Stress elicits adaptive responses from the brain, but it can also lead to maladaptive consequences. For example, stress can precipitate mental illness, including depression. Prolonged stress also causes damage to neurons in the hippocampus. Antidepressant drugs must be evaluated, not only for their ability to potentiate adaptive responses, but also to inhibit maladaptive consequences of stress. Ongoing research in our laboratory has compared the atypical tricyclic antidepressant, tianeptine, with the typical tricyclics, desipramine and imipramine, with respect to the effects of isolation and repeated restraint stress. Tianeptine and desipramine similarly attenuated isolation stress-induced increases in locus coeruleus and midbrain tyrosine hydroxylase mRNA levels and isolation-stress induced decreases in preproenkephalin mRNA levels in striatum and nucleus accumbens. However, tianeptine and imipramine differed in their effects in the cerebral cortex and hippocampus on 5HT2, and 5HT1A receptor levels but, surprisingly, produced similar effects on levels of the serotonin transporter labelled with [3H] paroxetine. Tianeptine also prevented stress-induced reductions in the length and number of branchpoints of dendrites of CA3 pyramidal neurons in hippocampus; comparison with effects of typical tricyclics are ongoing. Tianeptine also blocked effects of corticosterone treatment to reduce branching and length of CA3 dendrites. These actions of tianeptine may be due to interactions between 5HT and excitatory amino acids in the mossy fiber terminals on CA3 pyramidal neurons. Taken together, these results indicate that tianeptine has unique properties compared to some other antidepressant drugs, but shares in common with those drugs the ability to attenuate stress effects on tyrosine hydroxylase gene expression and on the serotonin transporter. It remains to be seen whether these actions are the basis of a common antidepressant action.

Perinatal maternal high-fat (HF) diet programmes offspring obesity. Obesity is associated with overactivation of the endocannabinoid system (ECS) in adult subjects, but the role of the ECS in the developmental origins of obesity is mostly unknown. The ECS consists of endocannabinoids, cannabinoid receptors (cannabinoid type-1 receptor (CB1) and cannabinoid type-2 receptor (CB2)) and metabolising enzymes. We hypothesised that perinatal maternal HF diet would alter the ECS in a sex-dependent manner in white and brown adipose tissue of rat offspring at weaning in parallel to obesity development. Female rats received standard diet (9 % energy content from fat) or HF diet (29 % energy content from fat) before mating, during pregnancy and lactation. At weaning, male and female offspring were killed for tissue harvest. Maternal HF diet induced early obesity, white adipocyte hypertrophy and increased lipid accumulation in brown adipose tissue associated with sex-specific changes of the ECS’s components in weanling rats. In male pups, maternal HF diet decreased CB1 and CB2 protein in subcutaneous adipose tissue. In female pups, maternal HF diet increased visceral and decreased subcutaneous CB1. In brown adipose tissue, maternal HF diet increased CB1 regardless of pup sex. In addition, maternal HF diet differentially changed oestrogen receptor across the adipose depots in male and female pups. The ECS and oestrogen signalling play an important role in lipogenesis, adipogenesis and thermogenesis, and we observed early changes in their targets in adipose depots of the offspring. The present findings provide insights into the involvement of the ECS in the developmental origins of metabolic disease induced by inadequate maternal nutrition in early life.

Neurons containing catecholamine, indoleamine, and gamma-aminobutyric acid (GABA) were identified by immunohistochemistry in the chameleon retina. Tyrosine hydroxylase (TH) and serotonin (5HT) were observed mostly in two subtypes of orthotopic amacrine cells differing in their soma size and process distribution within the IPL. Some labelled cells were displaced either to the IPL (5HT) or to the GCL (TH and 5HT). A multiplicity of retinal cell types contained GABA including cones, horizontal, amacrine, and ganglion cells. Our results confirmed those obtained in the retinas of other lizards except for the presence of interstitial and displaced amacrine cells containing TH or 5HT of which this is the first report.

A fundamental anatomical feature of retinal neurons is that they form planar mosaics. Each mosaic can be described by its density, pattern, and regularity (non-randomness). As part of ongoing studies to quantitatively describe the anatomy of regenerated retina in the goldfish, we determined the planimetric density and regularity of the mosaic of dopaminergic interplexiform cells in patches of regenerated retina and compared this to the mosaic generated de novo. In addition, we selectively ablated dopaminergic neurons with the neurotoxin 6–hydroxydopamine (6–OHDA) before inducing local regeneration and determined whether or not the absence of the extant dopaminergic neurons modulated the planimetric density or number of regenerated ones. The results showed that dopaminergic neurons are regenerated at higher planimetric densities and in less orderly arrays than normal. Furthermore, there was no statistical difference in the density or number of regenerated cells in normal retinas and retinas treated with 6–OHDA.

