Proteins of the postsynaptic density.

An analysis was made of the protein composition of a fraction of postsynaptic densities (PSDs) prepared from rat brain. Protein makes up 90% of the material in the PSD fraction. Two major polypeptide fractions are present, based on sodium dodecyl sulfate polyacrylamide gel electrophoresis. The major polypeptide fraction has a molecular weight of 53,000, makes up about 45% of the PSD protein, and comigrates on gels with a major polypeptide of the synaptic plasma membrane. The other polypeptide band has a molecular weight of 97,000, accounts for 17% of the PSD protein, and is not a prominent constituent of other fractions. Six other polypeptides of higher molecular weight (100,000-180,000) are consistently present in small amounts (3-9% each). The PSD fraction contains slightly greater amounts of polar amino acids and proline than the synaptic plasma membrane fraction, but no amino acid is usually prominent. The PSD apparently consists of a structural matrix formed primarily by a single polypeptide or class of polypeptides of 53,000 molecular weight. Small amounts of other specialized proteins are contained within this matrix.

Isolation of postsynaptic densities from rat brain.

Most synapses in the central nervous system exhibit a prominent electron-opaque specialization of the postsynaptic plasma membrane called the postsynaptic density (PSD). We have developed a procedure for the isolation of PSDs which is based on their buoyant density and their insolubility in N-lauroyl sarcosinate. Treatment of synaptic membranes with this detergent solubilizes most plasma membranes and detaches PSDs from the plasma membrane so that they can be purified on a density gradient. Isolated PSDs appear structurally intact and exhibit those properties which characterize them in tissue. The isolated PSDs are of the size, shape, and electron opacity of those seen in tissue; they stain with both ethanolic phosphotungstic acid and bismuth iodide-uranyl lead and the fraction contains cyclic 3',5'-phosphodiesterase activity. Quantitative electron microscope analysis of the PSD fraction gives an estimated purity of better than 85%. Inasmuch as the PSD is associated primarily with dendritic excitatory synapses, our PSD fraction represents the distinctive plasma membrane specialization of this specific synaptic type in isolation.

Tumor necrosis factor alpha: activity dependent expression and promotion of cortical column sleep in rats.

Cortical surface evoked potentials (SEPs) are larger during sleep and characterize a sleep-like state in cortical columns. Since tumor necrosis factor alpha (TNF) may be involved in sleep regulation and is produced as a consequence of waking activity, we tested the hypothesis that direct application of TNF to the cortex will induce a sleep-like state within cortical columns and enhance SEP amplitudes. We found that microinjection of TNF onto the surface of the rat somatosensory cortex enhanced whisker stimulation-induced SEP amplitude relative to a control heat-inactivated TNF microinjection. We also determined if whisker stimulation enhanced endogenous TNF expression. TNF immunoreactivity (IR) was visualized after 2 h of deflection of a single whisker on each side. The number of TNF-IR cells increased in layers II-IV of the activated somatosensory barrel column. In two separate studies, unilateral deflection of multiple whiskers for 2 h increased the number of TNF-IR cells in layers II-V in columns that also exhibited enhanced cellular ongogene (Fos-IR). TNF-IR also colocalized with NeuN-IR suggesting that TNF expression was in neurons. Collectively these data are consistent with the hypotheses that TNF is produced in response to neural activity and in turn enhances the probability of a local sleep-like state as determined by increases in SEP amplitudes.

Racial Differences in Misclassification of Healthy Eating Based on Food Frequency Questionnaire and 24-Hour Dietary Recalls.

