VIP-sensitive adenylate cyclase, guanylate cyclase, muscarinic receptors, choline acetyltransferase and acetylcholinesterase, in brain tissue afflicted by Alzheimer's disease/senile dementia of the Alzheimer type.

Biochemical parameters were determined in autopsy material from several brain regions of thirteen patients with Alzheimer's disease/senile dementia of Alzheimer type (AD/SDAT) (mean age 75 years) and from brains of ten age-matched controls (mean age 76 years). Choline acetyltransferase specific activity was significantly lower in the nucleus caudatus, putamen, left thalamus, hippocampus and the cortex from gyrus hippocampus and the temporal lobe in AD/SDAT, acetylcholinesterase specific activity was significantly lower in the hippocampus, parietal and left frontal lobe in AD/SDAT samples than in corresponding samples from aged-matched controls. A compensatory increase of muscarinic receptors was found in the nucleus caudatus and left frontal lobe samples in AD/SDAT. Guanylate cyclase activity was not significantly altered in AD/SDAT in the brain regions examined. The basal, non-stimulated activity of adenylate cyclase was significantly (p less than 0.05) elevated in hippocampus samples from AD/SDAT patients and the enzyme activity stimulated by the vasoactive intestinal polypeptide VIP (2 microM) or forskolin (10 microM) was also elevated in AD/SDAT although not significantly.

The effect of progesterone and its metabolites on the interictal epileptiform discharge in the cat's cerebral cortex.

The antiepileptic effect of progesterone, 5-alpha-pregnane-3,20-dione, 3-alpha-hydroxy-5-alpha-pregnane-20-one, and 3-alpha-hydroxy-5-beta-pregnane-20-one were tested in an experimental animal model, and compared with the effect of clonazepam. The steroids were dissolved in serum from ovariectomized cats. Ovariectomized adult cats were used and spontaneous epileptic discharges were generated by placing small pieces of penicillin-soaked filter papers on the ipsi and contralateral cerebral cortex. The frequency and amplitude of the interictal epileptiform spikes were recorded, and analysed in a computer. The changes in frequency and amplitudes were calculated. The drugs were infused during 20-s periods into one cerebral hemisphere via the ipsilateral lingual artery with speeds of 1.1, 3.4 and 6.3 ml min-1. A penicillin focus on the contralateral hemisphere served as a simultaneous control. Progesterone and clonazepam showed similar inhibitory effects on epileptiform interictal spiking (median reduction of spike frequency 21%, cf. Table I). The 5-alpha-pregnane-3, 20-dione was generally less potent than progesterone (median reduction 9%) and the 5-alpha- and 5-beta-pregnanolones were two to three times more potent than progesterone (54-66% reduction). The latency of the inhibitory effect was 4-10 s measured from the entrance of the infusion into the lingual artery. The depression lasted 10-20 min. It is concluded that the pregnanolones have strong antiepileptic properties. The rapid onset of effect indicates that the steroids may interact with the neuronal function at the membrane or synaptic levels.

A method for recording effects of anti-epileptic drugs on interictal discharge in the cat's cerebral cortex. Factors determining the distribution of external carotid artery infusions.

