Reversal effect of sulpiride on rotational behaviour of rats with unilateral frontal cortex ablation: an alternative explanation for the pharmacological mechanism of its antidepressant effect.

The antidepressant effect of sulpiride has been generally explained as the result of its preferential blocking effect on self-inhibitory presynaptic dopamine autoreceptors at low doses. Low dose haloperidol has the same blocking effect. In rats with unilateral ablation of the frontal cortex, methamphetamine administration induced mild contralateral rotation 10 days after the operation. We examined whether low dose sulpiride and haloperidol would have the same effect on this rotational model. High dose sulpiride (100 mg/kg) or low dose haloperidol (0.05 mg/kg) prevented this methamphetamine-induced rotation. However, low dose (15 mg/kg) sulpiride clearly reversed the direction of rotation. This reversal effect of low dose sulpiride is not explained by the preferential blocking effect on dopamine autoreceptors. The results suggest that low dose sulpiride, unlike low dose haloperidol, has a prominent blocking effect on D2 receptors in the frontal cortex. This unique effect of sulpiride may be relevant to its clinical antidepressant and anxiolytic effects at low doses.

TAG-1-deficient mice have marked elevation of adenosine A1 receptors in the hippocampus.

TAG-1 is a neural recognition molecule in the immunoglobulin superfamily that is predominantly expressed in the developing brain. Several lines of evidence suggest that TAG-1 is involved in the outgrowth, guidance, and fasciculation of neurites. To directly assess the function of TAG-1 in vivo, we have generated mice with a deletion in the gene encoding TAG-1 using homologous recombination in embryonic stem cells. Gross morphological analysis of the cerebellum, the spinal cord, and the hippocampus appeared normal in TAG-1-deficient mice. However, TAG-1 (-/-) mice showed the upregulation of the adenosine A1 receptors determined by [(3)H]cyclopentyl-1,3-dipropylxanthine in the hippocampus, and their greater sensitivity to convulsant stimuli than that in TAG-1 (+/+) mice. We suspect that the subtle changes in neural plasticity induced by TAG-1 deficiency during development cause the selective vulnerability of specific brain regions and the epileptogenicity in TAG-1 (-/-) mice.

Upregulation of brain somatostatin and neuropeptide Y following lidocaine-induced kindling in the rat.

Male Sprague-Dawley rats received a daily injection of 60 mg/kg of lidocaine (> 30 days). Twenty percent of rats developed convulsions (kindled rats) and remaining rats did not show convulsions (non-kindled rats). The level of immunoreactive somatostatin (IR-SRIF) in kindled rats was significantly increased in amygdala than that in non-kindled rats and control rats. Immunoreactive neuropeptide Y (IR-NPY) contents in kindled rats were significantly increased in amygdala, hippocampus, cortex and striatum compared to non-kindled and control rats. The expression of SRIF mRNA in kindled rats produced a significant increase in amygdala, while NPY mRNA in kindled rats showed an elevated expression in both amygdala and hippocampus. These results coincide with the previous findings with the elevated expression of SRIF and NPY mRNA in electrically and pharmacologically kindled models, suggesting the important role of these peptides in the kindling phenomenon.

Internalization and down-regulation of muscarinic acetylcholine receptors in cerebellar granule cells of tenascin-gene deficient mice.

The expression of tenascin-C on oligodendrocytes parallels the migration of granule cells in the developing cerebellum, indicating a role for tenascin-C as a guide for granule neurons to find their proper locations. In this study, cultured cerebellar granule neurons from tenascin-C-knockout mice were used to examine the role of tenascin-C in agonist-induced muscarinic acetylcholine receptor down-regulation. Exposure of granule cells from wild-type or tenascin-C-negative mice to the muscarinic acetylcholine receptor agonist carbachol (1 mM) resulted in normal sequestration of cell-surface muscarinic acetylcholine receptors as assessed by [3H]N-methylscopolamine binding; however, down-regulation of total muscarinic acetylcholine receptors, measured with [3H]quinuclidinyl benzilate, was inhibited in granule cells from tenascin-C-negative mice. Remarkably, incubation of the tenascin-C-negative cells with the microtubule stabilizer taxol (10 microM) restored down-regulation of total muscarinic acetylcholine receptors to normal levels. We speculate that agonist-induced down-regulation of muscarinic acetylcholine receptors is functionally associated with tenascin-C-regulated microtubule structures in the developing cerebellum.

