. However, parvalbumin immunopositive neurons were more sensitive than calbindin immunopositive neurons to the neurotoxic effects of kainic acid. Although the reason for this increased sensitivity of parvalbumin striatal neurons to kainic acid is unclear, these results suggest that the neurotoxicity produced by kainic acid is different to that occurring with quinolinic acid and ibotenic acid.
Differential effects of acute dopaminergic D1 and D2 receptor antagonists on proneurotensin mRNA expression in rat striatum.
The effect of acute dopamine (DA) antagonist treatment on neuronal proneurotensin (NT) mRNA was investigated in the rat striatum using a technique of non-radioactive in situ hybridisation. Adult Wistar rats were given a single intraperitoneal injection of either raclopride (D2 antagonist), SCH 23390 (D1 antagonist) or its inactive isomer SCH 23388 and left to survive for 3 h. Their brains were rapidly removed and striatal sections processed for in situ hybridisation using an alkaline phosphatase (AP) labelled oligonucleotide specific for NT mRNA. Blockade of the DA D2 receptors by a single injection of raclopride resulted in an increase in the number of NT mRNA containing cells in the dorsal lateral rim of the striatum adjacent to the corpus callosum. In contrast, no such increase was observed following blockade of the DA D1 receptors with SCH 23390. These findings demonstrate that NT mRNA expression is differentially regulated in the adult rat striatum by selective D1 and D2 antagonists.
Prolonged and selective induction of Fos-related antigen(s) in striatal neurons after 6-hydroxydopamine lesions of the rat substantia nigra pars compacta.
Unilateral 6-hydroxydopamine (6-OHDA) lesions of the rat substantia nigra lead to a large widespread and long-lasting (greater than 3 months) increased expression of Fos-related antigen(s) (FRAs) in striatal neurons ipsilateral to the side of the lesion. However, Fos and Jun expression were only very slightly increased in a few scattered neurons in the dopamine-denervated striatum. These results demonstrate that FRAs are induced long-term in striatal neurons following dopamine-depletion. This increased production of FRAs may be related to neuropeptide and/or D2 dopamine receptor upregulation that also occurs in the dopamine-denervated striatum.
Dopaminergic D1 and D2 receptor antagonists decrease prosomatostatin mRNA expression in rat striatum.
The effect of acute dopamine receptor antagonist treatment on cellular prosomatostatin mRNA expression was investigated in the adult rat striatum using the technique of non-radioactive in situ hybridization. Adult female Wistar rats were given a single intraperitoneal injection of either raclopride (D2 antagonist), SCH 23390 (D1 antagonist) or the D1 (S) enantiomer SCH 23388. Animals were killed either 1, 3 or 9 h following the single i.p. injection and their brains rapidly removed. Striatal sections were then processed for in situ hybridization using an alkaline phosphatase-labelled oligonucleotide probe complementary to a portion of the rat somatostatin cDNA. Blockade of dopamine D1 and D2 receptors resulted in a significant decrease in the cellular content of prosomatostatin mRNA. However, no change in the number of prosomatostatin mRNA containing striatal cells was observed following any of the treatments at any time point. These findings demonstrate that the cellular content of prosomatostatin mRNA in the adult rat striatum is influenced by selective dopamine D1 and D2 receptor antagonists. Further, these findings are consistent with a functional interaction between dopamine and somatostatin in the rat striatum.
NMDA and kainic acid receptors have a complementary distribution to AMPA receptors in the human cerebellum.
The distributions of N-methyl-D-aspartate (NMDA), alpha-amino-3-hydroxy-S-methyl-4-isoxazole propionic acid (AMPA) and kainic acid (KA) receptors were determined in the human cerebellum using autoradiography. In contrast to the cerebral cortex, where KA receptors have a complementary distribution to NMDA and AMPA receptors, AMPA receptors were concentrated in the cerebellar molecular layer while NMDA and KA receptors were concentrated in the granular layer.
Effects of hypoxia-ischemia and seizures on neuronal and glial-like c-fos protein levels in the infant rat.
Unilateral carotid ligation in immature rats, followed by 2 h of hypoxia led to ischemic cell change from 2 h after the insult, on the ligated side of the brain. There was a time-dependent induction of immunoreactive c-fos protein in neurones but not glia or ependyma on the non-ligated side of the brain. Induction only occurred in rats that had seizures post hypoxia-ischemia. In the ligated hemisphere c-fos protein was induced in glial-like cells in the corpus callosum, fornix/fimbria and internal capsule and in ependymal cells lining the lateral ventricle starting from 2 h after hypoxia but subsiding by 3 days. No neuronal c-fos induction was seen in areas showing neuronal damage. MK-801 or carbamazepine, which prevented hypoxia-ischemia-induced seizures, also prevented c-fos induction in the non-ligated hemisphere while MK-801 was associated with increased c-fos induction in hippocampal neurones from the ligated side, as well as in glial-like and ependymal cells. These results suggest several processes are involved following the hypoxic-ischemic insult. Firstly, severe hypoxia-ischemia is associated with a reduction in neuronal c-fos protein levels, probably as a result of neuronal failure and death. Secondly, post hypoxic seizures cause c-fos induction in surviving neurones. Thirdly, glial-like from regions in which there is neural loss also exhibit induction of c-fos, which may be important for their subsequent proliferation or for the production of growth factors.
