differential effects of voluntary ethanol consumption on dopamine output in the nucleus accumbens shell of roman high and low avoidance rats a behavioral and brain microdialysis study

The Roman high(RHA) and low-Avoidance (RLA) rats were selectively bred for rapid vs poor acquisition of two-way active avoidance behavior. These lines differ in numerous behavioral traits, with RLA rats being more fearful/anxious than RHA rats, and the latter being novelty-seekers and showing larger intake of, and preference for, addictive substances including ethanol (ETH). Moreover, several differences in central dopaminergic, serotonergic, and GABAergic functions have been reported in these two lines. Since those neural systems are involved in the regulation of ETH consumption, it was considered of interest to investigate: 1) the differences in ETH intake and preference between RHA and RLA rats, 2) the effects of ETH on DA release in the shell of the nucleus accumbens (AcbSh) using brain microdialysis. ETH solutions of increasing concentrations (2% - 10%) were presented on alternate days in a free choice with water. To examine ETH intake and preference stability, animals were subsequently switched to daily presentations of 10% ETH for 10 consecutive days. RHA rats consumed significantly larger amounts of ETH and displayed higher ETH preference than did RLA rats throughout the acquisition and maintenance phases. Following chronic exposure to ETH the animals were habituated to a restricted access to ETH schedule (2% ETH, 2 h per day × 4 days) before surgical implantation of a dialysis probe in the AcbSh. Under these experimental conditions, voluntary ETH intake (2%, 1 h, p.o.) produced a significant increase in accumbal DA output in RHA rats but not in their RLA counterparts. Finally, the i.p. administration of ETH (0.25 g/kg) to na?ve Roman rats produced a significant increment in accumbal DA output only in RHA rats. These results indicate that the mesolimbic dopaminergic system of RHA rats is more responsive to the effects of ETH than that of RLA rats

Dopamine, Noradrenaline and Differences in Sexual Behavior between Roman High and Low Avoidance Male Rats: A Microdialysis Study in the Medial Prefrontal Cortex

Roman High- (RHA) and Low-Avoidance (RLA) outbred rats, which differ for a respectively rapid vs. poor acquisition of the active avoidance response in the shuttle-box, display differences in sexual activity when put in the presence of a sexually receptive female rat. Indeed RHA rats show higher levels of sexual motivation and copulatory performance than RLA rats, which persist also after repeated sexual activity. These differences have been correlated to a higher tone of the mesolimbic dopaminergic system of RHA rats vs. RLA rats, revealed by the higher increase of dopamine found in the dialysate obtained from the nucleus accumbens of RHA than RLA rats during sexual activity. This work shows that extracellular dopamine and noradrenaline (NA) also, increase in the dialysate from the medial prefrontal cortex (mPFC) of male RHA and RLA rats put in the presence of an inaccessible female rat and more markedly during direct sexual interaction. Such increases in dopamine (and its main metabolite 3,4-dihydroxyphenylacetic acid, DOPAC) and NA were found in both sexually naïve and experienced animals, but they were higher: (i) in RHA than in RLA rats; and (ii) in sexually experienced RHA and RLA rats than in their naïve counterparts. Finally, the differences in dopamine and NA in the mPFC occurred concomitantly to those in sexual activity, as RHA rats displayed higher levels of sexual motivation and copulatory performance than RLA rats in both the sexually naïve and experienced conditions. These results suggest that a higher dopaminergic tone also occurs in the mPFC, together with an increased noradrenergic tone, which may be involved in the different copulatory patterns found in RHA and RLA rats, as suggested for the mesolimbic dopaminergic system

BDNF, trkB and PSA-NCAM in the hippocampus of Roman rats after forced swimming

The selective breeding of Roman High- (RHA) and Low-Avoidance (RLA) rats are considered as a genetic model of resilience to stress-induced depression and of vulnerability to that trait, respectively1. There is evidence that alterations in neuronal plasticity in the hippocampus and other brain areas are critically involved in the pathophysiology of mood disorders. Here, we investigated on immunochemical occurrence of Brain-derived neurotrophic factor (BDNF), tyrosine-kinase receptor trkB and polysialilated form of the neural cell adhesion molecule (PSANCAM) in the hippocampus of the Roman rat lines under baseline conditions and after acute forced swimming (FS). Western blot (WB) analyses showed that, in basal conditions, the relative levels of BDNF, trkB and PSA-NCAM markedly differed, appearing lower by 48%, 25% and 65%, respectively, in RLA vs RHA rats. WB analyses carried out after FST showed no differences between baseline and FST rats. In tissue sections, BDNF-, trkB- and PSA-NCAM-like immunoreactivity (LI) showed a distinctive labelling, mainly localized to proximal neuronal processes and nerve fibers distributed in the Ammon’s horn and dentate gyrus (DG). A number of PSA-NCAM-positive neurons in the subgranular layer of dentate gyrus also occurred. Densitometric analysis further showed differences in the hippocampal subregions. Thus, upon FST, BDNF-LI was less abundant in the CA3 sector of the Ammon’s horn of FST vs control RLA rats (-24%), whereas PSA-NCAM-LI was more abundant in the DG of RHA than RLA rats (+26%). Our findings suggest that an altered neuronal availability of and/or responsiveness to BDNF and inadequate dynamic events related to neuroplasticity may contribute to outline the molecular and morphological basis for the distinct vulnerability to stress-induced depression in the two rat lines

