Anxiety and platelet MAO levels after relaxation training

The authors measured platelet MAO activity with phenylethylamine and tryptamine substrates in a group of 20 subjects with chronic anxiety before and after they underwent relaxation training. Levels of anxiety were quantified using a self-rating scale. Posttreatment values for anxiety and enzyme activity were significantly lower than pretreatment values. Anxiety and enzyme activity levels were not significantly correlated at any stage of the study.

Incidence of retinal detachments following extracapsular cataract extractions. A prospective study

This is a preliminary report on a prospective study designed to determine the incidence of retinal detachment following planned extracapsular cataract extractions. The population consists of 454 eyes with a mean follow-up period of 23 months. The incidence of detachment is much lower than that reported for intracapsular extractions. The most significant finding to date is the importance of maintaining the posterior capsule and the vitreous face intact. The incidence of detachment when this is accomplished in normal eyes is 0.9%. The overall incidence of this complication in the entire series is 1.50%. The reported disadvantage of maintaining the posterior capsule is the 40% to 50% incidence of a secondary cataract. In this series, the incidence is 11%. The factors responsible for this low figure are enumerated.

Effects of acute and chronic administration of phencyclidine on tyrosine hydroxylase activity in rat striatum

Following a single dose of phencyclidine (PCP) striatal tyrosine hydroxylase (TH) activity was decreased 42% 15 min after PCP administration, but returned toward baseline levels by 45 min post-drug. Twenty-four hours after the 30th dose of PCP, TH activity remained depressed when compared to the chronic slaine controls. TH activity was not further depressed 15 or 45 min after the 31st dose of PCP.

MAO, DBH and COMT: the effect of anxiety

Anxiety, a common accompaniment of depression, can be a source of confusion in affective disorder research. The present study examined the effect of anxiety on platelet monoamine oxidase, RBC catechol-0-methyltransferase, and serum dopamine-beta-hydroxylase-enzymes frequently implicated in affective disorders. Levels of anxiety, plasma catecholamines and the enzymes mentioned above were quantified in groups of anxious subjects and mentally and physically healthy controls. Anxious subjects were found to have significantly higher levels of blood plasma catecholamines and platelet monoamine oxidase. significant positive correlations were demonstrated between plasma catecholamines and platelet monoamine oxidase, while significant inverse correlations were found between trait anxiety and COMT, norepinephrine and DBH, and COMT and DBH

Catechol-O-methyltransferase and catecholamines in anxiety and relaxation

Levels of anxiety, plasma epinephrine and norpinephrine, and red blood cell (RBC) catechol-O-methyltransferase (COMT) activity were measured before and after 4 weeks of relaxation training in a group of 15 drug-free, anxious subjects and at a similar interval in a group of 15 drug-free, healthy controls. The index group showed significant decreases in levels of anxiety and plasma epinephrine and norepinephrine after treatment. No changes were observed in the control values. RBC COMT did not show any significant differences in activity between the index and control groups and between the pre- and posttreatment values. Similarly, COMT activity levels failed to correlate with levels of anxiety and catecholamines before or after treatment. These findings indicate that anxiety is unlikely to have an effect on RBC COMT activity, whereas it has a direct effect on plasma catecholamines.

Amphetamine discrimination: onset of the stimulus

Rats were trained to discriminate 1.0 mg/kg (+)-amphetamine sulfate from saline in a two-lever operant procedure. The normal injection-to-session interval was fifteen minutes. When tested with amphetamine immediately after intraperitoneal injection, rats initially responded on the lever paired with saline in training, but quickly shifted to the lever paired with amphetamine in training. When tested with saline immediately after immediately after injection, animals responded appropriately for the saline treatment throughout the extinction test. The results show that (+)-amphetamine exerts discriminative response control within five minutes of intraperitioneal injection.

