Faculty Bibliography

We studied the distribution of puromycin-sensitive aminopeptidase (PSA) in well-defined human brain ares by Western immunoblot in an attempt to examine its possible role in schizophrenia. The schizophrenic brains were from suicide victims (n = 13) of either sex, with an age range of 30-60 yr (average 45). The controls were mostly victims of myocardial infarction (n = 12), of either sex and between 32 and 56 yr old (average 44). The brain regions were obtained within 48 h after death. After ultracentrifugation the PSA was quantified by Western blot analysis using a PSA antiserum. The distribution of the two most abundant antigens, MW 100 kDa (PSA-100) and 170 kDA (PSA-170), were compared. PSA-100 had peptidase activity, PSA-170 did not. PSA-100 was found in all of the region studied. In the control brain areas prefrontal cingulate and frontal cortices, thalamus, hippocampus, hypothalamus and outer globus pallidus contained significantly more PSA-100 than the corresponding areas from schizophrenic brain. PSA-170 was mostly found only in areas of schizophrenic brains. In three control brains, in one area of each, it could be detected, but the level in each of these regions was less than 30% of that in the corresponding schizophrenic area. PSA-170 was found in all the schizophrenic brains, in 20 of the 35 regions we studied, with parahippocampal cortex the highest (134 ng/g wet tissue) and frontal inferior cortex the lowest (9.3 ng/g wet tissue). It was not detectable in cerebral or cerebellar white matter. Our data show that the amounts and distribution of PSA-170, a protein of unknown function, is restricted mostly to schizophrenic brain areas. The difference is not due either to neuroleptic treatment of the patient or to the postmortem proteolysis of the brain samples

The release of ATP and ADP, the putative central neurotransmitters, from the isolated habenula preparation was investigated in the rat, at rest and during electrical stimulation, using the luciferin-luciferase assay and the creatine phosphokinase assay. Electrical field stimulation (2 Hz, 360 pulses) released a considerable amount of ATP (2450 +/- 280 pmol/g wet tissue) from the tissue; inhibition of the voltage Na+ entry by tetrodotoxin (1 microM) reduced significantly the evoked release (by 66.25 +/- 6.65%), but not the resting release of ATP. Endogenous ADP also appeared in the effluent, but its amount differed during resting condition and after stimulation from that of ATP, suggesting that the majority of the released compound is ATP in response to stimulation. When ATP was added to the tissue, it readily decomposed to ADP and AMP (Km = 811.6 +/- 68.88 microM, vmax = 23.1 +/- 2.75 nmol/min per prep., measured by high-performance liquid chromatography combined with ultraviolet detection), indicating that the habenula contains ectoATPases. In addition, the inactivation of extracellular ATP by the ectoATPase enzyme was also visualized by electron microscopic enzyme cytochemistry. The ectoATPase enzyme was present on the membranes of the dendrites and nerve terminals and in the synapses of the habenula. Taking into account the fact that ATP is ubiquitous in excitable cells (storage) and the findings published by Edwards et al. in 1992 ('ATP receptor-mediated synaptic currents in the central nervous system', Nature, Vol. 359, pp. 144-147), our data provides evidence for the release by axonal stimulation and extracellular decomposition of ATP, all needed for an endogenous substance qualified as a transmitter

Ibogaine is an indole alkaloid that has been suggested to have potential efficacy for interrupting dependency on stimulant drugs. The kappa-opioid and serotonin 5-HT3 systems may be involved in the action of ibogaine, related to their modulation of dopaminergic transmission. The kappa-opioid agonist U 62066 attenuated the in vitro stimulation-evoked efflux of tritium label from striatal tissue prelabeled with [3H]dopamine. In mice pretreated with ibogaine.HCI (40 mg/kg IP given 2 h prior or 2 x 40 mg/kg and animals killed 18 h later), the inhibitory effect of U 62066 on stimulation-evoked release of tritium was eliminated. The 5-HT3 agonist phenylbiguanide had a biphasic effect on stimulation-evoked release of tritium; at 10(-6) M phenylbiguanide, stimulation-evoked release was attenuated. At 10(-5) M the basal outflow of tritium was increased. Ibogaine pretreatment had no effect on basal or stimulation-evoked release in the presence of 10(-6) M phenylbiguanide, but increased the stimulation-evoked outflow of tritium in the presence of 10(-5) M phenylbiguanide. Cocaine (10(-6) M), a dopamine uptake blocker, increased the electrically-evoked release of dopamine; ibogaine pretreatment did not affect the enhanced electrically-induced release of [3H]dopamine by in vitro cocaine. The effects of ibogaine on the kappa-opioid and 5-HT3 receptors, located presynaptically on striatal dopamine terminals, modulating dopamine release may partly underlie its putative antiaddictive properties