The effects of central administration of neuropeptide Y on behavior of tenascin-gene knockout mice.

Tenascin-C (TN), an extracellular matrix glycoprotein, plays a pivotal role in the regulation of neuronal pattern formation. TN-gene deficient mice produced by homologous recombination show hyperlocomotive activities. We have recently demonstrated that neuropeptide Y (NPY) mRNA expression is reduced in the limbic area of the TN-gene knockout mouse brain, compared to that in wild-type mice. We now report the effect of NPY on the behavior of TN mutant mice. Intracerebroventricular injection of NPY transiently decreased the hyperlocomotion of TN mutant mice. Concurrently, mice given NPY showed anxiolytic behavioral change as assessed by an exploratory model. The results presented here suggest that the hyperlocomotion of TN mutant mice is partially derived from severe tensity.

Ethanol induces subtype-specific up-regulation of muscarinic acetylcholine receptor mRNA in neurohybrid cell lines.

Effects of sub-chronic ethanol treatment on the mRNA levels of muscarinc acetylcholine receptor (mAChR) subtypes were studied in two neurohybrid cell lines, NG108-15 and NCB-20. The former expresses only m4-mAChRs, while the latter expresses m1- and m4-mAChRs. Exposure to 200 mM ethanol for 1 to 3 days induced a time-dependent increase in the levels of m4-mAChR mRNA in NG108-15 and NCB-20 cells. In contrast, the levels of ml-mAChR mRNA and mAChR-mediated phosphoinositide hydrolysis in NCB-20 cells were unchanged. The ethanol-induced up-regulation of m4-mAChR mRNA was associated with a parallel increase in the levels of mAChR binding sites assessed by using [3H]quinuclidinyl benzilate. The mRNA up-regulation was closely correlated with a decrease in intracellular cyclic AMP concentration and the ethanol up-regulation was blocked by 8-bromo-cyclic AMP and forskolin, suggesting that m4-mAChR mRNA is under negative regulation by cyclic AMP. Thus, neurally-related cell lines are useful models for studying molecular mechanisms underlying ethanol-induced alteration of mAChR expression and function in the nervous system.

Reduced mRNA expression of neuropeptide Y in the limbic system of tenascin gene disrupted mouse brain.

Tenascin-C (TN), an extracellular matrix glycoprotein which reveals both neurite outgrowth-promoting and growth-inhibiting effects, is generated in the central nervous system. A previous study reported that TN-gene null mutant mice display hyperlocomotion and do not easily habituate to unfamiliar environments. Additionally, these mice display poor appetite, abnormal circadian rhythm and low pregnancy rate. The present study demonstrated that neuropeptide Y (NPY) mRNA expression is reduced in the limbic area of the TN gene-deficient mouse brain as compared to wild-type mice. NPY has been shown to affect emotion, circadian rhythm and food intake, and the present results suggest that the some behavioural abnormalities exhibited by TN-mutant mice may be in part due to the low level of expression of NPY mRNA in the limbic system.

Preprotachykinin A and cholecystokinin mRNAs in tenascin-gene knockout mouse brain.

Tenascin (TN), an extracellular matrix glycoprotein, exhibits various functions in the developmental stage of the mammalian brain. TN-gene deficient mice show abnormal behavior such as hyperlocomotion and poor swimming ability, and this abnormal behavior may derive from a low level of dopamine transmission in the striatum or hippocampus of the TN-gene disrupted mouse brain. We assayed preprotachykinin A (PPT) and cholecystokinin (CCK) mRNAs in the terminal fields of the dopamine neuron. The levels of PPT mRNA were significantly higher in the striatum, and the expression of CCK mRNA was markedly augmented in the hippocampus of the TN-knockout mice, compared to the wild or heterozygous mice. One possible explanation of the changes of PPT and CCK mRNA expressions is functional compensation against the low level of dopamine turnover rate in the TN-knockout mouse brain.

