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Biomedical subjects

G C Davis

Publications and source records attributed to G C Davis.

At least 73 records · Page 4Linked to original sources
PubMed1983

Pain enhances naloxone-induced hyperalgesia in humans as assessed by somatosensory evoked potentials.

The effect of 8 mg IV naloxone on pain appreciation was studied with electric shocks administered to the left forearm of 20 normal volunteers. Pain sensitivity was assessed with a psychophysical task and with evoked potentials (EP) to the pain stimuli which were found sensitive to opiate agonists and antagonists in previous experiments. Naloxone-induced hyperalgesia before and after 20 min of intermittent shock was assessed in a 3-day placebo crossover experiment designed to provide control comparisons of time effects. EP amplitude enhancement with naloxone was significantly greater following 20 min of shocks than preceding them, while pain judgments were not significantly affected. Thus, naloxone increases pain sensitivity, especially after prolonged pain stimulation. This finding is consistent with endorphin mediation of stress-induced analgesia and raises the question of whether this type of response decrement over time is related to the phenomena of habituation.

Adult↗
PubMed1983

Endorphins and pain.

Endorphinergic neurons certainly play a role in the brain's processing of painful stimuli. Endorphins act to alter pain appreciation at many levels within the central nervous system including spinal cord, midbrain, thalamus, and cortex. The activity of this pain-suppressing system may play a role in individual differences in the experience of pain. Endorphinergic mechanisms play a major role in analgesia associated with stress and acupuncture, and perhaps mediate placebo-induced analgesia. Chronic pain influences endorphinergic function perhaps depleting endorphinergic neurons of their neurotransmitters. Endorphin function and pain sensibility are prominently affected in affective illness and schizophrenia. It may be that endorphinergic neurons play a fundamental role in selective attention--a kind of sensory filtering of information flow--in somatosensory and other sensory modalities.

Analgesia↗
PubMed1982

Naloxone in chronic schizophrenic patients: neuroendocrine and behavioral effects.

Naloxone produced improvement in abnormal thought content in medicated chronic schizophrenic patients, but not in drug-free patients. In contrast, drowsiness and increases in plasma prolactin concentrations were seen only in drug-free schizophrenic patients. Although growth hormone concentrations increased in drug-free and medicated schizophrenic patients, the time course was different in the two groups. Neuroleptics appear to alter naloxone's clinical and neuroendocrine effects in chronic schizophrenic patients.

Adult↗
PubMed1981

Naloxone effects on beta-endorphin, cortisol, prolactin, growth hormone, HVA and MHPG in plasma of normal volunteers.

8 mg of naloxone were administered IV to 14 normal volunteers in a placebo-controlled, double-blind experiment. Plasma levels of beta-endorphin, cortisol, prolactin, growth hormone, HVA and MHPG were determined before and 45 min after administration. Naloxone elicited significant increases in cortisol and MHPG but did not change plasma levels of the other compounds. In an additional experiment on two subjects, 20 mg of naloxone caused elevations of beta-endorphin as well as of cortisol. This parallel increase indicates that the linkage between the secretion of beta-endorphin and ACTH/cortisol may be dose-dependent. The increase in MHPG is in agreement with the hypothesized association of noradrenergic hyperactivity and opiate withdrawal.

Adult↗
PubMed1981

Behavioral and biological effects of acute beta-endorphin injection in schizophrenic and depressed patients.

In this double-blind study, beta-endorphin, 4-15 mg, was administered intravenously to 6 schizophrenic and 4 depressed patients. There were neither significant differences in behavioral ratings between beta-endorphin and placebo for the overall group nor for either the schizophrenic or depressed subgroup. Clinical worsening and improvement were observed in individual schizophrenic patients. There was no evidence of late-appearing therapeutic effects in 4 schizophrenic patients rated for 5 consecutive days after placebo and drug infusions. In 1 patient 10 mg of beta-endorphin produced neuroendocrine effects comparable to those produced by 5 mg of intravenously administered methadone; in 2 other patients it produced large increases in circulating opioid activity as determined by radioreceptor assay. These biological data support the notion that parenterally administered beta-endorphin exerts significant opiate-like activity in vivo.

Adult↗
PubMed1980

Failure of naloxone to reduce manic symptoms.

The authors conducted a double-blind placebo-controlled study in which patients with a wide range of manic symptoms were administered 20 mg of naloxone subcutaneously. Naloxone failed to improve manic severity, activation-arousal, or elation-grandiosity for intervals up to 3 hours. Global nurse ratings of mania did not improve over an 8-hour period. The authors suggest that the question of endorphin involvement in mania has not been resolved and recommend clinical studies with longer acting oral narcotic antagonists such as naltrexone.

Affective Disorders, Psychotic↗
PubMed1980

Psychopathology and endorphins.

Suggestive evidence exists linking endorphins to the schizophrenic syndrome; narcotic antagonists appear to slightly attenuate some symptoms, attentional performance is improved and CSF opiate-binding substances are reported to be elevated in a sub-group of patients. Many fewer affectively ill patients have been studied and little evidence has accumulated suggesting a relationship between symptoms of affective illness and endorphins although CSF endorphins appear elevated in some manic-depressive patients and "pain patients" with depression have higher CSF endorphins than pain patients without depression. Catatonic symptoms as well as other psychomotor functions remain promising areas for study. Opioid effects on manic symptoms have been reported by only a few research groups and would benefit from study with longer-acting antagonists administered daily.

Bipolar Disorder↗