Vasoactive intestinal polypeptide (VIP) immunoreactive (IR) neurons in the rabbit retina constitute a population of wide-field amacrine cells. To better define this cell population, we examined the coexpression of VIP with other putative retinal transmitters or their biosynthetic enzymes, including γ-aminobutyric acid (GABA), tyrosine hydroxylase (TH), and somatostatin (SRIF). Colchicine-treated retinas were immersion fixed in 4% paraformaldehyde. The retinas were cut either perpendicular or parallel to the vitreal surface and processed by double-label immunofluorescence techniques using antibodies directed to VIP, GABA, TH, and SRIF. The immunoreactive staining patterns obtained with these antibodies were the same as those described in previous studies. GABA-IR neurons were localized to the proximal inner nuclear layer (INL) and ganglion cell layer (GCL) and processes were distributed throughout the inner plexiform layer (IPL). TH- and SR1F-IR neurons were sparsely distributed to the proximal INL and GCL, respectively. TH-IR processes ramified in laminae 1, 3, and 5, and SRIF-1R processes in laminae 1 and 5 of the IPL. Colocalization experiments showed that all VIP-IR neurons contain GABA immunoreactivity. In contrast, colocalization of VIP and TH or SRIF immunoreactivities was never observed. These results demonstrate that VIP-IR wide-field amacrines of the rabbit retina make up a neurochemically and morphologically distinct subpopulation of the GABA-IR amacrine cell population. Furthermore, VIP-IR amacrine cells constitute a distinct group with respect to the TH- and SRIF-IR amacrine cells.

A survey of the shapes of dopaminergic (DA) neurons in the retinas of representative vertebrates reveals that they are divisible into three groups. In teleosts and Cebus monkey, DA cells are interplexiform (IPC) neurons with an ascending process that ramifies to create an extensive arbor in the outer plexiform layer (OPL). All other vertebrates studied, including several primate species, have either DA amacrine cells or IPCs with an ascending process that either does not branch within the OPL or does so to a very limited degree. DA neurons of non-teleosts exhibit a dense plexus of fine caliber fibers which extends in the distal most sublamina of the inner plexiform layer (IPL). Teleosts lack this plexus. In all vertebrates, DA cells are distributed more or less evenly and at a low density (10–60 cells/mm2) over the retinal surface. Dendritic fields of adjacent DA neurons overlap. Most of the membrane area of the DA cell is contained within the plexus of fine fibers, which we postulate to be the major source of dopamine release. Thus, dopamine release can be modeled as occurring uniformly from a thin sheet located either in the OPL (teleosts) or in the distal IPL (most other vertebrates) or both (Cebus monkey). Assuming that net lateral spread of dopamine is zero, the fall of dopamine concentration with distance at right angles to the sheet (i.e. in the scleral-vitreal axis) will be exponential. The factors that influence the rate of fall – diffusion in extracellular space, uptake, and transport – are not yet quantified for dopamine, hence the dopamine concentration around its target cells cannot yet be assessed. This point is important in relation to the thresholds for activation of D1 and D2 dopamine receptors that are found on a variety of retinal cells.

Parkinson's disease (PD) is a debilitating neurodegenerative disorder arising from loss of dopaminergic neurons in the substantia nigra pars compacta and subsequent depletion of striatal dopamine levels, which results in distressing motor symptoms. The current standard pharmacological treatment for PD is direct replacement of dopamine by treatment with its precursor, levodopa (L-dopa). However, this does not significantly alter disease progression and might contribute to the ongoing pathology. Several features of PD make this disease one of the most promising targets for clinical gene therapy of any neurological disease. The confinement of the major pathology to a compact, localised neuronal population and the anatomy of the basal ganglia circuitry mean that global gene transfer is not required and there are well-defined sites for gene transfer. The multifactorial aetiology of idiopathic PD means that it is unlikely any single gene will cure the disease, and as a result at least three separate gene-transfer strategies are currently being pursued: transfer of genes for enzymes involved in dopamine production; transfer of genes for growth factors involved in dopaminergic cell survival and regeneration; and transfer of genes to reset neuronal circuitry by switching cellular phenotype. The merits of these strategies are discussed here, along with remaining hurdles that might impede transfer of gene therapy technology to the clinic as a treatment for PD.

