Prenatal administration of lipopolysaccharide induces sex-dependent changes in glutamic acid decarboxylase and parvalbumin in the adult rat brain.

RATIONALE: Recent clinical studies suggest GABA-ergic system abnormalities as a neuropathological mechanism of schizophrenia. OBJECTIVES: In the present study, we examined the effect of chronic prenatal lipopolysaccharide (LPS) administration on immunohistochemical changes of glutamate decarboxylase (GAD67) and parvalbumin (PV)-expressing neurons in the medial prefrontal cortex and hippocampus of rats. RESULTS: These data demonstrated that prenatal LPS administration during the final 2 weeks of pregnancy induced schizophrenia-like behavioral symptoms, such as deficits in sensorimotor gating (prepulse inhibition) and impairments in social interactions and exploration, in adult offspring. Moreover, immunohistochemical analysis revealed that in our neurodevelopmental model of schizophrenia, decreases in the total number of PV- and GAD67-positive neurons in the medial prefrontal cortices of adult females prenatally exposed to LPS were observed, whereas these immunochemical changes were primarily detected in the hippocampus of males. Additionally, a decrease in PV-labeled axon terminals of GABA-ergic cells, likely reflecting the perisomatic inhibitory innervation of pyramidal neurons, was observed in the medial prefrontal cortices in both sexes. CONCLUSION: This study provided evidence of a key role for the GABA system in neurodevelopment associated with the etiopathogenesis of schizophrenia and showed that the observed changes are sex-dependent. Moreover, this study is the first to present a model of schizophrenia based on prenatal LPS administration, which not only produced behavioral abnormalities but also changed the cytoarchitecture of the GABA inhibitory system.

Cocaine enhances ST8SiaII mRNA expression and neural cell adhesion molecule polysialylation in the rat medial prefrontal cortex.

The present study investigated whether cocaine (COC) administration evokes changes in the mRNA and protein levels of neural cell adhesion molecule (NCAM) and polysialylated neural cell adhesion molecule (PSA-NCAM) in the medial prefrontal cortex (mPFC) of rats. NCAM/PSA-NCAM is required for neuronal structural plasticity and is constitutively expressed in the mPFC. Rats were treated with a single dose of COC (15 mg/kg, i.p.), and mRNA levels of NCAM and the polysialyltransferases ST8SiaII and ST8SiaIV, enzymes involved in polysialylation of NCAM, were measured at 3, 6 and 24 h after COC treatment. At the same time points, the protein levels of NCAM and PSA-NCAM were measured via western blotting. Acute COC injection did not affect mRNA levels of NCAM and ST8SiaIV, but it increased the mRNA level of ST8SiaII 3 h after injection. At the same time point, an increase in PSA-NCAM, but not in NCAM, protein was observed. Morphological studies of PSA-NCAM protein expression patterns (immunocytochemistry/stereology) performed 3 h after COC administration revealed an enhancement of PSA-NCAM immunostaining in perisomatic-like sites and in the length density of PSA-NCAM-positive neuropil. Double immunofluorescence staining showed that PSA-NCAM perisomatic-like sites surround excitatory neurons. We also observed that a single injection of raclopride (0.4 mg/kg) or SCH 23390 (0.5 mg/kg), D2/D3 and D1 dopamine receptors antagonists, respectively, which were ineffective when given alone, abolished the effects of COC administration on mRNA and protein expression. The data in the present study indicate that COC administration may modify constitutive synaptic plasticity in the mPFC by increasing the NCAM polysialylation in perisomatic innervations of pyramidal neurons via activation of dopamine D1 and D2/D3 receptors.

The impact of maternal separation on the number of tyrosine hydroxylase-expressing midbrain neurons during different stages of ontogenesis.

