Feeding and body weight regulation after 6-OHDA application into the preoptic area

Chronic spinal cord electrical stimulation protects against 6-hydroxydopamine lesions

Although L-dopa continues to be the gold standard for treating motor symptoms of Parkinson's disease (PD), it presents long-term complications. Deep brain stimulation is effective, but only a small percentage of idiopathic PD patients are eligible. Based on results in animal models and a handful of patients, dorsal column stimulation (DCS) has been proposed as a potential therapy for PD. To date, the long-term effects of DCS in animal models have not been quantified. Here, we report that DCS applied twice a week in rats treated with bilateral 6-OHDA striatal infusions led to a significant improvement in symptoms. DCS-treated rats exhibited a higher density of dopaminergic innervation in the striatum and higher neuronal cell count in the substantia nigra pars compacta compared to a control group. These results suggest that DCS has a chronic therapeutical and neuroprotective effect, increasing its potential as a new clinical option for treating PD patients.

Reduced capacity in automatic processing of facial expression in restrictive anorexia nervosa and obesity

There is growing evidence that disordered eating is associated with facial expression recognition and emotion processing problems. In this study, we investigated the question of whether anorexia and obesity occur on a continuum of attention bias towards negative facial expressions in comparison with healthy individuals of normal weight. Thirty-three patients with restrictive anorexia nervosa (AN-R), 30 patients with obesity (OB) and 63 healthy age and social-economic status matched controls were recruited. Our results indicated that AN-R patients were more attentive to angry faces and had difficulties in being attentive to positive expressions, whilst OB patients had problems in looking for or being attentive to negative expressions independently of self-reported depression and anxiety. Our findings did not support the idea that AN-R and OB occur on a continuum. We found that AN-R was associated with a reduced capacity in positive facial expression processing, whereas OB was associated with a reduced capacity in negative facial expressions processing. The social relevance of our findings and a possible explanation based upon neuroscience are discussed.

A role for dopamine in feeding responses produced by orexigenic agents

Dopamine-deficient (DD) mice become hypophagic and die of starvation by 3 to 4 weeks of age unless dopamine is restored by daily treatment with l-3-4-dihydroxyphenylalanine (l-dopa). We demonstrate here that DD mice mount qualitatively normal counter-regulatory blood glucose responses to insulin and 2-deoxy-d-glucose (2-DG). However, unlike control mice, DD mice fail to eat in response to acute glucoprivation induced by insulin or 2-DG. They also have a severely blunted response to central administration of peptide YY (PYY). Viral-mediated restoration of dopamine synthesis to the central caudate putamen (CPu) of DD mice rescues feeding and survival. However, this treatment fails to restore insulin- and 2-DG-induced feeding despite normalizing feeding in response to food deprivation and PYY. Since dopamine signaling in the CPu is not sufficient for glucoprivation-induced feeding, we propose that this feeding behavior may be mediated by dopamine in an anatomically distinct brain region.

Evidence for a dopaminergic involvement in the renal action of centrally administered JA116a, a novel compound with possible dopaminergic activity, in rats

Intracerebroventricular (i.c.v.) administration of JA116a, induces an increase in urinary volume and sodium excretion in conscious male hydrated rats. The involvement of brain dopaminergic neurons in the JA116a renal action was investigated. Diuretic and natriuretic action of JA116a was blocked by haloperidol pretreatment. The renal effect was prevented by selective dopaminergic neuron, denervation by i.c.v. administration of 6-hydroxydopamine in combination with desmethylimipramine. Our results suggest that JA116a acts centrally, at least in part, via an interaction with endogenous dopamine neurons.

Feeding disturbances and EEG activity changes after amygdaloid kainate lesions in the rat

Kainic acid (KA), in various concentrations, was applied iontophoretically into the central nucleus of the amygdala. Microlesions with this cell specific neurotoxin caused body weight loss, hypo- or aphagia and hypo- or adipsia in a dose-dependent manner. EEG-examinations proved that even low doses of KA produced seizure activity; however, these epileptiform symptoms disappeared within the first 48 h after the operations. Thus, the lasting feeding disturbances produced by iontophoretic KA applications to the central nucleus of the amygdala (i.e., even these fine microlesions) were not related causally to the pathological EEG activity changes. Our findings, along with previous data, indicated that the body weight loss and feeding deficits were due to the KA-induced impairment of complex regulatory mechanisms.