Background: A number of gene expression studies have investigated changes induced by drug exposure, but few reports describe changes that persist following relapse. In this study, genomewide analysis of gene expression was conducted following an extinction session (90 min) in rats that expressed behavioral incubation of heroin-seeking and goal-directed behavior. As an important modulator of goal-directed behavior, the medial prefrontal cortex (mPFC) was the target of genomic analysis. Rats were trained to self-administer heroin during 3 h daily sessions for 14 d. Following the self-administration period, rats were reintroduced to the self-administration chambers for a 90-minute extinction session in which they could seek heroin, but received none. Extinction sessions were conducted on groups after either 1 d or 14 d of drug-free enforced abstinence to demonstrate behavioral incubation.

This study surveyed the distribution of tryptophan hydroxylase 2 (TPH2) mRNA, protein, and enzymatic activity throughout the male Sprague-Dawley rat brain. TPH2 is the genetic isoform of TPH that catalyzes the rate-limiting step in serotonin biosynthesis within the central nervous system. Although cell bodies of serotonergic neurons are located mainly in the raphe, serotonincontaining axons innervate many regions of the brain. In the present study, we assessed the levels of mRNA, protein expression, and enzyme activity of TPH2 in the rat raphe, ventral tegmental area (VTA), substantia nigra, hippocampus, cerebellum, dorsal striatum, nucleus accumbens, amygdala, and medial prefrontal cortex to more fully understand the distribution of this enzyme throughout the central nervous system. The pineal gland was used as a control tissue that expresses TPH1 (the peripheral enzyme), but not TPH2. As expected, the raphe showed the highest brain TPH2 activity and protein expression. In the contrast to other reports, however, the VTA followed the raphe as the region with the second-highest amount of TPH2 activity, mRNA and protein expression. There were significantly lower TPH activities and levels of TPH2 protein in the other regions. In addition, TPH2 immunocytochemistry demonstrated the presence of TPHpositive cell bodies within the VTA. The results of this study indicate that TPH2 and serotonergic signaling may play an important role in the mesolimbic/mesocortical reward pathway.

This study investigated patient-reported reasons for treat-and-release emergency department (ED) visits by Medicaid beneficiaries. An in-house-designed educational survey was conducted that consisted of 3 components: patient's health, patient's primary care, and patient's ED visit. An ED patient was asked an open-ended question about the reason for a recent ED visit. The patient's answer was classified into 1 of 3 types: health care service delivery issues, population behavior issues, and unavoidable ED visits. Among 2711 ED visits, 56% were related to health care service delivery issues (ie, access to care, primary care provider [PCP] availability), 2% were associated with population behavior issues, and 42% were unavoidable. For those ED visits related to PCP unavailability, 72% occurred during off-hours or weekends and 28% were because of no timely PCP appointments. The findings suggest that inadequate access to primary care is a major cause of potentially avoidable ED utilization in the Medicaid population.