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M T Lowy

Publications and source records attributed to M T Lowy.

47 records · Page 3Linked to original sources
PubMed1983

Opioid modulation of appetite.

The discovery of opiate receptors and endogenous opioid peptides within the central nervous system has resulted in a number of speculations concerning the physiological significance of these peptides. In the present article, we review the evidence suggesting a primary role for some of the opioid peptides as regulators of ingestive behavior. In particular, we elaborate a hypothesis in which we suggest that in some species opioid peptides may play a role as a tonic inducer of ingestive behaviors, held in check by a variety of neuropeptides and monoamines. This review explores in detail the role of the opioid peptides as major mediators of the reward system and as a link between reward and feeding behaviors. Finally, a teleological role for opioid peptides in species preservation, which may explain the discrepancies in the role of the opioid peptides in feeding behavior in different species is proposed. It is suggested that the feeding profile of the animal provides important clues as to whether or not the animal has an opiate-sensitive feeding system. We stress that interactions with ingested nutrients and the milieu interieur provide an important means by which animals modulate the opiate-entrained feeding drives.

Animals↗
PubMed1982

Drinking, but not feeding, is opiate-sensitive in hamsters.

The long-lasting opiate antagonist, naltrexone (NTX), was examined for its effects on various types of consummatory behavior in male golden hamsters and rats. Rat, but not hamster, 24 hr food and water intakes were significantly decreased by four daily NTX (10.0 mg/kg) injections. Hamsters displayed a minimal night to day feeding ratio compared to rats. Hamsters increased food intake following insulin (50 U/kg) administration, but not after 24 hr food deprivation (FD) or 2-deoxy-D-glucose (2-DG; 800 mg/kg) injections. NTX (1.0 and 10 mg/kg) had no effect on feeding, but markedly attenuated hamster drinking induced by 48 hr water deprivation or hypertonic saline injection. Dexamethasone (DEX), a glucocorticoid which depletes pituitary beta-endorphin and produces anorexia in rats, had no effect on daily hamster intake. Since the normal feeding profile of the hamster is similar to that of naloxone and DEX-treated rats, hamsters appear to lack an opiate-sensitive feeding system. In contrast, stimulated drinking behavior of hamsters operates through an opiate-sensitive mechanism. Thus, there are marked species differences concerning the involvement of endogenous opioids in consummatory behavior.

Animals↗
PubMed1981

Stereoselective effects of opiate agonists and antagonists on ingestive behavior in rats.

In male Sprague Dawley rats, the (-)-isomer of the opiate antagonist GPA 1843 (beta-9-methyl-5-phenyl-2-allyl-2'-hydroxy-6, 7-benzomorphan) produced dose-related decreases in nocturnal feeding and of hyperphagias induced by 2-deoxy-D-glucose (2-DG; 400 mg/kg) and 24 hr food deprivation (FD). The hyperphagia induced by insulin (10 U/kg) was not significantly decreased by GPA 1843. In contrast, comparable doses of the (+)-stereoisomer, GPA 1847, had no effect on nocturnal, 2-DG or FD hyperphagia. In addition, hyperphagia and hyperdipsia were observed following administration of the opiate agonist levorphanol, but not its stereoisomer, dextrorphan. Thus, the effects of these agents on consummatory behavior are mediated by a stereospecific interaction with opiate receptors, which further indicates that endogenous opiate peptides are involved in the expression of these opiate-related hyperphagias.

Animals↗
PubMed1979

Resolution and absolute configuration of trans-2-(2,5-dimethoxy-4-methylphenyl)cyclopropylamine, a potent hallucinogen analogue.

An hallucinogen analogue, trans-2-(2,5-dimethoxy-4-methylphenyl)cyclopropylamine (DMCPA), was resolved into ints two enantiomers by fractional crystallization of salts with d- or l-O,O-dibenzoyltartaric acid. A comparison of the ORD and CD curves of the N-5-bromosalicylidene derivatives of trans-2-phenylcyclopropylamine of known absolute configuration and of the title compound established the stereochemistry of the latter to be (1R,2S)-(-) and (1s,2r)-(+). We have earlier shown that the (-) isomer shows selective behavioral effects in cats and mice. In present study it was found that the (-) isomer selectively elicits rabbit hyperthermia when compared with the (+) isomer. In view of the stereoselective ability of the (-) isomer to elicit hallucinogen-like behavioral profiles in these animal models, the proof of absolute configuration lends further support to a new model which interrelates the active binding, conformation of phenethylamine hallucinogens to that of serotonin and tryptamines.

DOM 2,5-Dimethoxy-4-Methylamphetamine↗
PubMedDate not supplied

Relationship between plasma concentrations of immunoreactive beta-endorphin and food intake in rats.

Periods of increased food intake in male rats were characterized by significant elevations in the plasma concentrations of immunoreactive beta-endorphin (beta-ep). Administration of 2-deoxy-D-glucose (400 mg/kg) produced rapid and concurrent increases in both food intake and plasma beta-ep. Administration of insulin (10 units/kg) produced large delayed increases in food intake but only modest delayed increases in plasma beta-ep. Spontaneous nocturnal feeding was associated with increased plasma beta-ep. Increases in daytime food intake in rats subjected to 24 hr of food deprivation were also characterized by elevated plasma beta-ep. In all cases examined, those feeding behaviors in male rats which were subject to inhibition by naloxone were characterized by elevated concentration of plasma beta-ep.

Animals↗
PubMedDate not supplied

Experimental dissociation of food intake and plasma beta-endorphin following 2-deoxy-D-glucose in rats.

The present studies were undertaken to further assess the role of plasma beta-endorphin (beta-EP) in the hyperphagia induced by the glucose antimetabolite, 2-deoxy-D-glucose (2-DG). Plasma concentrations of immunoreactive beta-EP (ir-beta-EP) were measured at the end of the first hour of feeding in all animals treated with 400 mg/kg 2-DG. Previous studies had shown a consistent, positive association between 2-DG hyperphagia and plasma ir-beta-EP concentrations, but the present data revealed dissociations between hyperphagia and plasma ir-beta-EP. Dexamethasone administration blocked the 2-DG-induced rise in plasma ir-beta-EP, but had no effect on the 2-DG hyperphagia measured at 1 hour. Forced drinking of a 2% NaCl solution decreased 2-DG hyperphagia, but not the 2-DG induced rise in plasma ir-beta-EP. Thus, elevations in plasma ir-beta-EP are not necessary for the full expression of 2-DG-induced hyperphagia in dexamethasone-treated rats. Furthermore, decreased feeding responses to 2-DG could coexist with increased levels of plasma ir-beta-EP in NaCl-treated normal rats. Elevations in plasma ir-beta-EP do not appear to be the critical opiate link in 2-DG induced hyperphagia.

Animals↗
PubMedDate not supplied

Effects of intravenous and oral dexamethasone on selected lymphocyte subpopulations in normal subjects.

Our studies describe the effects of 1 mg oral (PO) and intravenous (IV) administration of dexamethasone (DEX) on certain subpopulations of circulating lymphocytes in normal subjects. We compared the outcomes of PO and IV DEX administration because of individual differences in gastro-intestinal absorption of DEX and the issue of noncompliance in patients undergoing the dexamethasone suppression test (DST). Both routes of DEX administration were equally effective in suppressing plasma cortisol levels below 5 micrograms/dl, the customary criterion level. Both routes of DEX administration also significantly decreased the percent and absolute number of CD4+ cells, the CD4+/CD8+ ratio, and the percent and absolute number of virgin, but not of memory, CD4+ cells.

Administration, Oral↗