Faculty Bibliography

The noncompetitive NMDA antagonist, MK-801, produces stimulant and rewarding effects that are mediated by a combination of dopamine-dependent and -independent mechanisms. It was recently demonstrated that, similar to amphetamine, the rewarding and locomotor effects of intraventricular (i.c.v.) MK-801 are potentiated by chronic food restriction. Because food restriction also increases c-Fos expression induced by i.c.v. amphetamine in several subcortical dopamine (DA) terminal areas, Fos-like immunoreactivity (FLI) induced by i.c.v. MK-801 was evaluated in an effort to identify responses that are common to amphetamine and MK-801 and similarly augmented by food restriction. Unlike amphetamine, MK-801 did not increase FLI in caudate-putamen, bed nucleus of the stria terminalis, or ventral pallidum. Similar to amphetamine, MK-801 increased FLI in cingulate cortex, central nucleus of the amygdala and nucleus accumbens (NAC) core, but in none of these areas was the response augmented by food restriction. In medial prefrontal cortex, retrosplenial cortex, and NAC shell, however, MK-801 induced FLI that was augmented by food restriction. An effect that is common to amphetamine and MK-801 is the augmentation of FLI by food restriction in NAC shell. It is therefore suggested that increased releasability of DA, or upregulation of the D-1 receptor linked signal transduction pathway, in NAC shell may mediate the enhanced behavioral sensitivity of food-restricted subjects to drugs of abuse

RATIONALE: Classical conditioning has been proposed to account for the hyperactivity observed in drug-free rats when placed in an environment previously paired with cocaine administration. However, an alternative explanation is that hyperactivity results from an inability of rats to habituate to the environment under the influence of cocaine. OBJECTIVES: In this study, preconditioning exposure to the test environment was increased from one session (standard procedure) to seven (modified procedure) to test the 'antihabituation' hypothesis. METHODS: After preconditioning exposure, six conditioning sessions took place over a 10-day to 13-day period. Paired rats received 10 mg/kg cocaine i.p. prior to activity sessions and saline i.p. upon return to the colony room. Unpaired rats received saline prior to and cocaine after activity sessions. Time-off rats were withheld from the activity boxes, but were subject to all other procedures during conditioning. On the test day, all rats received saline prior to activity sessions. RESULTS: In the standard procedure, paired rats exhibited significantly greater activity than unpaired rats on the test day, consistent with previous reports. In the modified procedure, mean activity (all rats) decreased between the first and last preconditioning sessions. Still, the paired group exhibited greater activity than the unpaired group on the test day, suggesting that a conditioned stimulant effect developed in habituated rats. Activity in the time-off group did not significantly differ from the unpaired group demonstrating the habituation had not dissipated over this time period. CONCLUSIONS: These results support the conclusion that hyperactivity observed on the test day was not a result of antihabituation effects of cocaine

In the past several years there has been a dramatic proliferation of drug-related sites on the Internet. This article reviews the information found at selected Internet drug information libraries, and comments on its accuracy and implications. Drug-related sites were found by initially performing an Internet search on "psychoactive drugs" and then exploring links among the sites identified. Sites were chosen on the basis of comprehensiveness of information and positive or tolerant attitude toward drug use. While all classes of drugs are discussed at these sites, the primary foci of interest are synthetic and naturally occurring hallucinogens. Many of the biological materials discussed are legal and readily available. Information surveyed at these sites was largely accurate regarding the effects of various substances and biological sources of psychoactive compounds. CONCLUSIONS: Internet drug information libraries contain large amounts of information about a wide variety of drugs, including previously little-known biological sources of hallucinogens. The availability of this information could have significant effects on patterns of drug use.

BACKGROUND: Previous research has provided evidence for brain abnormalities in schizophrenia, but their relationship to specific clinical symptoms and syndromes remains unclear. METHODS: With an all-male demographically similar sample of 53 schizophrenic patients and 29 normal control subjects, cerebral gray and white matter volumes (adjusted for intracranial volume and age were determined for regions in the prefrontal lobe and in the superficial and mesial temporal lobe using T1-weighted magnetic resonance imaging with 2.8-mm coronal slices. RESULTS: As a group, schizophrenic patients had wide-spread bilateral decrements in gray matter in the pre-frontal (7.4%) and temporal lobe regions (8.9%), but not in white matter in these regions. In the temporal lobe, gray matter reductions were found bilaterally in the superior temporal gyrus (6.0%), but not in the hippocampus and parahippocampus. While there were no overall group differences in white matter volumes, widespread decrements in prefrontal white matter in schizophrenic patients (n = 53) were related to higher levels of negative symptoms (partial r[49] = -0.42, P = .002), as measured by the Scale for the Assessment of Negative Symptoms. A post hoc analysis revealed that schizophrenic patients with high negative symptoms had generalized prefrontal white matter reductions (11.4%) that were most severe in the orbitofrontal subregion (15.1%). CONCLUSIONS: These results suggest that gray matter deficits may be a fairly common structural abnormality of schizophrenia, whereas reductions in prefrontal white matter may be associated with schizophrenic negative symptoms

The occurrence of multiple diagnoses in one patient is a phenomenon of major clinical and theoretical importance. This paper reviews the various factors involved in real and artifactual comorbidity. Important causes of spurious comorbidity are discussed, including invalidity of the individual diagnoses, use of inappropriate diagnostic paradigms, descriptive overlap of diagnostic criteria, ascertainment bias, and diagnostic bias. To illustrate some of the concepts discussed, two examples are presented: the comorbidity of schizophrenia and substance use disorders, and the comorbidity of posttraumatic stress disorder and major depression. The study of comorbidity can advance psychiatry by helping us to clarify our thinking about categories of illness and the boundaries between them, as well as the relationships among these categories.

