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Biomedical subjects

L S Harris

Publications and source records attributed to L S Harris.

At least 109 records · Page 6Linked to original sources
PubMed1980

Discriminative stimulus properties of the optical isomers of nicotine.

Rats were trained to discriminate 200 or 400 microgram/kg (-)nicotine from saline in a two-bar operant paradigm. Dose-response relationships for optically pure (-)- and (+)nicotine as well as antagonistic effects were examined in both groups of rats. The natural isomer (-)nicotine was approximately nine-times more potent than (+)nicotine. Mecamylamine produced equal blockade of the (-)- and (+)nicotine cues. Hexamethonium and atropine were without effect. These data demonstrate the possible stereospecificity of the central nicotinic receptor that mediates the stimulus effect produced by nicotine.

Animals↗
PubMed1980

PGD2 effects on rodent behavior and EEG patterns in cats.

Prostaglandin (PG) D2 was studied to determine the pharmacological effects of this PG on the central nervous system. PGD2 (0.45-4.05 mg/kg) decreased spontaneous locomotor activity in rats by as much as 66% of control, however, the neuromuscular coordination of mice, treated at the same doses of PGD2, was not impaired. PGD2 (0.05-4.05 mg/kg) also increased pentobarbital sleeping time in mice from 42% to 238% of control, in a dose-related manner. PGD2 did not prevent convulsions induced in response to electroshock or pentylenetetrazol. Cats monitored for EEG responses to PGD2 infusion displayed variable sensitivity to different doses (16-3000 microgram) of drug, however, the characteristic response to PGD2 was the conversion from a uniform low voltage, fast wave pattern to high voltage, slow waves. Cats administered PGD2 were sedated and sometimes catatonic, and displayed brief periods of hypotension, bradycardia, diarrhea, analgesia and hyperthermia at higher doses of the drug. Thus, PGD2 possesses sedative properties in rodents and cats and may have a role in the central nervous system.

Animals↗
PubMed1980

3H-delta 9-Tetrahydrocannabinol, 3H-cannabinol and 3H-cannabidiol: penetration and regional distribution in rat brain.

3H-delta 9-Tetrahydrocannabinol (3H-delta 9-THC), 3H-cannabidiol (3H-CBD) and 3H-cannabinol (3H-CBN) were administered (1 mg/kg) to male rats which were decapitated either 0.5, 1, 15, 30 or 90 min later. The plasma concentration was similar for all cannabinoids throughout the time course. After 5 min greater than 80% of the plasma radioactivity in each treatment was due to metabolites. Radioactivity rapidly entered brain after the administration of 3H-CBD, 3H-CBN, and 3H-delta 9-THC. The concentrations of unchanged 3H-CBD aand 3H-CBN in whole brain were higher than that of 3H-delta 9-THC 5 min after administration. Regional distribution of radioactivity in the brain after 5 min was similar for all three cannabinoids, the only significant difference being in hypothalamus. Coadministration of 3H-delta 9-THC with a five-fold excess of either CBD or delta 9-THC did not produce any significant alteration in the levels of radioactivity in brain or plasma 5 min after their injection. The difference in behavioral activity of delta 9-THC, CBD and CBN cannot be explained by penetrability or regional distribution in the brain.

Animals↗
PubMed1980

Isotope dilution technique for the estimation of l-alpha-[2-3H]-acetylmethadol and its metabolites in biological samples.

An isotope dilution technique for the determination of l-alpha-(2-3H)-acetylmethadol and its metabolites from biological samples is described. The parent drug and metabolites were extracted from biological samples with chlorobutane after the addition of unlabeled internal standards. The extracts were purified by two-dimensional thin-layer chromatography for quantification by gas-liquid chromatography and scintillation counting. Dinoracetylmethadol (NNAM) was found to be converted to 6-acetamido-4,4-diphenyl-3-heptanol (AMIDE) during the extraction procedure. The conversion of NNAM to AMIDE was confirmed by gas chromatography-mass spectrometry.

Animals↗
PubMed1980

Comparative studies of the pharmacological effects of the d- and l-isomers of codeine.

Opiates are known for their stereospecificity. The following studies show that l-codeine was active in the mouse tail-flick test as well as in the hot plate test whether given p.o. or s.c. The ED50 in the first test was 4.09 mg/kg s.c. (2.01-8.34 mg/ kg) and 13.41 mg/kg p.o. (6.91-26.0 mg/kg). In the second antinociceptive test, the ED50 was 20.66 mg/kg s.c. (11.52-37.08 mg/kg) and 20.47 mg/kg p.o. (14.63-28.57 mg/kg). The d-isomer of codeine was inactive ina both tests up to 100 mg/kg but caused hyperexcitability, convulsions and ultimately death. Although l-codeine was more potent than d-codeine inhibiting the cough reflex in the anesthetized cat, the d-compound did have good activity. The ED50 of the l-isomer was 0.27 mg/kgi.v. (0.14-0.47 mg/kg) and that of the d-isomer was 1.61 mg/kg i.v. (0.98-2.65 mg/kg). In these animals, l-codeine did not significantly affect the cardiovascular parameters at the doses tested, whereas d-codeine caused a significant but transient decrease in the blood pressure and heart rate. The specific and nonspecific properties of d- and l-codeine were further delineated in the opiate receptor binding assay. l-Codeine inhibited the stereospecific binding of 2.2 x 10(-9) M [3H]dihydromorphine in mouse brain homogenate with the IC50 being 1.6 x 10(-5) M (1.2 x 10(-5)--2.0 x 10(-5) M). d-Codeine had no effect up to 10(-4) M.

