Motor functions of the striatum in the rat: critical role of the lateral region in tongue and forelimb reaching

The findings of this study indicate a critical and selective role of the rat's lateral striatum in performance of tongue and forelimb reaching. To test the hypothesis of regional specificity of motor control in the striatum, the effects of bilateral, ibotenate-induced lesions of either the lateral or the medial regions of the striatum on reaching movements of the tongue and the forelimbs were examined. Lesions of the lateral striatum caused severe and chronic impairments of movement initiation, postural synergisms and amplitude of both tongue and forelimb reaches. In contrast, lesions of the medial striatum produced mild or no chronic alterations of these motor parameters. These findings support the hypothesis of a selective role of the lateral striatum in the initiation and execution of reaching movements.

Regionally selective roles of the rat's striatum in modality-specific discrimination learning and forelimb reaching

Rats with ibotenate lesions of either the medial striatum or the lateral striatum were trained in a forelimb reaching task and in acquisition, retention and reversal of either turn (left-right) discrimination or brightness (black-white) discrimination in a cross-shape maze. Compared with the controls, the rats with lesions of the medial striatum showed a reliable, modality-selective impairment in reversal of turn discrimination, but no significant impairment of reaching. In contrast, the rats with lateral striatal lesions showed a significant impairment of forelimb reaching, but not of reversal of either discriminations. Neither medial nor lateral lesions significantly affected acquisition and retention of both discriminations. The findings indicate a predominant role of the medial striatum in monitoring of directional responses, confirm the regionally specific role of the lateral striatum in reaching, and are interpreted to support the hypothesis of parallel motor and cognitive forebrain circuits comprising distinctive regions of the striatum.

Spontaneously recurrent seizures after intracerebral injections of kainic acid in rat: a possible model of human temporal lobe epilepsy

Intrastriatal injection of kainic acid in rats acutely induced repeated episodes of clonic convulsions. Spontaneously recurrent generalized seizures and a potentiation of the convulsant effects of phentylenetetrazol were then observed in most of the injected rats several weeks after surgery. In addition to marked loss of striatial neurons, limbic pathological alterations similar to those found in human temporal lobe epilepsy were observed in the brains of the kainic-acid treated rats. It is proposed that this preparation might serve as an animal model of human temporal lobe epilepsy.

Motor somatotopy in the striatum of rat: manipulation, biting and gait

The objective of this study was to examine the hypothesis of somatotopically organized motor functions in the striatum. In Experiment 1, ibotenate-induced lesions of the rostrolateral striatum in rats produced a transient decrease of ad libitum food intake, a more enduring decrease of body weight, and chronic impairments of food biting, holding of hard food pellets and feeding efficiency, with no apparent alterations of gait balance in a beam walking task. Lesions of the medial striatum had minimal or no reliable effects on any of the measured parameters. In Experiment 2, the motoric effects of ibotenate lesions restricted to either the dorsomedial or the dorsolateral or the ventrolateral regions of the rostral striatum were examined. Lesions of the dorsolateral striatum produced the most deleterious effect on holding postures of the forelimbs, whereas lesions of the ventrolateral striatum maximally affected food biting, feeding efficiency, ad libitum food intake, and body weight. No regional lesions affected gait balance. Dorsomedial striatal lesions did not affect any of the measured parameters. The findings support the hypothesis of a somatotopically organized role of the rostrolateral striatum in orofacial and forelimb motor control.

Dissociable motor roles of the rat's striatum conform to a somatotopic model

The findings of this study indicate distinctive roles of different regions of the rostral striatum of rat in segmental motor control. In order to test the hypothesis of somatotopically organized motoric functions in the striatum, the effects of bilateral ibotenate-induced lesions of either the dorsomedial or the dorsolateral or the ventrolateral regions of the rostral striatum on reaching movements of the tongue and the forelimbs were examined. Lesions of the dorsolateral region chronically impaired reaching movements of the forelimbs but not of the tongue. Lesions of the ventrolateral region impaired initiation and execution of reaching movements of both the tongue and the forelimbs, with the impairment of forelimb reaching being somewhat less severe than that produced by dorsolateral lesions. Neuronal loss in the medial striatum had no chronic effects on either movements. The impairments of reaching performance reflected failures of motor synergisms between tongue and head and between limb and paw, as well as alterations in the scaling of movement amplitude. These findings support the hypothesis of a motor somatotopy in the lateral region of the rat's rostral striatum and of a critical role of the lateral striatum in initiation, scaling, and coordination of reaching movements.

