The effect of cotinine on nicotine- and cocaine-induced dopamine release in the nucleus accumbens.

Cotinine is the major metabolite of nicotine. Nicotine is rapidly metabolized and has a short half-life, but cotinine is metabolized and eliminated at a much lower rate. Because of the resulting increase with time in the cotinine to nicotine ratio in the body, including in the brain, it is of interest to examine the effect of cotinine on nicotine-induced changes.

Mutations that increase acidity enhance the transcriptional activity of the glutamine-rich activation domain in stage-specific activator protein.

Sea urchin stage-specific activator protein (SSAP) activates transcription of the late H1 gene at the mid-blastula stage of development. Its C-terminal 202 amino acids form a potent glycine/glutamine rich activation domain (GQ domain) that can transactivate reporter genes to levels 5-fold higher than VP16 in several mammalian cell lines. We observed that, unlike other glutamine-rich activation domains, the GQ domain activates transcription to moderate levels in yeast.

Receptor systems participating in nicotine-specific effects.

It is generally accepted that self-administration of drugs is prompted primarily by a reward system driven by an increase in extracellular dopamine in the nucleus accumbens. Recent findings that dopamine increase in the accumbens can be caused by many other factors, among them stress, suggest a more complex mechanism, and possibly differences in the reward system for different compounds. In the present paper we compare the effects of receptor-specific antagonists on the increase of dopamine induced by nicotine with that induced by cocaine in the nucleus accumbens in conscious rats.

Changes in brain protease activity in aging.

We measured changes in protease activity with aging, conducting assays of cathepsin D and calpain II activities and the rate of degradation of cytoskeletal proteins, preparing the enzymes and substrates from young and aged brains. Calpain preparations added to the young and to the aged substrates were standardized with casein as substrate so that age-related changes in calpain specificity and substrate susceptibility were measured. Several age-related differences were observed in substrate susceptibility and in enzyme activity.

Effect of food deprivation on glutathione and amino acid levels in brain and liver of young and aged rats.

The effect of short-term food deprivation on glutathione (GSH) and amino acid levels in brain regions of young and aged rats was compared with changes observed in liver. Animals aged 3 months and 24 months were deprived of food for 48 h. GSH and amino acid levels from cerebral cortex, cerebellum, pons medulla, and liver were assayed and compared with levels in animals of the same age fed normal diets.

Effect of diet on tissue protease activity.

Rats 1, 3, 12, and 24 months old were fed diets low in protein (8% casein), and proteolytic activity in tissue from brain, liver, and lung was determined. After a low-protein diet was fed for 4 weeks to 1-month-old rats, there was a significant increase in cathepsin D activity in liver, and calpain activity was increased in lung. Little change was seen in proteolytic activity in brain.

Proteolytic activity is altered in brain tissue of rats upon chronic exposure to ozone.

Tissue from pons medulla of rats exposed in vivo to various levels of ozone was assayed for calpain and cathepsin D activity. Chronic exposure to ozone increased calpain activity, which was 35% to 46% higher in the homogenates of animals exposed to 1.0 ppm ozone than in those of animals exposed to 0.

Peroxidative stress effects on calpain activity in brain of young and adult rats.

Three hours after administration of the pro-oxidant 2-cyclohexen-1-one, calpain activity was significantly reduced in the brain of young rats, but not in the brain of adult rats, and cathepsin D activity remained unchanged. Addition of isovalerylcarnitine to the incubation medium increased calpain activity 5-7-fold, counteracting the effect of the pro-oxidant.

Dopamine releasing effect of phenylbiguanide in rat striatal slices.

The present study explored the mechanisms underlying the dopamine releasing effect of phenylbiguanide, a compound commonly used as a 5-HT3 receptor agonist. Phenylbiguanide, and also serotonin and 2-methyl-serotonin, enhanced the outflow of radioactivity from superfused rat striatal slices preloaded with [3H]dopamine. The presence of the dopamine uptake blocker nomifensin prevented the increase in outflow.

Effect of metaphit on dopaminergic neurotransmission in rat striatal slices: involvement of the dopamine transporter and voltage-dependent sodium channel.

Metaphit, an isothiocyanate analog of phencyclidine (PCP), increased the basal release of radioactivity (outflow) from perfused rat striatal slices preloaded with [3H]dopamine above levels observed with the dopamine uptake blocker nomifensin. Preperfusing the slices with metaphit, followed by its removal, attenuated the amphetamine- or dopamine-induced outflow. In slices prepared from reserpine-pretreated rats, the metaphit (100 microM)-induced outflow was reduced to that observed with 10 microM nomifensin, suggesting a vesicular releasing effect of metaphit in addition to dopamine uptake blockade.

Neuronal protein NP185 in avian and murine cerebellum: expression during development and evidence for its presence in nerve endings.

The neuronal protein NP185 is a neural tissue-specific protein isolated from clathrin-coated vesicles in brain. Using 8G8, a monoclonal antibody (MAb) characterized in our laboratory, we studied the expression and distribution of neuronal protein NP185 in developing avian cerebellum and in mature murine cerebellum. Furthermore, we compared these parameters to that of synapse-specific neuronal protein, synaptophysin, and an axon-specific (i.

Phosphoinositide hydrolysis induced by depolarization and sodium channel activation in mouse cerebrocortical slices.

