Neuroendocrinology of opioid peptides and their role in the control of gonadotropin and prolactin secretion.

The present study explored neuropeptide responses to nicotine from smoking. Habitual smokers smoked research cigarettes of known strength under controlled laboratory conditions while blood samples were withdrawn unobtrusively for subsequent biochemical analysis. To provide a metric that reflected total nicotine intake and total neurohormonal output, data were integrated over time. Subjects were relatively unresponsive in the low-nicotine (0.48 mg) condition. In the high-nicotine (2.87 mg) condition, there were significant positive correlations between integrated plasma nicotine and plasma arginine vasopressin (r=+0.985), its carrier protein neurophysin I (r=+0.944), and β-endorphin-β-lipotropin (r=+0.977), but not adrenocorticotropic hormone. Data from an experiment that used an extraction step to remove β-lipotropin corroborated the functional relationship between plasma nicotine and β-endorphin implied by the original findings. Taking into account recent research on the role of neuropeptides in the modulation of affective states and cognitive function as well as of other CNS activity, the present findings were interpreted as strengthening the hypothesis that nicotine-stimulated neuropeptide release provides positive reinforcement for smoking.

Neuroendocrine reactivity to nicotine in smokers

Administration of physostigmine to normal volunteers produced significant elevations in plasma cortisol and beta-endorphin immunoreactivity as well as alterations in mood, cognition, and behavior. These observations might be explained by a cholinergically mediated stress syndrome. However, peak elevations in plasma beta-endorphin immunoreactivity (but not in plasma cortisol) were significantly correlated with physostigmine-induced increases in depression ratings. These results suggest that a cholinergically mediated beta-endorphin pathway may be involved in the observed affective changes.

https://science.sciencemag.org/content/sci/209/4464/1545.full.pdf

Mood and behavioral effects of physostigmine on humans are accompanied by elevations in plasma beta-endorphin and cortisol

Peptides in the cerebrospinal fluid of neuropsychiatric patients: An approach to central nervous system peptide function

Although the ovarian production of sex steroids is of obvious physiological importance, recent studies suggest that peptides such as oxytocin, relaxin and inhibin are also synthesized in the ovary1–11. We report here the presence of immunoreactive (ir) β-endorphin, ir-adrenocorticotropic hormone (ACTH) and presumptive high molecular weight forms of both in extracts of sheep ovary, consistent with ovarian production from a common precursor. Our findings suggest that β-endorphin and ACTH are produced and secreted by the follicular cells, and that their production may be related to the oestrous cycle.

Immunoreactive β -endorphin in sheep ovary

A highly sensitive and specific homologous RIA for direct measurement of human β-endorphin (βh-EP) has been developed. This RIA can detect as little as 5 pg/tube and cross-reacts with human β-lipotropin (βh-LPH) by only 5% on a molar basis and 2% by mass. Although the inhibition of binding of [125I]βh-EP in the RIA by βh-LPH was parallel to the inhibition curve produced by the addition of unlabeled βh-EP, the curves obtained by the addition of ovine and porcine β-endorphins and ovine β-LPH were not parallel to the βh-EP curve. This indicates that the antiserum against βh-EP recognizes different antigenic determinants in the βh-EP molecule compared to the corresponding animal peptides. Assay cross-reaction with ovine β-EP (10%), porcine β-EP (5%), and ovine β-LPH (16%) was small. No cross-reaction with 22 other peptides was found. Quantitative recovery of βh-EP was obtained after addition of the peptide to human plasma, cerebrospinal fluid, and amniotic fluid. Control experiments in which increasing quanti...

A Specific Homologous Radioimmunoassay for Human β-Endorphin: Direct Measurement in Biological Fluids

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A Specific Homologous Radioimmunoassay for Human β-Endorphin: Direct Measurement in Biological Fluids