Dopamine in the nucleus accumbens core, but not shell, increases during signaled food reward and decreases during delayed extinction.

UNLABELLED: Microdialysis studies in rat have generally shown that appetitive stimuli release dopamine (DA) in the nucleus accumbens (NAc) shell and core. Here we examined the release of DA in the NAc during delivery of reward (food) and during extinction of food reward in the freely moving animal by use of in vivo microdialysis and HPLC. Fifty-two male Wistar rats were trained to receive food reward associated with appearance of cue-lights in a Skinner-box during in vivo microdialysis. Different behavioral protocols were used to assess the effects of extinction on DA and its metabolites. Results Exp. 1: (a) During a 20-min period of cued reward delivery, DA increased significantly in the NAc core, but not shell subregion; (b) for the next 60min period half of the rats underwent immediate extinction (with the CS light presented during non-reward) and the other half did not undergo extinction to the cue lights (CS was not presented during non-reward). DA remained significantly increased in both groups, providing no evidence for a decrease in DA during extinction in either NAc core or shell regions. (c) In half of the animals of the group that was not subjected to extinction, the cue lights were turned on for 30min, thus, initiating extinction to cue CS at a 1h delay from the period of reward. In this group DA in the NAc core, but not shell, significantly decreased. Behavioral analysis showed that while grooming is an indicator of extinction-induced behavior, glances toward the cue-lights (sign tracking) are an index of resistance to extinction. Results Exp. 2: (a) As in Exp. 1, during a 30-min period of cued reward delivery, DA levels again increased significantly in the NAc core but not in the NAc shell. (b) When extinction (the absence of reward with the cue lights presented) was administered 24h after the last reward session, DA again significantly decreased in the NAc core, but not in the NAc shell. CONCLUSIONS: (a) These results confirm the importance of DA release in the NAc for reward-related states, with DA increasing in the core, but not shell subregion. (b) They provide first evidence that during the withholding of expected reward, DA decreases in the NAc core, but not shell region. (c) This decrease in DA appears only after a delay between delivery of reward and extinction likely due to it being masked by persisting DA release. We hypothesize the decrease in extinction-induced release of DA in the NAc core to be a marker for the despair/depression that is known to accompany the failure to obtain expected rewards/reinforcers.

Intranasal administration of progesterone increases dopaminergic activity in amygdala and neostriatum of male rats.

We evaluated the effects of intranasal administration of progesterone (PROG) on the activity of dopaminergic neurons in the brain of anesthetized rats by means of microdialysis. Male Wistar rats were implanted with guide cannulae in the basolateral amygdala and neostriatum. Three to 5 days later, they were anesthetized with urethane, and dialysis probes were inserted. After a stabilization period of 2 h, four 30-min samples were collected. Thereafter, the treatment (0.5, 1.0 or 2.0 mg/kg of PROG dissolved in a viscous castor oil mixture, or vehicle) was applied into the nose in a volume of 10 microl (5 microl in each nostril). In other animals, an s.c. injection of PROG (1.0, 2.0 or 4.0 mg/kg) or vehicle was given. Samples of both application ways were collected at 30-min interval for 4 h after the treatment and immediately analyzed with high performance liquid chromatography and electrochemical detection. Intranasal administration of 2 mg/kg of PROG led to an immediate (within 30 min after the treatment) significant increase in the basolateral amygdala dopamine levels. In the neostriatum, the 2 mg/kg dose led to a delayed significant increase in dopamine. S.c. administration of 4 mg/kg of PROG was followed by a delayed significant increase in dopamine, both, in the basolateral amygdala and neostriatum, but smaller in magnitude in comparison to the intranasal treatment. This is the first study to demonstrate dopamine-enhancing effects of PROG, not only in the neostriatum, but also in the basolateral amygdala. Our results indicate that the intranasal route of administration of PROG is a more efficacious way for targeting the brain than the s.c. route.

Evidence for hemispheric specialization in the marmoset (Callithrix penicillata) based on lateralization of behavioral/neurochemical correlations.