Carbachol, a muscarinic receptor agonist and the sodium channel-activating agents, scorpion venom, veratridine, batrachotoxin and aconitine, were shown to stimulate the formation of [3H]inositol phosphates in [3H]inositol-labelled miniprisms, obtained from the cerebral cortex of the mouse. The inositol response to the Na+ channel-activating agents was inhibited by the sodium channel blocker tetrodotoxin (TTX), while the response induced by carbachol was partially resistant to TTX. The response to scorpion venom and the TTX-insensitive portion of the response to carbachol was additive, indicating different mechanisms.

Evidence for the involvement of Na+/Ca2+ exchange in the stimulation of inositol phospholipid hydrolysis by sodium channel activation and depolarization.

Amiloride, an inhibitor of the Na+/Ca2+ exchanger, blocked the hydrolysis of inositol phospholipids in mouse cerebrocortical slices induced by the sodium channel activator veratridine, by KCl, or by the sodium ionophore monensin; there was no inhibition by A 23187, a Ca2+ ionophore, or by serotonin. It is concluded that agents that increase intracellular Na2+ stimulate inositide hydrolysis by an indirect effect via Na+/Ca2+ exchange.

Oxidative metabolism of cocaine: comparison of brain and liver.

Norcocaine (NC) and N-hydroxynorcocaine (NHNC), products of the oxidative metabolism of cocaine, were examined in plasma, brain, and liver of mice injected intraperitoneally with cocaine. Plasma levels of NHNC were altered in vivo by inhibiting esterase activity with diazinon and chloral hydrate or activating esterase activity with phenobarbital, and activating the microsomal P-450 system with phenobarbital. Changes in plasma concentrations of NHNC resulted in similar changes in brain, which were often different from those in liver.

Cocaine disposition in the brain after continuous or intermittent treatment and locomotor stimulation in mice.

Intermittent s.c. and i.

Pharmacokinetics of systemically administered cocaine and locomotor stimulation in mice.

Cocaine and its metabolites were measured in plasma and brain from mice injected i.p. with cocaine and monitored for spontaneous locomotor behavior.

Prodynorphin processing by rat CNS fractions and purified enzymes: Formation of Dynorphin A 1-8 by sulfhydryl-activated carboxypeptidase and peptidyl dipeptidase.

The conversion of selected prodynorphin fragments to form the octapeptide Dynorphin A 1-8 was studied in rat brain or spinal cord fractions, and the results compared to the action of purified carboxypeptidases and angiotension converting enzyme. The particulates were shown to convert Dynorphin A or 1-13 to the octapeptide as measured by radioimmunoassay, and by reverse phase high performance liquid chromatography. Detergent extracts of these particulates contained and enzyme converting 1-13 to 1-12 with release of C-terminal lysine, and active over a wide pH range of 4.

Preferential action of rat brain cathepsin B as a peptidyl dipeptidase converting pro-opioid oligopeptides.

Purified rat brain cathepsin B (EC 3.4.22.

Effect of several amino acid phosphonates and other compounds on rat brain and kidney peptidases.

A series of N-terminal phosphonate derivatives, H2O3PCHPhNHR (R = Leu, Phe, Trp, and/or Tyr), were synthesized with the aim of mimicking phosphoramidon, a potent inhibitor of enkephalinase, while avoiding the lability of the scissile P-N bond. All of the N-phosphonobenzyl derivatives of the amino acids, including the substituted succinylhydrazobenzophenone compounds, were inactive toward rat brain aminopeptidase and rat kidney carboxypeptidase. The N-monobenzylphosphonobenzyl derivatives, PhCH2OPO(OH)CHPhNHR, of individual amino acids and several of the N-phosphonobenzyl dipeptides showed inhibition in the micromolar range toward the soluble exopeptidase but were inactive with both the brain and kidney endopeptidase.

Proteolytic activity in brains of rabbits treated with aluminum.

Aluminum injection in rabbits leads to neurofibrillary changes which are at light microscopic level similar to those found in Alzheimer's disease. We used this animal model to see whether changes in proteolytic activity occur that may affect protein degradation in the altered neurofibrillary structure. Rabbits were injected via the cisterna magna with aluminum chloride, and after ten days tissue was excised from the spinal cord, hippocampus, occipital lobe, and cerebellum.

Membrane-bound enzymes and their role in processing of the dynorphins and of the proenkephalin octapeptide Metenkephalin-Arg-Gly-Leu.

Synaptosomal membrane (SPM) bound exo- and endopeptidases cleave the dynorphins and Met-enkephalin-Arg-Gly-Leu at several sites to produce shorter fragments; among these are dynorphin 1-8 from 1-17, and Met-enkephalin from Met-enkephalin-Arg-Gly-Leu. The most vulnerable site is the Tyr-Gly bond cleaved by membrane-bound aminopeptidase(s), with the shorter peptides degraded more rapidly than the longer ones. A purified metalloendopeptidase sensitive to phosphoramidon inactivates the shorter peptide sequences at the Gly3-Phe4 bond, and the 1-13 and 1-17 sequences also at the Arg7-Ile8 bond.

Metabolism of a heptapeptide opioid by rat brain and cardiac tissue.

Met-enkephalin-Arg6-Phe7 (E7) is converted to Met-enkephalin by rat striatal membranes; in contrast, Leu-enkephalin (E5) is inactivated by cleavage at the Tyr-Gly (aminopeptidase) and Gly-Phe sites (metalloendopeptidase). Conversion of E7 is inhibited by MK-421, and inactivation of E5 is inhibited by bestatin and Thiorphan. Purified brain angiotensin converting enzyme (EC 3.