Distribution of the mt1 melatonin receptor in the guinea pig retina was immunocytochemically investigated using peptide-specific anti-mt1 receptor antibody. Western blots of the guinea pig retina showed a single band at approximately 37 kilodalton (kD) immunoreactive to the anti-mt1 antibody. The most intense immunoreactivity for the mt1 receptor was detected in the cell bodies of ganglion cells. Their dendrites and axons were also immunolabeled. Subpopulations of amacrine cells, the inner plexiform layer, and the outer plexiform layer also exhibited moderate to weak immunolabeling. The mt1-positive amacrine cells were located either at the vitreal border of the inner nuclear layer or displaced in the ganglion cell layer. Double immunolabeling using antibodies to the mt1 receptor and tyrosine hydroxylase revealed that the majority of dopaminergic amacrine cells showed mt1 immunoreactivity. Almost all the 1CA type dopaminergic cells were mt1 positive while the 2CA type cells less frequently exhibited mt1 immunoreaction. By double immunolabeling for the mt1 receptor and GABA, more than 50% of the mt1-immunoreactive amacrine cells were shown to be GABAergic neurons. Approximately one-third of the GABAergic amacrine cells were immunolabeled for the mt1 receptor. The present results demonstrate expression of the mt1 receptor in diverse neuronal cell types in the guinea pig retina and provide the first evidence for the direct effect of melatonin on dopaminergic and GABAergic amacrine cells via the mt1 receptor.

Electron immunocytochemistry was used to examine perivascular nerves of hamster mesenteric and renal arteries during hibernation and 2 h after arousal from hibernation. Vessels from cold-exposed but nonhibernating, and normothermic control hamsters were also examined. During hibernation the percentage of axon profiles in mesenteric and renal arteries that were immunopositive for markers of sympathetic nerves, tyrosine hydroxylase (TH) and neuropeptide Y (NPY), were increased 2–3 fold compared with normothermic and cold control animals. This increase was reduced markedly only 2 h after arousal from hibernation. The small percentage of nitric oxide synthase-1-positive axon profiles found in mesenteric (but not renal) arteries was also increased during hibernation and returned towards control values after arousal. In contrast, the percentage of perivascular axons immunostaining for vasoactive intestinal polypeptide (VIP), a marker for parasympathetic nerves, was reduced in mesenteric arteries during hibernation. There was no labelling of perivascular nerves for substance P in either mesenteric or renal arteries. It is suggested that the increase in percentage of TH- and NPY-immunostained perivascular nerves may account for the increased vasoconstriction associated with high vascular resistance that is known to occur during hibernation. The reduction in the percentage of axons positive for VIP in hibernating animals would contribute to this mechanism since this neuropeptide is a vasodilator.

Retrograde tracing with Fluoro-Gold (FG) was used to identify the complete population of knee joint sympathetic postganglionic efferents in the lumbar sympathetic chain of adult female Wistar rats. In 6 rats, the total number and distribution of FG-labelled neurons in the lumbar sympathetic chain was determined. The rat knee joint is supplied by an average of 187±57 sympathetic afferents with the majority at the L3 and L4 levels. Immunohistochemistry using antibodies specific for tyrosine hydroxylase (TH), somatostatin (SS) or vasoactive intestinal polypeptide (VIP) revealed that 33% of knee joint sympathetic afferents contained TH, 42% contained VIP, and none contained somatostatin. Retrograde tracing with FG provided accurate and reproducible labelling of the joint-innervating subpopulation of sympathetic efferent neurons. This model lends itself to the further study of the molecular responses of this neuronal population in the various disorders and conditions affecting joints.

Several experimental models have demonstrated that the central nervous system is functionally linked to the immune system by means of the autonomic nervous system. Samples of 36 lymph nodes of patients whose ages ranged from 16 to 69 y were studied. In order to demonstrate the existence and distribution of sympathetic nerve fibres, a polyclonal antibody antityrosine hydroxylase (TH), with the streptavidin-biotin system of detection, was used. TH-positive nerve fibres appeared in all reactive patterns of the lymph nodes studied. Thin nerve fascicles ramified at the hilar region and also in the connective tissue septae. Adventitial adrenergic nerve fibres were found following afferent, and to a lesser extent, efferent blood vessels. Another source of incoming nerve fibres was found at capsular level, accompanying blood vessels. On the arterial side, the innervation ceased before reaching the follicular arterioles. Our demonstration of innervation in postcapillary venules could support a regulatory role of adrenergic neurotransmitters in lymphocyte traffic. Occasional nerve fibres were also seen in T areas among parenchymatous cells. These findings confirm the existence of sympathetic innervation in human lymph nodes, and provide indirect evidence that the psychoneuroimmune axis could also exist in humans.

