Effect of chronic cold stress on catecholamine levels in rat brain

Inhibitory effects of catecholamines and maternal stress on aromatase activity in the fetal rat brain

OBJECTIVE

Aromatization in the the fetal brain is thought to be involved both in sex differentiation during early development and in adult sexual behavior. Although recently the relationship between aromatase and catecholamine has been discussed, the effect of stress on aromatase in the fetal brain has not been clarified. Therefore, in the present study, localization of aromatase and the inhibitory effects of catecholamines and maternal stress on aromatase activity in the fetal rat brain were examined.

METHODS

Localization of aromatase cytochrome P-450 using a specific polyclonal antiserum against human placenta aromatase was examined, and the inhibitory effects of dopamine and norepinephrine on aromatase activity in vitro were studied. Further, the influences of intrauterine stress on aromatase activity in the prenatal rat brain were evaluated in vivo.

RESULTS

Aromatase-immunoreactive neurons are located principally in the medial amygdaloid nucleus. Aromatase activity in the fetal rat brain was competitively inhibited by dopamine and norepinephrine, with Ki values of 120 microM and 100 microM, respectively. Aromatase activity in the fetal brain was significantly lower in stressed rats given 1.5% salt water (89.2 +/- 17.5 fmol/mg/hr; n = 4) (p < 0.05) than in the control group (123.1 +/- 10.0 fmol/mg/hr; n = 4).

CONCLUSION

Aromatase activity in the prenatal rat brain is influenced by catecholamine metabolism during intrauterine stress.

Dopamine-beta-hydroxylase activity in the locus coeruleus and hypothalamus in cold-stressed rats

Dopamine-beta-hydroxylase (DBH) activity was determined in the locus coeruleus, anterior hypothalamus and posterior hypothalamus of cold-stressed rats. In the acute cold stress, rats were exposed to an ambient temperature of 5 degrees C in a cold room for 5-20 min. In the chronic cold stress, rats were exposed to the same cold temperature for 4 hr once every day in the morning for periods ranging from 1 to 3 weeks. There was decreased DBH activity in the locus coeruleus following acute cold stress and increased activity in both the locus coeruleus and the anterior hypothalamus following the chronically repeated cold stress.

Possible interaction of environmental and biological factors in the etiology of schizophrenia. Review and integration

Possible interactions of genetic and environmental factors in the etiology of schizophrenia are discussed.

Studies on the significance of genetic-constitutional and environmental factors in determining specificity of behavioural and biochemical responses to stressors in humans and experimental animals are reviewed.

Studies of stress in schizophrenia are also revieweed and their possible relationships discussed.

Hypotheses related to the interaction of environmental factors and genetic constitutional factors in the production of acute schizophrenic psychosis in genetically predisposed people are presented. Research studies supporting such hypotheses are reviewed and discussed.

It is proposed that environmental pressures, by inducing a physiological state of stress or other biochemical physiological alterations, may be etiologically related to the development of acute schizophrenic psychosis by:

• Producing chemical substances that act as inducers of enzymes, in particular transmefhylating enzymes and those involved in the production of proteins, which may be related to the etiology of schizophrenia;

• Activating autoimmune processes which may be related to the etiology of schizophrenia;

• Changing levels of brain amines;

•Altering the permeability of the blood-brain barrier.