Cholecystokinin binding sites in the rat forebrain: effects of acute and chronic methamphetamine administration

A Personal Historical Perspective on Psychiatry in Japan During the Last 4 Decades

After graduating from University of Tsukuba in 1982, I joined the Department of Psychiatry at the same university. Due to the anti-psychiatry social movement and reports of incidents involving violence against in-hospital patients at psychiatric hospitals, psychiatric associations in Japan faced questions related to ethical awareness, making it a challenging environment for conducting clinical research. For this reason, the first half of my journey─my 20 years at the University of Tsukuba─was spent conducting basic research on animal models of schizophrenia. With respect to the onset of schizophrenia, I studied dopamine and related neuropeptides in the brain, as well as abnormalities in neurotransmission in the excitatory and inhibitory amino acid neurotransmission systems. In April 2002, I was appointed as a Department Chair at Juntendo University Koshigaya Hospital. I was responsible for overseeing many medical staff, including the clinical education of practicum students and resident physicians, as well as the training of psychiatric specialists. I was also involved in the management and operation of medical services provided at the mental health clinic that had 350 outpatients per day and saw the admission and discharge of 500 patients annually. Meanwhile, I became actively involved in activities related to perinatal mental health. In 2018, I was appointed as the Director of the Japanese Society of Perinatal Mental Health and worked diligently to improve medical care related to perinatal mental health in Japan through the development of perinatal mental health guidelines.

Autoradiographic study on the pharmacological characteristics of [3H]3-OH-PCP binding sites in rat brain

The pharmacological characteristics and the regional distribution of [3H]3-OH-PCP (1-[1(3-hydroxyphenyl)-cyclohexyl]piperidine) binding were investigated in rat brain by quantitative autoradiography. Kinetic analysis of [3H]3-OH-PCP binding revealed fast and slow components, in the association and dissociation studies. The regional distribution of binding closely corresponded to those of binding sites labeled by [3H]N-[l-(2-thienyl)-cyclohexyl]3,4-piperidine (TCP) and [3H](+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imi ne maleate (MK 801). High densities of [3H]3-OH-PCP binding sites were found in the stratum radiatum and orients of field CA1 in the hippocampus and in the outer layers of cerebral cortices. In contrast, low levels of binding were seen in the brain stem and the granular cell layer of the cerebellum. [3H]3-OH-PCP binding was strongly inhibited by MK 801 and 3-OH-PCP, while the potency of (+)-SKF 10047 in inhibiting [3H]3-OH-PCP binding was less in the cerebral cortex and hippocampus. The antagonists for the glutamate, glycine and polyamine recognition sites at the NMDA/PCP receptor complex displaced [3H]3-OH-PCP binding sites with a potency similar to that of [3H]MK 801. These findings suggest that the [3H]3-OH-PCP binding site is similar or identical to the PCP binding site labeled by [3H]TCP and [3H]MK 801.

Regulation of dopamine D2 receptor affinity by cholecystokinin octapeptide in fibroblast cells cotransfected with human CCKB and D2L receptor cDNAs

Alteration in dopamine (DA) and/or cholecystokinin (CCK) transmission in the CNS may be of relevance for schizophrenia. Previous findings in striatal membranes give indications of a modulation of DA D2 receptor affinity by CCKB receptor activation. In the present study receptor binding studies were performed in a mouse fibroblast cell line (L-hD2l/CCK), expressing both human D2 receptors (long form, D2L) and human CCKB receptors, and binding sites for [3H]CCK-8S (sulfated CCK octapeptide), the D2 agonist [3H]NPA and the D2 antagonist [3H]raclopride were found and characterized in saturation and competition experiments. 1 nM of CCK-8 caused a significant 38% increase in the KD value of the D2 agonist [3H]NPA binding sites in the L-hD2l/CCK cell membranes. This change was blocked by the CCKB receptor antagonist PD 134308 (50 nM). Furthermore, 1 nM of CCK-8 increased the KD value of the D2 antagonist [3H]raclopride binding sites by 34% (P < 0.05) in the L-hD2l/CCK cell membranes. Control cells (L-hD2l cells) expressing D2L receptors showed no specific [3H]CCK-8S binding sites and no modulation by CCK-8 of the D2L receptors. These findings indicate a modulation of the D2L receptor affinity by activation of the CCKB receptor also when they are coexpressed in a fibroblast cell line. One possible explanation of these data may include a receptor-receptor interaction between the CCKB and D2L receptors.

Quantitative autoradiographic localization of [3H]3-OH-PCP (1-(1(3-hydroxyphenyl)cyclohexyl)piperidine) binding sites in rat brain

Binding of a novel radioligand, [3H]3-OH-PCP (1(1(3-hydroxyphenyl) cyclohexyl)piperidine), to N-methyl-D-aspartate (NMDA) receptor-coupled and -uncoupled PCP sites was investigated in the rat brain. The highest densities of [3H]3-OH-PCP binding were observed in the hippocampal formation, notably in the stratum radiatum and oriens of CA1 region, and dentate gyrus. There were relatively high levels of binding in the olfactory system, superficial layer of cortices, the amygdala and the thalamus. In contrast, lower levels of binding were found in the globus pallidus, cerebellum, and brain stem, except for the superior colliculus. These findings demonstrate that [3H]3-OH-PCP binds to discrete regions within the rat brain. Its distribution is consistent with autoradiographic localization of [3H]TCP and [3H]MK-801 binding sites in the rat brain, suggesting that [3H]3-OH-PCP binds to NMDA/PCP ion-channel complexes in preference to sigma sites.

