Influence Of Neonatal Treatment Research Articles

Sexual Differentiation of Kiss1 Gene Expression in the Brain of the Rat

The Kiss1 gene codes for kisspeptins, which have been implicated in the neuroendocrine regulation of reproduction. In the brain, Kiss1 mRNA-expressing neurons are located in the arcuate (ARC) and anteroventral periventricular (AVPV) nuclei. Kiss1 neurons in the AVPV appear to play a role in generating the preovulatory GnRH/LH surge, which occurs only in females and is organized perinatally by gonadal steroids. Because Kiss1 is involved in the sexually dimorphic GnRH/LH surge, we hypothesized that Kiss1 expression is sexually differentiated, with females having more Kiss1 neurons than either males or neonatally androgenized females. To test this, male and female rats were neonatally treated with androgen or vehicle; then, as adults, they were left intact or gonadectomized and implanted with capsules containing sex steroids or nothing. Kiss1 mRNA levels in the AVPV and ARC were determined by in situ hybridization. Normal females expressed significantly more Kiss1 mRNA in the AVPV than normal males, even under identical adult hormonal conditions. This Kiss1 sex difference was organized perinatally, as demonstrated by the observation that neonatally androgenized females displayed a male-like pattern of adulthood Kiss1 expression in the AVPV. In contrast, there was neither a sex difference nor an influence of neonatal treatment on Kiss1 expression in the ARC. Using double-labeling techniques, we determined that the sexually differentiated Kiss1 neurons in the AVPV are distinct from the sexually differentiated population of tyrosine hydroxylase (dopaminergic) neurons in this region. Our findings suggest that sex differences in kisspeptin signaling from the AVPV subserve the cellular mechanisms controlling the sexually differentiated GnRH/LH surge.

Influence of neonatal treatment with the pyrethroid insecticide cypermethrin on the development of dopamine receptors in the rat kidney

The influence of neonatal treatment with the pyrethroid insecticide cypermethrin (( R, S) α-cyano-3-phenoxybenzyl(1 R, S)- cis- trans-3-(2,2-dichloro-vinyl)-2,2-dimethylcyclopropane carboxylate) on postnatal development of renal dopamine receptors was investigated by radioligand binding assay techniques. Treatment with cypermethrin was made on rats from the 10th to the 16th day after birth. Dopamine D 1-and D 2-like receptors were assayed in frozen sections of kidney of 21-, 30-, 60- and 90-day-old rats using as ligands of dopamine D 1- and D 2-like receptors [ 3H]([ R](+)-(chloro-2,3,4,5,-tetrahydro-5-phenyl-1,4,-benzazepin-al hemimaleate) (SCH 23390) and [ 3H]spiperone, respectively. Treatment with cypermethrin was without effect on the affinity ( K d value) or the density ( B max value) of dopamine D 1- and D 2-like receptors of rats of 21 days of age. In older groups, treatment with the compound reduced the affinity and increased the density of dopamine D 1-like receptors, whereas it was without effect on the affinity of dopamine D 2-like receptors and decreased their density. These findings indicate that neonatal treatment with the pyrethroid insecticide cypermethrin induces long-lasting impairment of renal dopamine D 1- and D 2-like receptors, and that kidney is a target of the toxic action of the compound. Renal dopamine receptor changes caused by cypermethrin are consistent with possible alterations of renal tubular function and of sympathetic neuroeffector modulation. The above data suggest also that, different from the adult, neonatal exposure to pyrethroid insecticides may induce toxic effects.

The influence of neonatal treatment with capsaicin on the control of blood pressure in adult rats in water-replete and water-deprived states.

