TH-ir Neurons Research Articles

Reinforcing properties of pups versus cocaine for fathers and associated central expression of Fos and tyrosine hydroxylase in mandarin voles (Microtus mandarinus)

The reciprocal interaction of pups and cocaine on reward effects in rodent mothers is known. However, it remains unclear whether such effects are apparent in father-offspring bonding. The mandarin vole (Microtus mandarinus) is a monogamous rodent with a high level of paternal care. We investigated the reinforcing properties of pups on vole fathers using a conditioned place preference paradigm across the postpartum period and looked for interactions and differences between the reinforcing effects of pups and cocaine. We also measured neuronal Fos and tyrosine hydroxylase (TH) expression underlying the preferences of fathers for pups or cocaine. Our data showed that fathers developed strong preferences for pups at various times (postnatal day 5–9, 13–17 and 19–23) without cocaine conditioning. Fathers showed a reduced preference for pups following simultaneous conditioning with cocaine. Although they preferred cocaine over postnatal day (PND) 5–9 pups, this preference was not detected for PND 13–17 pups. Fathers preferring cocaine exhibited an increase in Fos-immunoreactive neurons in the accumbens, medial nucleus of the amygdala, cingulate cortex, medial preoptic area and ventral tegmental area and had more TH-IR neurons in the ventral tegmental area compared to fathers preferring PND 5–9 pups. These results showed that similar to cocaine, mandarin vole pups elicit significant reward value to their fathers, but that paternal motivation is impaired by cocaine. A preference for cocaine over pups arose from the release of more dopamine and activation of a greater number of neurons within specific reward-associated neuronal subsets.

Blockade of mGluR5 Reverses Abnormal Firing of Subthalamic Nucleus Neurons in 6-Hydroxydopamine Partially Lesioned Rats

Activation of metabotropic glutamate receptor 5 (mGluRs) in the subthalamic nucleus (STN) results in burst-firing activity of STN neurons, which is similar to that observed in Parkinson's disease (PD). We examined the effects of chronic and systemic treatment with 2-methyl-6-(phenylethynyl)-pyridine (MPEP), a selective mGluR5 antagonist, in firing activity of STN neurons in partially lesioned rats by 6-hydroxydopamine (6-OHDA). In 6-OHDA-lesioned rats treated with vehicle, injection of 6-OHDA (4 microg) into the medial forebrain bundle produced a partial lesion causing 36% loss of tyrosine hydroxylase-immunoreactive (TH-ir) neurons in the substantia nigra pars compacta (SNpc). The 6-OHDA lesion in vehicle-treated rats showed an increasing firing rate and a more irregular firing pattern of STN neurons. Whereas chronic, systemic treatment of MPEP (3 mg/kg/day, 14 days) produced neuroprotecive effects on the TH-ir neurons and normalized the hyperactive firing activity of STN neurons in 6-OHDA partially lesioned rats. These data demonstrate that partial lesion of the nigrostriatal pathway increases firing activity of STN neurons in the rat, and chronic, systemic MPEP treatment has the neuroprotective effect and reverses the abnormal firing activity of STN neurons, suggesting that MPEP has an important implication for the treatment of PD.

CD200-CD200R dysfunction exacerbates microglial activation and dopaminergic neurodegeneration in a rat model of Parkinson's disease

