Relationship between electrocortical arousal and memory deficits in aged rats - effects of atipamezole alpha-2 antagonist

NEUROBIOLOGY OF AGING, VOLUME l 1, 1990 ABSTRACTS OF SECOND INTERNATIONAL CONFERENCE ON ALZHEIMER'S DISEASE ANIMAL MODELS Sections of brain from normal mice or clinically-ill mice infected with either the 87V or the ME7 strains of sheep scrapie were immunostained to show the localisation of ubiquitin protein conjugates or a specific marker of disease, the scrapie-associated fibril protein (PrP). In both scrapie models immunoreactive ubiguitin-protein conjugates were seen in thread-like structures found throughout the neuropil, in inclusion bodies within vacuolated neurones and in areas surrounding anti-PrP positive amyloid plaques. The PrP protein was visualised in diffuse deposits in highly vacuolated parts of the scrapieaffected brain, and focally in amyloid plaques, mieroglia and neuronal processes. The ubiquitin-protein conjugate staining of scrapie amyloid plaques is very similar to that seen in the plaques of Alzheimer's disease. The ubiquitinated intraneuronal inclusion bodies seen in scrapie resemble the granulovacuolar lesions also seen in Alzheimer's disease but appear much larger and possibly correspond to material in giant autophagic vacuoles. We suggest that these inclusions may be the result of ubiquitinated abnormal proteins being directed to the lysosomal system, and that scrapie and Alzheimer's disease share at least some common processes of neurodegenerat ion.

3()6 TRANSPLANTS OF MOUSE TRISOMY 16 HIPPOCAMFUS PROVIDE AN IN VIVO MODEL OF THE NEUROPATHOLOGY OF ALZHEIMER'S DISEASE. *IS-J. Richards, 1j.j. Waters, 2K. Beyreuther, 3C.L. Masters, 4C.R. Abraham, SC.M. Wischik and 1S.B. Dunnett. ~University of Cambridge, UK, 2University of Heidelberg, W. Germany, SUniversity of Melbourne, Australia, 4Boston University School of Medicine, USA and SLaboratory of Molecular Biology, Cambridge, UK. Trisomy 21 (Down syndrome) individuals develop neuropathological changes characteristic of Alzheimer's disease (AID). Markers associated with the familial AD region on human chromosome (chr.) 21 map to mouse chr. 16. Although breeding regimes exist to generate trisomy 16 (Tsl6) mice the effects of this aneuploidy are lethal at around embryonic day lS. By using embryonic neural tissue transplantation, we have been able to extend the life of Ts16 cortical tissues and have assayed them immunocytochemically for proteins associated with AD. We have undertaken a time couse of the development of the neuropathological features akin to AD. At 4 months survival, the grafts contain scattered cells as well as aggregates of cells immunoreactive for antibodies raised against the amyloid A4 protein, ~l-antichym°trypsin and Tau 6.423. Control grafts and host tissues were not immunoreactive with any of these antibodies. Confocal microscopy revealed distinctive patterns of intracellular granular staining of these proteins within the Tsl6 grafts which closely resembles the pattern of intracellular staining observed within AD cortical tissues. Amyloid staining was also seen extending extracellularly from immunoreactive cells. Furthermore, double staining immunofluorescence demonstrated cellular co-localization of amyloid A4 protein with c~c antichymotrypsin and with Tau 6.423. The proteins associated with AD neuropathology (and which are apparent within the Tsl6 grafts at 4 months survival) are not observed within the neural tissues of the Tsl6 embryo or within the trisomic grafts at 3 weeks survival. The detailed time course and sequence of events involved in the development of the neuropathology will be presented. 307

MICROGLIA ACTIVATION IN SCRAPIE-INDUCED AMYLOIDOSIS IN MURINE CNS J. Frackowiak, G. Wolfe, G.S. Merz, P. Casaccia, H.M. WisniewskL NYS Institute for Basic Research in Developmental Disabilities, Staten Island, New York, 10314 USA. Recently it has been shown that in Alzheimer's disease amyloid formation is associated with accumulation of activated microglia in the CNS. Microglia exhibit an increased expression of intracellular IL-1 and surface MHC antigens. Furthermore, morphological studies indicate that microglia are closely associated with amyloid plaques and display ultrastructural features suggestive of amyloid fiber

