Pituitary and hypothalamic concentration of met-enkephalin in young and old rats

Molecular hysteresis: residual effects of hormones and glucose on genes during aging

The basic concept of molecular hysteresis may be succintly summarized as follows in the following Limerick:. Hormones behave like Don Juan: They show up, do their thing, then they're gone. But when genes have been kissed Some effects may persist, And the melody still lingers on.

Effect of naltrexone on stress-induced bioactive prolactin release in aging male rats

Effects of the opiate receptor antagonist naltrexone (NALT, 10 mg/kg) on basal and novel environment stress-induced prolactin (PRL) release were examined in young (3-5 month) and old (22-24 month) male Copenhagen-Fischer 344 rats. Radioimmunoassay and Nb2 lymphoma bioassay were used to determine plasma immunoreactive (ir-) and bioactive (bio-) PRL levels, respectively. Although basal plasma irPRL levels were greater, bioPRL levels were significantly lower in old as compared to young rats. NALT induced significant decreases in basal plasma ir- and bioPRL concentrations in young rats, but had little or no effect on irPRL or bioPRL levels in old rats. Stress-induced elevations in irPRL levels were similar, but increases in bioPRL levels were attenuated in vehicle-treated old as compared to young rats. NALT pretreatment blocked stress-induced ir- and bioPRL release in both age groups. These results indicate that the role of endogenous opioid peptides (EOP) in regulating basal PRL secretion appears to be diminished, whereas EOP continue to be involved in stress-induced PRL release in the aging animal.

The effect of L-dopa upon in vitro dopamine release from the corpus striatum of young and old male rats

In the present experiments, we examined the effects of superfusion of L-DOPA upon in vitro dopamine (DA) release from the corpus striatum (CS) in young (2-4 months) and old (24 months) male rats. In Experiment I, responses to two successive increasing doses of L-DOPA (1.0 and 10 microM) indicated a clear age difference with DA release from CS of young rats significantly greater than that of old rats in response to the 10 microM dose of L-DOPA. Interestingly, CS fragments of young and old male rats responded marginally to the 1.0 microM L-DOPA infusion, and no significant differences between these two age groups were obtained. Since we have previously observed that the addition of naloxone to the superfusion medium restored the potassium stimulated DA release of old rats to that of young rats, in Experiment II, responses of CS tissue fragments of young and old rats superfused in medium with or without naloxone (100 microM) were tested with a single 10 microM L-DOPA infusion. The results of Experiment II indicated that the addition of naloxone to the superfusion medium did not alter the responses of CS tissue to L-DOPA in either young or old rats; however, the overall response of the young rats remained significantly greater than that of the old rats. Taken together, these results demonstrate a significant age-related decrement in the capacity of 10 microM L-DOPA to stimulate DA release from CS fragments.(ABSTRACT TRUNCATED AT 250 WORDS)

The importance of striatal interneurons in age-related effects upon potassium- and amphetamine-stimulated dopamine release

The ability of superfused corpus striatal tissue fragments to release endogenous dopamine (DA) in response to potassium (K+ 30 mM) stimulation was significantly attenuated in 18- to 24-month- compared to 2- to 4-month-old male rats. These age-related effects on K+ stimulation were completely abolished with the addition of tetrodotoxin (1 microM) to the superfusion medium. Moreover, no difference in stimulated DA release was obtained between these two age groups following amphetamine stimulation (10 microM).

Senescent change in tissue weight and immunoreactive beta-endorphin, enkephalin, and vasopressin in eight regions of C57BL/6J mouse brain and pituitary

Tissue weights and immunoreactive (IR) content and concentration of beta-endorphin, enkephalin, and vasopressin were assayed for senescent change in anterior pituitary, neurointermediate pituitary, hypothalamus, hippocampus, striatum, dorsolateral cortex, and pons-medulla, as well as residual brain samples remaining after the other dissections. Groups of naive male C57BL/6J mice, 8-12 months old and 28-32 months old, served as subjects. Old mice exhibited significant decline in anterior pituitary and hippocampus weight. Significant increases with age were found in pons-medulla weight. IR beta-endorphin content decreased in hypothalamus and neurointermediate pituitary. IR enkephalin decreased in striatum and dorsolateral cortex. IR vasopressin content increased in hypothalamus and residual brain. Assays were replicated in later experiments using additional subjects, for total Ns of up to 54 mice. Although significant overall results were always consistent in direction from replication to replication, the magnitude of age change exhibited considerable variability. Such results suggest that single experiments on age changes in neuropeptides, particularly those giving negative results, should be carefully scrutinized and replicated before their acceptance as evidence for a transmitter's stability or instability throughout the lifespan.

