Biomedical subjects

N S Gray

Publications and source records attributed to N S Gray.

24 records · Page 2Linked to original sources

PubMed1996

Effects of nicotine and amphetamine on latent inhibition in human subjects.

Latent inhibition (LI) is a phenomenon in which repeated non-reinforced exposure to a stimulus retards subsequent conditioning to that stimulus; it reflects a process whereby irrelevant stimuli become ignored, and has been the subject of study concerning attentional abnormalities in schizophrenia. Low doses of the indirect dopamine (DA) agonists, amphetamine and nicotine, disrupt LI in the rat. These drugs are believed to disrupt LI via DA release in the nucleus accumbens; LI in amphetamine- and nicotine-treated rats is reinstated by administration of the DA antagonist haloperidol. In human subjects, low doses of amphetamine abolish LI, and more recently haloperidol has been shown to potentiate LI. The present study investigated the effects of nicotine on LI in human subjects, and also attempted to replicate the abolition of LI by amphetamine. Nicotine failed to affect LI when administered either subcutaneously or by cigarette smoking. LI was, however, abolished in a group of subjects given 5 mg amphetamine 90 min before testing. Supplementary analyses of the data pooled from all three experiments showed that, in contrast to an earlier report, LI was no weaker in smokers than in nonsmokers.

Adult↗

PubMed1995

Latent inhibition in drug naive schizophrenics: relationship to duration of illness and dopamine D2 binding using SPET.

The dual aims of the study were (1) to examine the effect of neuroleptic medication on the expression of latent inhibition (LI) by studying LI in drug naive schizophrenic patients, and (2) to investigate the relationship between LI and dopamine D2 receptor binding in the basal ganglia using single photon emission tomography (SPET). Subjects constituted a sub-set of patients investigated in a major study of in vivo D2 receptor binding in schizophrenia (Pilowsky et al., 1993). Striatal D2 receptor binding was assessed in 15 neuroleptic naive schizophrenic patients and 13 healthy volunteers. The performance of subjects on a within-subject auditory latent inhibition paradigm was also assessed. There was found to be no significant difference in LI between schizophrenic patients and normal controls, both groups showing a strong within-subject LI effect. There was also found to be no association between LI and dopamine D2 receptor binding in either the left or the right basal ganglia. This lack of association indicates that LI is not directly related to post-synaptic D2 receptor levels in the striatum. LI was, however, found to be correlated with duration of illness in the schizophrenic group. Patients with a relatively short duration of illness (< 12 months) tended to show reversed, or absent, LI whereas patients with a longer illness duration (> 12 months) showed intact LI. The effect on LI of duration of illness is consistent with previous findings that LI is disrupted specifically in acute, but not chronic, schizophrenia. Previous studies have assumed that this pattern of results is due to the stabilising effect of long-term neuroleptic medication. The present findings in a sample of neuroleptic naive schizophrenic patients indicate that this is unlikely to be the case. Rather, it appears that the reinstatement of LI in schizophrenic patients over time is due to a factor(s) intrinsic to the evolution of the schizophrenic illness.

Adolescent↗

PubMed1994

Stereotypy, schizophrenia and dopamine D2 receptor binding in the basal ganglia.

Animal models suggest a relationship between disturbed striatal dopaminergic function and stereotyped behaviour. Several studies show increased stereotypy in schizophrenic patients compared to normal controls. We investigated the performance of 12 antipsychotic-drug-free schizophrenic patients, and 15 healthy control subjects on a neuropsychological measure of stereotypy--the two-choice guessing task--and correlated this with in vivo striatal dopamine D2 receptor binding, as measured by 123I-iodobenzamide single photon emission tomography. Patients and controls did not differ with respect to the measures of stereotypy derived from the task. However, there was a significant correlation between one of these measures (RR Information) and the degree of striatal D2 receptor binding asymmetry in the patient group only. In view of research connecting striatal and frontal lesions with stereotypy in animals and cognitive inflexibility in humans, these data could suggest a similar disturbance underlying the phenomenon in schizophrenia.

Adolescent↗

PubMed1992

Abolition of latent inhibition by a single 5 mg dose of d-amphetamine in man.

The performance of healthy volunteer subjects on an auditory latent inhibition (LI) paradigm was assessed following administration of a single oral dose of d-amphetamine or placebo. It was predicted that a low (5 mg), but not a high (10 mg), dose of d-amphetamine would disrupt LI. The prediction was supported with left ear presentation of the preexposed stimulus only. When the preexposed stimulus was presented to the right ear the predicted pattern of findings was not obtained. It is concluded that the dopaminergic system is involved in the mediation of LI in man and it is speculated that the interaction between amphetamine dose and ear of presentation of the preexposed stimulus may reflect normally occurring dopaminergic hemisphere asymmetry.

Acoustic Stimulation↗

PubMedDate not supplied

Insulin-like growth factor 1 and growth hormone binding protein in depression: a preliminary communication.

This study was undertaken in order to advance our understanding of the distal growth hormone axis in depression. Insulin-like growth factor 1 (IGF-1) and growth hormone binding protein (GHBP) were measured in a group of 19 depressed women and a group of 16 healthy women. Using a generalized linear model, IGF-1 levels were negatively correlated with age (p = 0.0001), influenced by menstrual phase (p = 0.016), and significantly increased in the depressed group (p = 0.02). Using the same type of analysis, GHBP was significantly related to menstrual phase (p = 0.0001) and body mass index (p = 0.0001), but was not significantly different in patients and controls. IGF-1 and GHBP were positively correlated among healthy subjects (r = 0.46, p = 0.08), but not among depressed patients (r = -0.16, p = 0.51), although these correlation coefficients were not statistically significantly different from each other. These findings confirm the importance of several physiological factors in the regulation of IGF-1 and GHBP, and suggest that depression further influences this regulation.

Adult↗

PubMedDate not supplied

Social support and postpartum African American women.

The birth of the first child is a major transitional period for the new mother and her family. Social support that women receive seems to buffer the changes experienced during the postpartum period. However, very little is written about the social support of postpartum African American women. The purpose of this pilot study was to investigate the difference between social support expected prenatally, and that actually received postpartally in African American primiparous women. Data were collected utilizing a modified version of the Postpartum Social Support Questionnaire. Findings revealed no significant differences in the social support expected, and what was actually received postpartally. This sample was somewhat unique in that the women were educated with at least a high school education, with a mean age of 25, and possessed health insurance (access to health care). Future research utilizing the tool with larger samples should be conducted to further validate the reliability and validity of the tool.

Adult↗