Two outbreaks of trichinellosis in the state of Northrhine-Westfalia, Germany, 1998.

Illness or death from trichinellosis is statutorily notifiable in Germany. Between nought and ten cases were reported each year from 1987 to 1997. From November 1998 to January 1999, however, 52 cases of trichinellosis were identified by the public health

Adrenergic agents inhibit rapid increases in cerebellar Purkinje cell glutamic acid decarboxylase (GAD67) mRNA levels after climbing fiber lesions or reserpine treatment.

Loss of the inferior olive-climbing fiber input to the cerebellar cortex after treatment with the neurotoxin 3-acetylpyridine (3-AP) has been reported to double the simple spike activity of the cerebellar Purkinje cell and eliminates complex spike activity. This is quickly followed by a three- to fourfold increase in Purkinje cell mRNA for the 67 kDa form of glutamic acid decarboxylase (GAD), a synthetic enzyme for the neurotransmitter GABA. Treatment with the indirectly acting sympathomimetic amphetamine or the direct acting beta 2 adrenergic agonist clenbuterol inhibited the increase in GAD67 mRNA, and this inhibition was blocked by pretreatment with the beta receptor antagonist propranolol. The activity-enhancing effect of 3-AP treatment on cerebellar neurons was confirmed by extracellular recordings. Clenbuterol treatment prevented the increase in neuronal firing without altering lesion induction or the loss of complex spikes, and propranolol treatment produced a partial reversal of the inhibitory effect of clenbuterol on the neuronal firing rate. These results suggest that beta receptor-mediated effects on cerebellar neuronal activity may prevent the increase in mRNA levels, but that firing rate-independent beta-mediated effects on genomic expression may also play a role. A role for noradrenergic systems in modulating GAD67 mRNA is also supported by the finding that reducing endogenous cerebellar norepinephrine levels by treatment with reserpine increased Purkinje cell GAD67 mRNA levels (250% of control), and this also was inhibited by clenbuterol treatment.

Rapid increases in cerebellar Purkinje cell glutamic acid decarboxylase (GAD67) mRNA after lesion-induced increases in cell firing.

Loss of the inferior olive-climbing fiber input to the cerebellar cortex doubles the simple spike activity of the cerebellar Purkinje cell. There is a 3- to 4-fold increase in Purkinje cell messenger RNA for the 67 kDa form of glutamic acid decarboxylase (a synthetic enzyme for the neurotransmitter GABA) within 4-5 h of the increase in electrical activity, suggesting a rapid response of mechanisms influencing neurotransmitter synthesis or stability to altered electrophysiological activity.

GABA levels and GAD immunoreactivity in the deep cerebellar nuclei of rats with altered olivo-cerebellar function.

Immunocytochemistry was used to examine the distribution, size, and density of glutamic acid decarboxylase immunoreactive (GAD+) puncta in two animal models with movement disorders, the genetically dystonic (dt) rat and rats with 3-acetylpyridine (3AP) lesions of the inferior olive. In both models, GAD activity is increased in the deep cerebellar nuclei (DCN) where the enzyme is localized primarily in the terminals of Purkinje cells. GABA levels were also measured in the DCN. The general distribution of GAD+ puncta in the DCN was similar in all groups. Immediately after the 3AP lesions, however, GABA levels were elevated in 3AP rats in comparison with both normal rats and age-matched dt rats. GAD+ puncta were also larger than normal in the 3AP group at this time, although the magnitude of this effect declined over a 2-week recovery period. Puncta density was decreased in the medial nucleus only in 25-day-old dt rats in comparisons with normal littermates. These findings are discussed in the context of previously reported differences in the firing rate of Purkinje cells in dt and 3AP-treated rats.

Increased glutamic acid decarboxylase (GAD) mRNA and GAD activity in cerebellar Purkinje cells following lesion-induced increases in cell firing.

Lesions of the inferior olive-climbing fiber projection to the cerebellar Purkinje cell were produced in adult rats using the neurotoxin 3-acetylpyridine. At 7 days post-lesion, glutamic acid decarboxylase (GAD) activity in Purkinje cell axons terminating in the lateral division of the deep cerebellar nucleus was significantly increased (+58%) above control levels. GAD mRNA levels in Purkinje cell bodies from the same animals were measured by in situ hybridization histochemistry using a radiolabeled cRNA probe for GAD mRNA. GAD mRNA was significantly elevated (+42%) above control at 7 days post-lesion. Because lesions of the climbing fiber system increase Purkinje cell firing rates, the results suggest that increased Purkinje cell activity induces transcription of GAD mRNA, which in turn results in increased GAD availability in Purkinje cell terminals.

