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Biomedical subjects

M D Schechter

Publications and source records attributed to M D Schechter.

At least 145 records · Page 8Linked to original sources
PubMed1980

Caffeine potentiation of apomorphine discrimination.

Rats were trained to discriminate between the stimulus properties of intraperitoneal 0.16 mg/kg apomorphine and saline in a two-lever, food-motivated operant task. Apomorphine, at doses different than the training dose, produced a dose-response relationship, whereas, caffeine (7.5-30 mg/kg) produced saline-like responding. However, co-administered of 15 mg/kg caffeine with 0.01, 0.02 or 0.04 mg/kg apomorphine potentiated the discriminative stimulus properties of these low apomorphine doses. This potentiation was antagonized by pretreatment with 0.25 mg/kg haloperidol. The results are consistent with the idea that caffeine, by virtue of being a phosphodiesterase inhibitor, may increase post-synaptic cyclic-AMP and this, in turn, may supersensitize the dopamine receptors and result in the potentiation of the apomorphine-induced dopaminergic responses.

Animals↗
PubMed1980

Different dopaminergic mechanisms for amfonelic acid, amphetamine and apomorphine.

Rats were trained to discriminate between the stimulus properties of intraperitoneal 0.16 mg/kg apomorphine and saline in a two-lever, food-motivated operant task. Employing the selected lever and the extended schedule performance measurements to indicate the generalization effect and perseverance of that effect, respectively, neither d-amphetamine nor amfonelic acid produced apomorphine-like discriminative properties. In contrast, administration of 0.1 or 0.2 mg/kg n-propylnoraporphine was observed to produce responses and perseverance on the apomorphine-appropriate lever that was similar to that seen after 0.16 mg/kg administration. The results of this behavioral experimentation are consistent with the notion that d-amphetamine, amfonelic acid and apomorphine may produce their dopaminergic effects by different mechanisms of action and the possibility of two sites of action for n-propylnoraporphine is discussed.

Amphetamine↗
PubMed1980

Effect of neuroleptics and tricyclic antidepressants upon d-amphetamine discrimination.

After rats were trained to differentiate between the effects of intraperitqoneal administration of 0.6 mg/kg d-amphetamine and saline, pretreatment with various neuroleptic drugs was observed to significantly inhibit d-amphetamine discrimination. Thus, trifluoperazine, haloperidol, fluphenazine, chlorpromazine and thioridazine, but not clozapine, decreased d-amphetamine-induced control of discriminative performance. The ED50s of the effective neuroleptics for this inhibition were similar to those reported for antagonism of amphetamine-induced stereotypic behavior in the rat and the slopes of the dose-response curves were parallel indicating a common site and mechanism of action, presumably blockade of postsynaptic dopaminergic receptors. In contrast, pretreatment with the tricyclic antidepressant agents, imipramine, nortryptiline and desipramine had no significant effect on the discrimination of a dose of d-amphetamine which produced a low degree of discriminative control. The results are viewed in relation to the "dopamine hypothesis" of schizophrenia and affective disorders and the use of this animal behavioral method for determining brain dopamine interactions is discussed.

Animals↗
PubMed1979

Non-specificity of "behavioral despair" as an animal model of depression.

When mice are forced to swim in a restricted space, they will cease attempts to escape and adopt a characteristic immobile posture which can be readily identified and timed. Imipramine decreased the duration of immobility in a 4 min swimming test in a dose-related manner. Likewise, caffeine, triiodothyronine and pentobarbital reduced immobility. These latter findings shed doubt upon the specificity of the behavioral despair swimming test to identify substances with antidepressant activity.

Animals↗
PubMed1979

Interaction between discrimination of drug states and external stimuli.

Rats learned a two-choice operant response by discriminating differences between external stimuli, internal (drug-produced) stimuli, or a combination of these two types of stimuli. Separate groups of rats were used for each stimulus condition. A tactile and visual external cue was superior to the ethanol-saline cue in producing stimulus control, but the group receiving both drug and external stimulus cues performed in a manner very similar to the external cue-only group. The two stimulus sources thus did not "add" to promote more rapid or complete discrimination. After acquisition of discrimination, previously coincident drug and external stimulus states were reversed to determine which stimulus source had more behavioral control. This test for stimulus selectivity indicated that the external stimulus had essentially complete control of response choice.