Analgesia↗
PubMed1979

Optically pure (+)-nicotine from (+/-)-nicotine and biological comparisons with (-)-nicotine.

Optically pure (+)-nicotine has been obtained from (+/-)-nicotine using a combination of d-tartaric acid and di-p-toluoyl-l-tartaric acid. As the di-d-tartrate salt, (+)-nicotine is less potent than (-)-nicotine di-l-tartrate in producing lethality in mice, on blood pressure in anesthetized rats, and in the isolated guinea-pig ileum, indicating substantial stereospecificity for nicotine receptors. Potency ratios are 0.14, 0.06, and 0.019, respectively.

Animals↗
PubMed1979

Susceptibility of Naegleria fowleri to delta 9-tetrahydrocannabinol.

Growth of the pathogenic amoeboflagellate Naegleria fowleri is inhibited by delta 9-tetrahydrocannabinol (delta 9-THC). delta 9-THC is amoebostatic at 5 to 50 micrograms/ml. delta 9-THC prevents enflagellation and encystment, but does not impair amoeboid movement. Calf serum at 10 and 20% (vol/vol) reduces the antiamoeba activity of delta 9-THC. Only 1-methoxy delta 8-tetrahydrocannabinol, of 17 cannabinoids tested, failed to inhibit growth of N. fowleri. Antinaeglerial activity was not markedly altered by opening the pyran ring, by converting the cyclohexyl ring to an aromatic ring, or by reversing the hydroxyl and pentyl groups on the benzene ring. delta 9-THC prevented the cytopathic effect of N. fowleri on African green monkey (Vero) cells and human epithelioma (HEp-2) cells in culture. delta 9-THC afforded modest protection to mice infected with N. fowleri.

Amebiasis↗
PubMed1979

Effects of cannabinoids on host resistance to Listeria monocytogenes and herpes simplex virus.

Previous investigations from our laboratories have demonstrated that cannabinoids possess immunosuppressive properties. The present studies were designed to determine whether these agents decrease host resistance to infections with Listeria monocytogenes and herpes simplex virus type 2. Host resistance was measured by changes in the 50% lethal dose of the pathogen in cannabinoid-treated and control mice. The effect of cannabinoids on resistance to L. monocytogens was dose dependent. Delta-9-tetrhydrocannabinol at doses of 38, 75, and 150 mg/kg suppressed resistance to infection by 10-, 17-, and 657-fold, respectively. Marijuana extract was less active but significantly reduced resistance to L. moncytogenes at all tested doses. Resistance to systemic herpes simplex virus type 2 infection was decreased 96-fold by delta-9-tetrahydrocannabinol, although marijuana extract was inactive. The doses and regimen of treatment with cannabinoids that produced significant decreases in host resistance were similar to those which caused suppression of delayed-type hypersensitivity to sheep erythrocytes. The possible mechanisms and public health aspects of the decreased host resistance produced by marijuana extract and its cannabinoids are discussed.

Animals↗
PubMed1979

Effects of systemic and intraventricular administration of cannabinoids on schedule-controlled responding in the squirrel monkey.

The effects of a number of cannabinoids in squirrel monkeys trained to respond on a chain fixed-interval fixed-ratio schedule of food presentation were determined after intraperitoneal (i.p.) and intraventricular (i.v.t.) administration. The order of potency was (+/-)-9-nor-9 beta-OH hexahydrocannabinol, 11-OH-delta 9-tetrahydrocannabinol, delta 9-tetrahydrocannabinol (delta 9-THC), cannabinol and cannabidiol. (+/-)-9-Nor-9 alpha-OH-hexahydrocannabinol was inactive at doses up to 3 mg/kg i.p. and 0.1 mg/kg i.v.t. Although the order of potency was the same by both routes of administration, the i.v.t./i.p. potency ratio differed markedly. This demonstrates the importance of route of administration in assessing structure-activity relationships of cannabinoids and suggests that differences in penetration to the central nervous system may be an important determinant of behavioral activity. Although 11-OH-delta 9-THC was more potent than the parent compound delta 9-THC by both routes, the potency difference was less after i.v.t. administration. It was also demonstrated that metabolic conversion of [3H]delta 9-THC does not take place in squirrel monkey brain when administered i.v.t. which could account for the direct i.v.t. effects of delta 9-THC. These observations suggest that metabolic conversion of delta 9-THC in the liver is not necessary for its behavioral effects.