OBJECTIVES: To examine the agreement in nutrient intake and alternate healthy eating indices (AHEI) between a self-administered Food Frequency Questionnaire (FFQ) and 24-hour recall (24HR) measurements of diet by race, among urban older women. DESIGN: Cross-sectional observational study. SETTING: Urban neighborhoods in Washington, DC, USA. PARTICIPANTS: Community-dwelling White and Black women aged 65 and older. MEASUREMENTS: In 2014 and 2015, 49 White and 44 Black older women were queried on diet using both FFQ and 24-hour recalls. The correlation coefficients of 55 nutrient intake measures and agreements on healthy eating classification between the two instruments were compared overall and by race. RESULTS: The mean correlation coefficient (rho) was 0.46 for Whites and 0.23 for Blacks. For 47 measures, rho was lower for Blacks. Whites had a strong correlation of ≥0.5 for 28 items, while Blacks had strong correlations for only 3 items. Based on FFQ, the mean (SD) of AHEI were 54.0 (10.3) for Whites and 45.9 (8.8) for Blacks (p<0.001). Based on 24HR, the mean (SD) were 43.9 (10.8) for Whites and 33.2 (9.6) for Blacks (p<0.001). Using 32 as the cutoff (40% of maximum AHEI score), 50% of Blacks and 14% of Whites were classified as eating unhealthy based on the 24HR, versus 2.6% and 0% based on the FFQ. CONCLUSION: The FFQ has limited ability to accurately assess nutrient intake among older Black women, and tends to underestimate racial differences in healthy eating. The FFQ should be further improved for use in racial disparities research of healthy eating in older age, using a larger sample of older women with racial and geographic diversities.

Racial Differences in Eating Patterns and Food Purchasing Behaviors among Urban Older Women.

OBJECTIVE: To examine differences in diet and food purchasing behaviors between Black and White older women living in urban neighborhoods. DESIGN: Cross-sectional observational study. SETTING: Urban neighborhoods in Washington, DC, USA. PARTICIPANTS: Community-dwelling White and Black women of age 65 and older. MEASUREMENTS: Participants were queried on diet via 24-hour recalls, food purchasing habits, their use of neighborhood resources and local travel patterns. Frequency and location of self-reported food purchasing and consumption were compared by race. RESULTS: In 2014 and 2015, 49 White and 44 Black older women were enrolled in the study. Compared to Whites, Blacks reported lower daily caloric intake (mean (SD) 1314 (404) vs. 1529 (448), p=0.02), with a higher percent of calories from protein and fat 1.8 (7.0), p=0.03), and a slightly higher polyunsaturated to saturated fat ratio (p=0.05). Blacks had substantially lower alternate healthy eating index (AHEI) (33.5 (10.2) vs. 43.9 (10.8) of 80 possible points, p<0.001), daily intake (grams) of total fiber (15.3 (8.1) vs. 22.9 (8.5), p<0.001), insoluble fiber (10.8 (6.9) vs. 15.9 (6.5), p<0.001), and soluble fiber (4.5 (2.0) vs. 6.9 (2.8), p<0.001). Blacks had lower intake of micronutrients, alcohol and caffeine. Blacks shopped for groceries less often (4.4 (3.0) vs. 6.2 (3.0) monthly; p=0.006) and spent a longer time traveling to stores (15.8 (9.1) vs. 11.5 (7.2) minutes per trip, p=0.02). A lower percent of Blacks walked to stores (14% vs. 40%, p=0.003) and a higher percent of Blacks rode in a car with someone else (33% vs. 6%, p<0.001). CONCLUSIONS: In an urban setting, food consumption and purchasing behaviors differed substantially between older Black and White women, which should be further investigated and considered to promote healthy eating in older populations.

Gender and Age Differences in Levels, Types and Locations of Physical Activity among Older Adults Living in Car-Dependent Neighborhoods.

