Predisposition to hypertension in rat pups from renal hypertensive dams

We determined that a predisposition to hypertension could be transmitted by a nongenetic, renal hypertensive (HT) mother to her pups. The pups of one-kidney: one clip Goldblatt (1K:1C) hypertensive female rats and of sham operated normotensive female rats were subjected to the 1K:1C procedure at 28 days of age and tail cuff blood pressures (BP) were determined. After surgical induction of hypertension, HT male pups of HT dams had a significantly greater (p less than .05) BP by 14 days after surgery (194 +/- 8 mm Hg) than did HT male pups of normotensive (NT) dams (169 +/- 6 mm Hg). A similar trend (p less than .08) was observed for the HT female pups of HT dams (185 +/- 7 mm Hg) compared to HT females from NT dams (163 +/- 4 mm Hg). Thus, in utero exposure of pups to a chronic HT state alters the response of the pups to the surgical induction of hypertension. Furthermore, the results suggest that transfer of a predisposition to hypertension from mother to offspring occurred during the pregnancy/lactation period.

Circadian patterns of serotonin (5-HT) accumulation after pargyline treatment in the rat hypothalamus during development

The purpose of this study was to determine if developmental changes in serotonin (5-HT) synthesis occur during maturation of the 5-HT circadian rhythm in the rat hypothalamus of 10- to 35-day-old rats. Pargyline (75 mg/kg, s.c.), a monoamine oxidase (MAO) inhibitor, was administered 30 min prior to decapitation. Hypothalamic 5-HT concentrations after pargyline treatment were measured at six time points over a 24-hr interval in male and female rat pups at 10, 20, 30 and 35 days of age. Daily fluctuations in hypothalamic 5-HT accumulation were detectable as early as 10 days of age in rats of both sexes. Since the influence of MAO on hypothalamic 5-HT concentrations was eliminated by pargyline treatment, the findings suggest that changes in tryptophan hydroxylase activity contribute significantly to daily and age-related patterns of 5-HT accumulation in the rat hypothalamus during development. Circadian rhythms in hypothalamic norepinephrine (NE) and dopamine (DA) also occurred during development; however, sex differences were not detected for these biogenic amines. Since catecholamine catabolism is not exclusively mediated by MAO, our findings are insufficient to conclude whether or not sex differences actually exist in patterns of these monoamines.

Developmental patterns of tyrosine hydroxylase activity in discrete central nervous system regions and serum LH and prolactin in the prepubertal rat

Changes in tyrosine hydroxylase (TH) activity in the whole hypothalamus and discrete nuclear regions of the limbic system were observed to occur from 10 to 40 days of age in the female rat. In the whole hypothalamus, TH activity increased between 10 and 30 days of age then decreased at 40 days of age. In the preoptic (POA) and suprachiasmatic nuclear areas (SCN), TH activity increased to peak values at 20 days then declined to baseline values at 25 days. However, an increase in TH activity of SCN was again noted at 39 days of age. TH activity in the amygdala area (AMYG) increased to peak values at 25 and 30 days with a return to baseline levels at 35 days, while in the median eminence (ME), TH activity increased at 20 days and remained elevated through 39 days of age. These results show that temporally distinct changes in TH activity occur during development in various areas of the brain. These changes may represent maturation of neuronal control systems known to be involved in adult reproductive function. Serum LH levels in the developing rat increased between days 10 and 25 then showed a precipitous drop at day 30 followed by increased values at days 35-39. Serum prolactin levels remained low through day 20, increased at days 25-30 then decreased on day 35 with a peak at day 37, prior to the onset of puberty. The inverse relationship of LH and prolactin at day 30 suggests a transient inhibitory (antigonadotropin) effect of increasing prolactin levels on LH at this time.(ABSTRACT TRUNCATED AT 250 WORDS)

Uptake of serotonin and norepinephrine in hypothalamic and limbic brain regions during the estrous cycle and the effect of neurotoxin lesions on estrous cyclicity

The temporal pattern of hypothalamic and limbic aminergic activity during the estrous cycle has been measured by changes in the serotonergic and noradrenergic neuronal uptake during the regular estrous cycle. Significant changes (p = 0.006, 0.01) in the uptake of 3H 5-HT and 3H NE were recorded in the suprachiasmatic nuclei (SCN) at 1200 hours on proestrus. Significant changes (p = 0.01, 0.018) in the uptake of 3H 5-HT in the preoptic area (POA) were found at 1200 hours on both diestrus and proestrus while median eminence (ME) 5-HT showed a significant increase only during proestrus (p = 0.001). In the amygdala (AMYG) 3H 5-HT uptake was significantly different at 1200 hours on diestrus and proestrus while 3H NE uptake was significant (p = 0.001) at 1200 hours only during proestrus. The plasma proestrous luteinizing hormone surge occurred at 1700 hours. The serotonin neurotoxin, 5,7-dihydroxytryptamine, was stereotaxically injected through a 30 gauge needle in concentrations of 5-10 micrograms/microliters/minute for 1 minute in various nuclear regions. In the SCN 4 or 5 day estrous cyclicity was interrupted by diestrus for average periods of up to 15 days; in the POA for periods of 10 days; in the ME for periods of 13 days; and in the AMYG for periods of up to 6 days. Sham injections of 5% ascorbic acid had no effect on cyclicity and following these periods of acyclicity rats resumed normal cycles. These lesion effects and patterns of uptake suggest a common timing mechanism utilizing serotonergic raphe systems for neuroendocrine control. Lesions with 5,7-DHT in all four brain regions disrupt cyclicity, but the greatest delays occur in the SCN and ME regions which are particularly critical to intrinsic neuroendocrine rhythms. Patterns of increase in reuptake capacity in all 4 regions occur 3 hours prior to the critical period for the plasma LH surge and may be an important mechanism for many types of neuroendocrine events including ovulation.

Plasma luteinizing hormone and prolactin levels and hypothalamic catecholamine synthesis in steroid-treated ovariectomized rats

The effects of estrogen (E) and progesterone (P) on synthesis rates and endogenous levels of hypothalamic norepinephrine (NE) and dopamine (DA) were determined in individual ovariectomized (OVX) rats. 3H-tyrosine (3H-T) was injected intra-arterially and the rate of its incorporation into 3H-DA and 3H-NE was determined at 10, 15, 30, and 45 min. Steroid treatment for 2 days effectively decreased plasma LH levels and elevated plasma prolactin (Prl) levels while endogenous levels of NE and DA were not affected. NE synthesis was not affected by steroid treatment. A significant increase in DA synthesis was correlated with low plasma LH levels, suggesting that DA inhibits LH release. The elevated plasma Prl levels seen in steroid-treated rats were correlated with increased DA synthesis in the hypothalamus. This may indicate that elevated plasma Prl levels stimulate dopaminergic neurons in a short-loop negative feedback fashion.