BackgroundIncreasing evidence suggests that microglial activation may participate in the aetiology and pathogenesis of Parkinson's disease (PD). CD200-CD200R signalling has been shown to be critical for restraining microglial activation. We have previously shown that expression of CD200R in monocyte-derived macrophages, induced by various stimuli, is impaired in PD patients, implying an intrinsic abnormality of CD200-CD200R signalling in PD brain. Thus, further in vivo evidence is needed to elucidate the role of malfunction of CD200-CD200R signalling in the pathogenesis of PD.Methods6-hydroxydopamine (6-OHDA)-lesioned rats were used as an animal model of PD. CD200R-blocking antibody (BAb) was injected into striatum to block the engagement of CD200 and CD200R. The animals were divided into three groups, which were treated with 6-OHDA/Veh (PBS), 6-OHDA/CAb (isotype control antibody) or 6-OHDA/BAb, respectively. Rotational tests and immunohistochemistry were employed to evaluate motor deficits and dopaminergic neurodegeneration in animals from each group. HPLC analysis was used to measure monoamine levels in striatum. Morphological analysis and quantification of CD11b- (or MHC II-) immunoreactive cells were performed to investigate microglial activation and possible neuroinflammation in the substantia nigra (SN). Finally, ELISA was employed to assay protein levels of proinflammatory cytokines.ResultsCompared with 6-OHDA/CAb or 6-OHDA/Veh groups, rats treated with 6-OHDA/BAb showed a significant increase in counts of contralateral rotation and a significant decrease in TH-immunoreactive (TH-ir) neurons in SN. A marked decrease in monoamine levels was also detected in 6-OHDA/BAb-treated rats, in comparison to 6-OHDA/Veh-treated ones. Furthermore, remarkably increased activation of microglia as well as up-regulation of proinflammatory cytokines was found concomitant with dopaminergic neurodegeneration in 6-OHDA/BAb-treated rats.ConclusionsThis study shows that deficits in the CD200-CD200R system exacerbate microglial activation and dopaminergic neurodegeneration in a 6-OHDA-induced rat model of PD. Our results suggest that dysfunction of CD200-CD200R signalling may be involved in the aetiopathogenesis of PD.

Striatal Pleiotrophin Overexpression Provides Functional and Morphological Neuroprotection in the 6-Hydroxydopamine Model

Neurotrophic factors are integrally involved in the development of the nigrostriatal system and in combination with gene therapy, possess great therapeutic potential for Parkinson's disease (PD). Pleiotrophin (PTN) is involved in the development, maintenance, and repair of the nigrostriatal dopamine (DA) system. The present study examined the ability of striatal PTN overexpression, delivered via psueudotyped recombinant adeno-associated virus type 2/1 (rAAV2/1), to provide neuroprotection and functional restoration from 6-hydroxydopamine (6-OHDA). Striatal PTN overexpression led to significant neuroprotection of tyrosine hydroxylase immunoreactive (THir) neurons in the substantia nigra pars compacta (SNpc) and THir neurite density in the striatum, with long-term PTN overexpression producing recovery from 6-OHDA-induced deficits in contralateral forelimb use. Transduced striatal PTN levels were increased threefold compared to adult striatal PTN expression and approximated peak endogenous developmental levels (P1). rAAV2/1 vector exclusively transduced neurons within the striatum and SNpc with approximately half the total striatal volume routinely transduced using our injection parameters. Our results indicate that striatal PTN overexpression can provide neuroprotection for the 6-OHDA lesioned nigrostriatal system based upon morphological and functional measures and that striatal PTN levels similar in magnitude to those expressed in the striatum during development are sufficient to provide neuroprotection from Parkinsonian insult.

P.4.d.001 The CRF1 receptor antagonist SSR125543 reduces long-term cognitive deficit induced by acute stress in mice, independently from the HPA axis

Little is known about the chemical coding of the brain neuronal circuitry activated by nociceptive signals of visceral origin. We characterized brain nuclei activated during isovolumetric phasic distension of the proximal colon (10 ml, 30 s on/off for 10 min) in conscious male rats, using Fos as a marker of neuronal activation and dual immunohistochemistry to visualize co-localization of Fos expression and oxytocin (OT), arginine-vasopressin (AVP), corticotrophin-releasing factor (CRF) or tyrosine hydroxylase (TH). Proximal colon distension, compared with sham distension, induced a robust increase in Fos-like immunoreactive (IR) neurons in the paraventricular nucleus (PVN), supraoptic nucleus (SON) and accessory neurosecretory nuclei of the hypothalamus, nucleus of the solitary tract (NTS) and ventrolateral medulla (VLM), and to a lower extent, in the locus coeruleus (LC) and Barrington nucleus. Fos-IR neurons in the PVN after colon distension were identified in 81% of OT-IR, 18% AVP-IR and 16% CRF-IR neurons, while in the SON it represented 36% of OT-IR and 16% AVP-IR. Catecholaminergic cell groups in the pons (LC) and medulla (VLM, NTS) were also activated by proximal colon distension. Of the TH-IR neurons in VLM and NTS, 74% and 42% respectively were double labeled. These results indicate that colon distension stimulates OT-, AVP- and CRF-containing hypothalamic neurons, likely involved in the integration of colonic sensory information to modulate autonomic outflow and pain-related responses. Activation of medullary catecholaminergic centers might reflect the afferent and efferent limbs of the functional responses associated to visceral pain.