Early life stressors have life-long functional and anatomical consequences. Though many neurotransmitters are involved in the functional impact of early life stress, dopamine seems to be important because of its roles in motor control, adaptation to stressful conditions, mood, cognition, attention and reward. Thus, in the present study, we investigated the way that early life stress, in the form of maternal separation (MS), affects the populations of tyrosine hydroxylase-immunoreactive (TH-IR) dopaminergic neurons in rat midbrain structures during ontogenesis. We included in the study the sub-regions of the substantia nigra (SN) and the ventral tegmental area (VTA). In both the control and MS rats, we found that the estimated total number of TH-expressing neurons fluctuated during ontogenesis. Moreover, MS influenced the number of TH-IR cells, especially in the SN pars reticulata (SNr) and VTA. Shortly after the termination of MS, on postnatal day (PND) 15, a decrease in the estimated total number of TH-IR neurons was observed in the SNr and VTA (in both males and females). On PND 35, MS caused a transient increase in the number of TH-IR cells only in the SNr of female rats. On PND 70, MS affected the number of TH-IR neurons in the VTA of females; specifically, an increase in the number of these cells was observed. Additionally, MS did not alter TH-IR cell sizes or the total levels of TH (measured by Western blot analysis) in the SN and VTA for all stages of ontogenesis in both males and females. The results from the study herein indicate that early life stress has enduring effects on the populations of midbrain TH-expressing dopaminergic neurons (especially in female rats), which are critically important for dopamine-regulated brain function throughout ontogenesis.

Prenatal lipopolysaccharide treatment enhances MK-801-induced psychotomimetic effects in rats.

The aim of this study was to evaluate the effect of prenatal lipopolysaccharide (LPS) treatment, which is an animal developmental model of schizophrenia, on MK-801-induced psychotomimetic behavioral changes and brain aminergic system activity in adult offspring. Repeated LPS (1 mg/kg) injection in rats, that had started from 7th day of pregnancy and was continued every second day till delivery, resulted in a long-lasting disruption of prepulse inhibition (PPI) and elevation of locomotor activity in their offspring. The prenatally LPS-treated rats showed hypersensitivity to MK-801 (0.1 and 0.4 mg/kg) as evidenced by the enhancement of acoustic startle amplitude, reduced PPI, and enhanced locomotor activity. These behavioral changes were accompanied by a decrease in the dopamine and its metabolite, DOPAC concentration in the frontal cortex, enhanced dopaminergic system activity in the striatum and no changes in noradrenaline (NA) level. Furthermore, the significant augmentation of 5-HT and 5-HIAA content in the frontal cortex of females only was detected. No changes in the cortical NA tissue level were found. Summing up, the present study demonstrated that the activation of the immune system in prenatal period led to persistent behavioral hypersensitivity to psychotomimetic action of a non-competitive NMDA receptor antagonist, and attention/information processing deficits. The foregoing data indicate that prenatal administration of LPS model some of the clinical aspects of schizophrenia and these behavioral effects are connected with neurochemical changes.

Maternal separation affects the number, proliferation and apoptosis of glia cells in the substantia nigra and ventral tegmental area of juvenile rats.

Adverse early life experiences can increase the risk of psychiatric and neurological disorders as the result of interference with brain development and maturation. In the present study, we tested whether early life stress, that is, maternal separation (MS), affects cell number, cell proliferation and constitutive apoptotic processes in the substantia nigra (SN) and the ventral tegmental area (VTA) of juvenile male and female rats. It was found that MS decreased the total number of glia but not neuronal cells in the SN pars compacta (SNc) and VTA of males. Moreover, MS reduced the number of S-100ß-immunoreactive (IR) glial cells in the SN of females and in the VTA of males. It was also observed that MS decreased the rate of proliferation (as measured by Ki-67-immunoreactivity) in the SN pars reticulata (SNr) and VTA of both males and females. Additionally, MS reduced the number of TUNEL-positive cells in the SNc of both males and females and in the SNr and VTA of males only. Moreover, MS decreased the number of cleaved caspase-9-IR cells in the SN and VTA of male rats. Cleaved caspase-9 was present in microglia cells, which exhibited the morphological hallmarks of apoptosis, but not in neuronal, astrocytic or oligodendrocytic cells. On the contrary, MS increased the number of cleaved caspase-3-IR cells in the SN and VTA of both male and female rats. Cleaved caspase-3-IR cells did not display signs of apoptosis and had an astrocytic phenotype (S-100ß-IR). In males exposed to MS, a decrease in caspase-3 enzymatic activity in the SN was also observed. In summary, the results of the present study revealed that early life stress affects the number, proliferation and naturally occurring apoptosis of glia cells in the SN and VTA in a sex-dependent manner and consequently may impair brain functions that are regulated by these structures.