BACKGROUND: A thorough understanding of gender differences in physical activity is critical to effective promotion of active living in older adults. OBJECTIVES: To examine gender and age differences in levels, types and locations of physical activity. DESIGN: Cross-sectional observation. SETTING: Car-dependent urban and rural neighborhoods in Worcester County, Massachusetts, USA. PARTICIPANTS: 111 men and 103 women aged 65 years and older. MEASUREMENTS: From 2012 to 2014, participants were queried on type, frequency and location of physical activity. Participants wore an accelerometer for 7 consecutive days. RESULTS: Compared to women, men had a higher mean daily step count (mean (SD) 4385 (2122) men vs. 3671(1723) women, p=0.008). Men reported higher frequencies of any physical activity and moderate-to-vigorous physical activity, and a lower frequency of physical activity inside the home. Mean daily step counts and frequency of physical activity outside the home decreased progressively with age for both men and women. Women had a sharper decline in frequencies of self-reported physical activity. Men had a significant decrease in utilitarian walking, which women did not (p=0.07). Among participants who reported participation in any physical activity (n=190), more women indicated exercising indoors more often (59% vs. 44%, p=0.04). The three most commonly cited locations for physical activity away from home for both genders were streets or sidewalks, shopping malls, and membership-only facilities (e.g., YMCA or YWCA). The most common types of physical activity, performed at least once in a typical month, with over 40% of both genders reporting, included light housework, brisk walking, leisurely walking, and stretching. CONCLUSION: Levels, types and location preferences of physical activity differed substantially by gender. Levels of physical activity decreased progressively with age, with greater decline among women. Consideration of these gender differences is necessary to improve the effectiveness of active living promotion programs among older adults.

Obesity and the risk of myocardial infarction in 27,000 participants from 52 countries: a case-control study.

BACKGROUND: Obesity is a major risk factor for cardiovascular disease, but the most predictive measure for different ethnic populations is not clear. We aimed to assess whether markers of obesity, especially waist-to-hip ratio, would be stronger indicators of myocardial infarction than body-mass index (BMI), the conventional measure. METHODS: We did a standardised case-control study of acute myocardial infarction with 27 098 participants in 52 countries (12,461 cases and 14,637 controls) representing several major ethnic groups. We assessed the relation between BMI, waist and hip circumferences, and waist-to-hip ratio to myocardial infarction overall and for each group. FINDINGS: BMI showed a modest and graded association with myocardial infarction (OR 1.44, 95% CI 1.32-1.57 top quintile vs bottom quintile before adjustment), which was substantially reduced after adjustment for waist-to-hip ratio (1.12, 1.03-1.22), and non-significant after adjustment for other risk factors (0.98, 0.88-1.09). For waist-to-hip ratio, the odds ratios for every successive quintile were significantly greater than that of the previous one (2nd quintile: 1.15, 1.05-1.26; 3rd quintile: 1.39; 1.28-1.52; 4th quintile: 1.90, 1.74-2.07; and 5th quintiles: 2.52, 2.31-2.74 [adjusted for age, sex, region, and smoking]). Waist (adjusted OR 1.77; 1.59-1.97) and hip (0.73; 0.66-0.80) circumferences were both highly significant after adjustment for BMI (p<0.0001 top vs bottom quintiles). Waist-to-hip ratio and waist and hip circumferences were closely (p<0.0001) associated with risk of myocardial infarction even after adjustment for other risk factors (ORs for top quintile vs lowest quintiles were 1.75, 1.33, and 0.76, respectively). The population-attributable risks of myocardial infarction for increased waist-to-hip ratio in the top two quintiles was 24.3% (95% CI 22.5-26.2) compared with only 7.7% (6.0-10.0) for the top two quintiles of BMI. INTERPRETATION: Waist-to-hip ratio shows a graded and highly significant association with myocardial infarction risk worldwide. Redefinition of obesity based on waist-to-hip ratio instead of BMI increases the estimate of myocardial infarction attributable to obesity in most ethnic groups.

The susceptibility of the glycoprotein from the purified (Na+, K+)-activated adenosine triphosphatase to tryptic and chymotryptic degradation with and without Na+ and K+.

Purified (Na+, K+)-activated adenosine triphosphatase ((Na+, K+)-ATPase, ATP phosphohydrolase, EC 3.6.1.3) has been subjected to trypsin and chymotrypsin hydrolysis. The glycoprotein is much more resistant to proteolysis than the large chain. This differential susceptibility to proteolysis is not due to differences in the number of trypsin or chymotrypsin sensitive bonds because the two subunits are equally susceptible to proteolysis after isolation by preparative gel electrophoresis in sodium dodecyl sulfate. It is also not due to steric "shielding" of the glycoprotein by the large chain or its proteolytic products: (1) The rate of digestion of the glycoprotein is not increased after 90% of the large chain is digested. (2) The majority of the large chain peptides are released into the supernatant upon degradation. It is concluded that the greater resistance of the glycoprotein to proteolysis is due to its native conformation. In the absence of the large chain, the susceptibility of the glycoprotein to tryptic degradation by K+ and Na+. The evidence suggests that this decreased susceptibility was due to conformational changes in the glycoprotein. These specific ligand effects on proteolysis of the glycoprotein suggests that the glycoprotein may participate in Na+ and K+ binding by (Na+, K+)-ATPase.

