Sound frequency dependence of duration mismatch negativity recorded from awake rats.

Aims: The brain function that detects deviations in the acoustic environment can be evaluated with mismatch negativity (MMN). MMN to sound duration deviance has recently drawn attention as a biomarker for schizophrenia. Nonhuman animals, including rats, also exhibit MMN-like potentials.

Neonatal exposure to an inflammatory cytokine, epidermal growth factor, results in the deficits of mismatch negativity in rats.

Perinatal exposure to epidermal growth factor (EGF) induces various cognitive and behavioral abnormalities after maturation in non-human animals, and is used for animal models of schizophrenia. Patients with schizophrenia often display a reduction of mismatch negativity (MMN), which is a stimulus-change specific event-related brain potential. Do the EGF model animals also exhibit the MMN reduction as schizophrenic patients do? This study addressed this question to verify the pathophysiological validity of this model.

Epidermal growth factor signals attenuate phenotypic and functional development of neocortical GABA neurons.

Phenotypic development of neocortical GABA neurons is highly plastic and promoted by various neurotrophic factors such as neuregulin-1. A subpopulation of GABA neurons expresses not only neuregulin receptor (ErbB4) but also epidermal growth factor (EGF) receptor (ErbB1) during development, but the neurobiological action of EGF on this cell population is less understood than that of neuregulin-1. Here, we examined the effects of exogenous EGF on immature GABA neurons both in culture and in vivo and also explored physiological consequences in adults.

Chronic phencyclidine treatment induces long-lasting glutamatergic activation of VTA dopamine neurons.

Use of phencyclidine (PCP) can mimic some aspects of schizophrenia. However, the underlying mechanism is unclear. Administration of PCP is known to activate mesolimbic dopamine pathway.

The role of the hippocampo-prefrontal cortex system in phencyclidine-induced psychosis: a model for schizophrenia.

Phencyclidine (PCP) is a psychotomimetic drug that induces schizophrenia-like symptoms in healthy individuals and exacerbates pre-existing symptoms in patients with schizophrenia. PCP also induces behavioral and cognitive abnormalities in non-human animals, and PCP-treated animals are considered a reliable pharmacological model of schizophrenia. However, the exact neural mechanisms by which PCP modulates behavior are not known.

Role of the lateral preoptic area and the bed nucleus of stria terminalis in the regulation of penile erection.

To elucidate the role of the preoptic area (POA) in the regulation of penile erection, we examined the effects of electrical stimulation in and around the POA on penile erection in rats, which was assessed by changes in pressure in the corpus spongiosum of the penis (CSP) and electromyography (EMG) of the bulbospongiosus (BS) muscle. In unanesthetized and anesthetized rats, four types of responses were induced by stimulation in and around the POA; (1) normal type responses, which were similar to spontaneously occurring erections, characterized by slow increase in CSP pressure and sharp peaks concurrent with BS muscle bursting; (2) muscular type responses, which included sharp CSP pressure peaks (muscular component) with almost no vascular component; (3) mixed type responses, which included a sequence of high-frequency CSP peaks followed by low-frequency CSP peaks; and (4) micturition type responses, which had higher-frequency and lower-amplitude CSP peaks than other responses which were identical to those of normal micturition. In unanesthetized condition, erections were evoked by stimulation of the lateral preoptic area (LPOA), medial preoptic area (MPOA), bed nucleus of the stria terminalis (BST), paraventricular nucleus (PVN), reuniens thalamic nucleus (Re) and lateral septum (LS).

Penile erection and micturition events triggered by electrical stimulation of the mesopontine tegmental area.

The cholinergic neurons in the laterodorsal tegmental nucleus (LDT) play a crucial role in the regulation of rapid eye movement (REM) sleep. Because penile erection occurs during REM sleep, the involvement of the LDT in penile erection was examined in unanesthetized head-restrained rats. To detect penile erection, corpus spongiosum of the penis (CSP) pressure was measured through a telemetric device with simultaneous bulbospongiosum (BS) muscle EMG recording through stainless wires.

Suppressive effect of acupuncture stimulation to the sacral segment on the state of vigilance and the brainstem cholinergic neurons.

The effects of acupuncture stimulation to the sacral segment on the electroencephalogram (EEG) and activity of the cholinergic neurons in the laterodorsal tegmental nucleus (LDT) were examined in urethane-anesthetized rats. When EEG was small amplitude and higher frequency, the stimulation to the sacral segment induced large amplitude and slow EEG with latencies ranged from 45 sec to 12 min, and durations from 48 sec to 56 min. The stimulus induced EEG is composed of significant increase in delta power and significant decrease in theta and beta powers.

Tripartite relationship among P300, clinical features and brain structure in neuroleptic-naive schizophrenia.

Auditory P300 abnormalities in schizophrenia patients have been repeatedly reported by many studies. However, reported relationships among P300 abnormalities, clinical features and other biological variables, such as abnormalities in structural brain imaging, are notably discrepant. This is partially due to the inclusion of patients who have had long-term administration of neuroleptics and those from whom this treatment has been withdrawn.

Activation of medial prefrontal cortex by phencyclidine is mediated via a hippocampo-prefrontal pathway.

Phencyclidine (PCP) is a psychotomimetic drug that elicits schizophrenia-like symptoms in healthy persons, and administration of PCP to animals is used as a pharmacological model of schizophrenia. We recently demonstrated that systemic administration of PCP to rats produces long-lasting activation of medial prefrontal cortex (mPFC) neurons with augmentation of locomotor activity, whereas direct application of PCP to mPFC neurons has little effect on their firing activity. These findings suggest that PCP-induced activation of mPFC neurons is elicited mainly via excitatory inputs from regions outside the mPFC.

Different effects of phencyclidine and methamphetamine on firing activity of medial prefrontal cortex neurons in freely moving rats.

The purpose of this study was to compare the effects of systemically administered MAP with those of phencyclidine (PCP), both of which induced comparable locomotor activity, on firing activity of medial prefrontal cortex (mPFC) neurons in freely moving rats. The results show that, unlike PCP, acutely administered MAP produced little changes in firing activity of mPFC neurons.

Effects of acupuncture to the sacral segment on the bladder activity and electroencephalogram.

Using urethane-anaesthetized rats, the effects of acupunctural stimulation to the sacral segment on the urinary bladder activity and cortical electroencephalogram (EEG) were examined. The acupuncture suppressed urinary bladder activity in 36 of 68 trials. On many occasions (22/36 trials), suppression was accompanied by an increase in EEG amplitude.