A correlative study between behavioral, neurochemical and hormonal measures was conducted on male black tufted-ear marmoset monkeys (Callithrix penicillata). Behavioral analysis was performed in order to examine the effects of confrontation with a natural predator (taxidermized oncilla cat, Felis tigrina). The subjects were subjected to four trials without predator, six confrontation trials with predator present, and four trials with the predator removed. Handedness was analyzed by the frequency with which they performed scratching, grooming and hanging behaviors with the left or right hands. The animals' brains were subjected to ex vivo neurochemical analysis of several structures from both hemispheres. The content of monoamines, acetycholine and metabolites were analyzed by HPLC-ED. Plasma levels of cortisol and adrenocorticotrophic hormone (ACTH) were analyzed by chemoluminescence immunoassay. Testosterone plasma concentration was determined by radioimmunoassay. Higher levels of dopamine and acetylcholine were detected in the right caudate/putamen, in comparison to the left. For the remaining areas, similar levels were observed in both hemispheres. A hand preference between and within the behaviors scored was not detected. However, correlative analyses revealed complex interactions between the behavioral and neurochemical measures, particularly in the left hemisphere. Lateralized correlations were found in relation to brain site, type of behavior, neurochemical parameter and treatment condition, thus providing evidence for functional brain asymmetries in this species. Interhemispheric comparisons of neurochemical/behavioral correlations appear to be a promising approach towards delineating hemispheric specialization of functions in this, and perhaps, other species.

Correlations between hypothalamus-pituitary-adrenal axis parameters depend on age and learning capacity.

Glucocorticoid hormones are released after activation of the hypothalamus-pituitary-adrenal (HPA) axis and in the brain can modulate synaptic plasticity and memory formation. Clear individual differences in spatial learning and memory in the water maze allowed classification of groups of young (3 months) and aged (24 months) male Wistar rats as superior and inferior learners. We tested 1) whether measures of HPA activity are associated with cognitive functions and aging and 2) whether correlations of these measures depend on age and learning performance. Basal ACTH, but not corticosterone, was increased in aged rats, with the stress-induced ACTH response exaggerated in aged-inferior learners. Aged-superior learners had lower expression of glucocorticoid receptor and CRH mRNA in the parvocellular paraventricular nucleus of the hypothalamus compared with all other groups. Hippocampal mineralocorticoid receptor and glucocorticoid receptor mRNAs differed modestly between groups, but steroid receptor coactivator and heat-shock-protein 90 mRNAs were not different. Strikingly, correlations between HPA axis markers were dependent on grouping animals according to learning performance or age. CRH mRNA correlated with ACTH only in aged animals. Parvocellular arginine vasopressin mRNA was negatively correlated to basal corticosterone, except in aged-inferior learners. Corticosteroid receptor mRNA expression showed a number of correlations with other HPA axis regulators specifically in superior learners. In summary, the relationships between HPA axis markers differ for subgroups of animals. These distinct interdependencies may reflect adjusted set-points of the HPA axis, resulting in adaptation (or maladaptation) to the environment and, possibly, an age-independent determination of learning ability.

Aged endothelial nitric oxide synthase knockout mice exhibit higher mortality concomitant with impaired open-field habituation and alterations in forebrain neurotransmitter levels.

Endothelial nitric oxide synthase (eNOS) has been implicated in various brain and peripheral pathologies such as renal failure, heart failure or stroke. Consequently, the mortality rate of aged eNOS knockout mice (eNOS-/-) was higher than that of age-matched (18-22 months old) controls. Only seven of the original 14 eNOS-/- animals that participated in the study reached the age of 18 months or older, whereas no control mice died during this life span. In order to assess the behavioral and neurochemical consequences of chronic eNOS deficiency we examined whether the surviving aged eNOS-/- mice showed changes in terms of motor, emotional, exploratory and neurochemical parameters. Aged eNOS-/- mice showed reduced exploratory activity in the open-field with no habituation observable neither within sessions nor after repeated exposures. Pole test performance of eNOS-/- mice was comparable to controls. In the elevated plus-maze eNOS-/- mice did not differ from controls in terms of time spent in and entries into arms, but showed less locomotion on the open arms. The most prominent neurochemical alterations in the forebrains of aged eNOS-/- mice were: (a) increased acetylcholine levels in the neostriatum; (b) decreased noradrenaline concentrations in the ventral striatum; and (c) lower serotonin levels in the frontal cortex and ventral striatum. The present findings suggest that mice which survived chronic eNOS-deficiency into old age, show some behavioral and neurochemical phenotypes distinct from adult eNOS-/- mice.

Enhanced maze performance and reduced oxidative stress by combined extracts of zingiber officinale and ginkgo biloba in the aged rat.