5-HT1A receptors mediate detrimental effects of cocaine on long-term potentiation and expression of polysialylated neural cell adhesion molecule protein in rat dentate gyrus.

The present study investigated the involvement of 5-HT(1A) receptors in the inhibitory effect of single administration of cocaine (COC, 15 mg/kg i.p.) on the induction of long-term potentiation (LTP) in slices of rat dentate gyrus (DG), prepared 30 min and 2 days after COC administration. These effects of COC were blocked by an antagonist of 5-HT(1A) receptors, WAY 100635 (0.4 mg/kg i.p.), which had been administered 20 min before COC. The detrimental effect of COC on LTP in slices prepared 30 min after COC administration could be prevented by blocking glucocorticoid receptors (GRs) using mifepristone (RU 38486, 10 mg/kg s.c. given 1 h before COC), similar as in slices obtained 2 days after COC as reported previously [Mackowiak et al. (2008) Eur J Neurosci 27:2928-2937]. After a single administration of an agonist of 5-HT(1A) receptors, 8-OH-DPAT, (0.5 mg/kg i.p.), the level of LTP in slices prepared 2 days later was significantly decreased resembling the effect of COC. This effect of 8-OH-DPAT was antagonized by WAY 100635 (0.4 mg/kg i.p.), administered 20 min before 8-OH-DPAT and by RU 38486, given 1 h before 8-OH-DPAT. COC-induced inhibition of LTP could be blocked by the inhibitor of mitogen-activated protein kinase kinase 1/2 (MEK1/2), SL 327 (50 mg/kg i.p.), administered 1 h before COC, but not by the inhibitor of phosphatidylinositol 3-kinase (PI3-kinase), LY 294002 (80 mg/kg i.p.). COC-induced reduction in the number of polysialylated neural cell adhesion molecule (PSA-NCAM)-positive neurons in rat dentate gyrus could also be prevented by WAY 100635, given 20 min before COC. These data indicate that the indirect 5-HT(1A) receptor activation by a single COC administration and subsequent stimulation of extracellular signal-regulated kinases (ERK 1/2) signaling pathway result in a decrease of the potential for long-term increase in synaptic efficacy in rat DG lasting at least two but less than 7 days, most likely via activation of the hypothalamic-pituitary-adrenal (HPA) axis.

Activation of CB1 cannabinoid receptors impairs memory consolidation and hippocampal polysialylated neural cell adhesion molecule expression in contextual fear conditioning.

We investigated the role of CB1 receptors in hippocampal-dependent memory consolidation mediated by polysialylated neural cell adhesion molecule (PSA-NCAM) during contextual fear conditioning (CFC). The CB1 receptor agonist 3-(1,1-dimethylheptyl)-(-)-11-hydroxy-Delta(8)-tetrahydrocannabinol (HU-210) (0.1 mg/kg) was given immediately after training during the memory consolidation phase, and freezing behavior was measured 24 h after conditioning. Administration of HU-210 attenuated freezing behavior measured in CFC. Western blot analysis showed that CFC induced a decrease in the expression of NCAM-180, but did not change the level of NCAM-140 and increased PSA-NCAM expression measured 24 h after training in the rat hippocampus. HU-210 (0.1 mg/kg) injection did not affect the reduction in NCAM-180 levels induced by CFC, but it blocked the increase in PSA-NCAM expression. Since the dentate gyrus (DG) of the hippocampus is known to be involved in memory consolidation and expresses a high level of PSA-NCAM protein, we measured the effects of CFC and HU-210 administration on PSA-NCAM-immunoreactive (IR) cells in the DG. CFC caused an increase in the number of PSA-NCAM-IR cells in the DG, but not K(i)-67- or doublecortin (DCX)-IR cells. This increase in PSA-NCAM-IR cells was abolished by HU-210 injection. Administration of the CB1 receptor antagonist N-(piperidin-1-yl)-5-(4-iodophenyl)-1-(2,4-dichlorophenyl)-4-methyl-1H-pyrazole-3-carboxamide (AM-251) (3 mg/kg immediately before HU-210) inhibited the effects of HU-210 on freezing behavior and PSA-NCAM expression in the DG. These results indicate that activation of CB1 receptors disturbs consolidation of fear memory in CFC, likely by affecting PSA-NCAM expression in the DG, which plays an important role in synaptic rearrangement during the formation of memory traces.