Avoidance, operant and locomotor behavior in rats with neostriatal injections of kainic acid

Compared with saline injected controls, rats with bilateral injections of kainic acid (KA) in the dorsal neostriatum showed increased locomotor response to d-amphetamine, increased resistance to extinction and impaired acquisition and retention of passive avoidance. The KA injection resulted in loss of local neurons in the dorsal neostriatum, with no appreciable damage either to dopaminergic terminals or to extrinsic myelinated axons, thus supporting both the selective neurotoxic action of KA on neuronal perikarya and the proposed similarity of KA-induced neostriatal lesions with those found in the caudate-putamen of patients with Huntington's disease. Although loss of hippocampal neurons was occasionally observed, the behavioral results could not be wholly attributed to hippocampal damage, since rats with no demonstrable extrastriatal lesions were not less impaired than those with hippocampal damage. An altered arousal reaction to stressful situations might account for the learning and memory impairments of the KA neostriatal rats.

Homotaurine (3 aminopropanesulfonic acid; 3APS) protects from the convulsant and cytotoxic effect of systemically administered kainic acid

Pretreatment of rats with homotaurine (3 aminopropanesulfonic acid; 3APS), a synthetic gamma-aminobutyric acid (GABA) analog, protected from the convulsant and cytotoxic action of systemically injected kainic acid (KA). Wet dog shaking (WDS) behavior was significantly reduced. Taurine, an inhibitory non-GABA-mimetic amino acid, and muscimol (another direct GABA-agonist) reduced the number of seizures and lesions in the brain but were less effective than homotaurine. Progabide (a GABA-agonist) did not modify kainic acid effects. The neurotoxicity of kainic acid could have been due to repetitive convulsive activity. Activation of GABA-mediated inhibition is an effective, but not the determinant means of preventing KA-induced abnormalities.

Evidence against a role of the rat's dorsal noradrenergic bundle in selective attention and place memory

In Experiment 1, 6-hydroxydopamine-induced lesions of the dorsal noradrenergic bundle (DNB) in rats did not impair either acquisition of non-delayed alternation, retention of non-delayed alternation, or performance of alternation with delays in a T-maze, whether or not the goal arms of the maze were visually distinctive. These results were in contrast with those of a previous report indicating that DNB lesions impair learning of spatial alternation. In Experiment 2, the lack of a reliable effect of DNB lesions on learning performance of spatial alternation was confirmed. However, the rats with DNB lesions showed an impairment of spontaneous alternation. The negative results of the present study do not support either the hypothesis that depletion of forebrain noradrenaline impairs selective attention or the hypothesis that such depletion induces an amnesia for past places. On the other hand, the finding of impaired spontaneous alternation is consistent with previous observations suggesting that depletion of forebrain noradrenaline impairs habituation of fear reactions.

Kainic acid injections in the striatum alter the cataleptic and locomotor effects of drugs influencing dopaminergic and cholinergic systems

Rats with bilateral injections of kainic acid into the striatum were tested for their motor responsiveness to drugs influencing dopaminergic and cholinergic systems. The kainic acid-induced lesions potentiated the locomotor response to both the dopaminergic agonist, d-amphetamine, and the cholinergic antagonist, scopolamine, attenuated the cataleptic response to the dopaminergic antagonist, haloperidol, and potentiated the cataleptic acid and convulsive responses to the cholinergic agonist, pilocarpine. The analogy of these pharmacological effects with those induced by similar drugs in patients with Huntington's disease supports the view that this animal preparation is a useful model of Huntington's disease. The opposite effects of haloperidol and pilocarpine on catalepsy in kainic acid-lesioned rats suggest that more work should be done to elucidate the mechanism behind this conflict before full support can be given to its use as a model system for evaluating possible pharmacotherapy in Huntington's disease.