The common brush-tailed possum Trichosurus vulpecula is a small diprotodont marsupial common to both urban and natural environments. This is the first analysis of the neurotransmitter content of its retinal cells and, as the possum is a nocturnal forager, it was appropriate to begin with the dopaminergic amacrine cells that form an essential link in the modulation of the rod pathways subserving nocturnal vision. These results were compared with those from another diprotodont, the marsupial wallaby or quokka (Dann, 1996) to establish whether the dopaminergic systems were similar between these two diprotodont marsupials and also to compare these findings with those of other mammals. This study describes a population of amacrine cells in the possum retina that were immunolabelled with an antibody raised against tyrosine hydroxylase (TH). These TH-immunoreactive (IR) cells were located within the inner nuclear layer (INL) and their dendrites predominantly ramified within the most sclerad layers of the inner plexiform layer (IPL). The TH-IR amacrines formed a sparse cell population, of around 2400 cells, distributed over the entire retina. There was little evidence of a concentration gradient except for a slight elevation in density in the naso-temporal axis in dorsal retina. The formation of rings within the dendritic plexus, a feature common to TH-IR cells in other species, was also present in the possum and these appeared relatively frequently. This latter finding was rather unexpected since, in the marsupial quokka (Dann, 1996), the TH-IR dendrites formed fewer rings despite having the same density of TH-IR amacrines as the possum. This suggests that there may be subtle differences in the way the rod pathways are interconnected even within the same marsupial group and may also be a reflection of relative rod dominance across species.

The presence of a cholinergic innervation of arterioles within the gut wall is suggested by pharmacological studies of nerve mediated vasodilatation, but attempts to identify nerve cells that give rise to cholinergic vasodilator fibres have yielded discrepant results. In the present work, antibodies to the vesicular acetylcholine transporter protein (VAChT) were used to investigate the relationships of immunoreactive nerve fibres to submucosal arterioles. Comparison was made with cerebral arteries, which are known to be cholinergically innervated. Double labelling immunohistochemical techniques revealed separate VAChT and tyrosine hydroxylase (TH) immunoreactive (IR) fibres innervating all sizes of arteries of the submucosa of the stomach, ileum, proximal colon, distal colon and rectum as well as the cerebral arteries. Arterioles of all digestive tract regions had greater densities of TH-IR innervation than VAChT-IR innervation. In the ileum, double labelling for VAChT-IR and VIP-IR or calretinin-IR showed more VAChT-IR than either VIP-IR or calretinin-IR fibres. Calretinin-IR and VAChT-IR were colocalised in a majority of calretinin-IR axons, but VIP-IR and VAChT-IR were not colocalised. All calretinin-IR nerve cells in submucous ganglia were immunoreactive for choline acetyltransferase, but only 1–2% of VIP-IR nerve cells were immunoreactive. Extrinsic denervation of the ileum did not alter the distribution of VAChT-IR fibres, but it eliminated TH-IR fibres. Removal of myenteric ganglia (myectomy) did not alter the distribution of fibres with VAChT or TH-IR. This work thus provides evidence for cholinergic innervation of intrinsic arterioles throughout the digestive tract and indicates that the fibres in the small intestine originate from submucosal nerve cells.

Double-label immunocytochemistry was used to investigate the colocalisation of various neuropeptides and the enzymes nitric oxide synthase (NOS) and tyrosine hydroxylase (TH) in intramural ganglia of the human male urinary bladder neck and trigone. Postmortem specimens were obtained from 7 male infants and children ranging in age from 2 mo to 3 y who had died as a result of cot death or accidental trauma. On average 60% of the intramural neurons were non-TH-immunoreactive (-IR) (i.e. presumptive cholinergic) and 40% were TH- and DbβH-IR (i.e. noradrenergic). Within the non-TH-IR population, calcitonin gene-related peptide (CGRP) was found in 65% of cells, neuropeptide Y (NPY) in 90%, nitric oxide synthase (NOS) in 45%, somatostatin (SOM) in 90%, and vasoactive intestinal polypeptide (VIP) in 40%. The corresponding values for the TH-IR neurons were CGRP (54%), NPY (70%), NOS (58%), SOM (73%) and VIP (40%). All the observed bombesin (BOM)-immunoreactivity was colocalised with TH while 90% of VIP and almost all the CGRP was colocalised with NPY. Less than 5% of neurons were immunoreactive for substance P (SP) or met-enkephalin (m-ENK) and some of these also contained TH. Varicose nerve fibres were seen in close proximity to some of the intramural neurons, the majority of such varicosities showing immunoreactivity to CGRP, VIP or TH. Less common were pericellular varicosities immunoreactive to NPY, SOM or SP. These results demonstrate the neurochemical heterogeneity of intramural neurons in the human bladder neck and provide indirect evidence for the complexity of the peripheral innervation of the human urinary bladder.

Cet article étudie les principaux mécanismes de régulation de la transmission dopaminergique et s'efforce d’identifier les gènes dont la mutation serait susceptible d'altérer cette transmission.