Dopamine D1-like receptors agonist SKF 38393 increases cFOS expression in the paraventricular nucleus of the hypothalamus--impact of acute and chronic cocaine.

The present study indicates that activation of dopamine D1-like receptors by administration of SKF 38393 leads to dose-dependent (doses: 5, 10 and 20 mg/kg) increases in the expression of cFos proteins in the rat paraventricular nucleus of the hypothalamus (PVN). This effect was abolished by administration of SCH 23390, a dopamine D1-like receptor antagonist (0.5 and 1 mg/kg, given 30 min before SKF 38393--10 mg/kg), suggesting that the apparent effect is specific for activation of dopamine D1-like receptors. Expression of cFos after SKF 38393 (10 mg/kg) was observed in some, but not all, CRF-immunoreactive neurons, as well as in small portion of oxytocin- but not vasopressin-immunoreactive neurons (double-immunofluorescence experiments). There were also certain populations of nuclei that showed expression of cFos but did not co-localize with the above markers. We also found that both acute and repeated (once daily for 5 consecutive days) exposure to cocaine (25 mg/kg) attenuated the induction of cFos expression triggered by SKF 38393 when administered 24 hours after single or the last dose of cocaine (25 mg/kg). Attenuation was observed at the same level after single and chronic exposure to cocaine, indicating a rapid functional down-regulation of dopamine D1-like receptors that are resistant to subsequent doses of cocaine. These data provide evidence for the functional role of dopamine D1-like receptors in the PVN and indicate a functional adaptation of dopamine D1-like receptors following a single dose of cocaine without further progression of adaptation or resistance of D1-like receptor-mediated genomic function in the course of repeated cocaine intake.

A search for colocalization of serotonin 5-HT2A and 5-HT1A receptors in the rat medial prefrontal and entorhinal cortices--immunohistochemical studies.

Recently developed antipsychotic drugs ameliorating the negative symptoms of schizophrenia act not only on dopamine D2 receptors but also on serotonin 2A (5-HT2A) and 1A (5-HT1A) receptors in specific regions of the cerebral cortex. Since it is not yet known whether serotonin 5-HT1A and 5-HT2A receptors coexist in the same population of neurons in the cortex, the present study investigated their colocalization in the rat medial prefrontal (MPC) and entorhinal (EC) cortices. Using antibodies that recognize epitopes specific to the serotonin 5-HT2A or 5-HT1A receptors, studies employing confocal microscopy have shown that in the MPC 5-HT2A receptors are preferentially, if not exclusively, present on the pyramidal neurons and that 5-HT1A-immunopositive material is present in the axonal hillocks and, to lower extend, in cytoplasm of presumably pyramidal cell bodies. With the regard of labeling of active receptors (i.e. present in shafts and axonal hillocks) we found that about 38% of neurons positive for the presence of serotonin 5-HT2A receptors, are also positive for serotonin 5-HT1A receptors in the MPC. In the EC, only 22% of serotonin 5-HT2A-positive neurons were positive for serotonin 5-HT1A receptor-immunoreactivity. In the respect of cytoplasmatic serotonin 5-HT1A receptor-immunoreactivity (possibly inactive receptors), 65% and 73% of serotonin 5-HT2A receptor-positive neurons were colocalized with serotonin 5-HT1A receptors in the MPC and EC, respectively. Data obtained on serotonin 5-HT2A and 5-HT1A receptor localization provide anatomical grounds for at least three distinct populations of pyramidal neurons, one governed only by 5-HT2A, one only by 5-HT1A and one by both types of serotonin receptors.

Impact of postnatal blockade of N-methyl-D-aspartate receptors on rat behavior: a search for a new developmental model of schizophrenia.