Autoradiographic localization of CCK-8 binding sites in the rat brain: effects of chronic methamphetamine administration on these sites

The effects of chronic methamphetamine (MAP) administration (at a dose of 4 mg/kg for 14 days) on [3H]pCCK-8 binding sites in the rat brain were investigated by an in vitro quantitative receptor autoradiographic technique. The number of [3H]pCCK-8 binding sites was significantly reduced in layers III and IV of the medial frontal, anterior, and posterior cingulate cortices, in layers II-IV of the retrosplenial cortex, in layers III-VI of the dorsal insular cortex, and in the reticular nucleus of the thalamus, compared to these numbers in a control group of rats that received physiologic saline. Further, chronic methamphetamine administration led to a significant increase in the number of these binding sites in layer I of the entorhinal cortex. These findings indicate the CCK peptides in the limbic lobe may be closely related to the development of the behavioral changes associated with methamphetamine sensitization. In addition, these results provide supporting evidence for the involvement of the limbic system in the pathophysiology of schizophrenia.

Changes at cholecystokinin receptors induced by long-term treatment with diazepam and haloperidol

Fourteen days administration of haloperidol (1 mg/kg daily) prevented the motor depressant effect of caerulein (an agonist at cholecystokinin receptors, 15 micrograms/kg) and the antagonistic effect of caerulein (100 micrograms/kg) against (+)-amphetamine (5 mg/kg) induced hyperlocomotion in mice. The antiaggressive effect of caerulein (40 micrograms/kg) in saline-treated mice was replaced by increased aggressiveness after long-term haloperidol and diazepam (5 mg/kg daily) treatment. The anticonvulsant effect of caerulein (125 micrograms/kg) against picrotoxin (10 mg/kg) induced seizures was abolished after 14 days diazepam, but not after haloperidol, treatment. The above described changes in the mouse behaviour are probably related to the development of subsensitivity at CCKA receptors, whereas the CCKB receptor subtype becomes more sensitized to the action of caerulein after long-term haloperidol and diazepam treatment.

The effects of corticotropin-releasing hormone on peptidergic neurons in the rat forebrain

Our previous study showed that intracerebroventricular (ICV) administration of corticotropin-releasing hormone (CRH) produced a significant increase in locomotor activity at a dose of 1 microgram and slow stereotypy with prominent grooming at a dose of 10 micrograms. In addition, the ICV administration of CRH caused a significant increase in dopamine (DA) and norepinephrine turnover (NE) in various forebrain regions. The present study was designed to investigate the effects of the ICV administration of CRH on cholecystokinin (CCK), neuropeptide Y (NPY), somatostatin (SOM) and gamma-amino butyric acid (GABA) in the rat forebrain. The ICV administration of 1 and 10 micrograms CRH caused a marked reduction in CCK-like immunoreactivity (CCK-LI), NPY-LI and SOM-LI in the medial frontal cortex (MFC) and anterior cingulate cortex (Ant.CC), whereas it induced an increment of NPY-LI in the nucleus accumbens (NAc) and striatum. Increased SOM-LI and decreased NPY-LI were observed in the hippocampus following the ICV administration of CRH at both doses. The ICV administration of CRH caused a significant decrease in the BAGA content in the MFC, ant.CC, NAc and striatum. Taken together with our previous findings, these results indicate that the ICV administration of CRH induced classical neurotransmitter and neuropeptide abnormalities in the central nervous system which resulted increased emotionality, especially anxiety, in rats.

The effects of intraperitoneally administered phencyclidine on the central nervous system: behavioral and neurochemical studies

The effects of intraperitoneally (IP) injected phencyclidine (phencyclohexyl piperidine; PCP) on the metabolism of dopamine (DA) and cholecystokinin-like immunoreactivity (CCK-LI) in the rat brain were investigated in connection with PCP-induced behavioral changes. The predominant behavior change elicited by 2.5 mg/kg PCP was locomotion, while with higher doses (5 and 10 mg/kg) sniffing, swaying and falling were observed in addition to the enhanced locomotor activity. Backpedaling and rotation were observed in 10 mg/kg PCP-treated rats. IP injection of PCP caused a dose-related increase in the levels of DA and 3,4-dihydroxy-phenylacetic acid (DOPAC) in the medial frontal cortex (MFC) and anterior cingulate cortex (ant.CC) without any changes in the nucleus accumbens (NAc) or striatum. CCK-LI in the MFC, ant.CC and NAc was decreased in a dose-dependent manner following IP injection of PCP. These findings support the evidence that PCP selectively activates the mesocortical DA systems. Furthermore, our results indicate a functional relationship between the mesocortical DA neurons and intrinsic CCK containing cortical neurons, and the change in the activity of the intrinsic CCK-containing cortical neurons in these two areas, perhaps due to an alteration in DA transmission, might be involved in behavioral changes after PCP injection.

Effects of chronic methamphetamine treatment on the binding parameters of [3H]SCH 23390, a selective D1-dopamine receptor ligand, in the rat brain

Following the determination of the binding characteristics of [3H]SCH 23390 using slide-mounted tissue sections of molded minced forebrain, the effects of chronic methamphetamine (MAP) treatment (at a dose of 4 mg/kg for 14 days) on D1 receptors in the rat brain were studied using quantitative receptor autoradiography. There were no differences in both Kd(app) and Bmax values between vehicle- and MAP-treated rats, indicating that D1 receptors might not be involved in the development of behavioral sensitization in chronically MAP-treated rats.