The discriminative stimulus properties of 2,5-dimethoxy-4-methylamphetamine (DOM): differentiation from amphetamine

Rats were trained in a two-lever operant procedure to discriminate either 1.0 mg/kg (+)amphetamine or 1.5 mg/kg DOM from saline. Rats trained to discriminate DOM from saline showed generalization with the DOM training condition when tested with mescaline or 2,5-dimethoxy-4-ethylamphetamine (DOET), but not when tested with (+)amphetamine or methylphenidate. Both isomers of DOM generalized with racemic training compound, the (-)isomer being more potent. The DOM stimulus was completely blocked by the serotonin (5-HT) antagonists cinanserin and methysergide, but not by the peripheral 5-HT antagonist xylamidine nor the dopamine antagonist haloperidol. Rats trained to discriminate (+)amphetamine from saline generalized with the amphetamine training condition when tested with methylphenidate but not when tested with mescaline, DOET, racemic DOM, or either isomer of DOM. The amphetamine stimulus was blocked by pretreatment with haloperidol but not by cinanserin, methysergide, or xylamidine. The results show that, despite their structural similarity, amphetamine and DOM induce pharmacologically distinct stimuli.

Metabolism correlates of cocaine-induced stereotypy in rats

An increase in stereotyped behavior was observed in rats injected daily with cocaine (40 mg/kg, IP), as compared with the first day. This increase persisted 14 days after discontinuation of the drug treatment, and corresponded to increased levels of 3H-cocaine norcocaine and benzoylecgonine in brain. Pretreatment of the animals with SKF-522A, an inhibitor of cocaine demethylation, produced a decrease in stereotypy rating and concomitantly a lower level of 3H-norcocaine in the brain. The role of this metabolite in the production of cocaine-induced stereotyped behavior is discussed.

Generalization of norcocaine to the discriminative stimulus properties of cocaine

In rats trained to discriminate 10 mg/kg cocaine from 1 mg/kg saline, norcocaine, the N-demethylated metabolite, at doses of 2.5 mg/kg, 5 mg/kg and 10 mg/kg, produced a dose response curve similar to that of cocaine and generalized to cocaine at the two higher doses. As with cocaine, the discriminative stimulus produced by the norcocaine was partially attenuated by the dopaminergic antagonist pimozide and the amine depletor reserpine. Benzoylecgonine, benzoylnorecgonine and ecgonine methyl ester in doses of 10 mg/kg and 20 mg/kg did not generalize to cocaine.

The uptake of 6-methoxy-1,2,3,4-tetrahydro-beta-carboline and its effect on 5-hydroxytryptamine uptake and release in blood platelets

The uptake of 6-methoxy-1,2,3,4-tetrahydro-beta-carboline (6-MeOTHBC, 5-methoxytryptoline) by rabbit blood platelets was studied by using 3H-labelled compound. A high rate active uptake (Km 6.6 micron), which was inhibited by 5-hydroxytryptamine (5-HT) and cinnanserine, and a slow rate uptake, not inhibited by 5-HT were observed. The intracellular distribution of 3H-6-MeOTHBC in platelets clearly differed from that of 14C-5-HT. 6-MeOTHBC also competitively inhibited the high-rate active (but not the slow passive) uptake of 14C-5-HT, being more active than 5-HT itself. The spontaneous release of the newly taken-up 14C-5-HT from platelets was increased only with high concentrations of 6-MeOTHBC.

Comparison of inhibition of monoamine uptake by cocaine, methylphenidate and amphetamine

Amphetamine and methylphenidate both inhibited the uptake of 3H-norepinephrine (NE) and 3H-dopamine (DA) although the activity (as measured by I50 and Ki values) of d-amphetamine was lower with respect to uptake of the two catecholamines in synaptosomes from thalamus-hypothalamus and and striatum. Cocaine was a much stonger inhibitor of 3H-5-hydroxytryptamine (5-HT) uptake in septum-caudate synaptosomes than amphetamine or methylphenidate. The I50 values were 70, 118 and 570 micron for cocaine, methylphenidate and d-amphetamine, respectively. The results of the present study suggested that a serotonergic system may be involved in the stimulant properties of cocaine. It may also explain certain differences in pharmacological activities between cocaine and the other two stimulants as described in the literature.