Tyrosine hydroxylase activity and its mRNA level in dopaminergic neurons of tenascin gene knockout mouse.

We have recently demonstrated that some tenascin (TN) gene-knockout mice display abnormal behaviors, and that these abnormal behaviors stem from a low level of dopamine transmission in the brain. In the present study, we elucidated that tyrosine hydroxylase (TH) activity in the frontal cortex, striatum, and hippocampus of TN-knockout mice which showed abnormal behavior was significantly decreased. Also, the TH mRNA level of the midbrain was decreased by 43% in these animals compared with values for wild-type mice. These results suggest that the low dopamine turnover rate in some areas of the brain of TN-knockout mice accompanied by motor defects is due, at least in part, to the reduction in TH activity caused by diminished TH mRNA expression, and that TN-knockout mice exhibit abnormal behaviors in the presence of low levels of TH-gene expression.

Effects of cholecystokinin-B receptor antagonist on dopamine system in tenascin mutant mice.

The aim of this study was to investigate the effect of cholecystokinin (CCK) receptor antagonist on the abnormal behavior and dopamine (DA) transmission of tenascin (TN)-gene knockout mice. Recently, we demonstrated that TN-gene deficient mice show hyperlocomotion that is related to reduced DA transmission and tyrosine hydroxylase (TH) activities in the brain. In this report, we show that the intraperitoneal administration of a CCK-B receptor antagonist, PD135158 (0.1 mg/kg), but not a CCK-A receptor antagonist, lorglumide, inhibited hyperlocomotion. Moreover, PD135158 reversed the low levels of DA turnover rate and TH activities in the striatum of TN-gene knockout mouse brain. These results suggest that CCK-B receptor is involved in the behavior of TN-gene knockout mouse through striatal DA transmission.

Paradoxical behavioral response to apomorphine in tenascin-gene knockout mouse.

Tenascin is a large extracellular matrix glycoprotein which is highly expressed in the developing nervous system. To examine the role of tenascin in vivo, we have produced mice in which the tenascin-gene is inactivated. These animals did not easily habituate to unfamiliar circumstances and displayed hyperlocomotion. A dopamine receptor agonist, apomorphine, reduced this hyperlocomotion dose dependently, but this phenomenon was not due to the appearance of apomorphine-induced stereotypic behavior, suggesting that tenascin-gene mutant mice have a paradoxical behavioral response to apomorphine compared to wild-type mice.

Differential expression of c-fos mRNA in rat prefrontal cortex, striatum, N. accumbens and lateral septum after typical and atypical antipsychotics: an in situ hybridization study.

The regional difference in the expression of c-fos mRNA induced by typical and atypical antipsychotics was determined in prefrontal cortex, striatum, N. accumbens and lateral septum in rats by in situ hybridization. Two typical antipsychotics, haloperidol (2 mg/kg) and fluphenazine (2 mg/kg), and three atypical antipsychotics, (-)sulpiride (100 mg/kg), clozapine (20 mg/kg) and OPC-14597 (40 mg/kg), were used. Brains were fixed with 4% paraformaldehyde 45 min after drug administration (i.p.). Brain sections of 30 microns-thickness were made in a cryostat and hybridized with 35S-labelled for c-fos oligonucleotide probe. These sections were apposed to X-ray films and the autoradiograms were semi-quantitatively analysed by computer-assisted densitometry. All antipsychotics used increased c-fos mRNA expression in N. accumbens shell, a region of the forebrain associated with limbic systems. On the other hand, two typical antipsychotics (haloperidol and fluphenazine) that cause a high incidence of acute motor side effects increased the expression of c-fos mRNA in the dorsolateral striatum, an extrapyramidal region primarily involved in motor control. Only clozapine induced c-fos mRNA in the medial prefrontal cortex and lateral septum. These results strongly suggest that the shell region of N. accumbens may be a common site of therapeutic action of antipsychotics.

