Long-term amphetamine treatment attenuates or reverses the depression of neuronal activity produced by dopamine agonists in the ventral tegmental area

Neuronal activity was recorded from the ventral tegmental area (VTA) of immobilized, locally anesthetized rats on the day immediately following long-term treatment (twice daily for 6 consecutive days) with saline, 1.0 or 5.0 mg/kg $\text{d}$-amphetamine ($\text{d}$-AMPH). Each rat was challenged intravenously with $\text{d}$-AMPH (beginning with 0.0625 mg/kg) or with 0.005 mg/kg apomorphine. Treatment with $\text{d}$-AMPH significantly reduced the ability of this drug to inhibit VTA activity. In fact, nearly half of the neurons in the high-dose treatment group were excited by $\text{d}$-AMPH, whereas only 20% of control neurons showed this response. Moreover, apomorphine routinely accelerated firing rate in the VTA following treatment with 5.0 mg/kg $\text{d}$-AMPH but this response was never observed in control neurons, not even in those that were excited by $\text{d}$-AMPH. Thus, tolerance appears to develop to the ability of dopamine agonists to inhibit VTA activity and this effect may be mediated, at least in part, by a subsensitivity of inhibitory dopamine autoreceptors.     

Stereoselectivity in the metabolism of drobuline (d1-1-(isopropylamino) -4,4-diphenyl-2-butanol) a new anti-arrhythmic agent

The metabolism of drobuline has been examined in the dog, rabbit, rat, guinea pig and hamster. In the dog, unlike the other species, glucuronide conjugation is the major route of metabolism. The structure of the conjugate has been established as an O-glucuronide by isolation using HPLC following by field desorption mass spectral analysis. When the separate $\text{d}$- and $\text{l}$-isomers of drobuline were administered to a series of dogs the $\text{l}$-isomer reached plasma levels approximately three time higher than those of the $\text{d}$-isomer. Deuterium labeled drobuline was synthesized and resolved by multiple crystallizations of the malate salts. Racemic mixtures containing $\text{d}$₆-$\text{d}$ and $\text{h}$₆-$\text{l}$ drobuline and $\text{d}$₆-$\text{l}$ and $\text{h}$₆-$\text{d}$ drobuline were prepared and analyzed by GC-MS as the pentafluoropropionate derivatives. When either racemic mixture was administered to dogs (10 mg/kg, p.o.) the plasma levels of the $\text{l}$-isomer were found to be approximately three times those of the $\text{d}$-isomer. Using these deuterium labeled mixtures the disposition of the two isomers has been examined in the isolated perfused dog liver, in hepatocytes and isolated microsomes. The results indicate that the difference in plasma levels of the $\text{d}$- and $\text{l}$-isomers is not dependent upon stereospecific absorption or excretion but rather it is caused by metabolism of the $\text{d}$-isomer at a faster rate than that of the $\text{l}$-isomer.     

Evidence that opiate receptors mediate suppression of hypertonic saline-induced drinking in the mouse by narcotic antagonists

The effects of naloxone, its $\text{dextro}$-stereisomer, and five other narcotic antagonists were determined on water intake induced by intracellular dehydration in the mouse. The intraperitoneal administration of a 2M sodium chloride solution served as the model for intracellular dehydration. $\text{1}$-Naloxone (0.01-10 mg/kg) reduced drinking in a dose-dependent fashion with an ED₅₀ of 0.55 mg/kg. In contrast, $\text{d}$-naloxone failed to suppress water consumption at doses up to 10 mg/kg. The other narcotic antagonists tested --- naltrexone, diprenorphine, levallorphan, oxilorphan, and nalorphine --- also produced dose-dependent decreases in water consumption. The order of potency of these narcotic antagonists in suppressing water intake was highly correlated with their orders of potency in other procedures involving the opiate receptor. The stereoselectivity and order of potency suggest that the suppressant effects of the narcotic antagonists on drinking induced by hypertonic saline administration in the mouse are mediated through an opiate receptor-dependent mechanism.     

Influence of prenatal d-amphetamine administration on development and behavior of rats.

Beginning on the fifth day of gestation, rats were administered 1 or 3 mg/kg of $\text{d}$-amphetamine sulfate s.c. twice daily until term. The administration of $\text{d}$-amphetamine caused a dose-related increase in pup mortality. However, the increase in pup death could not be correlated with any gross pathological signs. The surviving 3 mg/kg amphetamine pups were analyzed for changes in motor behavior and brain biogenic amine levels. It was found that the amphetamine offspring showed a marked reduction in the ability to habituate to new surroundings, and this effect persisted for at least three months after birth. On day 35, brain levels of norepinephrine in the “amphetamine” offspring were decreased 21 percent. On day 84, in the “amphetamine offspring,” norepinephrine levels were reduced 18 percent in both the diencephalon and brainstem; dopamine levels were reduced 21 percent in the brainstem compared to control offspring.     

