Molecular pharmacological approach to the disturbances of brain neuron circuits involved in schizophrenia

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A psychotomimetic drug methamphetamine (MAP) produces a neuroleptic-responsive schizophreniform psychosis in humans while phencyclidine (PCP) psychosis includes neuroleptic-resistant symptoms which are indistinguishable from those of schizophrenis. Acute administration of MAP (4.8 mg/kg, subcutaneously (s.c.)) caused a widespread induction of nuclear c-Fos-like immunoreactivity in rat brain at 56-80 postnatal days in a dopamine antagonist-sensitive manner. The greatest density of c-Fos positive cells was found in the pyriform cortex and olfactory tubercle followed by the entorhinal cortex, II-VI layrs of the neocortex, striatum, amygdala, nucleus accumbens, septal unclei, granular cell layr of the cerebellum, thalamus, hypothalamus, substantia nigra, etc. In 8-day-old neonatal rats, acute injection of these drugs failed to cause c-fos expression from the laver II htrough V of the neocortex, but induced the proto-oncogene product in a deeper aprt of the layr VI of the neocortex, the pal … More eocortex (including the pyriform and entorhinal cortex) and the above subcortical areas. MAP-induced c-Fos positive cells in the neocortex increased in number and distribution with postnatal development and showed the adult pattern after 21-23 postnatal days. The distribution patterns of c-Fos-positive cells after PCP treatment were different from those after MAP.Thus, a single injection of PCP (5-10mg/kg, s.c.) produced the dense expression of c-Fos-like immunoreactivity in the deeper layrs (IV-VI) of the neocortex and pyriform cortex, but the very sparse expression in the striatum, olfactory tubercle and superficial layrs (I-III) of the necortex in the young adult periods in a dopamine antagonist-resistant fashion. These expression patterns were similar to those of a selective NMDA receptor antagonist dizocilpine. In the neonatal periods, PCP induced very low levels of c-Fos-like immunoreactivity in the neocortex while the pyriform cortex was dense with c-Fos positive cells. PCP-induced c-Fos-immunostaining in th brain showed the adult pattern after 21-25 postnatal days. The above developmental changes in the patterns of c-fos expression in the neocortical areas might reflect differences in responsive neuronal circuits to the drugs between the neonatal and young adult periods. Because acute or long-term behavioral effects of these drugs alter around the third week of postnatal life, these results suggest that the maturation of certain neuronal circuits in the neocortex might be crucial for the acquisition of the adult patterns of behavioral responses or motor functions. We have nowtried to identify molecules contributing to such developmental changes in the discrete brain regions because these molecules should play a pivotal role in expression and regulation of psychomotor functions that may be disturbed in schizopherenic patients. To this end, we have employed a RNA arbitarily primed PCR technique for the detection of cDNAs that represent developmentally regulate Less