Neurochemical analysis of the tyrosine hydroxylase expression in methamphetamine-sensitized rats.

To elucidate the expression of TH mRNA in MAP-induced behavioral sensitization, rats were daily injected with MAP (5 mg/kg i.p.) or saline for 14 days. Progressive enhancement was observed in MAP-induced stereotyped behavior. After 7 days of discontinuation of MAP treatment, the rats were decapitated and the brains were prepared for either in situ hybridization or Northern blot hybridization. In situ hybridization revealed that the signals of TH mRNA were localized to the dopaminergic perikarya of substantia nigra and ventral tegmental area in the midbrain, and Northern blot analysis showed that the levels of TH mRNA in these areas decreased by 37% compared to that in the saline-treated controls. These findings indicate that MAP-induced dopaminergic hyperactivity is not associated with enhanced expression of TH gene mRNA.

Differential effects of butyrate and dibutyryl cAMP on mRNA levels of muscarinic acetylcholine receptor subtypes expressed in neurohybrid cell lines.

NCB-20 cells expressed m1- and m4-muscarinic acetylcholine receptor (mAChR) mRNAs, while NG108-15 cells expressed only m4-mAChR mRNA. Butyrate induced a time-dependent increase in the level of m1-mAChR mRNA with no change in the m4-mAChR mRNA level in NCB-20 cells. Similarly, butyrate did not affect the m4-mAChR mRNA level in NG108-15 cells. In contrast, dibutyryl cAMP caused a significant time-dependent decrease in the level of m4-mAChR mRNA in NCB-20 and NG108-15 cells as well as m1-mAChR mRNA in NCB-20 cells. Our results suggest that these two differentiating agents are important physiological regulators of the transcription and/or stability of the mRNA of certain mAChR subtypes expressed in these two neurohybrid cell lines.

Changes in cholecystokinin mRNA expression in methamphetamine-induced behavioral sensitization.

Neuropeptide cholecystokinin (CCK) mRNA was measured in the rat brain subchronically treated with methamphetamine (MAP). Male Wistar rats were injected daily with MAP (3 or 6 mg/kg, i.p., once a day) or saline for 14 days. Progressive reinforcement was observed in MAP-induced stereotyped behaviors. After 7 or 14 days of discontinuation, the rats were decapitated and the brains were prepared for Northern blot analysis using 32P-labeled cDNA probes. Northern blot analysis revealed that the levels of CCK mRNA in the frontal cortex and the hippocampus of 3 or 6 mg/kg MAP-treated rats were significantly decreased, compared to the saline-treated controls. These findings indicate that the alteration in CCK mRNA levels in the frontal cortex and the hippocampus of MAP-treated rats persisted for at least 2 weeks and might be involved in the expression of MAP-induced long-lasting behavioral sensitization (reverse tolerance).

Abnormal behavior and neurotransmissions of tenascin gene knockout mouse.

To examine the role of tenascin (TN) in vivo, we have produced mice in which the TN gene is inactivated. In behavioral studies, TN-knockout mice showed abnormal behavior such as hyperlocomotion and poor swimming ability. Biochemical analysis revealed that serotonin (5-HT) and dopamine (DA) transmission was decreased in the cerebral cortex, the hippocampus, or the striatum of TN-knockout mouse brain. The intraperitoneal administration of the DA receptor agonist, LY171555 (0.5 mg/kg, BW), inhibited the hyperlocomotion, and swimming behavior was transiently improved by the treatment with the 5-HT receptor agonist, 1-(4-iodo-2,5-dimethoxyphenyl)-2-aminopropane hydrochloride. These findings suggest that TN may play an important role in neurotransmissions related to behavior.

The reduction of preprotachykinin mRNA in the methamphetamine-induced behavioral sensitization.