In vitro and in vivo inhibition by zopiclone of benzodiazepine binding to rodent brain receptors.

Up to now the only drugs known to be able to inhibit the binding of benzodiazepines to rodent brain receptors are members of this chemical family.Zopiclone (RP 27 267), a new drug with a pharmacological profile similar to that of chlordiazepoxide and nitrazepam but entirely different chemically from benzodiazepines, has been tested for its ability to inhibit benzodiazepine binding. $\text{In vitro}$ and $\text{in vivo}$ studies have shown that zopiclone is able to inhibit the binding of [³H] diazepam and [³H] flunitrazepam to brain receptors. The potency of zopiclone is quite comparable to that of diazepam and nitrazepam $\text{in vitro}$ and to that of chlordiazepoxide $\text{in vivo}$.These results confirm the pharmacological similarities existing between zopiclone and the benzodiazepines.     

The effects of narcotic analgesics and narcotic antagonists on ganglionic transmission in the rat.

The effects of narcotic analgesics, narcotic-antagonist analgesics and narcotic antagonists on ganglionic transmission in the superior cervical ganglia of the rat were studied $\text{in}$$\text{vivo}$ and $\text{in}$$\text{vitro}$. $\text{In}$$\text{vivo}$ administration of morphine, meperidine, methadone, pentazocine or naltrexone blocked ganglionic transmission. Levorphanol, cyclazocine, nalorphine and naloxone had no effect on ganglionic transmission in this procedure. $\text{In}$$\text{vitro}$ studies confirmed the $\text{in}$$\text{vivo}$ results with the exception of levorphanol, cyclazocine and nalorphine, which were also found to block ganglionic transmission $\text{in}$$\text{vitro}$. In both preparations, naloxone did not antagonize the effect of morphine, suggesting that the effects of morphine and the other opiates were nonspecific. Similar potency of $\text{d}$- and $\text{l}$-isomers of pentazocine and cyclazocine support this conclusion. The observation that naltrexone blocked ganglionic transmission, but the other pure narcotic antagonist, naloxone, was inactive is somewhat unique to this test procedure and possibly significant.     

D-LSD binding to brain homogenates: possible relationship to serotonin receptors

Using a rapid filtration technique we find stereospecific high-affinity $\text{d}$-LSD binding (4 × 10^?9M, half-saturation) in brain fractions from a number of subcortical as well as cortical brain regions. Among the putative neurotransmitters tested only serotonin effectively displaces $\text{d}$-LSD from this specific binding site. Moreover, only the serotonin-displaceable component of binding is saturable in a high-affinity range. No change is observed in specific $\text{d}$-LSD binding in forebrain homogenates from rats in which ascending serotonergic pathways are destroyed by lesions in the raphe nucleus. We conclude that a vast majority of the $\text{d}$-LSD binding sites may be associated with a postsynaptic serotonin receptor rather than a presynaptic receptor associated with serotonergic (raphe) inputs.     

Complete,reversible, drug-specific tolerance to stimulation of locomotor activity by caffeine

The development of tolerance to caffeine-induced stimulation of locomotor activity was evaluated in rats maintained chronically on average daily doses of 160 mg/kg or more of caffeine by the method of scheduled access to drinking water containing the drug. Dose-response curves were determined for caffeine (6.25–100 mg/kg) and $\text{d}$-amphetamine (0.39–6.4 mg/kg) during chronic drug treatment. In addition, the caffeine curve was redetermined 2–3 weeks after removal of the drug from the drinking water. A control group that had scheduled access to drug-free tap water was also tested. Caffeine produced dose-related increases in the locomotor activity of the controls but failed to modify locomotor activity of the chronic caffeine group. In contrast, $\text{d}$-amphetamine increased locomotor activity of both groups comparably. Spontaneous locomotor of the chronic caffeine group was reduced significantly for 4 days after drug-free tap water was substituted for the caffeine solution. The return of spontaneous locomotor activity to baseline values was associated with restored sensitivity to caffeine-induced stimulation of locomotor activity. Thus, chronic administration of caffeine to rats results in the development of tolerance to caffeine-induced stimulation of locomotor activity that is virtually complete, pharmacologically specific, and fully reversible when drug treatment is stopped. Decreases in spontaneous locomotor activity after abrupt termination of chronic caffeine administration follow a time course consistent with a drug withdrawal syndrome.     

