Behavior, striatal and nucleus accumbens field potential patterns and dopamine levels in rats given amphetamine continuously

PAOPA, a potent dopamine D2 receptor allosteric modulator, prevents and reverses behavioral and biochemical abnormalities in an amphetamine-sensitized preclinical animal model of schizophrenia

Allosteric modulators are emerging as new therapeutics for the treatment of psychiatric illnesses, such as schizophrenia. Conventional antipsychotic drugs are typically dopamine D2 receptor antagonists that compete with endogenous dopamine at the orthosteric site, and block excessive dopamine neurotransmission in the brain. However, they are unable to treat all symptoms of schizophrenia and often cause adverse motor and metabolic side effects. The binding profile of allosteric modulators differs, as they interact with their receptor at a novel binding site and their activity is determined by physiological signaling. In collaboration, our laboratories have synthesized and evaluated over 185 compounds for their allosteric modulatory activity at the dopamine D2 receptor. Of these compounds, PAOPA is among the most potent allosteric modulators, and has been shown to be effective in treating the MK-801 induced preclinical animal model of schizophrenia. The objective of this study was to evaluate PAOPA's ability to prevent and reverse behavioral abnormalities in an amphetamine-sensitized preclinical animal model of schizophrenia. Amphetamine sensitized rats were given PAOPA during sensitization and following sensitization to determine whether PAOPA is able to prevent and reverse behavioral abnormalities. Furthermore, changes in post-mortem dopamine levels were measured by high performance liquid chromatography in various brain regions. The results presented demonstrate that PAOPA is able to prevent and reverse behavioral and biochemical abnormalities in an amphetamine-sensitized animal model of schizophrenia.

Individual differences in amphetamine sensitization: dose-dependent effects

Rats were screened for locomotor activity in a novel environment and divided into high (HR) or low (LR) responders based on whether their locomotor score for the first hour was above or below the median. In the first experiment, HR and LR rats were compared for their locomotor response following repeated administration of either 0.0, 0.5, 1.0, or 1.5 mg/kg d-amphetamine sulfate (AMPH). Injections of either 0.5 or 1.0 mg/kg AMPH produced higher locomotor activity in HR rats than in LR rats. Furthermore, there was a correlation between the locomotor response to novelty and the response to either 0.5 or 1.0 mg/kg AMPH. In addition, whereas both groups of rats developed the same degree of sensitization to 0.5 mg/kg AMPH, only the HR rats developed pronounced sensitization to repeated administration of 1.0 mg/kg AMPH. When both HR and LR were considered, there was a significant correlation between response to novelty and the extent of sensitization to the locomotor-stimulating properties of 1.0 mg/kg AMPH. There were no differences in locomotor activity or sensitization between HR and LR rats following the highest dose of AMPH (1.5 mg/kg). In a separate experiment, HR and LR rats were compared for locomotor activity following a series of intracranial infusions of AMPH. There were no overall differences in locomotor activity between the HR and LR groups following AMPH infusions into either the nucleus accumbens (NACC) or the anterior dorsal striatum (ADS). However, the locomotor activity scores in the novel environment significantly correlated with the locomotor response to 3.0 micrograms AMPH infused into either the NACC or ADS.(ABSTRACT TRUNCATED AT 250 WORDS)