Metabolism of opioid peptides by cerebral microvascular aminopeptidase M.

Aminopeptidase M (EC 3.4.11.2), which can degrade low molecular weight opioid peptides, has been reported in both peripheral vasculature and in the CNS. Thus, we have studied the metabolism of opioid peptides by membrane-bound aminopeptidase M derived from cerebral microvessels of hog and rabbit. Both hog and rabbit microvessels were found to contain membrane-bound aminopeptidase M. At neutral pH, microvessels preferentially degraded low molecular weight opioid peptides by hydrolysis of the N-terminal Tyr1-Gly2 bond. Degradation was inhibited by amastatin (I50 = 0.2 microM) and bestatin (10 microM), but not by a number of other peptidase inhibitors including captopril and phosphoramidon. Rates of degradation were highest for the shorter peptides (Met5- and Leu5-enkephalin) whereas beta-endorphin was nearly completely resistant to N-terminal hydrolysis. Km values for the microvascular aminopeptidase also decreased significantly with increasing peptide length (Km = 91.3 +/- 4.9 and 28.9 +/- 3.5 microM for Met5-enkephalin and Met5-enkephalin-Arg6-Phe7, respectively). Peptides known to be present within or in close proximity to cerebral vessels (e.g., neurotensin and substance P) competitively inhibited enkephalin degradation (Ki = 20.4 +/- 2.5 and 7.9 +/- 1.6 microM, respectively). These data suggest that cerebral microvascular aminopeptidase M may play a role in vivo in modulating peptide-mediated local cerebral blood flow, and in preventing circulating enkephalins from crossing the blood-brain barrier.

Carbohydrate composition of central nervous system synapses. Analysis of isolated synaptic junctional complexes and postsynaptic densities.

The composition of specialized structures present at synapses within the central nervous system was elucidated by biochemical analysis of fractions enriched in synaptic junctional complexes and postsynaptic densities. The results indicate that the synaptic junctional complex is primarily protein together with some glycoproteins. The synaptic junctional complex proteins are similar in amino acid composition to synaptic membrane proteins; they are not expecially rich in basic residues, as previously suggested. The major carbohydrates present in the synaptic junctional complex and postsynaptic density glycoproteins are mannose, galactose, and glucosamine, with lesser amounts of fucose, N-acetylneuraminic acid, and galactosamine. Comparison with the synaptic membrane fraction indicates that galactose is more concentrated in the synaptic junctional complex and mannose in the postsynaptic density. Glucose is dramatically enriched in both these fractions. Sucrose binding during isolation may partially account for the glucose enrichment.

Expression of simple epithelial keratins 8 and 18 in epidermal neoplasia.

A systematic study of keratin expression in epidermal lesions (six actinic keratoses, 10 Bowen's disease, seven squamous cell carcinomas) has been undertaken by using a large panel of monospecific monoclonal antibodies to individual keratins. Expression of differentiation-specific keratins was frequently delayed or lost from dysplastic regions. Novel expression of the embryonic, or simple epithelial, keratins 8 and 18 was widely observed in intradermal areas of poorly differentiated squamous cell carcinomas. In addition, the most proliferative of in situ malignancies (Bowen's disease) also contained small numbers of cells expressing simple epithelial keratins. These observations suggest that the expression of simple epithelial keratins may be of functional importance in malignancy of keratinocytes and could be related to tumor invasion and/or to changes in epithelial-mesenchymal interactions.

Conversion of B1 kinin receptor-mediated vascular relaxation to contraction.