Quantitative autoradiography reveals selective changes in cerebellar GABA receptors of the rat mutant dystonic.

In the rat mutant dystonic (dt), glutamic acid decarboxylase (GAD) activity in the deep cerebellar nuclei (DCN) is elevated compared to normal littermates. The distribution of this increase within the DCN, and the effect upon GABA receptor density, was assessed in 25-d-old animals. GAD activity was increased 45, 41, and 74% in the medial, interpositus, and lateral divisions of the DCN, respectively. Autoradiographic analysis of GABAA receptor density, using the ligand 3H-muscimol (MUSC), revealed a significant decrease in MUSC binding in the DCN of the mutant. No changes in the binding of the benzodiazepine ligand 3H-flunitrazepam (FLU) were found in the DCN. At 18 other sites, including motor areas in the brain stem, midbrain, and forebrain, no significant changes were found in either MUSC or FLU binding. There also was a failure to find any significant changes in dt animals in the binding of ligands which label the muscarinic cholinergic receptor, dopamine D2 receptor, or serotonin 5-HT2 receptor. The results support earlier findings that GABAergic activity is increased in Purkinje cell terminals of the dt mutant and suggest that in response to this enhanced activity, GABA receptors in the DCN are down-regulated. At other levels of the neuraxis no consistent changes were found in any of the variables studied, suggesting that cerebellar dysfunction may be a primary component of the dystonic syndrome.

Purkinje cell activity in rats following chronic treatment with harmaline.

Harmaline and related alkaloids produce a fine, generalized motor tremor with a frequency of 8-14 Hz in many mammalian species. The tremor is though to be initiated by the synchronous activation of cells in the inferior olive. Repeated administration of the drug at tremorogenic doses results in the rapid development of tolerance in the rat. Since the generation of cerebellar cyclic 3',5'-guanosine monophosphate by harmaline or apomorphine is reduced in harmaline-tolerant rats, it is possible that the site of tolerance is the olivocerebellar system. The present study used extracellular single unit recording techniques to determine whether harmaline tolerance was associated with changes in the firing patterns of Purkinje cells in the cerebellar vermis of the rat. In non-tolerant animals, the majority (8/13) of Purkinje cells recorded in the vermis responded to harmaline with a rhythmic increase in complex spike rate and a prolonged suppression of simple spikes. In harmaline-tolerant animals, only one cell in 14 could be identified that showed this response. In these animals, a variety of responses not encountered in experimentally naive animals were observed. Since the complex spike activity of Purkinje cells is presumed to reflect the activity of climbing fibers originating in the cells of the inferior olive, the results of the studies reported here support the conclusion that a reduction in the synchronous activation of cells at the olivocerebellar level blocks the appearance of tremor in harmaline-tolerant animals.

Spontaneous and harmaline-stimulated Purkinje cell activity in rats with a genetic movement disorder.

The genetically dystonic rat (dt) displays a complex movement disorder in the absence of morphological defects in the nervous system. This mutant is also insensitive to the tremorogenic effects of harmaline. Because harmaline is known to act on the cells of the inferior olive to induce activity at the tremor frequency in the olivocerebellobulbar pathway, this pathway has been investigated as a possible site of a defect in the dt rat. Biochemical studies suggested the presence of abnormalities at the level of the Purkinje cell or its afferent input. Thus, the present study investigated the harmaline response of Purkinje cells in dt rats and unaffected littermate controls with extracellular single-unit recording techniques. The spontaneous, simple spike and complex spike firing rates of dt rats were significantly lower than those of normal littermate controls. In normal rats, 2 responses to systemic harmaline injection were seen. Simple spikes were either completely suppressed for periods of 30-180 min, or were intermittently suppressed, pausing repeatedly for periods of 1-18 sec. Cells that showed complete suppression of simple spike activity also showed increased frequency and rhythmicity of complex spikes. In dt rats, intermittent simple spike responses were seen in a proportion (41%) similar to that in normal rats (53%). However, the proportion of cells showing high-frequency, rhythmic, complex spikes and complete suppression of simple spikes was low in the dt rats in comparison with littermate controls (18 versus 47%). In addition, 41% of the cells from dt rats displayed no change, or an anomalous change, in firing patterns in response to harmaline. Since the rhythmic activation of olivary neurons that results in the rhythmic, complex spike discharge of Purkinje cells is assumed to be responsible for the appearance of harmaline tremor, the failure of the dt rat to display tremor is most likely due to a failure at the olivocerebellar level, rather than at a site efferent to the cerebellum.