Animals↗
PubMed1978

Lack of blockade of central dopaminergic receptors by narcotics: comparison with chlorpromazine.

d-Amphetamine and saline were used as discriminative stimuli in rats. After 0.6 mg/kg d-amphetamine administration, food reinforcement was contingent upon pressin 1 lever in 2-lever operant chamber. Responding on the other lever was reinforced only after saline injection of equal volume. The animals learned to discriminate between d-amphetamine and saline to a criterion of 85% correct. Administration of 2.5, 5.0 and 7.5 mg/kg morphine, and 0.02 and 0.04 mg/kg fentanyl produced saline-appropriate responses. Pretreatment with morphine and fentanyl had no significant effect on the d-amphetamine induced discriminative stimulus. In contrast, 1.25 and 2.5 mg/kg chlorpromazine antagonized d-amphetamine discrimination. These results indicate that despite their similar effect on brain dopamine turnover, morphine and fentanyl do not act on the same receptor site(s) as the neuroleptics, that is, they probably do not block brain dopamine receptors.

Animals↗
PubMed1978

Stimulus properties of d-amphetamine as compared to l-amphetamine.

Rats were trained to discriminate between d-amphetamine and saline. The discriminable ED50 values for amphetamine isomers were calculated from dose--response curves and the potency ration was 4.9 Co-administration of the ED50s was shown to produce synergistic effects suggesting that the amphetamine isomers may share a common site of action.

Amphetamine↗
PubMed1977

Amphetamine discrimination as a test for anti-parkinsonism drugs.

Rats were trained and tested on a two-lever discrimination task based upon the presence or absence of 0.8 mg/kg d-amphetamine. After 80% criterion performance was attained, dopaminergic drugs reported to be effective in the treatment of Parkinson's disease were tested to investigate their ability to produce d-amphetamine-like responding. Amantidine (50 mg/kg), apomorphine (2.5 mg/kg), n-propylnoraporphine (0.1, 0.2 and 1.0 mg/kg), and piribedil (25 mg/kg) were all observed to produce d-amphetamine-appropriate responding. These results indicate that discriminative behavior controlled by d-amphetamine is mediated by central dopaminergic systems and the use of this technique in the evaluation of potential anti-Parkinsonism drugs is discussed.

Amantadine↗
PubMed1977

Caffeine potentiation of amphetamine: implications for hyperkinesis therapy.

Neither 0.05 mg/kg d-amphetamine nor 15 mg/kg caffeine alone produce amphetamine-like responding in rats trained in two-lever operant chambers to discriminate 0.8 mg/kg d-amphetamine from saline. The co-administration of the two drug doses produced responding similar to the 0.8 mg/kg d-amphetamine dose. A suggestion for the mechanism of action and a regimen of administration for caffeine in hyperkinetic children are discussed.

Animals↗
PubMed1976

Nicotine-induced weight loss in rats without an effect on appetite.

Rats were administered 0.8 mg/kg nicotine (as base) i.p. 2 or 3 times a day for 5 weeks, and their mean body weights were observed to be significantly lower than those of control groups administered 0.9% saline on a similar regimen. The reduction in body weight after chronic nicotine administration proved highly replicable and was produced in the absence of a significant decrease in food consumption. Upon cessation of nicotine administration, the mean body weights of the rats returned to control group levels. Administration of phenylbenzoquinone, an agent that stimulated sensory pain receptors, failed to produce a similar decrease in body weight. Likewise, pretreatment with cholinergic blocking drugs, mecamylamine and hexamethonium did not antagonize the nicotine-induced decrease in body weight. Application of these results to the human smoking habit and possible mechanisms of actions are discussed.

Animals↗
PubMed1976

The discriminative stimulus properties of nicotine, d-amphetamine and morphine in dopamine depleted rats.