Arterial blood pressures and heart rates were measured in water-replete and in water-deprived (48 h) conscious, adult rats that had received capsaicin (50 mg kg-1) or its vehicle neonatally. Resting arterial blood pressures and heart rates in capsaicin-treated rats were not different from the controls in either the water-replete or the water-deprived state. Inhibition of the vascular actions of vasopressin (with 1-beta-mercapto,-beta, beta-cyclopentamethylenepropionic acid, 8-D-arginine vasopressin, (d(CH2)5DAVP] had no significant effect on blood pressures in the water-replete animals but caused a significant hypotension in water-deprived rats; the magnitude of the hypotension was the same irrespective of whether the animals had received capsaicin or its vehicle. During angiotensin converting enzyme inhibition (with captopril) and ganglion blockade (with pentolinium), the vasopressin-mediated blood pressure recovery was more gradual in the capsaicin-treated animals than in the controls, but after 60 min blood pressures were similar in all groups. Collectively the results indicate that although the full development of vasopressin-dependent mechanisms following acute hypotension takes longer when a large proportion of unmyelinated afferent fibres have been destroyed by neonatal treatment with capsaicin, 48 h of water deprivation results in a normal involvement of vasopressin-dependent mechanisms in the maintenance of blood pressure.

The influence of neonatal treatment with guanethidine on the development of isolation-induced hypertension in adult rats.

Rats housed individually in glass metabolism cages develop hypertension. Since previous experiments have provided some evidence for the involvement of the sympathetic nervous system in the maintenance of the hypertension, the present work was designed to explore the possible involvement of the sympathetic nervous system in the genesis of isolation-induced hypertension. Male and female Wistar rats were treated neonatally with guanethidine, with a protocol designed to produce an extensive peripheral sympathectomy; control rats received saline. The effects of isolation on systolic blood pressure and fluid and electrolyte balances were studied when the rats were mature. Guanethidine-treated rats did not develop hypertension in response to isolation whereas control rats did. There were no significant differences between the fluid and electrolyte balances of the guanethidine-treated rats compared with controls throughout the period of isolation. It is concluded that a fully functional sympathetic nervous system is required for the development of isolation-induced hypertension, but its involvement is not through a modulation of renal function.

The ontogenetic development of the striatal dopaminergic system and the influence of neonatal treatment with 6-hydroxydopa

The ontogenetic development of the striatal dopaminergic system and the influence of neonatal treatment with 6-hydroxydopa

Influence of neonatal treatment with 6-hydroxydopa on clonidine-induced locomotor stimulation in the infant rat.

Influence of neonatal treatment with 6-hydroxydopa on clonidine-induced locomotor stimulation in the infant rat.

Neonatal sterilization of rodents with steroid hormones: 5. A note on the influence of neonatal treatment with estradiol benzoate or testosterone propionate on steroid metabolism in the brain and testes of adult male rats

The influence of neonatal treatment with androgens or estrogens in rats was evaluated by measuring in the testes and the brain of adult animals the conversion of 4-androstene-3, 17-dione, 3β-hydroxy-5-androstene-17-one, 3β-hydroxy-5-pregnen-20-one, and testosterone. In the testes, neonatal treatment with estradiol benzoate produced an enzymatic defficiency manifested by decreased utilization of C-21 precursor and 17-oxo reduction. Neonatal treatment with testosterone propionate produced an increase in 17β-hydroxyoxidase activity and decrease in the activity of 17-oxo reductase. In addition, the amounts of testoster-one and androstenedione in the brain of treated rats were significantly decreased suggesting an alteration in the permeability of the blood-brain barrier.

Neonatal sterilization of rodents with steroid hormones: 3. Influence of neonatal treatment with testosterone propionate or estradiol benzoate on steroids in plasma of adult male rats

The influence of neonatal estrogen or androgen treatment was compared in adult male rats by measuring disappearance of testosterone, 4-androstene-3,17-dione, 3β-hydroxy-5-androsten-17-one and 3β-hydroxy-5-pregnen-20-one from plasma. It was found that neonatal treatment with estradiol benzoate altered the rate of transformation of testosterone in plasma when measured 20 min after intravenous injection; the relative specific activity of β-hydroxy-5-pregnen-20-one and β-hydroxy-5-androsten-17-one was apparently decreased, whereas that of testosterone and androstenedione was increased.

Influence of neonatal treatment on maternal behavior: A confounding variable

Postparturitional rats when given a choice of either an experimentally treated (hypothermia and rotated) or a control neonate, significantly preferred the control. Experimental treatment of one half the litter disrupted maternal retrieving scores for all offspring. The results suggest that early experience studies may have a serious confounding variable.