Regional specialization of motor functions in the rat striatum: implications for the treatment of parkinsonism

1. Behavioral studies of rats with ibotenic acid-induced lesions of distinctive regions of the rostral striatum demonstrated clearcut motoric impairments after lesions of the lateral striatum, but not after lesions of the medial striatum. 2. Differential effects of dorsolateral and ventrolateral lesions on segmental bodily movements indicated a somatomotor map in the lateral region. 3. Neurotoxic lesions of the lateral striatum produced deficits of motor energizing analogous to those of human parkinsonism. 4. These results support the hypothesis that neurodegenerative processes affecting the lateral striatum (putamen) in humans may specifically account for parkinsonian symptoms. 5. The implications of this hypothesis for the treatment of parkinsonism using the grafting technique are discussed.

Intact selective attention in rats with lesions of the dorsal noradrenergic bundle

Mason's hypothesis (1980) was tested that lesions of the dorsal noradrenergic bundle (DNB), which induce depletion of forebrain noradrenaline, alter performance of discrimination tasks because they retard habituation to naturally attractive, but instrumentally irrelevant, stimuli. In Experiment 1, groups of rats with either vehicle or 6-hydroxydopamine injections into the DNB were assigned to five different discrimination tasks in a cross-maze with black and white goal arms. The tasks were acquisition and reversal of position, visual, or turn discrimination, and acquisition of visual or turn discrimination followed by a shift to the alternative discrimination. In spite of evidence that the rats preferred to attend more to the visual stimuli of the goal arms than to directions of turns, lesions of the DNB did not impair acquisition and reversal of turn discrimination with visual stimuli irrelevant, and did not facilitate performance of turn-to-visual shift. In fact, the lesions did not alter performance of any tasks. In Experiment 2, control and noradrenaline-depleted rats were trained in a task of light-dark discrimination followed by shift to position discrimination in a Y-maze. At the onset of training, the rats of both groups reliably avoided the bright goal arm and responded to the dark goal arm, thus demonstrating predominant attention for the relevant brightness stimuli rather than the irrelevant position stimuli. The DNB lesions impaired acquisition of brightness discrimination only when the positive stimulus was the illuminated goal arm, and they did not alter shift performance. These results do not support the hypothesis at test. On the other hand, they indicate that DNB lesions in the rat can impair habituation of light avoidance.

Experimental influences on catalepsy

Normal saline-injected rats were tested repeatedly on a standard catalepsy test. With repeated testing the animals showed a progressive increase in their catalepsy scores. It is suggested that this behaviour may be a form of tonic immobility and should be controlled for in catalepsy experiments.

Enhanced neophobia but normal plasma corticosterone levels in rats with dorsal noradrenergic bundle lesions

The effects of dorsal noradrenergic bundle (DNB) lesions on plasma corticosterone levels were determined in male albino rats. DNB lesions did not affect baseline plasma corticosterone levels. Furthermore, the increased corticosterone levels produced by various environmental manipulations did not differ between control and DNB lesioned groups. However, the lesioned group did exhibit longer latencies to eat familiar food in novel environments, as well as to eat novel foods in a familiar environment. Latencies to eat novel food in novel environments did not differ between the two groups and this was attributed to a "ceiling" effect. These endocrinological data fail to support the hypothesis that the enhanced "neophobia" observed in DNB lesioned rats is due to an increase in the intensity of the emotional reaction to novel stimuli. The data do not preclude the possibility, however, that the enhanced neophobic reactions reflect impaired habituation to these stimuli.

On the role of the dorsal noradrenergic bundle in learning and habituation to novelty

In Experiment 1, the performance of vehicle control rats and rats with 6-hydroxydopamine-induced lesions of the dorsal noradrenergic bundle (DB) was examined in acquisition and extinction of bar pressing and in spontaneous and food-reinforced alternation in a T-shape maze. Plasma corticosterone levels in basal conditions, after chronic food restriction, after transportation to a novel environment, and after sessions of either rewarded or nonrewarded bar pressing were assayed. DB lesions produced a significant decrease of spontaneous alternation and a significant but small resistance to extinction, without reliably altering either corticosterone responses or instrumental spatial alternation. In Experiment 2, bar-press extinction and instrumental alternation were reexamined in new groups of control rats and rats with DB lesions without any blood collection procedures. The DB lesions did not reliably alter either behaviors on any measures. Taken together, these data indicate no consistent effects of forebrain noradrenaline depletion on either extinction or spatial memory or pituitary-adrenocortical function. However, the impairment of spontaneous alternation found in a previous study was confirmed. These findings are discussed in terms of the proposed roles of the dorsal noradrenergic bundle in learning and habituation to novelty.