Elevation of plasma tyrosine after a single oral dose of L-tyrosine.

Plasma tyrosine concentrations in twelve normal, fasting human subjects were significantly elevated 2–8 hours after they ingested 100 mg/kg or 150 mg/kg tyrosine. Mean plasma tyrosine levels were maximal after 2 hours, rising from $\text{69 ± 3.9}\text{to}\text{154 ± 9.5}\text{nmols/ml}\text{(}\text{X}\text{±}\text{SEM}\text{)}$ after the 100 mg/kg dose and to 203 ± 31.5 nmols/ml after the 150 mg/kg dose (p ≤ 0.001 for both doses). The mean tyrosine ratio (defined as the ratio of plasma tyrosine concentration to the sum of the concentrations of six other neutral amino acids that compete for the same blood-brain barrier uptake system) increased from $\text{0.10 ± 0.02}\text{to}\text{0.28 ± 0.04 (}\text{X}\text{±}\text{SEM}\text{)}$ 2 hours after the 100 mg/kg dose (p ≤ 0.001) and to 0.35 ± 0.05 2 hours after the 150 mg/kg dose (p ≤ 0.005). No side effects of orally-administered L-tyrosine were noted.     

Glutamate transport in pig heart mitochondria. Binding and structural properties of high-glutamate affinity proteolipid: Reconstitution studies

Previously, a proteolipid that can bind glutamate with high affinity has been isolated from pig heart mitochondrial membranes. A final affinity chromatography on γ-methylglutamate-albumin coreticulated on glass fiber was necessary. This procedure includes long dialysis steps which tend to denature the high-glutamate affinity proteolipid.Here is described a new method of isolation which avoids long dialysis steps and yields greater amounts of the high-glutamate affinity proteolipid.The binding of glutamate or aspartate on high-glutamate affinity proteolipid has been studied by gel filtration, by equilibrium dialysis or by a new procedure of rapid centrifugation based on the insolubility of high-glutamate affinity proteolipid in water. The latter method permits the detection of low and high affinity sites for glutamate with a $\text{K}{}_{\mathrm{<mtext>d</mtext>}}$ 60 mM and 55 μM, respectively. Among a series of analogues, aspartate appeared to be the best competitor: $\text{K}{}_{\mathrm{<mtext>d</mtext>}}\text{= 30 μ}\text{M}$ and two $\text{K}{}_{\mathrm{<mtext>i</mtext>}}$ values, 0.37 mM (at high glutamate concentration) and 3.8 μM (at low glutamate concentration). High-glutamate affinity proteolipid binds 0.4 nmol of glutamate but only 0.1 nmol of aspartate per mg protein. The sites for glutamate and aspartate appear to be different but interdependent.In the presence of high-glutamate affinity proteolipid, externally added glutamate stimulated the efflux of aspartate from preloaded liposomes.High-glutamate affinity proteolipid contains cardiolipin, phosphatidyl choline and phosphatidyl ethanolamine the distribution of which is different from that of the inner membrane.The effects of various phospholipases, trypsin, and thiol reagents were studied on the binding of glutamate. High-glutamate affinity proteolipid binds 9 nmol $\text{N-}\text{ethylmaleimide}$ per mg protein but only 6.1 nmol in the presence of glutamate. The dissociation of high-glutamate affinity proteolipid caused by thiol reagents yielded a soluble protein fraction with higher affinity for glutamate.Electrophoresis and an immunological approach allowed the detection and titration of the glutamate dehydrogenase and aspartate aminotransferase present in high-glutamate affinity proteolipid in inhibited forms, the latter being 26-fold more concentrated than the former.     

Theoretical studies on the modes of binding of some of the derivatives of d-mannose to concanavalin A