Here we assessed the effects of i.g. administration of Zingicomb (ZC), a mixture of zingiber officinale and ginkgo biloba extracts, on learning and memory, and on indicators of oxidative stress in aged rats. Effects of ZC (1 and 10 mg/kg) were investigated in 22-24 months old Wistar rats using the Morris water maze, in which they show deficient performance as compared to 3 months old rats in the undrugged state (days 1 and 2). Treatment was administered on days 3 and 4 of training, then over 7 days with training discontinued, and again on days 5 and 6 when training was resumed. Thereafter chronic treatment was maintained over 5 months. 1 mg/kg ZC improved escape learning in the water maze. The two capital indicators of oxidative stress in brain homogenates, the amount of oxidized proteins (assessed as carbonyl group containing proteins) and lipid peroxidation, were significantly reduced in ZC treated animals. Thus, ZC, which had previously been shown to improve inhibitory avoidance learning and to have anxiolytic properties in adult animals, might also facilitate spatial learning in aged animals, and reduces indices of oxidative stress in brain tissue after chronic treatment.

Dissociation between anxiolytic and hypomnestic effects for combined extracts of zingiber officinale and ginkgo biloba, as opposed to diazepam.

Previous work has shown that Zingicomb (ZC), a combination preparation of zingiber officinale and ginkgo biloba, exerts anxiolytic-like effects in the elevated plus-maze (EPM), possibly related to 5-HT antagonistic properties of its components. The first experiment of this study was performed to gauge the specificity of the anxiolytic action of ZC with respect to the mixture ratio of the single components in the combination preparation. Two different combinations of zingiber officinale and ginkgo biloba extracts (ratio of components: 1:1 or 1:2.5) were compared with the standard ratio adjusted for ZC (2.5:1). Each combination was administered intragastrically (I.G.) in five doses (0.01 to 10 mg/kg) before the rats were tested on the EPM. Zingicomb at 1 mg/kg elevated the time spent on the open arms, scanning of the open arms and excursions into the ends of the open arms, whereas the two other combinations (1:1 and 1:2.5) did not influence rats' behavior on the EPM in the entire dose range tested. With regard to the memory-disrupting effects of anxiolytics, particularly of diazepam (DZP), a second experiment was performed to compare the effects of ZC (0.5, 1, 10 mg/kg, I.G.) and DZP (1 or 5 mg/kg, I.P.) on the performance of rats in two different learning tasks. Rats were treated with DZP or ZC prior to the learning trial of a one-trial step-through inhibitory avoidance task. Retention testing 24 h later showed impaired retention for rats injected with DZP at 5 mg/kg but not for animals that had received ZC prior to training. In a further experiment, rats were treated once daily with DZP or ZC prior to the training trials in a water maze. Injections of DZP at 5 mg/kg impaired place and cue learning, whereas the treatment with ZC did not influence the navigation performance in the maze. The present results indicate that the anxiolytic-like effects of ZC are specific in that only the mixture ratio of zingiber officinale and ginkgo biloba adjusted for the phytopharmacon was active in the EPM. Furthermore, ZC did not interfere negatively with the performance on an inhibitory avoidance and a water maze task, as opposed to DZP. This finding is interesting with regard to other studies that have revealed a similar dissociation between anxiolytic and memory-disrupting effects for chemically defined 5-HT antagonists, especially for those acting at 5-HT3 receptors.

Dental health of elderly in retirement homes of two cities in south Croatia--a cross-sectional study.

OBJECTIVE: A survey of dental health status was conducted in institutionalized elderly in South Croatia in order to assess the oral health of the elderly population. PARTICIPANTS: In 274 institutionalised elderly from five retirement homes in Split and Korcula we registered dental status according to World Health Organization criteria. The mean age of the patients was 81 +/- 8; there were 220 female and 54 male subjects. RESULTS: A total of 192 (70.0%) were totally edentulous, and additional 39 (14.2%) were edentulous in one jaw. A significantly higher prevalence of edentulousness with the increasing age was recorded. The mean number of remaining sound teeth, decayed teeth and radices relictae in the elderly decreased with increasing age. CONCLUSIONS: The elderly population in retirement homes in South Croatia has poor dental health. This calls for action to improve dental health and implement some special features in the dental health service programs for the institutionalised elderly.

