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Biomedical subjects

J L Meyerhoff

Publications and source records attributed to J L Meyerhoff.

102 records · Page 6Linked to original sources
PubMed1975

Dopamine and norepinephrine levels in the nucleus accumbens, olfactory tubercle and corpus striatum following lesions in the ventral tegmentalarea.

Dopamine and norepinephrine levels were examined in 3 forebrain regions following unilateral lesions either in the ventral medial tegmental area (VMT) or in the substantia nigra. The dopamine and norepinephrine content of the nucleus accumbens, olfactory tubercle and corpus striatum were assayed ipsilaterally and contralaterally in unilaterally lesioned rats sacrificed 2, 5, 10, and 20 days after the placement of the lesions. In the nucleus accumbens and olfactory tubercle ipsilateral dopamine levels were significantly reduced below the contralateral levels at 2 days, and were decreased by 56% and 65%, respectively, 10 days after the lesion. A 30% reduction of dopamine levels occurred in corpus striatum as well, following lesions in the VMT. Lesions in the substantia nigra decreased ipsilateral dopamine levels by 68% in the corpus striatum, without affecting dopamine levels in the olfactory tubercle or nucleus accumbens. Norepinephrine levels on the side ipsilateral to the lesion did not significantly differ from contralateral levels in any of the 3 regions following lesions either in the VMT or in the substantia nigra. These results demonstrate the specificity of projection in the mesolimbic dopamine system as suggested by the original histofluorescence studies.

Animals↗
PubMed1975

Effects of heroin on lever pressing for intracranial self-stimulation, food and water in the rat.

Male rats maintained with continuous access to levers for intracranial self-stimulation (ICSS), water, and food were subjected to five consecutive daily injections of heroin (5 mg/kg). Rates of lever pressing for ICSS were increased in 8 rats, 2--6 hrs after administration of heroin. Rates of lever pressing for water and food were not significantly changes during this period. Naloxone (5 mg/kg) pretreatment attenuated by 82% the facilitative effect of heroin on ICSS. A second group of 8 rats maintained at reduced ICSS rates failed to show an increase in lever pressing for ICSS with heroin. The facilitative effect of heroin described in this study is consistent with previously reported studies describing the effects of morphine on ICSS.

Animals↗
PubMedDate not supplied

Small groups in programmed environments. Behavioral and biological interactions.

This paper reviews a research program undertaken within a laboratory environment that was designed and constructed to support behavior analyses of individual and group performance effectiveness viewed conceptually within the context of a small-scale human microsociety. Summarized are previous research emphases and findings in relationship to (1) conditions that sustain group cohesion and productivity and that prevent social fragmentation and performance deterioration, (2) motivational effects resulting from the programmed consequences of individual and group performance requirements, and (3) behavioral and biological effects resulting from a change in group size. A more detailed description is presented of the results of a recent series of experiments that were conducted to assess performance and hormonal effects of replacing an established group participant with a novitiate member. The significance of these investigative undertakings is to be understood in terms of emergent environmental, motivational, and behavioral-biological principles having practical relevance for the establishment and maintenance of small-scale human social systems.

Environment, Controlled↗
PubMedDate not supplied

Comparison of the effects of CRF and stress on levels of pituitary cyclic AMP and plasma ACTH in vivo.

We have previously reported that acute stress increases levels of rat pituitary cyclic AMP in vivo. The present study was conducted to test the hypothesis that stress-induced increases in pituitary cyclic AMP in vivo were mediated via CRF. We compared the effects of various stressors with the effects of CRF or epinephrine administration on pituitary cyclic AMP and plasma ACTH responses in vivo. Stressors, epinephrine or CRF increased levels of pituitary cyclic AMP. Pituitary cyclic AMP response to either immobilization or CRF was much greater at light onset than at lights off in rats maintained on a 12 hr light:12 hr dark lighting regimen. In rats with pituitary stalk transections, footshock did not increase levels of pituitary cyclic AMP, suggesting that some factor of central origin was required for this stress response. Exogenous CRF administration did increase levels of pituitary cyclic AMP in stalk-transected rats, while epinephrine increased levels in sham-operated but not in stalk-transected rats. Antisera to CRF markedly decreased pituitary cyclic AMP response to exogenous CRF administered 6 min following antisera and partially attenuated pituitary cyclic AMP response to forced running. Taken as a whole these data support a major role for CRF in the pituitary cyclic AMP response to stress.

Adrenocorticotropic Hormone↗
PubMedDate not supplied

Psychologic stress increases plasma levels of prolactin, cortisol, and POMC-derived peptides in man.

Stressful social interactions have been shown to elicit increases in heart rate as well as in plasma levels of epinephrine, norepinephrine, and cortisol in humans. We sought to determine whether a competitive oral examination would affect plasma levels of the pituitary hormones ACTH, beta-endorphin, beta-lipotrophic hormone, and prolactin in a group of healthy young males. Seven min after beginning the examination, heart rate increased 27% and plasma levels of ACTH, beta-endorphin, beta-lipotropic hormone and prolactin rose 59%, 79%, 42%, and 46%, respectively, compared to values shortly before the examination. These hormone values returned to initial levels after the subjects returned to the waiting room. Plasma cortisol changes were similar in direction to those of ACTH but occurred about 15 min later. The present study demonstrates that a stressful social interaction can elicit rapid increases in plasma levels of the proopiomelanocortin derived peptide hormones and prolactin in man.

Adrenocorticotropic Hormone↗