Mesocorticolimbic Glutamatergic Pathway

The mesocorticolimbic dopamine (DA) system plays important roles in reward, motivation, learning, memory, and movement. This system arises from the A10 region, comprising the ventral tegmental area and three adjacent midline nuclei (caudal linear nucleus, interfascicular nucleus, and rostral linear nucleus of the raphe). DAergic and GABAergic neurons are intermingled in this region with recently discovered glutamatergic neurons expressing the vesicular glutamate transporter 2 (VGluT2). Here, we show by in situ hybridization and immunohistochemistry that there are two subpopulations of neurons expressing VGluT2 mRNA in the A10 region: (1) a major subpopulation that expresses VGluT2 but lacks tyrosine hydroxylase (TH; VGluT2-only neurons), present in each nucleus of the A10 region, and (2) a smaller subpopulation that coexpresses VGluT2 and TH (VGluT2-TH neurons). By quantitative real-time PCR, we determined the mRNA copy numbers encoding VGluT2 or TH in samples of individual microdissected TH immunoreactive (IR) neurons. Data from both in situ hybridization and from mRNA quantification showed that VGluT2 mRNA is not present in every TH-IR neuron, but restricted to a subset of TH-IR neurons located in the medial portion of the A10 region. By integration of tract tracing, in situ hybridization, and immunohistochemistry, we found that VGluT2-only neurons and VGluT2-TH neurons each innervate both the prefrontal cortex and the nucleus accumbens. These findings establish that in addition to the well-recognized mesocorticolimbic DA-only and GABA-only pathways, there exist parallel mesocorticolimbic glutamate-only and glutamate-DA pathways.

Estrogenic regulation of dopaminergic neurons in the opportunistically breeding zebra finch

Steroid-induced changes in dopaminergic activity underlie many correlations between gonadal hormones and social behaviors. However, the effects of steroid hormones on the various behaviorally relevant dopamine cell groups remain unclear, and ecologically relevant species differences remain virtually unexplored. We examined the effects of estradiol (E2) manipulations on dopamine (DA) neurons of male and female zebra finches ( Taeniopygia guttata), focusing on numbers of tyrosine hydroxylase-immunoreactive (TH-ir) cells in the A8–A15 cell groups, and on TH colocalization with Fos, conducted in the early A.M., in order to quantify basal transcriptional activity. TH is the rate-limiting enzyme for catecholamine synthesis, and specifically DA in the A8–A15 cell groups. In contrast to other examined birds and mammals, reducing E2 levels with the aromatase-inhibitor Letrozole failed to alter TH-ir neuron numbers within the ventral tegmental area (VTA; A10), while increasing neuron numbers in the central gray (CG; A11) and caudal midbrain A8 populations. Consistent with findings in other birds, but not mammals, we also found no effects of E2 manipulations (Letrozole or Letrozole plus E2 replacement) on TH-Fos colocalization in any location. In accordance with previous observations in both mammals and birds, E2 treatment decreased the number of TH-ir neurons in the A12 population of the tuberal hypothalamus, a cell group that inhibits the release of prolactin. In general, males and females exhibited similar TH-ir neuron numbers, although males exhibited significantly more TH-ir neurons in the A11 CG population than did females. These results suggest partial variability in E2 regulation of DA across species.