Lack of association between burning mouth syndrome and hematinic deficiencies.

The aim of our investigation was to evaluate possible connection between burning mouth syndrome and hematinic deficiencies, a hypothesis previously reported in the literature with contradictory results. Serum levels of iron, vitamin B12, folic acid, calcium and magnesium were determined in 41 (aged 31-87 years, mean 68,7 yrs) patients with burning mouth syndrome and 35 matched controls (35-83, mean 63 yrs). Serum iron levels were determined according to Fairbanks and Klee. Levels of vitamin B12 and folic acid were determined on commercially available kits (Imx12 and Imx folate assay, Abbot Park lab, IL, USA) on Imx analyser. Calcium and magnesium levels were determined using atomic absorption spectrophotometry. No statistically significant differences in serum levels of iron, folic acid, calcium and magnesium were found between patients with burning mouth syndrome and controls. Statistically significant lowered vitamin B12 levels were found in patients with burning mouth syndrome. Our results suggest that serum deficiencies of iron, folic acid, calcium and magnesium are not etiological factor in patients with burning mouth syndrome.

Oral health in SFR Yugoslavia in 1986.

A pilot oral health epidemiological survey using WHO assessment forms was conducted in Yugoslavia in the year 1986. The study population consisted of 2600 persons aged 6, 12, 15, 18, 35-44, and over 65 yr. The survey included 22 towns (11 developed and 11 underdeveloped) in the six Republics and two Provinces of Yugoslavia. The results showed the prevalence of dental caries in the Yugoslav population to be very high (98.7% in 12-yr-olds). The mean decayed, missing, and filled teeth (DMF) scores were as follows: 6.1 at age 12 yr, 9.6 at age 15, 10.9 at age 18, 18.0 at age 35-44, and 28.0 in persons aged over 65 yr. Assessment of the periodontal status showed calculus to be the predominant disorder in the age groups 18 and 35-44 yr, while loss of sextants prevailed in persons aged over 65 yr.

Classification of periodontal diseases.

The classification of periodontal diseases used and taught in the Department of Periodontology at The University of Sarajevo, Yugoslavia is presented and explained. The classification is the result of nearly 20 years' work. It is based on the inflammatory process and a combination of topography, morphology, pathology and aetiology of periodontal diseases.

The central role of the general practitioner in the treatment of periodontal disease.

This paper is based on experience of periodontal practice in Yugoslavia, Bosnia and Herzegovina respectively. Factors of relevance to the multidisciplinary approach to periodontal therapy are the level of development of public health, the teaching curricula in periodontology in dental schools, the organization of public dental health services (demand only or systematic oral care services) including the target groups and the dentist to population ratios. Quantification of periodontal treatments, the Community Periodontal Index of Treatment Needs (CPITN) and the recent analysis of the American Academy of Periodontology on periodontics in the twenty-first century are also of great relevance. Periodontology is a higher level discipline of public as well as dental health. The specialist periodontist carries out all the treatments in periodontology undertaken by the general dental practitioner and more specialized treatments not usually performed by the generalist.

Alveolar bone resorption in the skulls.

In this report the quantitative relationship between the alveolar bone and cervical part of the teeth in millenary intervals of human existence is reported. In this study 115 skulls were examined of which 27 belonged to the 1st, 22 to the 10th and 66 to the 20th century. The skulls belonged to persons of both sexes older than 20 years. Each group mentioned was divided into four subgroups according to the age persons (20-29, 30-39, 40-49, 50+). It measured tooth-cervical-height index (TCH-index) according to Davies and coll. The resorptive changes on the alveoli are increasing in the older age, the alveolar resorption is greater on the vestibular than interdental side, the higher values of alveolar resorption in the skulls of the 20th century are statistically significant in relation to the skulls from the 1st and 10th century.

Distance from source of reward as a marker for extinction-induced "despair": modulation by the antidepressants clomipramine and citalopram.