We have previously reported that des-Arg9-bradykinin can relax the phenylephrine-precontracted rabbit mesenteric artery through B1 kinin receptor stimulation and the subsequent release of prostaglandins. In the present study, we have found that this relaxant response can be converted to a contractile response by the cyclooxygenase inhibitor indomethacin. Contraction was dose-dependent and was blocked by the B1 receptor antagonist [Leu8]des-Arg9-bradykinin, with a pA2 value obtained by Schild regression similar to that reported for relaxation in the absence of indomethacin. Des-Arg10-kallidin (ED50 = 5.0 +/- 0.9 X 10(-9) M) was 16 times more potent than des-Arg9-bradykinin (ED50 = 8.1 +/- 0.8 X 10(-8) M) in contracting the indomethacin-treated artery and was also blocked by [Leu8]des-Arg9-bradykinin. In contrast, only 13 out of 24 indomethacin-treated vessels contracted in response to bradykinin, which had only one tenth and one 160th the potency (ED50 = 9.9 +/- 1.8 X 10(-7) M) of des-Arg9-bradykinin and des-Arg10-kallidin, respectively. B1 kinin receptor-mediated contraction in the presence of indomethacin was unaffected by the dual cyclooxygenase-lipoxygenase inhibitor BW 755c. These results indicate that des-Arg-kinins can stimulate both relaxation and contraction of the phenylephrine-precontracted rabbit mesenteric artery through stimulation of B1 kinin receptors. The relaxation is dependent on the release of prostaglandins, while the contraction may represent a direct effect.

A topographically organized gamma-aminobutyric acid projection from the ventral pallidum to the nucleus accumbens in the rat.

Anatomical and electrophysiological studies have indicated that a reciprocal projection from the ventral pallidum back to the nucleus accumbens exists and has functional relevance. In this study, the topographical projection from the ventral pallidum to the nucleus accumbens was examined by using retrograde tracing with fluoro-gold iontophoresed in subcompartments of the nucleus accumbens in rats combined with either in situ hybridization for glutamic acid decarboxylase and preproenkephalin mRNA or substance P immunoreactivity. Deposits made into the medial nucleus accumbens preferentially labeled neurons in the medial ventral pallidum, while deposits into the dorsolateral nucleus accumbens, at or lateral to the anterior commissure, labeled primarily cells in the dorsal and lateral ventral pallidum. A mediolateral to rostrocaudal topography was also observed, with the medial deposits preferentially labeling cells in rostral ventral pallidum and the lateral deposits resulting in retrogradely labeled cells in the ventral pallidum below the crossing of the posterior anterior commissure (subcommissural) as well as below the globus pallidus (sublenticular). The majority of cells retrogradely labeled with fluoro-gold were double-labeled for glutamic acid decarboxylase mRNA. In contrast, very few retrogradely labeled neurons in the ventral pallidum were double labeled for mRNA for preproenkephalin. These data demonstrate a topographically organized projection from the ventral pallidum to the nucleus accumbens that is primarily gamma-aminobutyric acid (GABA)-ergic and reciprocal to the GABAergic projection from the nucleus accumbens to the ventral pallidum.

Effect of structural modification of enol-carboxamide-type nonsteroidal antiinflammatory drugs on COX-2/COX-1 selectivity.

Meloxicam (5), an NSAID in the enol-carboxamide class, was developed on the basis of its antiinflammatory activity and relative safety in animal models. In subsequent screening in microsomal assays using human COX-1 and COX-2, we discovered that it possessed a selectivity profile for COX-2 superior to piroxicam and other marketed NSAIDs. We therefore embarked on a study of enol-carboxamide type compounds to determine if COX-2 selectivity and potency could be dramatically improved by structural modification. Substitution at the 6- and 7-positions of the 4-oxo-1,2-benzothiazine-3-carboxamide, alteration of the N-methyl substituent, and amide modification were all examined. In addition we explored several related systems including the isomeric 3-oxo-1,2-benzothiazine-4-carboxamides, thienothiazines, indolothizines, benzothienothiazines, naphthothiazines, and 1,3- and 1,4-dioxoisoquinolines. While a few examples were found with greater potency in the COX-2 assay, no compound tested had a better COX-2/COX-1 selectivity profile than that of 5.