Rats permanetly depleted of central dopamine (DA) via 6-OHDA neonatally were studied in relation to their ability to discriminate various psychoactive drugs from saline using a two-bar operant procedure. DA rats learned to discriminate both morphine (4 mg/kh) and d-amphetamine (0.9 mg/kg) as rapidly as controls and exhibited similar sensitivity when dose-generalization studies were conducted. However, DA rats appeared to tolerate higher doses of the same drug better than controls indicating that they were more tolerant to behavioral disruption. It was suggested that the behavioral disruption. It was suggested that the behavioral disruption usurons. DA rats had more difficulty learning to discriminate nicotine than controls. In fact the peripherally injected nicotine stimulus generalized to hippocampal (Hp) injections in controls but was not observed in DA rats. These data suggest that part of nicotine's discriminative stimulus properties may be contingent upon the integrity of a Hp-DA connection.

Animals↗
PubMed1975

Dopaminergic mediation of the interoceptive cue produced by d-amphetamine in rats.

After rats were trained to differentiate between the effects of d-amphetamine and saline in a state-dependent task, pretreatment with the tyrosine hydroxylase inhibitor, alpha-methyl-p-tyrosine, significantly decreased amphetamine discrimination. Pretreatment with the dopamine-beta-hydroxylase inhibitor, disulfiram, or with the tryptophan hydroxylase inhibitor, p-chloro-phenylalanine, was observed to have no effect on the rats' ability to discriminate d-amphetamine. Administration of haloperidol, a selective dopamine receptor blocker, completely abolished the amphetamine discrimination, whereas alpha- and beta-adrenergic receptor blockade had no effect. Apomorphine, a dopamine receptor stimulant, produced amphetamine-like responses and this was, likewise, abolished by pretreatment with haloperidol. These data suggest that dopaminergic systems mediate the interoceptive cue produced by d-amphetamine in rats, and these results are discussed in relation to possible dopamine mediation of amphetamine psychosis and paranoid schizophrenia.

Animals↗
PubMed1975

Evidence for a cortical locus for the stimulus effect of nicotine.

This study investigated the stimulus properties of nicotine in the rat with the objective of determining the time course of the nicotine-produced interoceptive cue and its relationship to specific brain levels of the drug. The behavioral task employed was shock-escape in a T-maze apparatus. After the injection of nicotine entrance into the nicotine-correct arm of the T-maze resulted in termination of a 0.6 mA shock. When saline was administered, entrance into the opposite arm was rewarded by termination of shock. A high level of discrimination between nicotine and saline was obtained and the degree of discrimination was observed to decrease as the length of time period between nicotine administration and the test of discrimination was increased. This decline in discrimination was closely correlated with the decline in brain levels of nicotine in the cortex suggesting that the stimulus effect of nicotine is directly related to the concentration of nicotine in the cortex.

Animals↗
PubMed1975

Adopted children in their adoptive families.

The adoptive process can produce unusual stresses on the child, and biologic and adoptive parents, from prenatal to postnatal life, and through the various phases of physical and pscyhological development. Because of the possibility of these children and their families falling into the "at risk" category with greater potential for psychological and social problems, the pediatrician is of primary importance in diagnosis and counseling. The pediatrician can be of major help in properly diagnosing emotional, behavioral and/or learning problems occurring in adopted children. There must be a thorough evaluation of the child and his family to understand and properly treat symptomatic behavior. The pediatrician can give advice regarding developmental milestones, and especially help the adoptive parents in appreciating their conscious and unconscious attitudes so as to enhance attachment behaviors. Pediatricians are the consultants to whom parents turn for advice regarding the timing of telling about adoption. This advice needs to be individualized according to the specific child's needs. Using a developmental conceptual framework, the pediatrician is in the best position to help the parents and their adopted children with their feelings about societal attitudes and how these can most appropriately be handled. Along this line, the pediatrician can give help and advice when and if the adoptee decides to search for his biologic parents. There is a need to clarify laws which seal the original birth certificate permitting those adoptees who wish to attain a knowledge of potentially related disease processes and an identity with his own genealogical past to do so. This would also allow the adoptee to offer his own children information about their own genetic pool and an awareness of adoption as one of the most valuable and historically significant child rearing practices.

Adoption↗