Despair-related withdrawal behaviors are common symptoms of major depression (MD) and can be ascribed to a loss or absence of former rewarding events. Extinction of negatively reinforced escape behavior in the Morris Water Maze has been shown to induce despair-like behavior. A new animal model of depressive-like behavior is based on the extinction of positively reinforced behavior, which was shown to induce spatial avoidance of the former source of reward and biting of the operandum. Treatment with antidepressants attenuated these extinction-induced behaviors, suggesting that they reflect a depressive-like state. Here we present a methodological variation of this depression model. We employed an elongated operant chamber rather than a two-compartment procedure with the intent to establish a flowing gradient of withdrawal from the source of reward, rather than an all-or-none binary measure. Furthermore, instead of employing extinction of lever-pressing behavior, we applied a cued fixed-time food-delivery schedule. Sixty adult male Wistar rats (n=12/group) were trained to receive a food reward after appearance of a cue-light (fixed interval 90s) in an elongated Skinner-box of 72 cm length. Prior to extinction, the animals were treated for 9 days with either 7.5 or 10mg/kg of the tricyclic antidepressant clomipramine, 7.5 or 10mg/kg of the selective serotonin reuptake inhibitor (SSRI) citalopram or vehicle. Subsequent testing in an open field was carried out to investigate potential effects of the antidepressants on locomotor- and anxiety-like behavior. An overall increase in distance from the feeder and biting behavior was found over the course of the extinction trials. Both, citalopram and clomipramine decreased the distance from the pellet feeder during the initial extinction trials compared to the vehicle-treated group. The attenuation of withdrawal behavior by the antidepressants supports the hypothesis that avoidance/withdrawal behavior during extinction trials can serve as a marker for extinction-induced depression and suggests the utility of this paradigm as a rodent model of depression.

Antidepressants reduce extinction-induced withdrawal and biting behaviors: a model for depressive-like behavior.

The withholding of expected rewards results in extinction of behavior and, hypothetically, to depression-like symptoms. In a test of this hypothesis, we examined the effects of extinction of food-reinforced lever-pressing on collateral behaviors that might be indices of depression. Operant extinction is known to be aversive to the organism and results in avoidance behavior. We hypothesized that avoidance of, or withdrawal from, the former source of reward may serve as a marker for "despair." Adult male Wistar rats (n=6-7 animals per group) were exposed to a Skinner box attached to a second compartment of the same size, providing opportunity for the animals to leave the operant chamber and to enter the "withdrawal" compartment. The animals spent a portion of the time during the extinction trials in this second chamber. To assess the predictive validity of this behavior as a potential marker of "despair," we tested the effects of chronic administration of two common antidepressant drugs on this measure. The tricyclic antidepressant imipramine (20 mg/kg) as well as the selective serotonin reuptake inhibitor citalopram (20 mg/kg) reduced the number of entries and time spent in the withdrawal compartment. We propose that entries into and time spent in the withdrawal compartment may operationalize "avoidance," a core symptom of major depression. Rearing as well as biting behaviors during the extinction trials were also attenuated by the antidepressant treatment. These results lend support to the hypothesis that extinction of positively reinforced operants evokes behaviors that reflect elements of "despair/depression" because these behaviors are modulated by antidepressant treatment. The avoidance of the operant chamber as a consequence of extinction, together with rearing and biting behaviors, may serve as useful measures for the testing of antidepressant treatments.

Neurokinin3-R agonism in aged rats has anxiolytic-, antidepressant-, and promnestic-like effects and stimulates ACh release in frontal cortex, amygdala and hippocampus.

Neurokinin-3 receptors (NK(3)-R) are localized in brain regions which have been implicated in processes governing learning and memory as well as emotionality. The effects of acute subcutaneous (s.c.) senktide (0.2 and 0.4 mg/kg), a NK(3)-R agonist, were tested in aged (23-25 month old) Wistar rats: (a) in an episodic-like memory test, using an object discrimination task (this is the first study to test for deficits in episodic-like memory in aged rats, since appropriate tests have only recently became available); (b) on parameters of anxiety in an open field test, (c) on indices of depression in the forced swimming test and (d) on the activity of cholinergic neurons of the basal forebrain, using in vivo microdialysis and HPLC. Neither the saline-, nor senktide-treated aged animals, exhibited episodic-like memory. However, the senktide-, but not the vehicle-treated group, exhibited object memory for spatial displacement, a component of episodic memory. Senktide injection also had anxiolytic- and antidepressant-like effects. Furthermore, the active doses of senktide on behavior increased ACh levels in the frontal cortex, amygdala and hippocampus, suggesting a relationship between its cholinergic and behavioral actions. The results indicate cholinergic modulation by the NK(3)-R in conjunction with a role in the processing of memory and emotional responses in the aged rat.