GABA and enkephalin projection from the nucleus accumbens and ventral pallidum to the ventral tegmental area.

GABAergic and enkephalinergic afferents to the ventral tegmental area were investigated in the rat using retrograde tracing techniques combined with in situ hybridization. Following iontophoretic deposit of Fluoro-Gold in the ventral tegmental area labeling in the forebrain was most dense in the shell of the nucleus accumbens, rostral ventromedial ventral pallidum and diagonal band of Broca. A smaller density was also observed in the lateral septum. In these forebrain regions, the portion of retrogradely labeled cells that contained mRNA for glutamate decarboxylase ranged from 25% to 50%, whereas only 5% to 15% were double-labeled for preproenkephalin mRNA. Cells double-labeled with either glutamate decarboxylase or preproenkephalin mRNA were most numerous in the lateral septum, shell of the nucleus accumbens, rostral ventral pallidum and diagonal band of Broca. Large Fluoro-Gold deposits which invaded the medial substantia nigra resulted in a significant number of retrogradely labeled cells in the core of the nucleus accumbens, and a portion of these neurons also contained mRNA for glutamate decarboxylase or preproenkephalin. These data demonstrate the presence of GABAergic and enkephalinergic neurons projecting from the nucleus accumbens, ventral pallidum and diagonal band of Broca to the ventral tegmental area.

The mediodorsal nucleus of the thalamus in rats--I. forebrain gabaergic innervation.

The aim of this study was to determine whether forebrain neurons projecting to the mediodorsal nucleus of the thalamus in rats express glutamate decarboxylase messenger RNA as a marker for GABAergic neurons. Forebrain glutamate decarboxylase messenger RNA-containing neurons that project to the mediodorsal nucleus were identified using a combination of retrograde tracing with Fluoro-Gold and in situ hybridization for the messenger RNA encoding the 67,000 molecular weight synthetic enzyme for GABA. Glutamate decarboxylase messenger RNA-containing afferents to the mediodorsal nucleus were observed in the olfactory tubercle, vertical limb of the diagonal band of Broca, ventral pallidum, sublenticular substantia innominata, globus pallidus, lateral preoptic area, bed nucleus of the stria terminalis and reticular nucleus of the thalamus. The largest proportions of glutamate decarboxylase messenger RNA-containing afferents to the mediodorsal nucleus were observed in the vertical limb of the diagonal band, ventral pallidal parts of the olfactory tubercle and the reticular nucleus of the thalamus. Somewhat fewer glutamate decarboxylase messenger RNA-containing, retrogradely labeled neurons were observed in the subcommissural ventral pallidum and sublenticular substantia innominata. These data suggest that a GABAergic projection from the basal forebrain to the mediodorsal nucleus of the thalamus can influence the function of this nucleus.

Topography and functional role of dopaminergic projections from the ventral mesencephalic tegmentum to the ventral pallidum.

A dopaminergic projection from the ventral tegmental area to the ventral pallidum was identified in the rat using anterograde tract tracing and combined retrograde tracing-immunocytochemistry. The projection was found to be topographically organized such that fibers innervating the ventromedial ventral pallidum arose from neurons located along the midline nuclei of the ventral mesencephalon, including the nucleus interfascicularis and nucleus linearis caudalis. Ventral tegmental neurons situated more laterally, in the nucleus parabrachialis pigmentosus and nucleus paranigralis, projected to the ventromedial and dorsolateral ventral pallidum. The substantia nigra did not supply a major contribution to this projection. The proportion of ventral tegmental area dopaminergic neurons projecting to the ventral pallidum ranged from approximately 30% to 60%. The functional significance of the projection is indicated since intra-ventral pallidum microinjections of dopamine elicited a dose-dependent increase in locomotor activity. Furthermore, whereas pretreatment of the ventral pallidum with the GABAA agonist muscimol has been shown to attenuate opioid-induced locomotor activity elicited from the ventral pallidum, it did not attenuate the dopamine-induced motor response. Thus, while mu-opioids in the ventral pallidum may presynaptically regulate GABAergic efferents from the nucleus accumbens, it appears that the dopaminergic input directly influences the ventral pallidal output neuron which is involved in locomotion.

