ABSTRACT
Frontal and parietal components of somatosensory evoked potentials (SEPs) following median nerve stimulation and scalp potentials preceding myoclonic jerks (jerk-locked averaging, JLA) were compared in 6 patients with cortical reflex myoclonus. Giant potentials were found over the parietal cortex in both conditions. Prominent frontal activity was detected following median nerve stimulation which, however, was absent in jerk-locked averages. Therefore an identical generator of the giant SEP and the JLA is unlikely. As the frontal component is lacking in jerk-locked averaging, the spontaneous jerks produced in our experimental paradigm are believed to be due to spontaneous hyperactivity of the parietal cortex rather than to pathologically enhanced transcortical reflexes.
Subject(s)
Cerebral Cortex/physiopathology , Evoked Potentials, Somatosensory/physiology , Myoclonus/physiopathology , Adolescent , Adult , Electric Stimulation , Electroencephalography , Female , Frontal Lobe/physiopathology , Humans , Male , Median Nerve/physiology , Middle Aged , Myoclonus/etiology , Parietal Lobe/physiopathologyABSTRACT
In rats, probenecid exhibits a dose-dependent increase in the concentration of cyclic adenosine 3',5'-monophosphate (cAMP) in cisternal cerebrospinal fluid (CSF). Maximal accumulation is reached 2 h after IP administration at a dosage of 150 mg/kg body weight. Serum levels of cAMP are unchanged after 200 mg/kg probenecid. In vitro investigations show an inhibitory effect of probenecid on the uptake of cAMP into the isolated choroid plexus of the rabbit. A non-competitive inhibition of probenecid on a high affinity fraction of cyclic nucleotide phosphodiesterase from rat brain homogenates is demonstrated with an inhibitor constant of 3.4 X 10(-3M. The results appear to validate the "probenecid test" for cAMP in clinical diagnostics.
Subject(s)
Brain/drug effects , Cyclic CMP/cerebrospinal fluid , Cytosine Nucleotides/cerebrospinal fluid , Phosphoric Diester Hydrolases/metabolism , Probenecid/pharmacology , Animals , Brain/enzymology , Choroid Plexus/drug effects , Dose-Response Relationship, Drug , Kinetics , Male , MuridaeABSTRACT
Adenosine 3',5'-monophosphate (cyclic AMP), 5-hydroxyindoleacetic acid (5-HIAA) and homovanillic acid (HVA) were determined in the cerebrospinal fluid of patients with respiratory disorder and hypersomnia and in control patients. Patients with the sleep apnoea syndrome confirmed polygraphically showed elevated levels of cyclic AMP and 5-HIAA. Cyclic AMP levels were inversely correlated with arterial Po(2), measured under resting conditions. The level of HVA also was raised, but the change was not statistically significant.
Subject(s)
Cyclic AMP/cerebrospinal fluid , Homovanillic Acid/cerebrospinal fluid , Hydroxyindoleacetic Acid/cerebrospinal fluid , Phenylacetates/cerebrospinal fluid , Sleep Apnea Syndromes/cerebrospinal fluid , Disorders of Excessive Somnolence/cerebrospinal fluid , Female , Humans , Male , Middle Aged , Obesity/cerebrospinal fluidABSTRACT
The central metabolism of dopamine, serotonin, cyclic AMP and cyclic GMP was studied by use of the probenecid test in three patients with bismuth encephalopathy and in one patient with mercury encephalopathy. The accumulation of HVA and of cGMP in the cerebrospinal fluid was depressed during the acute phase of bismuth encephalopathy with severe hyposomnia, while it was increased in a patient with regression of clinical symptoms and normal in a patient with more advanced recovery. The patient with chronic mercury poisoning showing a severe cerebellar ataxia and rigidity had an almost complete suppression of HVA accumulation and an increase of cGMP accumulation. No pronounced differences of 5-HIAA and cAMP behavior were found. It is concluded that the central metabolism of dopamine and of cGMP is severely affected in bismuth and mercury encephalopathies.
