No abstract

Summary: Prior work has demonstrated that unilateral lesions of the nucleus basalis of Meynert (NbM) in ba boons induce a marked reduction in glucose utilization of the ipsilateral cerebral cortex, linearly proportional to the depression in cortical choline acetyltransferase (ChAT) activity achieved. Unexpectedly, there was also marked hypometabolism of the contralateral cerebral cortex, and glucose utilization recovered gradually on both sides de spite persistent deficit in cortical ChAT activity. To in vestigate the role of the corpus callosum (CC) in this bi lateral metabolic effect and subsequent recovery, three baboons were subjected to unilateral electrolytic NbM lesion >3 months following section of the anterior CC. Brain glucose utilization was sequentially studied by posThe nucleus basalis of Meynert (NbM) is the ma jor source of cholinergic projections to the cerebral cortex (Mesulam and Van Hoesen, 1976) and is con sistently involved in dementia of the Alzheimer type (Ezrin-Waters and Resch, 1986;Salamone, 1986;Olton and Wenk, 1987). The effects of cholin ergic deafferentation, obtained by unilateral stereo taxic NbM lesions, on the energy metabolism of the cerebral cortex are of interest because both cortical glucose utilization and oxygen consumption are re-

In vivo benzodiazepine receptor occupancy by increasing doses of CL 218,872 has been evaluated in the baboon Papio papio, using (11C) RO 15-1788 as specific radioligand and positron emission tomography as external detection system. Although BZR heterogeneity has been previously demonstrated in the brain of the living baboon using PET, we did not observe in our studies that CL 218,872 interacts preferentially with one of the BZR subtypes. The monophasic pattern of the dose dependent CL 218,872 displacement curve and the corresponding "in vivo Hill coefficient" near unity suggest that CL 218,872 binds in cerebral baboon cortex with a similar affinity with BZ1 as well as BZ2 subtypes. The anticonvulsant properties of CL 218,872 against bicuculline and allylglycine-induced seizures were correlated with benzodiazepine receptor occupancy by assessment of electroencephalographic activity during positron emission tomography studies. Our data confirmed in vivo the hypothesis of a partial agonist anticonvulsant activity of CL 218,872. At the same time, the use of a GABA-antagonist (bicuculline) or an inhibitor of the GABA synthesis (allylglycine) suggested the existence of an allosteric interaction between benzodiazepine receptors and GABA receptors.

Cortical glucose utilization was measured under light anaesthesia using positron emission tomography and 18F-fluorodeoxyglucose before and serially after stereotaxic anterior corpus callosum section in 3 adult baboons (Papio papio); in 1 animal needles were introduced but callosotomy was not performed ('sham' operation). Lesion efficacy was verified by x-ray computerized tomography and by postmortem examination which indicated effective anterior two-thirds callosal section in all 3 baboons, as well as a small contusional area in the medial frontal cortex. A two-way layout analysis of variance performed on the regional cerebral metabolic rate of glucose (CMRGlc) data obtained in the frontotemporal, temporal and occipital areas revealed significant effects for both the time and the region factors (P less than 0.00001 for each); the time effects indicated a significant initial metabolic depression (P less than 0.01) at day 11 and 18, and a subsequent recovery (P less than 0.01 to 0.05) at day 98. Average CMRGlc changes from preoperative values at successive studies were -23%, -27%, -17%, -8% and +2%, and -17%, -21%, -10%, -5% and +6% in the 'surgically approached' and the contralateral frontotemporal area, respectively. The frontotemporal/occipital CMRGlc ratio was significantly depressed at days 11, 18 and 32 (P less than 0.01, 0.01 and 0.05, respectively), indicating a transient postoperative alteration in the cortical metabolic pattern. In the 'sham' animal, surgery induced negligible metabolic effects. Our results indicate that effective anterior corpus callosum section induces a transient bilateral depression of cortical metabolism, which predominates in the anterior parts of the brain, while metabolic recovery suggests efficient neuronal adaptation. These functional effects in the cortex may underlie the transient behavioural changes that follow anterior callosotomy in man.

A 61-year-old male presented with a hypervascular variant of dysplastic gangliocytoma (Lhermitte Duclos disease) manifesting as gait disorder. Computed tomography and magnetic resonance imaging both showed enhancement of the tumor after injection of contrast medium. Angiography demonstrated a tumor stain. Histological examination showed a double-layered structure comprising an outer layer of myelinated axons and an inner layer of dysplastic granular cells, and numerous dilated thin-walled blood vessels. Partial resection of the tumor resulted in resolution of the neurological deficit.