Animals↗
PubMed1978

Caffeine elicited withdrawal signs in morphine-dependent rhesus monkeys.

In the dose range of 4.0--32.0 mg/kg s.c., caffeine produced most of the signs which are commonly seen after the administration of naloxone (0.05 mg/kg s.c.) to morphine-dependent monkeys. The signs designated as lying on side or abdomen, avoiding contact, vocalizing, crawling or rolling, restlessness or pacing, tremors, retching, vomiting, coughing, vocalizing when abdomen palpated, rigid abdomen and salivation were noted. A randomized and blind experimental design, which included vehicle and positive (naloxone) controls was used. The significance of the differences between total scores for the whole syndrome was tested by the Mann-Whitney U-test. In preliminary studies in naive monkeys, caffeine was found to elicit some withdrawal signs but the results were equivocal. Na benzoate also elicited some withdrawal signs in morphine-dependent monkeys at 32.0 mg/kg s.c., but few signs were seen in naive monkeys. Caffeine was found to be approximately 10X more active than Na benzoate in inhibiting cAMP phosphodiesterase activity in a neuroblastoma cell whole homogenate assay. These results are consistent with the observations of Collier and Francis that morphine abstinence in rodents is associated with increased brain levels of cAMP.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1978

Disposition of morphine in chronically infused rats: relationship to antinociception and tolerance.

Levels of morphine in brain and other biological materials were measured fluorometrically, and relationships were drawn to tail-flick activity and to tolerance development in rats treated chronically with the narcotic by i.p. infusion. Brain morphine concentration and tail-flick latency both increased with increasing dosage over the first 3 days of the 6-day infusion regimen. There was evidence of cellular tolerance within 24 to 48 hours after the beginning of infusion, with marked tolerance by day 6. Between days 3 and 6 a dispositional tolerance, evidenced by a dramatic fall in brain morphine concentration, also became apparent. After discontinuation of the infusion, the brain morphine dropped to extremely low levels by 24 hours, but significant tolerance to antinociceptive effects remained for 72 hours. Estimation of morphine in plasma, urine, peritoneal tissues and feces suggested several possible explanations for the dispositional tolerance observed. These include increased conjugation of morphine, increased fecal elimination and increased localization in muscle or peritoneal tissues with chronic infusion at relatively high doses. The present work thus examines the pharmacokinetics of morphine in the rat in a chronic treatment model that is currently being used in a number of laboratories for the rapid induction of drug tolerance and dependence.

Analgesics↗
PubMed1978

A study of the effect of delta 9-tetrahydrocannabinol (delta 9-THC) on mammalian salivary flow.

delta 9-Tetrahydrocannabinol (delta 9-THC) caused no change in either pilocarpine or acetylcholine (ACh)-stimulated salivary flow of the cat but significantly decreased salivary flow from the submaxillary gland of the car and dog during electrical stimulation of the chorda tympani. In contributing to this effect, delta 9-THC significantly decreased (47%) basal arterial blood flow to the submaxillary gland of the dog and markedly reduced (51%) the stimulated blood flow to the gland produced by electrical stimulation of the chorda tympani. The decrease in stimulated blood flow by delta 9-THC suggested an effect on the ACh of the gland. No decrease in the synthesis of ACh could be demonstrated in the submaxillary gland of the dog. A significant decrease (37%) in the release of ACh from transmurally stimulated guinea-pig ileum, a model tissue, was produced by delta 9-THC. These data suggest that delta 9-THC decreases electrically stimulated salivary flow by a mechanism involving the decrease in release of ACh which results in a reduction of blood flow to the submaxillary gland, and, also, less ACh for stimulation of the secretory cells of the gland.

Acetylcholine↗
PubMed1978

Structure-activity relationships of natural and synthetic cannabinoids in suppression of humoral and cell-mediated immunity.

Delta-9-Tetrahydrocannabinol (delta-9-THC) a psychoactive constituent of marihuana, has been shown in previous studies to suppress humoral and cell-mediated immunity. The objective of this study was to determine whether structural modification of delta-9-THC would result in a more potent immunosuppressant agent devoid of central nervous system activity. The ED50 for reduction of the humoral immune response to sheep erythrocytes as measured by spleen plaque forming cells/10(6) spleen cells was 70 mg/kg for delta-9-THC. Delta-8-THC, 1-methyl delta-8-THC and abnormal delta-8-THC were more potent with ED50 values of 14, 13 and 8 mg/kg, respectively. Cell-mediated immunity was evaluated by a delayed-type hypersensitivity response to sheep erythrocytes. At doses of 100 mg/kg s.c. for 4 days, the cannabinoids suppressed the delayed-type hypersensitivity response from 35 to 64%. These data show that the cannabinoids can cause immunosuppression which is not related to central nervous system activity since 1-methyl delta-8-THC and abnormal delta-8-THC have minimal central nervous system activity.

Animals↗