Some lumbar sympathetic neurons develop a glutamatergic phenotype after peripheral axotomy with a note on VGLUT 2-positive perineuronal baskets

Glutamate is the main excitatory neurotransmitter in the nervous system, including in primary afferent neurons. However, to date a glutamatergic phenotype of autonomic neurons has not been described. Therefore, we explored the expression of vesicular glutamate transporter (VGLUT) types 1, 2 and 3 in lumbar sympathetic chain (LSC) and major pelvic ganglion (MPG) of naïve BALB/C mice, as well as after pelvic nerve axotomy (PNA), using immunohistochemistry and in situ hybridization. Colocalization with activating transcription factor-3 (ATF-3), tyrosine hydroxylase (TH), vesicular acetylcholine transporter (VAChT) and calcitonin gene-related peptide was also examined. Sham-PNA, sciatic nerve axotomy (SNA) or naïve mice were included. In naïve mice, VGLUT 2-like immunoreactivity (LI) was only detected in fibers and varicosities in LSC and MPG; no ATF-3-immunoreactive (IR) neurons were visible. In contrast, PNA induced upregulation of VGLUT 2 protein and transcript, as well as of ATF-3-LI in subpopulations of LSC neurons. Interestingly, VGLUT 2-IR LSC neurons coexpressed ATF-3, and often lacked the noradrenergic marker TH. SNA only increased VGLUT 2 protein and transcript in scattered LSC neurons. Neither PNA nor SNA upregulated VGLUT 2 in MPG neurons. We also found perineuronal baskets immunoreactive either for VGLUT 2 or the acetylcholinergic marker VAChT in non-PNA MPGs, usually around TH-IR neurons. VGLUT 1-LI was restricted to some varicosities in MPGs, was absent in LSCs, and remained largely unaffected by PNA or SNA. This was confirmed by the lack of expression of VGLUT 1 or VGLUT 3 mRNAs in LSCs, even after PNA or SNA. Taken together, axotomy of visceral and non-visceral nerves results in a glutamatergic phenotype of some LSC neurons. In addition, we show previously non-described MPG perineuronal glutamatergic baskets.

Effects of Chronic, Systemic Treatment with the Dopamine Receptor Agonist R-Apomorphine in Partially Lesioned Rat Model of Parkinson's Disease: An Electrophysiological Study of Substantia Nigra Dopamine Neurons

Previous studies have suggested that R-apomorphine (R-APO), a non-selective dopamine (DA) receptor agonist, has neuroprotective effects in the experimental models of Parkinson's disease (PD). In this study, we investigated the effects of chronic, systemic treatment with R-APO in the firing activity of substantia nigra pars compacta (SNc) DA neurons in 6-hydroxydopamine (6-OHDA) partially lesioned rats. In the 6-OHDA-lesioned rats treated with vehicle, injection of 6-OHDA (20.1 microg) into the striatum produced a partial lesion causing 41% loss of tyrosine hydroxylase-immunoreactive (TH-ir) neurons in the SNc. In the partially lesioned rats, chronic, systemic treatment of R-APO (10 mg/kg/day, s.c., 11 days) attenuated loss of TH-ir neurons in the SNc. The partial lesion of the nigrostriatal pathway and R-APO treatment did not change the firing rate and firing pattern of DA neurons in the SNc of rats. In contrast, the R-APO treatment increased the number of spontaneously active DA neurons of the SNc in the partially lesioned rats, while the lesion decreased the number of spontaneously active DA neurons. In addition, the chronic R-APO treatment decreased the responsiveness of the DA neurons to intravenously administrated R-APO in the partially lesioned rats. These results indicate that chronic, systemic R-APO treatment has the neuroprotective effect, and reverses the decrease in the number of spontaneously active DA neurons in the SNc whereas the treatment induces a reduction in the sensitivity of DA receptors in the SNc to R-APO stimulation in this model.

Changes in vasoactive intestinal peptide and tyrosine hydroxylase immunoreactivity in the brain of nest-deprived native Thai hen

Hyperprolactinemia is associated with incubation behavior and ovarian regression in birds. To investigate the association of prolactin (PRL), vasoactive intestinal peptide (VIP), and dopamine (DA) with the neuroendocrine regulation of incubation behavior, changes in the number of visible VIP-immunoreactive (VIP-ir) neurons in the nucleus inferioris hypothalami (IH) and nucleus infundibuli hypothalami (IN) and tyrosine hydroxylase-immunoreactive (TH-ir) neurons in the nucleus intramedialis (nI) and nucleus mamillaris lateralis (ML) of incubating native Thai hens were compared with those of nest-deprived hens. TH was used as a marker for dopaminergic (DAergic) neurons. Blood samples were collected to determine PRL levels. The localization and the number of visible VIP-ir and TH-ir neurons were determined by immunohistochemistry. Disruption of incubation behavior was accompanied by a precipitous decline in plasma PRL levels. The number of visible VIP-ir neurons in the IH–IN and TH-ir neurons in the nI and ML were high during incubation and decreased when hens were deprived of their nests. This study indicated an association between VIP neurons in the IH–IN and DA neurons in the nI and ML with the degree of hyperprolactinemia, suggesting that the expression of incubation behavior in birds might be, in part, regulated by the DAergic input from the nI and ML to VIP neurons in the IH–IN and subsequent PRL release.