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formation. In order to further assess the possible role of microglia activation in the course of brain amyloidosis, the degree of activation of isolated microglia was studied in scrapie infected mice. As an experimental model of murine encephalopathy with and without amyloidosis, we used VM mice inoculated with 87V scrapie agent in cerebral cortex or cerebellum. Microglia were isolated by enzymatic digestion, Percoll density gradient separation and immunoadherence via cell surface Fc receptors. The purified population contained 92% of microglia, as assessed by FcR, C3R and nonspecific esterase expression. Microglia activation was assessed by measuring tumor necrosis factor (TNF) production after stimulation in vitro. Isolated microglia were also assayed for the expression of PrP (i.e. scrapie amyloid precursor protein), TNF, and IL-1 mRNAs by cytoplasmic dot hybridization. We found that microglia become activated in the course of scrapie disease, in both the amyloid and non-amyloid models. The relevance of the results to the amyloid formation in brain will be discussed. 308 R E L A T I O N S H I P BETWEEN E L E C T R O C O R T I C A L AROUSAL AND MEMOEY DEFICITS IN AGED RATE - EFFECTS O F ATIPAMEZOLE ALPHA 2 ANIAGON!ST. *P.J. Riekkinen I , P . Riekkinen Jr I , M. Aa]tonen I , J. Sirvib I , R. L a m m i n t a u s t a 2 . 1 D e p a r t m e n t of Neurology, University of Kuopio, Finland, 2Farmo s Group Ltd, Tu[ku, rini~nd Anatomical and e l e c t r o p h y s i o l o g i c a l properties of noraJrenergic neurons p r o j e c t i n g from the locus coeruleus to th~ forebraim suggest that this system plays a role in learni, g and memory. O y s f u n c t i o n of n o r a d l e n e r g i c system may also underlay some aspects of a g e - r e l a t e d cognitive deficits. The present studies were undertaken to investigate whether atipamezole an alpha-2 antagonist which increases the turnovi[ of n o r a d r e n a l i n e , would alleviate age ~elated deficits in e l e c t r o c o r t i c a l arousal (high voltage spindles) and learn ing/memory (passive avoidance task amd wate: maze task). The incidence of high voltage spindles was high in a subp o p u l a t i o n of aged rEts (24 montms) that was impaired in passive avoidance retention (PA), but the rest of the aged rats had only few HUEs. A diffelent sub-group of aged ratr~ was impaired in morris water maze (M~M) retention. No relationship was found between HVSs and MWM performance. Atip:,mezole (3 mg/kg, sc.), markedly de~reased the incidence o~ HVSs ir aged rats. P r e - r e t e n t i o n test injections of atipa mezole (3 mg/kg, s.c.) improved ~A performance. However, daily p o s t - t r a i n injections (3 mg/kg, s.c.) failed to improve either a c q u i s i t i o n or long-term retention (7 days interval) of mWM task. Atipamezo!e (3 mg/kg, ~.c.) had no effect on the PA or MWM behavior im young rats. The p r e s e t results suggest that the n o r a d : e n e r g i c pathology is invol,ed in the EEG and passive avoidance retention deficits found in old age. Furthermore, they ~uggest usefulness of a l p h a 2 antagonist in the treatment of age-zelated deficits of cognitive functions.

309 EFFECTS OF COMBINED INTRACEREBROVENTRICULAR INFUSION OF CHOLINE AND ORAL ADMINISTRATION OF CHOLINEHGIC DRUGS ON LEARNING IMPAIRMENT IN VENTRAL GLOBUS PALLIDUS-LESIONED RATS. *A. Ueki, K. Miyoshi. Department of Neuropsychiatry, Hyog~ College of Medicine, l-l, Mukogawa-cho, Nishinomiya, Hyogo 663 Japan. The nucleus basalis m a g n o c e l l u l a r i s (NBM) of the rat, a group of cholinergie neurons in the ventral corner of the globus pallidus, is homologous to the human nucleus basalis of M e y n e r t - - t h e structure c o m p l i c a t e d in the chollnergic hypothesis of memory impairment in A l z h e i m e r ' s disease. NBM lesioning was induced in the rat using the excitotoxin ibotenie acid. In the cortex of such rats, acetylcholine, choline a c e t y l t r a n s f e r a s e activity and reactivity to a c e t y l c h o l i n e s t e r a s e staining were diminished and significant deficit was observed in the acquisition and retention of the passive avoidance response. An a m e l i o r a t i n g effect on the learning disturbance in these rats was exhibited by ora] a d m i n i s t r a t i o n of I or 3 mg/Kg THA (9-amJno-I,2,3,4t e t r a h y d r o a c r i d i n e h y d r o c h l o r i d e ) and NIK-247 (9-amino2,3,5,6,7,8-hexahydro-IH-cyclopenta[b]qulnoline monohydrate hydrochloride). In the present study, the effects of combined or separate oral a d m i n i s t r a t i o n of THA (0.5 mg/Kg) or N|K 247 (0.5 mg/Kg) and i n t r a c e r e b r o v e n t r i c u l a r infusion of cho]ine using an osmotic m l n l p u m p were investigated by observing