The malfunction of glutamatergic neurotransmission in the neonatal or postnatal periods may be a risk factor for the appearance of neuroanatomical, neurochemical or functional changes that are characteristic of schizophrenia. Thus, the present study was undertaken to investigate whether blockade of N-methyl-d-aspartate (NMDA) receptors in the postnatal period influences rat behavior in tests characterizing schizophrenia-like deficits such as psychomotor agitation, impairments of sensorimotor gating, working memory, and intensity of social interactions. (E)-2-amino-4-methyl-5-phosphono-3-pentenoic acid (CGP 40116), a competitive antagonist of NMDA receptors, was given postnatally (1.25 mg/kg on days 1, 3, 6, 9; 2.5 mg/kg on days 12, 15, 18; and finally 5 mg/kg on day 21, all injections s.c.), and rats were tested at 60 days old. We found that blockade of NMDA receptors in the postnatal period led to an enhancement of exploration, mimicking psychomotor agitation, impairments in sensorimotor gating as measured by a prepulse-evoked inhibition of acoustic startle response, and an impaired working memory, as measured by an increase in the latency to achieve accurate rate of response in the delayed alternation task. Decreases in non-aggressive social interactions and increases in aggressive interactions were also observed. In addition to cognitive deficits typical of schizophrenia, rats treated postnatally with NMDA receptor antagonists also showed higher level of fear exhibited in the elevated plus maze. Thus, the blockade of NMDA receptors in the postnatal period may model deficits that are characteristic of schizophrenia.

Glutamatergic neurons of rat medial prefrontal cortex innervating the ventral tegmental area are positive for serotonin 5-HT1A receptor protein.

The present study was designed to investigate whether serotonin 5-HT1A receptor protein (5-HT1A receptor-immunoreactivity), is present on cortical pyramidal neurons of the rat medial prefrontal cortex (MPC) innervating the ventral tegmental area (VTA). Recent data stress the role of serotonin 5-HT1A receptors in the pathology of schizophrenia, and in the mechanism of action of novel antipsychotic drugs. It was found that approximately 52% of cells in layers II/III of the MPC whose axons initial segments were immunoreactive for serotonin 5HT1A receptor were also labeled with Fluoro-Gold (FG), a retrograde tracer injected into the VTA, indicating that certain portion of neurons forming glutamatergic innervations of the VTA may be controlled by serotonin 5-HT1A receptors. In deep cortical layers (V/VI) retrogradely labeled neurons never colocalized with serotonin 5-HT1A receptormmunoreactivity. These anatomical data indicate that serotonin 5-HT1A receptors might potentially control the excitability and propagation of information transmitted by the pyramidal cells to the VTA. Moreover, our results indicate that the drugs operating via serotonin 5-HT1A receptors in the MPC, might control from this level the release of glutamate in the VTA and restore function of glutamate neurotransmission, whose dysfunction is observed for example in schizophrenia.

Blockade of NMDA receptors in postnatal period decreased density of tyrosine hydroxylase immunoreactive axonal arbors in the medial prefrontal cortex of adult rats.

Malfunction of glutamatergic neurotransmission in postnatal period is considered to be a risk factor for development of schizophrenia. Thus, the present study investigates the impact of NMDA receptor blockade in the postnatal period on the density of tyrosine hydroxylase immunoreactive axonal arbors in the rat medial prefrontal cortex. Behavioral experiments revealed that adult rats (60 days old) treated in the postnatal period with a competitive antagonist of NMDA receptors, CGP 40116 (1.25 mg/kg on days 1, 3, 6, 9; 2.5 mg/kg on days 12, 15, 18; and finally 5 mg/kg on day 21, all injections s.c.), showed enhancement of the locomotor activity stimulated by quinpirole (0.3 mg/kg s.c.) and amphetamine (0.5 mg/kg s.c.), which suggests development of functional supersensitivity of dopaminergic systems. It has been found that CGP 40116, given in postnatal period decreased the density of tyrosine hydroxylase immunoreactive axonal arbors in the medial prefrontal cortex of adult animals. The decrease was observed in superficial (II/III) and deep (V/VI) layers of the medial prefrontal cortex, while the average length of tyrosine hydroxylase immunoreactive axonal arbors was increased in both superficial and deep cortical layers. Changes in the density of tyrosine hydroxylase immunoreactive axonal arbors have not been followed by a significant decrease in the content of tyrosine hydroxylase protein measured by Western blot. Thus, NMDA receptor blockade in the early period of life evokes changes in architecture of tyrosine hydroxylase immunoreactive axonal arbors and that malfunction of glutamatergic neurotransmission, in early period of life may produce anatomical changes which resemble those observed in the brains of schizophrenics.