Differential Effects of Voluntary Ethanol Consumption on Dopamine Output in the Nucleus Accumbens Shell of Roman High- and Low-Avoidance Rats: A Behavioral and Brain Microdialysis Study

The Roman high(RHA) and low-Avoidance (RLA) rats were selectively bred for rapid vs poor acquisition of two-way active avoidance behavior. These lines differ in numerous behavioral traits, with RLA rats being more fearful/anxious than RHA rats, and the latter being novelty-seekers and showing larger intake of, and preference for, addictive substances including ethanol (ETH). Moreover, several differences in central dopaminergic, serotonergic, and GABAergic functions have been reported in these two lines. Since those neural systems are involved in the regulation of ETH consumption, it was considered of interest to investigate: 1) the differences in ETH intake and preference between RHA and RLA rats, 2) the effects of ETH on DA release in the shell of the nucleus accumbens (AcbSh) using brain microdialysis. ETH solutions of increasing concentrations (2% - 10%) were presented on alternate days in a free choice with water. To examine ETH intake and preference stability, animals were subsequently switched to daily presentations of 10% ETH for 10 consecutive days. RHA rats consumed significantly larger amounts of ETH and displayed higher ETH preference than did RLA rats throughout the acquisition and maintenance phases. Following chronic exposure to ETH the animals were habituated to a restricted access to ETH schedule (2% ETH, 2 h per day × 4 days) before surgical implantation of a dialysis probe in the AcbSh. Under these experimental conditions, voluntary ETH intake (2%, 1 h, p.o.) produced a significant increase in accumbal DA output in RHA rats but not in their RLA counterparts. Finally, the i.p. administration of ETH (0.25 g/kg) to na?ve Roman rats produced a significant increment in accumbal DA output only in RHA rats. These results indicate that the mesolimbic dopaminergic system of RHA rats is more responsive to the effects of ETH than that of RLA rats

The Roman high- and low-avoidance rats differ in the sensitivity to shock-induced suppression of drinking and to the anxiogenic effect of pentylenetetrazole

Abstract The Roman high- (RHA) and low-avoidance (RLA) outbred rat lines are selected for respectively rapid vs. poor acquisition of active avoidant behavior. Emotional reactivity appears to be the most prominent behavioral difference between the two lines, with RLA rats being more fearful/anxious than their RHA counterparts. Accordingly, here we show that shock-induced inhibition of drinking behavior in the Vogel's test is significantly more pronounced in RLA than RHA rats. Thus, unpunished drinking activity is similar in both lines (38.1 ± 0.9 and 36.4 ± 0.6 licking periods/3 min in RLA and RHA rats, respectively), whereas under punished conditions (0.05 – 1.00 mA electric shocks delivered through the drinking tube) a more robust decrease in drinking behavior is observed in RLA vs. RHA rats. Moreover, fear-related behaviors like freezing and self-grooming are more frequent in RLA than RHA rats throughout the test. Similar results are obtained with the inbred RHA-I and RLA-I rats, which have been selected and bred through brother/sister mating of the outbred lines. In keeping with the above findings, we also show that, compared with their RHA counterparts, the outbred RLA rats are similarly responsive to the anticonflict effect of diazepam but more responsive to the proconflict effect of pentylenetetrazole in the Vogel's test. Collectively, these results reveal another behavioral trait distinguishing RHA from RLA rats and add experimental support to the view that the Roman lines/strains are a valid genetic model for the study of the neural underpinnings of fear/anxiety- and stress-related behaviors

Brain morphometry of preschool age children affected by autism spectrum disorder: Correlation with clinical findings

The aim of our study was to use a combined imaging and clinical approach to identify possible patterns of clinical and imaging findings in a cohort of preschool age autism spectrum disorder (ASD) patients. In order to identify imaging patterns that could be related to specific clinical features, a selected group of ASD patients (age range 3-6 years) without dysmorphic features, epilepsy or other major neurological signs, malformations or other lesions at MRI was subjected to brain volumetric analysis using semiautomatic brain segmentation. An age-matched group of typically developing children was subjected to the same analysis. Our results were consistent with previous literature: Total gray matter volume, total cortical gray matter volume and amygdalar volumes were significantly greater in the ASD group than the control group. When we divided the study group into subgroups on the basis of clinical findings such as high- or low-functioning, or verbal and nonverbal, the only significant difference between verbal and nonverbal subjects was in cerebellar hemispheric size. In conclusions, our results confirm that newer brain MRI techniques using semiautomatic brain segmentation can provide information useful for defining the differences between ASD patients and controls, particularly if they form part of an integrated approach between MRI and cognitive-behavioral and genetic data