Chronic, systemic treatment with a metabotropic glutamate receptor 5 antagonist produces anxiolytic-like effects and reverses abnormal firing activity of projection neurons in the basolateral nucleus of the amygdala in rats with bilateral 6-OHDA lesions

Although 2-methyl-6-(phenylethynyl)-pyridine (MPEP), a selective metabotropic glutamate receptor 5 antagonist, improves the motor symptoms of Parkinson's disease (PD), the effects of MPEP on the psychiatric symptom of PD and the mechanism involved are still unclear. In the present study, we examined the effects of MPEP in anxiolytic-like behavior and firing activity of projection neurons in the basolateral nucleus of the amygdala (BLA) in rats with 6-hydroxydopamine (6-OHDA) injected bilaterally into dorsal striatum. Rats were divided into three groups, sham-operated group, 6-OHDA lesion with vehicle treatment group and 6-OHDA lesion with MPEP treatment group. Injection of 6-OHDA (10.5 μg) into the dorsal striatum produced 31.5% loss of tyrosine hydroxylase immunoreactive (TH-ir) neurons in the SNpc. The 6-OHDA-lesioned rats showed anxiety behavior and the firing rate of BLA projection neurons decreased significantly compared with sham-operated rats, and no difference was found in the firing pattern of these neurons. Whereas chronic, systemic treatment of MPEP (3 mg/kg/day, i.p.; 14 days) attenuated loss of TH-ir neurons, produced anxiolytic-like effect and normalized the abnormal firing rate of projection neurons of the BLA in rats with the bilateral lesions. Systemic administration of cumulative apomorphine (10–160 μg/kg, i.v.) inhibited the firing rate of BLA projection neurons in sham-operated, 6-OHDA lesion with vehicle-treated and MPEP-treated rats, but the 6-OHDA lesion decreased the response of BLA projection neurons to apomorphine stimulation, while MPEP reversed the reactivity of these neurons. These data demonstrate that the partial lesion of the nigrostriatal pathway causes anxiety symptom and decreases firing rate of BLA projection neurons in the rat. Furthermore, chronic, systemic MPEP treatment has the neuroprotective and anxiolytic-like effects, and reverses the abnormal firing rate of BLA projection neurons, suggesting that MPEP has important implication for the treatment of PD.

Activity of Hypothalamic Dopaminergic Neurones During the Day of Oestrus: Involvement in Prolactin Secretion

A secretory surge of prolactin occurs on the afternoon of oestrus in cycling rats. Pituitary prolactin is inhibited by dopamine. We evaluated the activity of the neuroendocrine dopaminergic neurones during oestrus and dioestrus, as determined by dopaminergic activity in the median eminence and neurointermediate lobe of the pituitary, as well as Fos-related antigen expression in tyrosine hydroxylase (TH)-immunoreactive (ir) neurones of the arcuate nucleus (ARC) and periventricular nucleus (Pe). During oestrus, the 4-dihydroxyphenylacetic acid/dopamine ratio in the median eminence decreased at 16.00 h, coinciding with the increase in plasma prolactin levels. Similarly, the expression of Fos-related antigen in TH-ir neurones of Pe and rostral-, dorsomedial- and caudal-ARC also decreased at 16.00 h. On dioestrus, 4-dihydroxyphenylacetic acid/dopamine ratio in the median eminence and Fos-related antigen expression in TH-ir neurones of Pe and rostral-ARC decreased at 18.00 h, whereas prolactin levels were unaltered. No variation in dopaminergic activity was found in the neurointermediate lobe of the pituitary on either oestrus or dioestrus. The number of TH-ir neurones in the ARC and parameters of dopaminergic activity were found to be generally lower on oestrus compared to dioestrus. The transitory decrease in the activity of neuroendocrine dopaminergic neurones temporally associated with the prolactin surge on the afternoon of oestrus suggests a role for dopamine in the generation of the oestrous prolactin surge.