The Addition of an Immunosuppressant After Loss of Response to Anti-TNFα Monotherapy in Inflammatory Bowel Disease: A 2-Year Study

BACKGROUND

The addition of an immunosuppressant (IM) after loss of response to anti-TNFα monotherapy is an emerging strategy of therapeutic optimization in patients with inflammatory bowel disease (IBD). However, few clinical data have been reported to date. We aimed to evaluate the efficacy and safety of this selective combination therapy in patients with IBD.

METHODS

All consecutive patients with loss of response to anti-TNFα monotherapy despite an intensive dose optimization who added an IM from October 2014 to October 2016 were entered into a prospective database.

RESULTS

Among 630 patients treated with anti-TNFα agents during the study period, 46 (7.3%) added an IM. A total of 31 patients (67.4%) were treated with an intravenous anti-TNFα (infliximab, as originator or biosimilar), while 15 (32.6%) were treated with a subcutaneous anti-TNFα agent (10 adalimumab and 5 golimumab). The mean duration of follow-up was 12.8 ± 7.3 months. Twenty-one patients (45.7%) remained on combination therapy at the end of follow-up: 15 (32.6%) maintained a steroid-free remission, and 6 (13.0%) achieved a clinical response. In patients who experienced treatment success, the median value of C-reactive protein decreased from baseline to the end of follow-up (13.2 vs 3.0, P = 0.01; normal values <5 mg/L). Adverse events leading to treatment discontinuation were reported in 8 out of 46 patients (17.4%).

CONCLUSIONS

In the largest cohort on this argument reported to date, the addition of an IM was an effective and safe optimization strategy after loss of response to anti-TNFα monotherapy. Low doses of IM were sufficient to achieve a clinical response.

Simultaneous endoscopic ultrasound fine needle aspiration and endoscopic retrograde cholangio-pancreatography: Evaluation of safety

AIM: To investigate the rate of complications of endoscopic retrograde cholangio-pancreatography (ERCP) performed immediately after endoscopic ultrasound fine needle aspiration (EUS-FNA) in a large series of patients.

METHODS: Patients with the following conditions were considered candidates for EUS-FNA and ERCP: diagnosis of locally advanced or metastatic pancreatic lesion not eligible for surgery, and patients with pancreatic lesion of unknown nature causing jaundice. Data were prospectively collected on the following parameters: indication for FNA, EUS findings, pathological diagnosis, procedure duration of EUS-FNA and combined EUS-FNA and ERCP, and immediate and late complications.

RESULTS: From January 2004 to October 2006, 72 patients were deemed eligible for combined EUS and ERCP. In 25/72 EUS-FNA was performed to obtain a pathology diagnosis of lesions causing biliary obstruction, and ERCP sequentially performed to drain the biliary system. No immediate complications occurred except for two mild bleeding episodes post sphincterotomy. No late complications were recorded except for one patient who experienced fever, promptly recovered with antibiotic therapy.

CONCLUSION: Simultaneous approach appears to be feasible and safe. When possible, this can be considered the reference standard to avoid double sedation and reduce duration of the procedure and hospital stay.

Lateralized and compulsive exteroceptive orientation in rats treated with apomorphine

A new behavioral test afforded the original demonstration of a compulsive and extremely lateralized taxis for edges in a minority (16%) of rats treated with the dopamine (DA) receptor agonist apomorphine (APO) (1.25 mg/kg, s.c.). APO also induced a reliable lateralization of locomotor direction in a rotometer in 29% of rats. The lateralizing effects of the drug on taxis for edges and rotational direction were not reliably associated, however, suggesting that these effects of APO are independent of each other. Interhemispheric asymmetries of DA receptors in functionally distinctive brain regions may underlie the diverse lateralizing effects of APO in subpopulations of rats.