Tolerance to the tremorogenic effects of harmaline: evidence for altered olivo-cerebellar function.

Administration of the beta-carboline alkaloid, harmaline, causes the neurons of the inferior olive to fire synchronously and to act as a pacemaker for the generation of tremor. Rats treated daily with harmaline showed a progressive loss of drug-induced tremor. This tolerance was long-lasting and specific. No cross-tolerance was noted to the drug oxotremorine. Prevention or attenuation of tremor by pretreatment with diazepam or morphine preserved the tremorogenic capacity of harmaline when administered alone. These results suggest a relatively permanent change in the olivo-cerebello-bulbar pathway that underlies the generation of tremor induced by harmaline. Treatment with harmaline also increased cyclic 3',5'-guanosine monophosphate (cGMP) in the cerebellum, presumably through activation of the climbing fiber pathway from the inferior olive to the cerebellar cortex. These increases were attenuated after repeated treatment. These results suggest that the site of tolerance to the tremogenic effects of harmaline lies within the olivo-cerebellar system.

Neuropharmacological correlates of the motor syndrome of the genetically dystonic (dt) rat.

The research program described here has focused primarily on identifying sites of dysfunction in the central nervous system of rat mutants described as dystonic. The evidence strongly favors the position that there is a defect in the cerebellum of the dt rat. At present it seems reasonable to propose as a working hypothesis that there is a defect in the Purkinje cells that renders these neurons less sensitive to the excitatory neurotransmitters released by the climbing and parallel fibers. The finding that an abnormality in GAD activity in the deep cerebellar nuclei is relatively localized when first detected but spreads over time as the motor syndrome intensifies may indicate that there is a progressive decline in the function of the Purkinje cells. The fact that electrophysiological techniques detect a mixture of relatively normal and abnormal Purkinje cell activity in animals with advanced symptoms is consistent with such a proposal. Finding significant abnormalities in the cerebellum of the dt rat does not necessarily mean that this is the site of the primary defect responsible for the motor syndrome seen in these animals. We have failed to detect any signs of dysfunction in the basal ganglia, the presumed locus of a defect in human torsion dystonia. However, our investigations have been limited almost exclusively to the striatum. Thus, the possibility of defects at other sites, such as the globus pallidus or thalamus must be considered. Although we have not yet demonstrated that the abnormalities detected in the cerebellum are causally related to the behavior of the dt rat, the behavioral syndrome is consistent with a cerebellar defect. It has been suggested that the cerebellum is important for the continuing calibration of coordinated motor behavior. Important observations on the effects of cerebellar lesions have come from the study of the oculomotor system. Lesions in the cerebellum have been shown to eliminate the ability to recalibrate the saccadic eye movement system and to destroy the adaptive plasticity of the vestibulo-ocular reflex A cerebellar defect could result in a failure in motor learning or in the calibration of motor systems that must take place as the rat pup masters adult patterns of locomotion. We note that lesions of the climbing fiber system with 3-AP lead to some of the same biochemical effects seen in dt rats but do not produce an identical behavioral syndrome.(ABSTRACT TRUNCATED AT 400 WORDS)

Acute and chronic effects of climbing fiber lesions on cerebellar cyclic guanosine monophosphate.

The neurotoxin 3-acetylpyridine was administered to 20-day-old rats to produce lesions of the inferior olive-climbing fiber projection to the cerebellum. Cerebellar cGMP levels were determined 6 h, 24 h, 48 h, 7 days, 14 days and 20 days postlesion. A significant effect on cGMP was found only at 48 h (-28%) and 7 days (-45%) postlesion. The results are discussed with respect to the cellular localization of cGMP and the hypothesized relationship of cGMP to cerebellar Purkinje cell activity.

Temporal sequence of motor disturbances and increased cerebellar glutamic acid decarboxylase activity following 3-acetylpyridine lesions in adult rats.

Adult male rats were administered 75 mg/kg of the neurotoxin 3-acetylpyridine to produce lesions of the inferior olive-climbing fiber projection to the cerebellum. At selected times ranging from 6 h to 43 days postlesion, rats were evaluated for motor dysfunction, and glutamic acid decarboxylase (GAD) activity was determined in the deep cerebellar nuclei and cerebellar vermis. In the deep nuclei non-monotonic changes in GAD activity were found following climbing fiber destruction. Initially, there was a steady increase in GAD activity which peaked at 38% above control values 14 days postlesion. GAD activity then slowly declined, although it remained significantly above control levels at 43 days postlesion, the latest time point examined. In the vermis, GAD activity was significantly increased at 4 days postlesion (+8%) and remained at approximately this level throughout the experiment. The initial behavioral effects of climbing fiber loss included hypotonia and ataxia with severely reduced mobility. With time, the ataxia and hypotonia decreased and movements such as mud-walking and pivoting developed. As these behaviors diminished, other novel conditions such as movement-associated tremor and hopping appeared. These results are discussed in the context of the previously reported effects of climbing fiber lesions on the firing rates of Purkinje cells and deep nuclei cells.