The method utilizes infusion via the external carotid (ECA), the internal maxillary arteries and their anastomoses to the cerebral circulation. It takes into account the ipsilateral distribution of the carotid blood supply. A regular interictal epileptiform spiking from foci on both hemispheres was provided by local application to the cortical surface of small pieces of filter paper soaked in sodium benzylpenicillin, 100,000 IE ml-1. The infused drug affects the ipsilateral foci, and the contralateral one functions as a simultaneous untreated control. The stability of the interictal frequency and the effect of non-oxygen carrying solvents are described. The effect of changes in blood pressure, temperature and PCO2 are considered as well as the coupling between activity in ipsi- and contralateral foci. Experiments with infused radioactive microspheres were performed to determine the strictness of the ipsilateral distribution and the conditions under which it was upheld. With mean arterial blood pressures between 70 mm Hg and 170 mm Hg and infusion speeds between 1.0 ml min-1 and 6.3 ml min-1 the distribution to the contralateral cerebral hemisphere was 0.3% (SD 0.2, SEM 0.1). Infusions of [125I]albumin were used to determine the blood flow in ECA. The flow varied between 20 ml min-1 and 68 ml min-1. The higher values were seen when the extracerebral shunting was high. Conditions influencing the dilution of the infusion and its distribution within the brain were investigated. Important factors were carotid and cerebral blood flow, arterial blood pressure, speed and duration of the infusion, recirculation and cerebral temperature. Arterial PCO2, pH and PO2 should be carefully controlled. Computer-supported treatment of interictal spike frequency and amplitude, as well as of circulatory and respiratory parameters, was utilized. The method was tested in experiments with infusions of 5 alpha-pregnanolone. It was shown that infusions, shorter than the estimated circulation time, reduced the interictal spike frequency and amplitude recorded from the ipsilateral foci without effects on the contralateral ones.

Anticholinergic potency of psychoactive drugs in human and rat cerebral cortex and striatum.

The affinity of selected antipsychotic and antidepressant drugs for the muscarinic receptor was studied in membranes from both human and rat striatum and cerebral cortex. While there are regional differences in the anticholinergic potency of the drugs, there is good agreement between the obtained inhibition constants from the corresponding human and rat striatum (r: 0.98) and from human and rat cerebral cortex (r: 0.96). There is also good agreement between the obtained Ki values within one species: human cerebral cortex versus human striatum (r: 0.99) and for rat cerebral cortex and rat striatum (r: 0.87). Thus, the previously published quantitative estimates of the antimuscarinic activity of psychoactive drugs which were derived from studies on membranes from rat brain give an accurate estimate of the antimuscarinic activity in human brain. The drugs tested in this study include chlorpromazine acetophenazine, haloperidol, sulpiride, remoxipride (FLA-731 (-), a substituted benzamide), amitriptyline and two serotonin uptake blockers: norzimelidine and alaproclate.

In vivo and in vitro studies on the potentiation of muscarinic receptor stimulation by alaproclate, a selective 5-HT uptake blocker.

Alaproclate (10-60 mg/kg) injected i.p. into male mice potentiated and prolonged the oxotremorine and physostigmine-induced tremor in a dose-dependent manner. Atropine completely blocked the tremor caused by oxotremorine or physostigmine both in the presence and absence of alaproclate. Pretreatment with the 5-HT receptor antagonist metitepine completely blocked the enhancement of oxotremorine-induced tremor caused by alaproclate. Biochemical studies indicated that the above effects cannot be explained by assuming that alaproclate a) acts as a cholinergic agonist, b) inhibits the acetylcholine esterase, c) interferes with choline uptake or acetylcholine synthesis, or d) directly potentiates the release of acetylcholine. In ligand binding studies alaproclate was found to be a weak competitive inhibitor of muscarinic antagonist binding to membranes from the rat cerebral cortex, rat striatum, human cerebral cortex and human striatum. (Ki approximately 28-40 microM in all four tissues). The present results suggest that alaproclate may potentiate muscarinic responses by a mechanism involving serotonergic receptor mechanisms rather than by a direct interaction with the muscarinic cholinergic receptors.

Orthovanadate induces loss of muscarinic cholinergic binding sites.

In homogenates of corpus striatum from rats, incubated in the presence of adenosine triphosphate (2 mM) (45 min, 37 degrees C), a loss (approx. 50%) of muscarinic cholinergic binding sites could be detected using a 3H-3-Quinuclidinyl benzilate (3H-3-QNB) binding assay. We found that only vanadium-contaminated ATP induced loss of muscarinic binding sites. Orthovanadate (1 mM) alone in the absence of ATP induced loss (approx. 60%) of binding sites just as "vanadium-ATP" did.