Increased amyloid precursor protein expression and serotonergic sprouting following excitotoxic lesion of the rat magnocellular nucleus basalis: neuroprotection by Ca(2+) antagonist nimodipine

In the present study plastic neural responses to N-methyl-D-aspartate-induced excitotoxic lesions and the neuroprotective effects of the L-type voltage-dependent Ca(2+) channel antagonist nimodipine were investigated in the rat magnocellular nucleus basalis. Assessment of spontaneous behaviour in the elevated plus maze and small open-field paradigms on day 5 and day 14 post-surgery indicated anxiety and persistent hypoactivity of N-methyl-D-aspartate-lesioned rats, as compared with sham-operated controls. Nimodipine administration significantly alleviated the behavioural deficits. Quantitative histochemical analysis of acetylcholinesterase-positive fibre innervation of the somatosensory cortex and determination of the numbers of choline-acetyltransferase-positive proximal fibre branches of cholinergic projection neurons in the magnocellular nucleus basalis demonstrated a severe cholinergic deficit as a consequence of the excitotoxic lesion 14 days post-surgery. Nimodipine pre-treatment significantly attenuated the loss of cortical cholinergic innervation and preserved the functional integrity of cholinergic projection neurons in the magnocellular nucleus basalis. Double-labelling immunocytochemistry demonstrated increased amyloid precursor protein expression in shrinking and presumably apoptotic choline-acetyltransferase-positive neurons, whereas surviving cholinergic nerve cells were devoid of excessive amyloid precursor protein immunoreactivity. Moreover, as a consequence of N-methyl-D-aspartate infusion, rim-like accumulation of amyloid precursor protein-positive astrocytes was visualized in a penumbra-like zone of the excitotoxic injury. Furthermore, abundant sprouting of serotonergic projection fibres invading the damaged magnocellular nucleus basalis subdivision was demonstrated. Pharmacological blockade by the Ca(2+) antagonist nimodipine significantly attenuated both neuronal and glial amyloid precursor protein immunoreactivity and serotonergic fibre sprouting following N-methyl-D-aspartate infusion. The present data characterize plastic endogenous glial and neuronal responses in the magnocellular nucleus basalis model of acute excitotoxic brain damage. The increased amyloid precursor protein expression may indicate effective means of intrinsic neuroprotection, as secreted amyloid precursor protein isoforms are suggested to play a role in neuronal rescue following excitotoxic injury. From a pharmacological point of view, extensive sprouting of serotonergic projections in the damaged magnocellular nucleus basalis may also counteract N-methyl-D-aspartate excitotoxicity via serotonin-induced inhibition of Ca(2+) currents and membrane hyperpolarization. Hence, lesion-induced changes in spontaneous animal behaviour, such as anxiety and novelty-induced hypoactivity, may well be attributed to the considerable re-distribution of serotonergic projections in the basal forebrain. In conclusion, our present data emphasize a role of neuron-glia and neurotransmitter-system interactions in functional recovery after acute excitotoxic brain injury, and the efficacy of L-type Ca(2+) channel blockade by the selective 1,4-dihydropyridine antagonist nimodipine.

Neuroprotection against N-methyl-D-aspartate-induced excitotoxicity in rat magnocellular nucleus basalis by the 5-HT1A receptor agonist 8-OH-DPAT

The present study reports the neuroprotective efficacy of the 5-HT1A receptor agonists 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT) and ipsapirone against in vivo excitotoxic neuronal injury. Excitotoxic cell death was induced by injections of N-methyl-D-aspartate (NMDA) in the rat magnocellular nucleus basalis. The neurodegenerative effects were quantified by image analysis of the axonal density of the nucleus basalis projection to the somatosensory cortex visualized with acetylcholinesterase histochemistry. Pretreatment with 8-OH-DPAT--but not ipsapirone--1 h prior to NMDA infusion showed significant preservation of cortical cholinergic innervation in all doses tested. Furthermore, 8-OH-DPAT exhibited sustained efficacy under homeothermic conditions in which the body temperature was maintained at 36.8 +/- 0.1 degrees C. These data indicate that selective 5-HT1A receptor activation by 8-OH-DPAT protects against NMDA-induced excitotoxic neuronal damage, probably as a result of 5-HT1A receptor-mediated neuronal hyperpolarization.

Muscle computed tomography in adult-onset acid maltase deficiency

Nine patients with adult-onset acid maltase deficiency (Pompe's disease) were examined clinically and with computed tomography (CT). The CT scan showed early and severe involvement of the muscles of trunk and thighs, with selective sparing of the tensor fasciae latae, short head of biceps femoris, gracilis, and sartorius muscles. Shoulder and leg muscles were less affected. The disease spread over the years from trunk to extremities. Muscle strength and CT findings were positively correlated.

Selective decline of 5-HT1A receptor binding sites in rat cortex, hippocampus and cholinergic basal forebrain nuclei during aging

The effect of aging on 5-HT1A receptor binding in several forebrain areas associated with the basal forebrain cholinergic system was investigated in rats of 3-, 24- and 30-months-old by receptor autoradiography and biochemical binding assay using [3H]8-OH-DPAT as a ligand. Autoradiographic measurements demonstrated a marked region-specific decline of ligand binding in: (i) regions of the basal forebrain cholinergic cell groups, i.e. the medial septum, diagonal band nuclei and magnocellular nucleus basalis, (ii) the frontal and parietal neocortex and (iii) the dentate gyrus of the hippocampus. No change or only a slight decrease of the 5-HT1A receptor density was found in other areas investigated: the CA1 and CA3 sectors of hippocampus, the cingular and perirhinal cerebral cortex and the lateral septum. The autoradiographic findings were substantiated by the biochemical binding assay, which revealed a comparable loss of 5-HT1A receptor in the hippocampus and neocortex at the age of 30 months. The results clearly show that with increasing age the decrement of 5-HT1A receptor binding in the rat forebrain is remarkably region-selective and particularly affects the cholinergic cell groups that innervate cortex and hippocampus. This phenomenon appears to be especially significant in relation to the neuronal substrates underlying the age-related alterations of mood and cognition.