Effect of age on cisternal cerebrospinal fluid concentrations of monoamine metabolites in nonhuman primates

There are conflicting reports of the effects of aging on human neurotransmitter systems as estimated by monoamine metabolite concentrations in cerebrospinal fluid (CSF). These discrepancies may be due to sampling site, age or sex of the subjects or other variables that affect CSF metabolite determinations. Cisternal CSF concentrations of homovanillic acid (HVA), 3-methoxy-4-hydroxyphenyl-ethylene glycol (MHPG) and 5-hydroxyindoleacetic acid (5-HIAA), major metabolites of dopamine, norepinephrine and serotonin, respectively, were measured in rhesus monkeys (Macaca mulatta) of two age groups. Concentrations of HVA and MHPG were significantly lower in the older group of monkeys, whereas no changes in 5-HIAA were found. This supports the hypothesis that brain catecholamine concentrations decline with age.

Long-term effects of early social isolation in Macaca mulatta: changes in dopamine receptor function following apomorphine challenge

The hypothesis that early social isolation results in long-term alterations in dopamine receptor sensitivity was tested using older adult rhesus monkeys. Isolated and control monkeys were challenged with apomorphine (0.1 and 0.3 mg/kg), and the drug effects on spontaneous blink rate, stereotyped behavior, and self-injurious behavior were quantified using observational measures. Monoamine metabolites were quantified from cisternal CSF by HPLC-EC, prior to pharmacological challenge. Isolated and control monkeys did not differ in CSF concentrations of HVA, 5-HIAA, or MHPG. At the higher dose, apomorphine significantly increased the rate of blinking, the occurrence of whole-body stereotypies, and the intensity of stereotyped behavior (as measured by observer ratings) in isolated monkeys. The frequency of occurrence of self-injurious behavior was too low to allow for meaningful comparisons. These significant differences in response to apomorphine challenge support the hypothesis that long-term or permanent alterations in dopamine receptor sensitivity, as assessed by drug challenge, are a consequence of early social deprivation.

Diazepam inhibits neurulation through its action on myosin-containing microfilaments in early chick embryos

Diazepam (Valium/Roche) inhibited the morphogenesis of explanted stage 8 chick embryos in a dose-related manner. Diazepam, at concn of 400-500 micrograms/ml, preferentially inhibited closure of the neural tube. This inhibition was accompanied by a significant reduction in myosin content of the developing neuroepithelium. Diazepam can be used as a probe to study the contributory role of myosin in cellular and morphogenetic movements.