Behavioral pharmacology of sigma-ligands.

Sigma (sigma) receptors, first defined as a subclass of opioid receptors, later confounded with the high affinity phencyclidine (PCP) binding sites, now are regarded as unique binding sites, distinct from opiate and PCP receptors, and related to higher brain function. The investigation of functional significance of sigma receptors in the brain has been hampered for many years by relative lack of specific tool drugs and by the unavailability of their coherent classification into postulated agonists and antagonists. However, a potential involvement of sigma receptors in psychotic disorders was first suggested soon after their discovery. The sigma receptors are classified into two subtypes, sigma (1) and sigma (2) receptors, of which the first was recently cloned from rodent and human tissues while the second has not yet been fully characterized. Although the precise mechanism of the functional response of these receptors is still uncertain, it is accepted that sigma receptors can modulate a number of central neurotransmitter systems, including noradrenergic, glutamatergic and dopaminergic ones. The sigma receptors have been postulated to be involved in numerous pharmacological and physiological functions, including motor disorders, psychotic disorders, neuroprotective mechanisms. In the last years, a number of compounds with a high affinity and selectivity for sigma binding sites have been discovered and investigated for their therapeutic potential. In this review, we try to summarize the behavioral effects of sigma receptor ligands that have been described, and their activity in animal models related to some brain disorders, especially schizophrenia and affective disorders.

DOI, an agonist of 5-HT2A/2C serotonin receptor, alters the expression of cyclooxygenase-2 in the rat parietal cortex.

The hallucinogenic effect of DOI, serotonin 5-HT2A/2C receptor agonist, is known to be associated with the activation of cortical 5-HT2 receptors. However, the effect of DOI on excitability of cortical neurons and their subsequent function is still not quite understood. Previous immunohistochemical studies using Fos proteins expression as a marker of neuronal activity showed the involvement of arachidonic acid cascade, particularly cyclooxygenase metabolic pathway, in DOI-induced Fos proteins expression in the rat parietal cortex. DOI increases arachidonic acid release which is transformed itself via acceleration of cyclooxygenase metabolic pathway to biologically active metabolites, such as prostaglandins and thromboxanes. Since cyclooxygenase-2 (COX-2) expression correlates with neuronal activity, it was of interest to investigate whether DOI is capable of influencing the level of COX-2 protein and mRNA expression in the rat parietal cortex. It was observed that neurons which were positive for 5-HT2A receptors showed constitutive COX-2 immunoreactivity. It was found further, that COX-2 protein level was increased at 1 h, and returned to the control level at 3 and 6 h after DOI (5 mg/kg) administration. In contrast, DOI decreased the COX-2 mRNA expression at all tested time points (1 h, 3h and 6h after DOI treatment). The obtained results further support the suggestion that COX-2 activation and possibly arachidonic acid metabolites generated by COX-2 may be considered as important mediators of functional responses generated by activation of cortical 5-HT2A/2C receptors.

A search for colocalization of mglula receptors with CRF or NPY in the rat brain amygdala.

Excitatory neurotransmitter glutamate, as well as corticoliberin (CRF) and neuropeptide Y (NPY) play an important role in fear and anxiety. Among the brain structures engaged in these effects the important one is amygdala. In the present study, a single and double immunohistochemical staining techniques were used in order to visualize CRF, NPY and metabotropic glutamate receptors (mGluR1a) in rat amygdala. MGluR1a belongs to class of postsynaptic excitatory receptors and has a preferable somatic localization. CRF and NPY were localized using rabbit polyclonal antibodies, and mGluR1a using a mouse monoclonal one. Then, ABC-peroxidase and DAB or benzidine were used. Upon single immunostaining, NPY and CRF were found in some nerve cell bodies and fibres in the amygdala. The immunoreactivity of mGluR1 a was observed in some nerve cells, processes and fibres, especially on the border between the central and the basolateral nuclei and ventrally to that region. Double staining revealed mGluR1 a-IR on some CRF- and NPY-immunoreactive nerve cell bodies and processes. The obtained results indicate that mGlu1a receptors may control at least some NPY and CRF neurons in the amygdala.