The possible modes of binding for $\text{methyl}\text{-α-}\text{d}\text{-mannopyranoside}$, $\text{methyl}\text{-β-}\text{d}\text{-mannopyranoside}$, $\text{2-O-}\text{methyl}\text{-α-}\text{d}\text{-mannopyranoside}$, $\text{methyl-2-O-methyl}\text{-α-}\text{d}\text{-mannopyranoside}$ and $\text{methyl}\text{-α-}\text{d}\text{-N-}\text{acetylmannosamine}$ to concanavalin A have been investigated using theoretical methods. All these sugars, except $\text{methyl}\text{-α-}\text{d}\text{-N-}\text{acetylmannosamine}$, reach the active site of concanavalin A with a highly restricted number of binding orientations. Present investigations suggest that the failure of $\text{methyl}\text{-α-}\text{d}\text{-N-}\text{acetylmannosamine}$ to bind to concanavalin A is not so much due to steric factors as to repulsive electrostatic interactions. $\text{Methyl}\text{-2-O-}\text{methyl}\text{-α-}\text{d}\text{-mannopyranoside}$ can bind to concanavalin A in one mode whereas the other sugars can bind in more than one mode. The high potency of $\text{methyl}\text{-α-}\text{d}\text{-mannopyranoside}$ over $\text{methyl}\text{-β-}\text{d}\text{-mannopyranoside}$ is mainly due to the possibility of hydrophobic interactions of the α-methoxy group with Leu(99) or Tyr(100) and also due to the possibility of formation of better and more hydrogen bonds with the protein. A comparison of these data with those for the d-glucopyranosides suggests that the change of the hydroxyl at the C-2 atom from equatorial to axial orientation increases the stereochemically allowed region as well as the possible binding modes. From these studies it is also suggested that the overall shape of the oligosaccharides rather than the terminal or internal mannose alone affects the binding potency of saccharides to concanavalin A.     

Hemodynamic and cardiac actions of trazodone and imipramine in the anesthetized dog.

The relative cardiovascular effects of trazodone and imipramine were compared in two open-chest, anesthetized dog models. Trazodone lowered arterial blood pressure (0.3 mg/kg), slowed heart rate (3 mg/kg) and reduced myocardial contractile force (3–10 mg/kg) following i.v. administration. Low i.v. doses (0.05–0.15 mg/kg) of imipramine increased arterial blood pressure and heart rate, presumably as a consequence of its known anticholinergic properties and/or effects on neuronal catecholamine re-uptake mechanisms. Subsequent to administration of 1.5 and 5 mg/kg, however, the vascular and myocardial depressant effects of imipramine were evident. Trazodone (1–10 mg/kg, i.v.), unlike imipramine, effected a substantial level of $\text{alpha}$-adrenergic blockade $\text{vs.}$ a fixed challenge dose of norepinephrine, although less than that associated with phentolamine. Both trazodone and imipramine reduced aortic flow although $\text{via}$ different mechanisms. The reduction following administration of trazodone resulted from a decrease in heart rate whereas imipramine depressed aortic flow by lowering stroke volume.     

Further studies on the pharmacology of a false cholinergic transmitter, (2-hydroxyethyl) methyldiethylammonium (diethylcholine).

The pharmacology of a possible false cholinergic transmitter, (2-hydroxyethyl) methyldiethylammonium (diethylcholine, DEC) was studied with various preparations. It was found to inhibit the neuromuscular transmission of frog sciatic nerve-gastrocnemius muscle $\text{in}$$\text{vitro}$ with ED₅₀ of 1.93 (0.66 - 5.79) × 10⁻⁴ M. DEC was also found to inhibit dog chorda tympani-Wharton's duct (postganglionic parasympathetic neuro-effector junction) and cat superior cervical ganglionnictitating membrane (sympathetic ganglion) preparations $\text{in}$$\text{vivo}$ with ED₅₀'s of 6.2 (1.8 – 21.1) mg/kg and 12.0 (5.7 - 25.2) mg/kg, respectively. After blockade of these preparations with DEC, the former was still responsive to intravenous injection of pilocarpine (1 mg/kg) and choline (10 mg/kg) and the latter to close arterial injection of acetylcholine (100 μg/injection) and choline (3 mg/min infusion). These results support the idea that DEC paralyzes cholinergic neurons possibly through false cholinergic transmission without blocking the cholinergic receptor at the post-junctional membrane.     

The synthesis of methyl 4-O-(4-O-α-d-galactopyranosyl-β-d-galactopyranosyl)-β-d-glucopyranoside: The methyl β-glycoside of the trisaccharide related to Fabry's disease