Haloperidol induces Fos and related molecules in intrastriatal grafts derived from fetal striatal primordia.
Haloperidol induces Fos and related molecules (Fos-related antigens, FRAs) in adult striatal neurons. We tested whether a similar induction of Fos and FRAs by haloperidol injection would occur in fetal striatal neurons transplanted into adult quinolinic acid-lesioned striatum. We found that Fos and FRAs were induced in striatal neurons after haloperidol. This induction had a time course in transplanted neurons that was identical to the time course of induction in normal adult striatum. Furthermore, the relative numbers of Fos- and FRA-immunopositive neurons induced by haloperidol were identical for both transplanted and normal striatal neurons. These results provide the first demonstration that neurons in intrastriatal grafts derived from fetal striatal primordia have similar intracellular biochemical characteristics to normal adult striatal neurons.
Induction of Fos in glia-like cells after focal brain injury but not during wallerian degeneration.
Focal brain injury or perforant-path transections respectively led to an increase in the number of glial-fibrillary acidic protein (GFAP)-immunopositive astrocytes around the focal wound or in the terminal fields of the perforant path in the dentate molecular layer. This GFAP accumulation occurred 48-72 h after focal brain injury or perforant-path transection (wallerian degeneration). Focal brain injury also led to an accumulation of c-fos protein (Fos) in glial cells, ependyma and cells in the pia mater of the brain within 6 h of injury and this effect dissipated within 72 h. However, perforant-path lesions were not associated with accumulation of Fos in glial cells in the dentate molecular layer suggesting that c-fos induction in glial cells after injury is not necessary for GFAP accumulation. Induction of Fos in glia, ependyma and pia after focal brain injury may be associated with proliferation of these cells after injury.
MK801 induces c-fos protein in thalamic and neocortical neurons of rat brain.
MK801, a non-competitive NMDA receptor antagonist, leads to a dramatic induction of c-fos-like protein in neurons in deep layers of the neocortex, in dorsal and ventral midline thalamic nuclei and in neurons in the central grey of rat brain. This induction of c-fos by MK801 is dose- and time-dependent occurring within 2 h and dissipating by 24 h after injection (0.5-8.0mg/kg, i.p.). The mechanism of this paradoxical induction of c-fos by MK801 is unclear, however the pattern of induction appears to follow the distribution of the antagonist-preferring NMDA receptor site.
MK-801 induces c-fos protein in thalamic and neocortical neurons of rat brain.
MK-801, a non-competitive N-methyl-D-aspartate (NMDA) receptor antagonist, leads to a dramatic induction of c-fos-like protein in neurons in deep layers of the neocortex, in dorsal and ventral midline thalamic nuclei and in neurons in the central grey of rat brain. This induction of c-fos by MK-801 is dose-and time-dependent occurring within 2 h and dissipating by 24 h after injection (0.5-8.0 mg/kg, i.p.). The mechanism of this paradoxical induction of c-fos by MK-801 is unclear; however, the pattern of induction appears to follow the distribution of the antagonist-preferring NMDA receptor site.
MK-801, an antagonist of NMDA receptors, inhibits injury-induced c-fos protein accumulation in rat brain.
Unilateral lesions of the rat hippocampus produced by needle insertion lead to ipsilateral accumulation of c-fos protein in dentate granule cells and neurons in the piriform cortex, as well as in glial-like cells in the corpus callosum and in ependymal cells lining the lateral ventricle adjacent to the lesion site. C-fos protein was detected immunocytochemically using two different antibodies in formalin-fixed brain sections. The N-methyl-D-aspartate (NMDA) antagonist MK-801 produced a dose- and time-dependent inhibition of c-fos protein accumulation in dentate granule cells and in neurons in the piriform cortex, but did not affect glial or ependymal c-fos protein accumulation. MK-801 at 4 mg/kg injected two hours before lesion inhibited c-fos accumulation. Thus, c-fos protein accumulation in hippocampal neurons and in neurons in the piriform cortex induced after traumatic brain injury involves activation of NMDA receptors.
Sigma receptors are highly concentrated in the rat pineal gland.
The distribution of sigma (sigma) receptors in the rat brain was studied with autoradiography using [3H]1,3-di-ortho-tolyl-guanidine ([3H]DTG) as a ligand. The highest concentration of sigma receptors was seen in the pineal gland, an area which has not been previously studied. This result is of interest as both sigma receptors and the pineal gland have recently been shown to play a role not only in the nervous system but also in the immune and endocrine systems.