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Passive avoidance behavior changes produced by the atropinisation and the nucleus basalis lesion in rats

The purpose of this study was to examine the influence of impaired cholinergic function produced by the atropinisation or by bilateral electrolytic or neurotoxic lesions of the nucleus basalis magnocelluularis (NB) on the passive avoidance behavior in the rat. Namely, during the past decade numerous laboratories have implicated deficiencies in cholinergic function as contributing to the loss of memory in old age as well as the more severe cognitive disturbances occurring with Alzheimer's disease (AD). The degeneration of the cholinergic pathways innervating cortex and hippocampus appears to be the most important pathogenetic mechanism of the mental impairment characterizing the AD. The NB provides the primary cholinergic input to the cortical mantle. Lesions of the NB reduce cortical CAT and AChE activity, ACh release and choline uptake. The study was carried out on Wistar albino rats weighting 200-250 g. Atropine sulfate (6 mg/kg) was injected i.p. to intact animals half an hour before the passive avoidance test started. All the other animals were anesthetized and placed on a stereotaxic frame. Bilateral electrolytic NB lesions were made by using a direct current of 10 mA passed through a unipolar electrode for 10 sec. Bilateral neurotoxic lesions of the NB were made by application of 1.0 μg kainic acid in 1.0 μI sodium phosphate buffer. The coordinates for the lesion were 0.7 mm posterior ; 2.7 mm lateral and 8 mm ventral to the bregma. The sites of the .lesions were verified histologically after perfusion per the technique of Wolf (1971). After a 15 days lasting postoperative recovery period passed, each NB lesioned animal was subjected to the behavior test (the procedure of Ashford and Jones, 1976). The results of our experiments show that an impairment of the cholinergic function, either by the atropinisation or by the NB lesions, produced marked deficit in the passive avoidance behavior in rats.

passive avoidance; nucleus basalis lesion; rat

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