Glutamic acid decarboxylase activity in micropunches of the deep cerebellar nuclei of the genetically dystonic (dt) rat.

Glutamic acid decarboxylase (GAD) activity was measured in specific divisions of the deep cerebellar nuclei of rats with an inherited dystonia. In 16-day-old dystonic rats there was a significant increase in GAD activity only in the nucleus interpositus (+26%). In 20-day-old dystonic rats GAD activity in all 3 cerebellar nuclei (fastigial, interpositus, dentate) was significantly increased compared to normal controls. The results indicate a spread of the anatomical locus of the neurochemical abnormality with time. During this period (postnatal days 16-20) there is a progressive worsening of the motor disorder in the affected animals.

Alterations in the noradrenergic projection to the cerebellum of the dystonic (dt) rat.

The genetically dystonic rat (dt) has elevated resting levels of cerebellar norepinephrine (NE) in comparison with phenotypically normal littermates. This difference is not secondary to cerebellar hypoplasia. Increased NE is observed as early as postnatal day 12, when clinical symptoms have become evident. The elevation in cerebellar NE levels in the dt rat involves all cerebellar areas, but is not generalized to all terminal fields of the locus coeruleus. Elevations in cerebellar NE are followed developmentally by a reduction in sensitivity to the NE-depleting effects of reserpine, a change which is also confined to the cerebellum. The effects of amphetamine and the tyrosine hydroxylase inhibitor alpha-methyl-para-tyrosine were similar in normal and dt rats. Levels of the major cerebellar metabolite of NE, 3-methoxy-4-hydroxyphenylglycol, did not differ between mutant and normal animals. Nor were any changes noted in the number or affinity of beta-adrenergic receptors. These data indicate that there is a regional alteration in NE storage. Cerebellar morphology appears normal in the dt rat, except for a decrease in Purkinje cell size. This change and other evidence of biochemical abnormalities in the Purkinje cells suggest that the alterations in cerebellar NE in the dt mutant may be a secondary response to a functional change in the target neuron for this system, the Purkinje cell.

Lesions of the inferior olive increase glutamic acid decarboxylase activity in the deep cerebellar nuclei of the rat.

Inferior olive-climbing fiber lesions were made by administering 3-acetylpyridine to 16-day-old rats. This treatment produced multiple motor abnormalities which gradually improved over the subsequent 28 days. A significant increase in glutamic acid decarboxylase (GAD) activity was found in the deep cerebellar nuclei 24 h after treatment. This elevation increased with time, reaching 134% of control values 28 days after treatment. GAD activity in the cerebellar vermis also increased but did so more slowly and to a lesser degree than in the deep nuclei, reaching 114% of control values 28 days after treatment. The results suggest the operation of different mechanisms in producing the increased GAD activity in the different areas.

Decreased cerebellar 3',5'-cyclic guanosine monophosphate levels and insensitivity to harmaline in the genetically dystonic rat (dt).

The dystonic rat (dt) is an autosomal recessive mutant displaying a complex motor syndrome that includes sustained axial twisting movements. The syndrome is correlated with increased glutamic acid decarboxylase activity in the deep cerebellar nuclei and increased cerebellar norepinephrine levels in comparison with phenotypically normal littermates. Biochemical, behavioral, and anatomical techniques were used to investigate the possibility that the abnormalities noted in the cerebellum of the dt rat were indicative of altered function of the major projection neurons of the cerebellar cortex, the Purkinje cells. Phenotypically normal rats showed tremor in response to harmaline, a drug that acts on the inferior olive to produce bursting in the climbing fiber pathway. Dystonic rats were insensitive to the effects of harmaline but did respond to oxotremorine. Levels of the cyclic nucleotide 3',5'-cyclic guanosine monophosphate, a biochemical marker for Purkinje cells, increased in response to harmaline in normal rats but were significantly lower in dystonic rats under both basal and harmaline-stimulated conditions. Purkinje cell soma size was reduced in the dystonic rats but no other morphological correlates of the behavioral or biochemical deficits were noted. Taken together with other observations on this mutant, the results suggest an impairment in the cerebellum or in its connections with lower brainstem and spinal cord sites.

alpha 1-Adrenergic receptor binding in the spontaneously hypertensive rat.