To study the role of the preprotachykinin A (PPT) mRNA in methamphetamine (MAP)-induced behavioral sensitization, rats were daily injected within MAP (3 or 6 mg/kg, i.p., once a day) or saline for 14 days. Progressive enhancement was observed in MAP-induced stereotyped behavior. After 7 or 14 days of discontinuation of MAP treatment, the rats were decapitated and the brains were prepared for Northern blot analysis using a 32P-labeled oligonucleotide probe. Northern blot analysis revealed that the level of PPT mRNA in the striatum of 3 or 6 mg/kg MAP-treated rats was significantly decreased, compared to that in the saline-treated controls. These findings indicate that PPT mRNA expression plays an important role in MAP-induced long-lasting behavioral sensitization and dopamine hyperactivity.

Cloning of the cDNA encoding neural adhesion molecule F3 from bovine brain.

We cloned a bovine cDNA encoding the neural adhesion molecule F3 and analyzed its nucleotide sequence. The coding region consisted of 3054 bp encoding 1018 amino acid (aa) residues. The M(r) calculated from the deduced aa sequence was 113,383. Bovine F3 had 93, 94 and 77% aa identity with the mouse, human and chicken homologs, respectively. Bovine F3, similar to those of chicken and human, was devoid of two aa residues (Ile-Thr) in the sixth immunoglobulin type C2-like domain, as compared with the mouse homolog. Parts of bovine F3 protein were overproduced in Escherichia coli. The antibodies raised against the recombinant proteins in rabbits reacted specifically with F3. F3 protein was detected in cerebellum, cerebrum and spinal cord in Western blot analysis.

Halothane prevents MK-801 neurotoxicity in the rat cingulate cortex.

Subcutaneous administration of the N-methyl-D-aspartic acid (NMDA) antagonist, MK-801, to adult rats causes a toxic vacuole reaction in neurons of the posterior cingulate cortex which is readily detected in histological sections 4 h following MK-801 administration. Certain drugs that facilitate neurotransmission at gamma-aminobutyric acidA (GABAA) receptors block this neurotoxic action of MK-801. The anesthetic actions of halothane (fluothane) are thought to be due, at least in part, to an interaction with GABAA receptors. In the present study, we investigated the effect of halothane on MK-801 neurotoxicity. When halothane was administered for either 1 or 2 h, then terminated immediately prior to MK-801 treatment, the vacuole reaction detected 4 h later was almost as severe as in controls not exposed to halothane. Administration of halothane for 1 h after MK-801 injection postponed but did not prevent a relatively full vacuole reaction. However, when rats were kept under halothane anesthesia continuously throughout the 4 h period following MK-801 administration, the vacuole reaction was completely prevented. We postulate that halothane blocks MK-801 neurotoxicity by a facilitative action at GABAA receptors. Because halothane's duration of action is fleeting compared to the very long duration of action of MK-801, the efficacy of halothane in blocking MK-801 neurotoxicity varies in direct proportion to the length of time following MK-801 treatment that the rat brain is exposed to halothane.

Methamphetamine-induced dopaminergic hyperactivity is not accompanied with increase in tyrosine hydroxylase mRNA of the rat midbrain.

Tyrosine hydroxylase (TH) mRNA was measured in the midbrain of rats treated repeatedly with methamphetamine (MAP). Male Sprague-Dawley rats were daily injected with MAP (5 mg/kg, i.p., once daily) or saline for 14 days. Progressive augmentation was observed in MAP-induced stereotyped behaviors. After one week of abstinence, the rats were decapitated and the brains were prepared for either in situ hybridization using non-radioactive cRNA probes or Northern blot analysis using 32P-labeled cDNA probes. In situ hybridization showed that the signals of TH mRNA were localized to the dopaminergic perikarya in the midbrain and were reduced in MAP-treated animals compared to the controls. Northern blot analysis revealed that the level of TH mRNA in the midbrain of MAP-treated rats was decreased by 37% compared to the controls, which was close to the statistical significance (P = 0.053). These results indicate that the dopaminergic hyperactivity caused by repeated MAP treatment is not associated with enhanced transcription of the TH gene.