Effects of imidazoline antihypertensive drugs on sympathetic tone and noradrenaline release in the prefrontal cortex.

1. The aim of the present study was to compare the effects of the centrally acting antihypertensive drugs rilmenidine, moxonidine, clonidine and guanabenz on sympathetic tone with their effects on noradrenaline release in the cerebral cortex. In particular, the hypothesis was tested that rilmenidine and moxonidine, due to their high affinity for sympatho-inhibitory imidazoline I(1) receptors and low affinity for alpha(2)-adrenoceptors, lower sympathetic tone without causing an alpha(2)-adrenoceptor-mediated inhibition of cerebrocortical noradrenaline release. 2. In rats anaesthetized with urethane, blood pressure and heart rate were measured and the concentration of noradrenaline in arterial blood plasma was determined. The release of noradrenaline in the medial prefrontal cortex was estimated by microdialysis. Intravenous administration of rilmenidine (30, 100, 300 and 1000 microg kg(-1)), moxonidine (10, 30, 100 and 300 microg kg(-1)), clonidine (1, 3, 10 and 30 microg kg(-1)) and guanabenz (1, 3, 10 and 30 microg kg(-1)) led to dose-dependent hypotension and bradycardia; the plasma noradrenaline concentration also decreased. After the two highest doses, all four drugs lowered noradrenaline release in the prefrontal cortex. At doses eliciting equal hypotensive and sympatho-inhibitory responses, rilmenidine and moxonidine inhibited cerebral cortical noradrenaline release at least as much as clonidine and guanabenz. 3. The results show that rilmenidine and moxonidine lower cerebrocortical noradrenaline release at doses similar to those which cause sympatho-inhibition. This effect was probably due to an alpha(2)-adrenoceptor-mediated inhibition of the firing of locus coeruleus neurons and, in addition, to presynaptic inhibition of noradrenaline release at the level of the axon terminals in the cortex. The results argue against the hypothesis that rilmenidine and moxonidine, due to their selectivity for sympatho-inhibitory I(1) imidazoline receptors, do not suppress noradrenergic neurons in the central nervous system.

Immunohistochemical evidence for localization of NMDAR1 receptor subunit on dopaminergic neurons of the rat substantia nigra, pars compacta.

Non-fluorescent, double-labeling techniques were used in order to investigate whether NMDAR1 receptor subunits are localized on dopaminergic (i.e. tyrosine hydroxylase-positive) neurons of the rat substantia nigra, pars compacta. It has been found that NMDAR1 receptor subunits are highly abundant in the pars compacta neurons and their dendritic processes. It was also found that vast majority, if not all, of pars compacta neurons which are positive for the presence of NMDAR1 receptor subunits are dopaminergic ones. It is concluded that if NMDAR1 receptor subunits, an indispensable element of functional NMDA receptor ion channel complex, is co-assembled with other subunits of NMDA receptor ion channel complex, NMDA receptors might directly control the activity of dopaminergic neurons.

[The involvement of 5-HT1a serotonin receptors in the pathophysiology and pharmacotherapy of schizophrenia]. / Udzial receptorów serotoninowych 5-HT1A w patofizjologii i farmakoterapii schizofrenii.