The mediodorsal nucleus of the thalamus in rats--II. Behavioral and neurochemical effects of GABA agonists.

The aim of this study was to determine how GABA receptors in the mediodorsal nucleus of the thalamus in rats might contribute to the regulation of locomotor behavior. Microinjections of the GABAB and GABAA agonists, baclofen and muscimol, into the mediodorsal nucleus produced dose-dependent increases in locomotion that were blocked by co-administration of the GABAB antagonist, 2-hydroxysaclofen. Microinjection of baclofen along the midline, lateral into the ventrolateral thalamus or into the lateral ventricles produced significantly smaller dose-dependent increases in locomotion, indicating that the anatomical locus for baclofen-induced locomotion resides in the mediodorsal nucleus. The motor response elicited by microinjected baclofen was associated with a reduction in dopamine metabolism in the prefrontal cortex and an increase in metabolism in the core of the nucleus accumbens, but not in the accumbal shell or the dorsolateral striatum. These results suggest that GABAergic afferents to the mediodorsal nucleus may oppose a tonic inhibitory tone on locomotor activity. The data also suggest that the motor response produced by baclofen in the mediodorsal thalamus may arise by inhibiting the projections to the prefrontal cortex which modulate mesocorticolimbic dopamine transmission.

Topographical distribution of down-regulated muscarinic receptors in rat brains after repeated exposure to diisopropyl phosphorofluoridate.

Quantitative receptor autoradiography demonstrated that muscarinic receptors were down-regulated in Wistar rats after repeated exposure to diisopropyl phosphorofluoridate. The density of receptors was decreased to 60-85% of the controls. Reductions in muscarinic receptor binding were observed in cortex, caudate-putamen, lateral septum, hippocampal formation, superior colliculus, and pons. The density of muscarinic receptors was unchanged in thalamic and hypothalamic nuclei, periaqueductal grey, cerebellum, inferior colliculus and reticular formation of the brain stem. The down-regulation of muscarinic receptors in forebrain structures, such as cortex, caudate-putamen and hippocampus, may be important in the adaptation to the behavioral effects of organophosphate poisons.

Substance P in the ventral pallidum: projection from the ventral striatum, and electrophysiological and behavioral consequences of pallidal substance P.

The ventral pallidum of the basal forebrain contains a high concentration of substance P and receives a massive projection from the nucleus accumbens. The present study was designed to determine whether the accumbens serves as a source for substance P-containing fibers in the ventral pallidum and characterize the function of this tachykinin peptide within the ventral pallidum. By combining in situ hybridization for messenger RNA of the substance P prohormone, beta-preprotachykinin, with Fluoro-Gold retrograde labeling from iontophoretic deposits in the ventral pallidum, a population of substance P-containing neurons was demonstrated in the shell and core components of the nucleus accumbens and the ventromedial striatum. The function of substance P within the ventral pallidum was characterized at the level of the single neuron, and the behaving animal. Electrophysiological assessment revealed that approximately 40% of the 97 ventral pallidal neurons tested were readily excited by microiontophoretic applications of substance P or a metabolically stable agonist analog, DiMeC7 [(pGlu5, MePhe8, MeGly9)-substance P5-11]. Response characteristics were distinguished from glutamate-induced excitations by a slower onset and longer duration of action. Recording sites of tachykinin-sensitive neurons were demonstrated to be located throughout the ventral pallidum and within high densities of fibers exhibiting substance P-like immunoreactivity. When behaving rats received microinjections of DiMeC7 into this same region, the animals displayed an increase in motor activity, with a response threshold of 0.1nmol per hemisphere. These results verify the existence of a substantial substance P-containing projection from the nucleus accumbens to the ventral pallidum. The projection likely serves to excite ventral pallidal neurons for these neurons readily increased firing following local exposure to tachykinins. Furthermore, an increase in motor behavior appears to be a consequence of this neuronal response.