Increased sympathetic outflow from the central nervous system to the periphery may contribute to the initiation of hypertension in spontaneously hypertensive rats (SHR). As this alteration in sympathetic activity may be mediated in part by alpha-adrenergic receptors in the central nervous system, the current study examined alpha 1-adrenergic receptors in various brain areas of SHR and normotensive Wistar-Kyoto control rats (WKY). The alpha 1-adrenergic receptor number and apparent affinity constants of brain sections of both young prehypertensive animals (4 weeks old) and mature hypertensive animals (12 weeks old) were studied with the alpha 1-adrenergic receptor antagonist [3H]WB-4101 to label the alpha-adrenergic receptor. Five brain regions were studied: rostral hypothalamus, caudal hypothalamus, locus ceruleus, nucleus tractus solitarius, and frontal cortical poles. In comparison to normotensive controls, mature hypertensive rats had a significantly greater density (p less than 0.05) of the alpha 1-adrenergic receptors in the rostral hypothalamus (+11%), caudal hypothalamus (+25%), and frontal cortical poles (+20%). Significantly greater (p less than 0.05) alpha 1-adrenergic receptor density was found in the rostral hypothalamus (+27%), caudal hypothalamus (+60%), and locus ceruleus (+39%) of the young prehypertensive SHR compared with age-matched WKY. These results indicate the presence of altered adrenergic receptor systems in the brains of genetically hypertensive animals and suggest that changes in the receptor systems take place during establishment of the hypertension.

Decreased catalepsy response to haloperidol in the genetically dystonic (dt) rat.

The rat mutant dystonic displays an autosomal recessive neurological disease characterized by slow, twisting movements of the limbs and trunk. Rats displaying clinical signs also show a decreased behavioral response to the dopaminergic blocker, haloperidol. Investigation of the development of the cataleptic response to haloperidol in the dystonic (dt) rat indicated that the response of the dt rat in the bar test is similar to that of normal littermates until after the appearance of clinical symptoms in the mutants on postnatal day 10. Mutant rats did not differ from their normal littermates in response to another cataleptic agent, morphine. Assessment of the integrity of the nigrostriatal dopamine (DA) system did not indicate the presence of any degenerative process or of any alterations in DA metabolism. No reliable differences were found between normal and dt rats in striatal DA levels or turnover rates; in DA levels in response to gamma-hydroxybutyrolactone; or in the number and affinity of striatal DA muscarinic acetylcholine receptors. Nor did qualitative light microscopic examination of Golgi-impregnated tissue from dt rats indicate the presence of any morphological abnormalities in the striatum. These findings suggest that dystonic symptoms can occur in the absence of an alteration in striatal DA metabolism and that the dt rat may have a defect in a pathway efferent to the striatum.

Alterations in cerebellar glutamic acid decarboxylase (GAD) activity in a genetic model of torsion dystonia (rat).

Glutamic acid decarboxylase (GAD) activity was studied in specific brain regions of a newly identified genetic (rat) model of human torsion dystonia. GAD activity was found to be significantly increased in the deep cerebellar nuclei of dystonic rats at 16, 20, and 24 days of age. GAD activity in the other regions examined (vermis, cerebellar hemispheres, caudate nucleus, and globus pallidus) did not differ from that of age-matched normal littermate controls. Diazepam treatment significantly reduced the frequency of dystonic movements in the mutant.

Yohimbine and rauwolscine reduce food intake of genetically obese (obob) and lean mice.

Multiple behavioral and neurochemical abnormalities are found in the genetically obese mouse, obob , including hyperphagia, elevated hypothalamic norepinephrine (NE) levels, and increases alpha-1 receptor density. The obese mutant also responds abnormally to neuropharmacological agents. In the current study the alpha-2 receptor blockers yohimbine and rauwolscine were administered to food-restricted (6-hour food access) obob and lean mice. Yohimbine and rauwolscine significantly reduced the 3- and 6-hour food intake of both obob and lean mice. The obob mice were, however, more sensitive to this anorectic effect than lean mice. Effective anorectic doses of yohimbine did not affect water intake in water-deprived lean mice, suggesting a specific effect of the drug upon food intake. Low doses (50 and 100 micrograms) of the alpha-2 agonist clonidine increased the 1-hour food intake of obob mice, but did not affect the food intake of lean mice. No differences were found between obob and lean mice in the number of alpha-receptors in the hypothalamus. The results suggest that modification of NE release by manipulation of alpha-2 receptor can alter food intake, and that the obob mutant is particularly sensitive to this effect.