Many studies of schizophrenic brains indicate the dysfunction of dopamine and glutamate systems in the prefrontal and frontal cortex. It seems that better understanding of mechanisms regulating functions of these neuronal cortical systems could contribute to creation of new drugs acting in the cortex selectively. This might be profitable in cognition of dysfunction and negative symptoms in schizophrenia. This article presents preclinical data concerning the role of 5-HT1A serotonin receptors in the modulation of cortical dopamine system and in psychotomimetic effects of non-competitive NMDA receptor antagonists. Neurochemical studies have shown that 5-HT1A receptor agonists increase dopamine release in the rat prefrontal cortex on the one hand, and they inhibit the augmentation of dopamine release induced by stress or amphetamine, on the other. However, the increase of dopamine release induced by non-competitive NMDA receptor antagonists is blocked by 5-HT1A receptor antagonists. Blockade of 5-HT1A receptors seems to be important also in reduction of most psychotomimetic effects induced by non-competitive NMDA antagonists both involving (locomotor hyperactivity, working memory impair) and not involving (sensorimotor gating deficits) dopamine mechanism. Thus, binding with 5-HT1A receptors can be an important site for the regulation of cortical dopamine system, both in physiological conditions and in disregulation of the system induced by stress, psychostimulants or psychotomimetics. On the other hand, 5-HT1A receptors modulate most of psychotomimetic effects of non-competitive NMDA receptor antagonists. The above results of preclinical investigations indicate that 5-HT1A receptor can be involved in the pathology of schizophrenia, what is partly confirmed by clinical postmortem studies of schizophrenic brains. These studies showed the increase of 5-HT1A receptor density in prefrontal and frontal cortex in schizophrenic brains. It also seems that 5-HT1A receptors might be a good target for the antipsychotic drugs. Although the clinical studies have demonstrated controversial data, maybe further studies using substances with selectivity to 5-HT1A receptors would help to determine more precisely the role of these receptors in pathology and pharmacotherapy of schizophrenia.

Metyrapone, an inhibitor of corticosterone synthesis, blocks the kainic acid-induced expression of HSP 70.

It is shown in the present study that metyrapone (100 mg/kg), an inhibitor of corticosterone synthesis, given twice, 30 min before and 6 h after kainic acid (10 mg/kg) administration, blocks the kainic acid-evoked induction of heat shock proteins 72 kDa (HSP 70). Specifically, it was observed that metyrapone completely prevented kainic acid-induced appearance of HSP 70 in the rat amygdala, habenula, parietal cortex, and significantly decreased the number of HSP 70-positive neurons in the CA1, CA3, and CA4 subregions of hippocampus. The reduction in HSP 70 induction was paralleled by a complete prevention of the kainic acid-induced rise in the circulating corticosterone level by metyrapone; however, in applied doses metyrapone evoked slight enhancement of blood corticosterone. Despite the fact that metyrapone blocked/attenuated the kainic acid-evoked induction of HSP 70, its administration did not affect the behavioral effects of kainic acid, regarded as "limbic status epilepticus." It is concluded that the blockade of corticosterone synthesis might have neuroprotective effects in the pathological states associated with the overstimulation of glutamatergic receptors.

WAY 100135, an antagonist of 5-HT1A serotonin receptors, attenuates psychotomimetic effects of MK-801.

In the present study, we investigated whether the antagonist of 5-HT1A receptors, WAY 100135, was capable of modifying the psychostimulant and psychotomimetic effects of MK-801, a non-competitive antagonist of NMDA receptors. It was found that: 1) WAY 100135 (10 and 20 mg/kg, but not 1.25, 2.5, and 5 mg/kg) transiently, in a dose dependent manner, attenuated the locomotor stimulant effects of MK-801 (0.4 mg/kg). Given alone, WAY 100135 had no effect on the locomotor activity of rats; 2) WAY 100135 (1.25 and 2.5 mg/kg, but not 10 or 20 mg/kg), attenuated or abolished the disruptive effects of MK-801 on the sensorimotor gating measured in a prepulse-induced inhibition of the acoustic startle response paradigm. WAY 100135 in all tested doses had no effect on the sensorimotor gating or amplitude of the acoustic startle response; 3) WAY 100135 (1.25, 2.5 mg/kg, but not 5 mg/kg) attenuated the detrimental effects of MK-801 on working memory and selective attention, measured in a delayed alternation task. Again, given alone, WAY 100135 did not influence the behavior of rats in that experimental paradigm; and 4) MK-801 (0.4 mg/kg) had no effect on the 5-HT1A receptor mRNA level in rat hippocampus, measured 2 and 24 hours after MK-801 administration. These data indicate that 5-HT1A receptors might be involved in the psychotomimetic effects of non-competitive NMDA receptor antagonists. In addition, 5-HT1A serotonin receptor antagonists and partial agonists may have potential antipsychotic properties.