Immunoreactive beta-endorphin in the plasma, pituitary and hypothalamus of young female rats on the day of estrus and intact and chronically castrated old constant estrous female rats

Immunoreactive beta-endorphin (IR-beta-ENDO) was compared in the plasma, pituitary and hypothalamus of young female rats on the day of estrus and old constant estrous (CE) female rats, and in intact and chronically castrated old CE female rats. The concentration of IR-beta-ENDO in the plasma and the content and concentration of IR-beta-ENDO in the neurointermediate lobe of the pituitary were significantly greater in the old CE female rats than in the young female rats on the day of estrus. The content and concentration of IR-beta-ENDO in the anterior pituitary and hypothalamus were similar in the two age groups. To determine if estrogen contributed to the increase in plasma and pituitary levels of IR-beta-ENDO observed in the old animals, a group of old CE female rats were castrated and compared to sham operated control CE rats. Thirty days after castration, levels of plasma, pituitary and hypothalamic IR-beta-ENDO were comparable in the intact and the chronically castrated old female rats. These data indicate that in old CE female rats, plasma and pituitary IR-beta-ENDO are significantly increased in comparison to young female rats on the day of estrus, and that these increased levels of IR-beta-ENDO observed in old female rats do not appear to be influenced by gonadal estrogen.

Decreased content of met-enkephalin-like peptides in superior cervical and coeliac ganglia of aged rats

Enkephalin like peptides seem to have an important regulatory role at ganglia level. The aim of the present study is to investigate whether the content of enkephalin-like peptides in sympathetic ganglia is affected by the aging process. The results show that the enkephalin like peptides content is low in superior cervical and coeliac ganglia of aged rats (25 months). The age-related decrease of enkephalin content in these structures may be of importance in determining an altered sympathetic control during aging.

Age related changes of enkephalin in rat spinal cord

Met-enkephalin immunoreactive material content was found to be decreased in the cervical and thoracic segments of the spinal cord from rats aged 25 months as compared to young, 3-month-old, rats. No age-related variations were detectable at the lumbar level. Bio-Gel P 30 column chromatography of thoracic segment extracts indicates that the composition of the immunoreactive material is similar in the two age-groups investigated. At the thoracic level opiate receptor binding was also measured. Opiate receptor number is increased in the thoracic segments of the spinal cord from older rats. These age-related changes in immunoreactive Met-enkephalin content and opiate receptor number at spinal levels may contribute to determine an altered pain sensitivity during aging.

Immunoreactive beta-endorphin in the plasma, pituitary and hypothalamus of young and old male rats

Immunoreactive beta-endorphin (IR-beta-ENDO) was measured in the plasma, pituitary, and hypothalamus of young (3-5 mo.) and old (19-23 mo.) male Sprague-Dawley rats, using a specific radioimmunoassay. Plasma IR-beta-ENDO in old male rats (3.44 +/- 0.54 ng/ml) was more than three times higher than values observed in young male rats (1.00 +/- 0.10 ng/ml). Pituitary content and concentration of IR-beta-ENDO also were significantly greater in the old (5.85 +/- 0.51 microgram/gland and 1.17 +/- 0.10 microgram/mg protein) than in the young (3.53 +/- 0.29 microgram/gland and 0.78 +/- 0.06 microgram/mg protein) male rats. The content of IR-beta-ENDO in the hypothalamus of old and young rats was nearly the same (43.45 +/- 2.47 and 49.88 +/- 6.35 ng/hypothalamus, respectively), whereas the concentration of IR-beta-ENDO in the hypothalamus of the old male rats (3.89 +/- 0.25 ng/mg protein) was approximately 50% lower than that observed in the young male rats (7,80 +/- 0.85 ng/mg protein). These changes in plasma, pituitary, and hypothalamic IR-beta-ENDO may contribute to the increase in prolactin and decrease in gonadotropins observed in old male rats, since beta-ENDO administration is known to produce these effects on prolactin and gonadotropin secretion.

Effect of age on sensitivity to pain and brain opiate receptors

Age-related differences in sensitivity to pain as induced by heat and electrical shock were seen among groups of rats; 2-3, 6-12, and 24 months of age. These are differences were at least partially obliterated by naloxone treatment, suggesting that changes may occur in the endogenous opioid system during aging. In contrast to higher pain thresholds in older animals, however, are decreased concentrations of opiate receptors in the frontal poles, striatum and hippocampus. Anterior cortex and amygdala exhibit a trend toward decreased concentration with increased age, but this is not significant. No age changes in binding affinity occur in any of the brain regions examined. Possible explanations for the apparent discrepancy between altered receptors and response include: higher endogenous opioid levels in aged rats, mediation of pain sensitivity by brain regions other than those examined, difficulties inherent in attempting to localize age changes at a single step in such a complex process, and possibly differential spinal pathways mediating the various types of pain.