The exceptional properties of 9‐methyl‐β‐carboline: stimulation, protection and regeneration of dopaminergic neurons coupled with anti‐inflammatory effects

Beta-carbolines (BCs) are potential endogenous and exogenous neurotoxins that may contribute to the pathogenesis of Parkinson's disease. However, we recently demonstrated protective and stimulatory effects of 9-methyl-BC (9-me-BC) in primary dopaminergic culture. In the present study, treatment with 9-me-BC unmasked a unique tetrad of effects. First, tyrosine hydroxylase (TH) expression was stimulated in pre-existing dopa decarboxylase immunoreactive neurons and several TH-relevant transcription factors (Gata2, Gata3, Creb1, Crebbp) were up-regulated. Neurite outgrowth of TH immunoreactive (THir) neurons was likewise stimulated. The interaction with tyrosine kinases (protein kinase A and C, epidermal growth factor-receptor, fibroblast growth factor-receptor and neural cell adhesion molecule) turned out to be decisive for these observed effects. Second, 9-me-BC protected in acute toxicity models THir neurons against lipopolysaccharide and 2,9-dime-BC(+) toxicity. Third, in a chronic toxicity model when cells were treated with 9-me-BC after chronic rotenone administration, a pronounced regeneration of THir neurons was observed. Fourth, 9-me-BC inhibited the proliferation of microglia induced by toxin treatment and installed an anti-inflammatory environment by decreasing the expression of inflammatory cytokines and receptors. Finally, 9-me-BC lowered the content of alpha-synuclein protein in the cultures. The presented results warrant the exploration of 9-me-BC as a novel potential anti-parkinsonian medication, as 9-me-BC interferes with several known pathogenic factors in Parkinson's disease as outlined above. Further investigations are currently under way.

Estrogen Reduces BDNF Level, but Maintains Dopaminergic Cell Density in the Striatum of MPTP Mouse Model

ABSTRACTDegeneration of dopaminergic (DA) axons in the striatum triggers upregulation of striatal trophic activity and striatal DA neuronal number in animal models of Parkinson's disease (PD). The present study investigated the effects of 17β-estradiol (E2) on brain-derived neurotrophic factor (BDNF) expression and the density of DA neurons in the striatum of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) mouse model in correlation with nigrostriatal DA innervation. Adult male C57Bl/6 mice were treated with E2 or vehicle for 11 days. Following 5 days of E2 or vehicle pretreatment, animals were injected with MPTP on day 6. On day 11, all mice were sacrificed, and the striatum were collected and processed for tyrosine hydroxylase (TH) and BDNF immunohistochemistry. Striatal TH-immunoreactive (IR) neurons were counted. Extent of DA innervation and BDNF expression in the striatum were assessed by measuring optical density of TH and BDNF immunoreactivity, respectively. Pretreatment with E2 partially prevented DA denervation and decreased striatal BDNF upregulation triggered by MPTP, but maintained the density of striatal TH-IR neurons to that observed in MPTP group. These findings suggest that estrogen protection of nigrostriatal DA axons against MPTP as well as preservation of the striatal TH-IR cell density in MPTP/E2 mice may be not mediated by BDNF.

Role of neurokinin-1 expressing neurons in the locus coeruleus on ventilatory and cardiovascular responses to hypercapnia

We assessed the role of NK-1 receptors (NK1R) expressing neurons in the locus coeruleus (LC) on cardiorespiratory responses to hypercapnia. To this end, we injected substance P-saporin conjugate (SP-SAP) to kill NK-1 immunoreactive (NK1R-ir) neurons or SAP alone as a control. Immunohistochemistry for NK1R, tyrosine hydroxylase (TH-ir) and Glutamic Acid Decarboxylase (GAD-ir) were performed to verify if NK1R-expressing neurons, catecholaminergic and/or GABAergic neurons were eliminated. A reduced NK1R-ir in the LC (72%) showed the effectiveness of the lesion. SP-SAP lesion also caused a reduction of TH-ir (66%) and GABAergic neurons (70%). LC SP-SAP lesion decreased by 30% the ventilatory response to 7% CO(2) and increased the heart rate (fH) during hypercapnia but did not affect MAP. The present data suggest that different populations of neurons (noradrenergic, GABAergic, and possibly others) in the LC express NK1R modulating differentially the hypercapnic ventilatory response, since catecholaminergic neurons are excitatory and GABAergic ones are inhibitory. Additionally, NK1R-ir neurons in the LC, probably GABAergic ones, seem to modulate fH during CO(2) exposure, once our previous data demonstrated that catecholaminergic lesion does not affect this variable.