Induced tolerance to the discriminative stimulus properties of cocaine

Twenty-five male Sprague-Dawley rats were trained in five two-lever operant chambers on a DRL-15 sec schedule of positive food reinforcement to discriminate 10 mg/kg cocaine from 1 ml/kg saline. Following acquistions of discrimination a counterbalanced design of extinction tests was performed before and after repeated administration of 20 mg/kg cocaine or saline (three times a day at five hr intervals for seven days). The extinction tests consisted of testing responses of animals following 1 ml/kg saline, 2.5 mg/kg cocaine, or 5 mg/kg cocaine. The results showed no significant difference in animals' level choice before and after repeated injection with saline. However, the percent cocaine lever choice with the two doses of cocaine was lower after repeated administration of cocaine than before the repeated injections. This indicates tolerance developed to the discriminative stimulus properties of cocaine.

Inhibition of the metabolism of cocaine by SKF-525A

In vitro and in vivo studies in rats indicate cocaine to be metabolized primarily in the liver to form benzoylecgonine and norcocaine. The formation of these metabolites was significantly hindered by SKF-525A, a microsomal enzyme inhibitor. In in vivo studies, pretreatment of rats with SKF-525A prior to receiving cocaine resulted in increased amounts of unchanged cocaine in the brain. No accompanying increase in spontaneous motor activity was observed for these animals, indicating a possible role for metabolites in the stimulant action of cocaine.

Neurochemical effects of cocaine following acute and repeated injection

Following repeated injection in the rat, cocaine decreased the concentration of serotonin in the septum-caudate and increased the metabolism of hypothalamic norepinephrine and also striatal dopamine to a lesser extent. Furthermore, cocaine significantly decreased the activity of the rate-limiting enzyme, tryptophan hydroxylase. In a comparative study d-amphetamine and methylphenidate were found to exert an effect opposite to cocaine in the activation of tryptophan hydroxylase. These findings indicate that cocaine may lower central serotonin function by decreasing its availability for neural transmission. This could account for the stimulation of locomotor activity observed after cocaine administration.

In vitro alteration of the subcellular distribution of 3H-reserpine in the rat forebrain by delta 9-tetrahydrocannabinol

delta 9-Tetrahydrocannabinol (delta 9-THC) has been reported to attenuate both reserpine-induced serotonin depletion and reserpine-induced hypothermia. We have observed that delta 9-THC preincubation led to a dose-responsive increase in the amount of 3H-reserpine bound to a crude mitochondrial fraction of rat forebrain. The experiments reported here further characterize this phenomenon. Preincubation with delta 9-THC produced a shift in the localization of 3H-reserpine from the incubation medium and the microsomal supernatant (decrease of 66%) to the crude mitochondrial (CM) pellet (increase of 154%). The CM pellet was subfractionated both by differential centrifugation after osmotic shock and by layering on a five-step discontinuous sucrose gradient and centrifuging at 80,000 x g. Osmotic shock with 0.032 M sucrose and centrifugation revealed that the delta 9-THC-induced increase in 3H-reserpine was contained in both the synaptic vesicle fraction (247%) and the fraction containing myelin, ruptured synaptosomes and mitochondria (324%). Separating the CM fraction into five component parts showed that delta 9-THC increased the 3H-reserpine bound by about 275% in the three fractions containing myelin, membrane fragments or mitochondria. Even more dramatic increases (greater than 1000%) were observed in the two fractions containing cholinergic and non-cholinergic nerve endings. In addition, we have determined that many other drugs which are believed to have membrane mediated mechanisms have no effect on the amount of 3H-reserpine bound to the crude mitochondrial fraction. Although other possibilities exist, these data support the hypothesis that delta 9-THC retards the action of reserpine by altering the normal distribution of reserpine in various membrane components of the rat brain.

Effect of short- and long-term treatment with cocaine on rat brain tryptophan hydroxylase

Short-term (5 days) treatment with cocaine (10 mg/kg, i.p.) inhibited the soluble tryptophan hydroxylase while the particulate enzyme was essentially unchanged. In contrast, long-term (45 days) treatment resulted in an increased activity of the particulate enzyme and a return to normal of the soluble enzyme activity.