As part of a program to synthesize the ceramide trisaccharide (1) related to Fabry's disease, methyl 4-O-(4-O-α-$\text{d}$-galactopyranosyl-β-$\text{d}$-galactopyranosyl)-β-$\text{d}$-glucopyranoside (12) was prepared. Methyl β-lactoside (2) was converted into methyl 4-O-(4,6-O-benzylidene-β-$\text{d}$-galactopyranosyl)-β-$\text{d}$-glucopyranoside (4). Methyl 2,3,6-tri-O-benzoyl-4-O-(2,3,6-tri-O-benzoyl-β-$\text{d}$-galactopyranosyl)-β-$\text{d}$-glucopyranoside (7) was synthesized from 4 through the intermediates methyl 2,3,6-tri-O-benzoyl-4-O-(4,6-O-benzylidene-2,3-di-O-benzoyl-β-$\text{d}$-galactopyranosyl)-β-$\text{d}$-glucopyranoside (5) and methyl 2,3,6-tri-O-benzoyl-4-O-(2,3-di-O-benzoyl-β-$\text{d}$-galactopyranosyl)-β-$\text{d}$-glucopyranoside (6). The halide-catalyzed condensation of 7 with 2,3,4,6-tetra-O-benzyl-$\text{d}$-galactopyranosyl bromide (8) gave methyl 2,3,6-tri-O-benzoyl-4-O-[2,3,6-tri-O-benzoyl-4-O-(2,3,4,6-tetra-O-benzyl-α-$\text{d}$-galactopyranosyl)- β-$\text{d}$-galactopyranosyl]-β-$\text{d}$-glucopyranoside (10). Stepwise deprotection of 10 led to 12, the methyl β-glycoside of the trisaccharide related to Fabry's disease.     

A formal synthesis of 18-hydroxyestrone

A formal synthesis of $\text{dl}$-18-hydroxyestrone has been achieved by the preparation of $\text{dl}$-3-methanesulfonyloxy-13β,17β-dicarboxy-18--norestra-1,3,5(10)-triene anhydride, the dextrorotatory enantiomer of which is an intermediate in Barton's conversion of $\text{d}$-estrone to $\text{d}$-1β-hydroxyestrone (KC-6A).     

Enkephalin analogues eliciting analgesia after intravenous injection

Extensive study of structure-activity relations in enkephalin-like peptides has led to analogues which are up to 70 times more potent than Leu-enkephalin $\text{in vitro}$ in the electrically-stimulated guinea pig ileum preparation, and which are analgesic in the mouse hot-plate test at doses as low as 5mg/kg following intravenous administration.     

Inhibition of platelet thromboxane A2 synthase activity by sodium 5-(3′-pyridinylmethyl)benzofuran-2-carboxylate

This report outlines the activity of a new thromboxane synthase inhibitor sodium, 5-(3-pyridinymethyl)-2-benzofurancarboxylate, (U-63557A). U-63557A is a potent inhibitor of the thromboxane synthase in human platelets $\text{in}$$\text{vitro}$, as well as in rhesus monkey platelets $\text{ex vivo}$. A single oral dose of 3.0 mg/kg U-63557A inhibits the platelet thromboxane synthase in rhesus monkeys approximately 80% for at least 12 hrs. U-63557A has been administered to monkeys twice a day, (10 mg/kg) for 14 days, without evidence of drug tachyphylaxis or rebound. U-63557A does not inhibit thrombin-stimulated PGI₂ biosynthesis in human endothelial cells, the 5-lipoxygenase in human neutrophils, or the cyclo-oxygenase in a variety of test systems. In anesthetized dogs, U-63557A injected i.v. at 0.1 at 5 mg/kg prevented the blockage of stenosed coronary arteries caused platelet aggregation,. Similar effects were obtained by oral administration of 1–5 mg/kg. The thromboxane synthase inhibitor was more efficacious than cyclooxgenase inhibitors and equal to PGI₂ in efficacy. Under appropriate conditions the protective effects of U-63557A could be reversed by i.v. cylooxygenase inhibitors suggesting that its efficacy dependened in part of endogenous PGI₂ formation. Due to its specificity, oral activity, and extended duration of action, U-63557A is a promising compound for the evaluation of the role of thromboxane synthase in a variety of patho[hysiological states.     

Regulatory T cells in pregnancy: V. Allopregnancy-induced T-cell-suppressor factor is H-2 restricted and bears la determinants

Spleen cells of allogeneically pregnant mice at the second week of second to fourth parity contain suppressor T cells capable of suppressing an MLR of maternal responders and releasing a soluble factor. The genetic restrictions of this factor have been studied in a $\text{H}\text{-2}{}^{\mathrm{<mtext>k</mtext>}}\text{H}\text{-2}{}^{\mathrm{<mtext>d</mtext>}}$ system using $\text{k}\text{d}$ or $\text{d}\text{k}$ pregnancies, and responder cells from $\text{k}\text{d}$ recombinants. The factor appeared to be IC subregion restricted. Furthermore, its activity could be removed by passage on insolubilized anti-Ia immune serum. Although factor-releasing suppressor cells are antigen specific the factor itself does not appear so, possibly implicating a mixture of fine specificities.