PACAP Expression in Explant Cultured Mouse Major Pelvic Ganglia

The major pelvic ganglia (MPG) contain both parasympathetic and sympathetic postganglionic neurons and provide much of the autonomic innervation to urogenital organs and components of the lower bowel. Whereas many parasympathetic neurons were found to express vasoactive intestinal polypeptide (VIP), no MPG neurons exhibited immunoreactivity for pituitary adenylate cyclase-activating polypeptide (PACAP). However, in 3-day cultured MPGs, numerous PACAP-IR cells and nerve fibers were present, and transcript levels for PACAP increased significantly. In 3-day cultured MPGs, PACAP immunoreactivity was seen in cells that were also immunoreactive for VIP or neuronal nitric oxide synthase, but not tyrosine hydroxylase, indicating that PACAP expression occurred preferentially in MPG parasympathetic postganglionic neurons. Transcript levels for the VPAC2, but not VPAC1 or PAC1 receptor, also increased significantly following 3days in culture. Transcript levels of activating transcription factor 3 (ATF-3), a marker of cellular injury, were increased 64-fold in 3-day explants, and ATF-3-IR nuclei were evident in both TH-IR and nNOS-IR neurons as well as in non-neuronal cells. In sum, these results demonstrate that, although only the parasympathetic neurons in explant cultured MPGs increase expression of PACAP, both sympathetic and parasympathetic postganglionic neurons in the cultured MPG whole-mount increase expression of ATF-3.

Early life protein restriction alters dopamine circuitry

Adverse prenatal environment, such as intrauterine growth retardation (IUGR), increases the risk for negative neurobehavioral outcomes. IUGR, affecting approximately 10% of all US infants, is a known risk factor for attention deficit hyperactivity disorder (ADHD), schizophrenia spectrum disorders and addiction. Mouse dams were fed a protein deficient (8.5% protein) or isocaloric control (18% protein) diet through pregnancy and lactation (a well validated rodent model of IUGR). Dopamine-related gene expression, dopamine content and behavior were examined in adult offspring. IUGR offspring have six to eightfold over-expression of dopamine (DA)-related genes (tyrosine hydroxylase (TH) and dopamine transporter) in brain regions related to reward processing (ventral tegmental area (VTA), nucleus accumbens, prefrontal cortex (PFC)) and homeostatic control (hypothalamus), as well as increased number of TH-ir neurons in the VTA and increased dopamine in the PFC. Cyclin-dependent kinase inhibitor 1C (Cdkn1c) is critical for dopaminergic neuron development. Methylation of the promoter region of Cdkn1c was decreased by half and there was a resultant two to sevenfold increase in Cdkn1c mRNA expression across brain regions. IUGR animals demonstrated alterations in dopamine-dependent behaviors, including altered reward-processing, hyperactivity and exaggerated locomotor response to cocaine. These data describe significant dopamine-related molecular and behavioral abnormalities in a mouse model of IUGR. This animal model, with both face validity (behavior) and construct validity (link to IUGR and dopamine dysfunction) may prove useful in identifying underlying mechanisms linking IUGR and adverse neurobehavioral outcomes such as ADHD.

