Effects of morphine on brain histamine, antinociception and activity in mice

1. The effect of morphine on the histamine content of the mouse brain has been investigated. The changes in the brain histamine level have been related to morphine-induced analgesia and morphine-induced changes in locomotor activity. 2. With doses of morphine between 1 and 5 mg/kg there was a significant increase in histamine levels. The time required to produce a maximal rise in the brain histamine level with 5 mg/kg of morphine was 15 min. 3. There was a significant decrease in brain histamine levels with doses of morphine between 7-5 and 100 mg/kg. The time at which the greatest decrease was produced with 50 mg/kg was 30 min. 4. The time couse of the alteration of brain histamine by morphine did not correlate with its antinociceptive activity. Both the 5 and 50 mg/kg doses of morphine produced analgesia in mice whereas brain histamine levels were increased and decreased, respectively. 5. Pretreating mice with compounds which modify histaminergic function did not modify the antinociceptive action of morphine. 6. Morphine produced a biphasic effect on locomotor activity when the dose was increased from 0-5 through to 100 mg/kg. Doses up to 2-5 mg/kg caused a reduction of activity and doses above this produced significant increases. 7. There appears to be an inverse relationship between the morphine-induced changes of brain histamine and the morphine-induced changes in locomotor activity.

Optimal fluoridation--The concept and its application to municipal water fluoridation

Optimal fluoridation has been defined as that fluoride exposure which confers maximal cariostasis with minimal toxicity and its values have been previously determined to be 0.5 to 1 mg per day for infants and 1 to 1.5 mg per day for an average child. Total fluoride ingestion and urine excretion were studied in Marin County, California, children in 1973 before municipal water fluoridation. Results showed fluoride exposure to be higher than anticipated and fulfilled previously accepted criteria for optimal fluoridation. Present and future water fluoridation plans need to be reevaluated in light of total environmental fluoride exposure.

The effects of raising alveolar PCO2 and ventilation separately and together on the sensitivity and setting of the baroreceptor cardiodepressor reflex in man

1. The effects of changes in ventilation and/or alveolar P(CO2) on the baroreflex control of heart rate have been studied in seven experiments on six young men and women who had been trained to control tidal volume and respiratory frequency at various levels independent of alveolar P(CO2), during hyperoxia.2. Intravenous phenylephrine provoked transient rises of directly measured arterial pressure during which individual systolic pressures (P) were linearly related to the following pulse interval (I). Baroreflex sensitivity was expressed as the slope of the regression of I on P, and reflex setting (I(ref)) as I at a single reference arterial pressure (= mean P for the experiment).3. Voluntary control of breathing had little effect on heart rate and arterial pressure (baroreflex setting), but diminished reflex sensitivity.4. Hypercapnia regularly caused tachycardia at the reference pressure (i.e. baroreflex setting lowered). The response was completely or partly reproduced by change of P(A, CO2) at constant ventilation in four subjects but not in two others; in them change of ventilation at constant P(A, CO2) completely mimicked the effect of free-breathing hypercapnia.5. Values of baroreflex sensitivity were relatively scattered. Hypercapnia caused a fall in baroreflex sensitivity in three subjects whether ventilation was fixed or free to rise. After separating the effect of voluntarily controlling ventilation, ventilation per se was without effect on reflex sensitivity.6. It is concluded that hypercapnia and hyperpnoea have separate effects on the baroreflex, the relative magnitudes of which differ from one subject to another. Baroreflex setting and sensitivity vary independently in response to change of ventilation and of P(A, CO2).

Effects of acid etchants on dentin

The ability of acid etchants to penetrate dentin was tested under simulated clinical conditions. No penetration of the dentinal tubules by acid was detected by use of two different test methods, although pronounced roughening of the treated surfaces was observed.

Comparison of the dose-response effects of morphine on brain amines, analgesia and activity in mice

1. Noradrenaline, dopamine, 5-hydroxytryptamine and 5-hydroxyindoleacetic acid concentrations in the mouse brain were measured 30 min after subcutaneous injection of doses of morphine ranging from 0.1 to 100 mg/kg: motor activity was also measured.2. The noradrenaline concentration in the mouse brain was reduced by moderate (2 to 20 mg/kg) but not by high (above 20 mg/kg) and low (below 2 mg/kg) doses of morphine.3. The dopamine concentration in the mouse brain was reduced by moderate (1 to 20 mg/kg) doses but was raised by high doses (above 20 mg/kg) of morphine.4. The 5-hydroxytryptamine concentration in the mouse brain was reduced by moderate (1 to 20 mg/kg) doses of morphine but not by high (above 20 mg/kg) and low (below 1 mg/kg) doses of morphine.5. The 5-hydroxyindoleacetic acid concentration was not affected by low doses (0.1 to 2 mg/kg), raised by a dose of 5 mg/kg, lowered by doses of 10-50 mg/kg and not affected by 100 mg/kg of morphine.6. These results are discussed with reference to the possible implication of changes in monoamines for the analgesic and behavioural effects of morphine.

How does the striate cortex begin the reconstruction of the visual world?

The striate cortex transforms the topographic representation of visual space in the lateral geniculate body into a Fourier transform or frequency representation at the complex cell level via the intermediary simple cell stage of "strip integration." Each of these three stages contains essentially the same amount of information, which expresses a conservation of information principle; however, the form of the information is changed. In the transform domain, invariant descriptions of visual objects can be derived to serve as the basic sets required for pattern recognition and memory. We believe that our experimental and theoretical findings are fundamental for understanding the functional organization of the striate cortex.

Modification of morphine analgesia by drugs affecting adrenergic and tryptaminergic mechanisms

The effects of drugs that modify adrenergic or tryptaminergic mechanisms were tested on the analgesic action of morphine in mice. Analgesia was assessed by the hot plate method and phenylquinonewrithing method. Reserpine antagonized the analgesic action of morphine in both tests, the maximal effects occurring 6–8 h after the administration of reserpine. p-Chlorophenylalanine antagonized the analgesic action of morphine as assessed by the writhing method but not by the hot plate method. The analgesic action of morphine was not modified in either test by pretreatment with α-methyl-p-tyrosine, propranolol, phentolamine or methysergide. These results suggest that the analgesic action of morphine, as measured in the writhing test, may be mediated by 5-hydroxytryptamine but that other mechanisms may be involved in the hot plate test.