Objective Bromocriptine and other dopamine D2 receptor agonists can affect a range of behaviors in nonhuman primates, particularly those behaviors associated with motor and mental function, such as suppressant behaviors and hallucinatory-like behaviors in monkeys. Besides bromocriptine, the dysfunction of the rapid eye movement sleep （REM） mechanism may also contribute to hallucinations. Dissociation of wakefulness, REM, and non-REM （NREM） can cause a series of psychotic symptoms. Methods In present study, we simultaneously recorded auditory evoked potentials （AEP） from five cerebral regions in monkeys during normal and psychotomimetic states to investigate and compare state-dependent changes in AEE Results Phase reversal of peak-to-baseline amplitude of 250 ms component （PBA250） in dorsolateral prefrontal cortex was common characteristic of hallucinatory-like and REM, and that hallucinatory-like and REM shared the equivalent modulatory orderliness of the PBA250 in dorsolateral prefrontal cortex. This result suggests that hallucinatory-like and REM share an equivalent electrophysiological modulatory in dorsolateral prefrontal cortex. Conclusion Our results reveal that emergence of the N250 in dorsolateral prefrontal cortex is an exclusive marker that may help to discern whether hallucinatory-like behaviors is exhibited, which suggests that dorsolateral prefrontal cortex may be the most pivotal region for exhibition of hallucinatory-like behaviors.
Background Although dopamine transporter （DAT） is essential for addiction, the effect of additive drugs on DAT function is still controversial, especially for opiates. We investigated the functional changes of dopamine transporter in striatum of rhesus monkeys during acute morphine injection and its abstinence. Methods Four rhesus monkeys, 6 to 9 years old, two male and two female, were examined for 12 days. Single photon emission computed tomography （SPECT） was performed with ^99Tc^m-TRODAT-1 as the radiopharmaceutical dopamine transporter agent during different stages of acute morphine injection and its abstinence. The ratios of SPECT signal between striatum and cerebellum （ST/CB） were calculated. Results The ST/CB ratio declined significantly on the first day of morphine injection and continued declining with more morphine injections. After abstinence, the ratio increased with time, but was still significantly lower on the 5th day of abstinence than the normal level. Conclusions In rhesus monkey, acute morphine injection has both rapid and lasting effects on DAT by downregnlating its function. The decline was partially reversible following morphine abstinence. The results suggest that striatum is one effective target of morphine and that the DAT function in striatum is one indicator for morphine addiction.