Comparative anatomy of the locus coeruleus in humans and nonhuman primates

The locus coeruleus (LC) is a dense cluster of neurons that projects axons throughout the neuroaxis and is located in the rostral pontine tegmentum extending from the level of the inferior colliculus to the motor nucleus of the trigeminal nerve. LC neurons are lost in the course of several neurodegenerative disorders, including Alzheimer's and Parkinson's diseases. In this study we used Nissl staining and tyrosine hydroxylase (TH) immunoreactivity to compare the human LC with that of closely related primate species, including great and lesser apes, and macaque monkeys. TH catalyzes the initial and rate-limiting step in catecholamine biosynthesis. The number of TH-immunoreactive (TH-ir) neurons was estimated in each species using stereologic methods. In the LC of humans the mean total number of TH-ir neurons was significantly higher compared to the other primates. Because the total number of TH-ir neurons in the LC was highly correlated with the species mean volume of the medulla oblongata, cerebellum, and neocortical gray matter, we conclude that much of the observed phylogenetic variation can be explained by anatomical scaling. Notably, the total number of LC neurons in humans was most closely predicted by the nonhuman allometric scaling relationship relative to medulla size, whereas the number of LC neurons in humans was considerably lower than predicted according to neocortex and cerebellum volume.

Localization of tyrosine hydroxylase immunoreactive neurons in the forebrain of the guppy Poecilia reticulata

The current study reports for the first time the distribution of tyrosine hydroxylase immunoreactive (TH-ir) neurons in the forebrain of the guppy Poecilia reticulata. Numerous small TH-ir neurons were observed in the olfactory bulbs, located mainly in the periphery of the bulbs. The TH-ir telencephalic neurons are localized in the ventral telencephalic area where they are grouped in three distinct nuclei (Vv,Vd and Vp) composed of a small number of cells forming a continuous strip. The largest number of forebrain TH-ir neurons was observed in the diencephalon where both small and larger neurons are present. Diencephalic TH-ir neurons are subdivided in large nuclei located in the preoptic region (nSC, nPOp and nPOm), the thalamus (nDM), the pretectal region (nPPv and nAP), the hypothalamus (nPP and nRP) and the posterior tuberculum (nPT). Many diencephalic nuclei are distributed in periventricular regions and no TH-ir cells were observed in the paraventricular organ. A comparative analysis indicates that the present observations are consistent with the general pattern of TH-ir neurons distribution reported for the forebrain of other teleosts, but with some interspecies variability present, mainly in the diencephalon. This paper also provides valuable neuroanatomical information for P. reticulata, a teleost frequently used in toxicological tests, for future studies investigating the effects of environmental pollutants on the catecholaminergic system.

Effects of epigallocatechin gallate on rotenone-injured murine brain cultures

Green tea polyphenol epigallocatechin-3-gallate (EGCG) is reported to have antioxidant abilities and to counteract beneficially mitochondrial impairment and oxidative stress. The present study was designed to investigate neuroprotective effects of EGCG on rotenone-treated dissociated mesencephalic cultures and organotypic striatal cultures. Rotenone is a potent inhibitor of complex I of the respiratory chain, which in vitro causes pathological and neurochemical characteristics of diseases in which mitochondrial impairment is involved, e.g., Parkinson's disease. Treatment with EGCG (0.1, 1, 10 muM) alone had no significant effects on mesencephalic cultures. In striatal slice cultures, EGCG led to a significant increase of propidium iodide (PI) uptake and 4-amino-5-methylamino-2',7'-difluorofluorescein diacetate (DAF-FM), but not dihydroethidium (DHE) fluorescence intensity. Rotenone (20 nM on the eighth DIV for 48 h) significantly decreased the numbers and the neurite lengths of TH ir neurons by 23 and 34% in dissociated mesencephalic cell cultures compared to untreated controls. Exposure of striatal slices to rotenone (0.5 mM for 48 h) significantly increased PI uptake, and DAF-FM and DHE fluorescence intensities by 41 and 136 and 19%, respectively, compared to controls. Against rotenone, in dissociated mesencephalic cultures, EGCG produced no significant effect on either the number or neurite lengths of THir neurons compared to rotenone-treated cultures, but EGCG significantly decreased PI uptake by 19% and DAF-FM fluorescence intensity by 19 and 58%, respectively, compared to increase in rotenone-exposed striatal slices. On the other hand, EGCG did not affect superoxide (O(2) (-)) formation as detected with DHE. These data indicate that EGCG slightly protects striatal slices by counteracting nitric oxide (NO(.)) production by rotenone. In conclusion, EGCG partially protects striatal slices but not dissociated cells against rotenone toxicity.