7 days beyond cessation of insulin treatment) elevation of threshold in ad libitum fed rats and, more transiently, reversed the threshold-lowering effect of food restriction. Acute insulin treatment (3 mU, 15 min prior) also elevated threshold in food-restricted rats. These results are consistent with the hypothesis that insulin modulates sensitivity of a brain reward system and that hypoinsulinemia may be the common factor in food restriction and diabetes that accounts for the enhancement of perifornical LHSS

Chronic food restriction enhances behavioral responsiveness to amphetamine and other abused drugs. Because this effect is evident when drugs are administered intracerebroventricularly (i.c.v.) as well as systemically, it would seem to reflect increased sensitivity of a neural substrate rather than a change in drug disposition. In the present study, c-Fos immunohistochemistry was used to evaluate whether the magnitude and pattern of cellular activation induced by i.c.v. amphetamine is altered by a regimen of food restriction previously shown to potentiate amphetamine reward. In the absence of amphetamine challenge, there was generally no difference in brain Fos-like immunoreactivity (FLI) between ad libitum fed and food-restricted rats. In response to amphetamine (50 microg), both groups displayed increased FLI in caudate-putamen, nucleus accumbens, bed nucleus of the stria terminalis, ventral pallidum, central nucleus of the amygdala, and cingulate cortex. With the exception of cingulate cortex and caudal caudate-putamen, a significantly greater response was observed in brain regions of food-restricted rats. These results indicate that food restriction augments a cellular immediate early gene (IEG) response to acute amphetamine in brain regions known to mediate rewarding and other behavioral effects of psychostimulants. The difference between these results and those produced by sensitizing regimens of psychostimulant exposure are discussed, as are possible endocrine factors that could be involved in the modulatory effect of food restriction on cellular and behavioral responses to amphetamine

BACKGROUND: Schizophrenics show deficits in sensorimotor gating, as measured by prepulse inhibition of acoustic startle (PPI). The goal of this investigation is to further characterize PPI and habituation deficits in schizophrenia, and to examine whether differing subgroups of schizophrenics would show comparable PPI deficits. METHODS: PPI was measured in 24 male schizophrenic subjects (9 acutely decompensated inpatients and 15 stable outpatients) and in 20 age-matched normal control subjects. Schizophrenic subjects were rated for positive and negative symptoms at the time of testing. RESULTS: Schizophrenic subjects showed deficits in prepulse inhibition and habituation as compared to normal subjects. Similar latency facilitation was produced by the prepulse in both groups. Acutely decompensated inpatients and stable outpatients did not differ in percent PPI. PPI did not correlate with severity of positive or negative symptoms. CONCLUSIONS: These results suggest that schizophrenic subjects have impaired central inhibitory mechanisms as measured by PPI, and support the hypothesis that periods of relative clinical remission are not accompanied by normalization of sensorimotor gating

In hippocampal membranes, the selective 5-hydroxytryptamine (5-HT(1A)) receptor agonists 8-hydroxy-dipropylaminotetralin (8-OH-DPAT) and N,N-dipropyl-5-carboxamidotryptamine (N,N-DP-5-CT) stimulated guanosine-5'-O-(3-thio)triphosphate ([(35)S]GTPgammaS) binding by 130 to 140%; binding stimulated by nonselective agonists (5-HT and 5-CT) was approximately 30% greater. However, the selective 5-HT(1A) receptor antagonist N-[2-[4-(2-methoxyphenyl)-1-piperazinyl]ethyl]-N-2-pyridinyl-cyclohex anecarboxamide (WAY100,635) completely abolished the increases produced by 8-OH-DPAT and N,N-DP-5-CT but only eliminated 70% of that elicited by 5-CT. The rank potency order of the tested agonists was identical with their rank order of affinity for 5-HT(1A) receptors [5-CT congruent with N,N-DP-5-CT > R-(+)-8-OH-DPAT > 5-HT > ipsapirone]. Racemic 8-OH-DPAT and the partial agonist ipsapirone exhibited lower intrinsic activity than R-(+)-8-OH-DPAT. R-(+)-8-OH-DPAT also stimulated [(35)S]GTPgammaS binding in cortex, but not in striatum, which lacks 5-HT(1A) receptors. Partial irreversible inactivation of 5-HT(1A) receptors, in vitro with phenoxybenzamine (0.3 or 1 microM) or in vivo with N-ethoxycarbonyl-2-ethoxy-1,2-dihydroquinoline (1 mg/kg), reduced the maximal response produced by R-(+)-8-OH-DPAT but did not alter its EC(50). In autoradiographic sections, R-(+)-8-OH-DPAT stimulated [(35)S]GTPgammaS binding in 5-HT(1A) receptor-rich regions (dorsal hippocampus, 123%; lateral septum, 111%; midhippocampus, 110%; dorsal raphe nucleus, 83%; medial prefrontal cortex, approximately 60%). The EC(50) of R-(+)-8-OH-DPAT did not vary significantly among brain regions (46-96 nM). Partial irreversible blockade of 5-HT(1A) receptors in brain sections (phenoxybenzamine, 10 microM) reduced the maximal response without altering the EC(50) in both the hippocampus and dorsal raphe. Despite prior evidence that dorsal raphe somatodendritic 5-HT(1A) autoreceptors exhibit high receptor/effector coupling efficiency (receptor reserve) compared with postsynaptic receptors in hippocampus, there was no evidence of a difference at the level of receptor/G protein coupling