ABSTRACT
Neonatal handling has long-lasting effects on behavior and stress reactivity. The purpose of the present study was to investigate the effect of neonatal handling on the number of dopaminergic neurons in the hypothalamic nuclei of adult male rats as part of a series of studies that could explain the long-lasting effects of neonatal stimulation. Two groups of Wistar rats were studied: nonhandled (pups were left undisturbed, control) and handled (pups were handled for 1 min once a day during the first 10 days of life). At 75-80 days, the males were anesthetized and the brains were processed for immunohistochemistry. An anti-tyrosine hydroxylase antibody and the avidin-biotin-peroxidase method were used. Tyrosine hydroxylase-immunoreactive (TH-IR) neurons were counted bilaterally in the arcuate, paraventricular and periventricular nuclei of the hypothalamus in 30-æm sections at 120-æm intervals. Neonatal handling did not change the number of TH-IR neurons in the arcuate (1021 + or - 206, N = 6; 1020 + or - 150, N = 6; nonhandled and handled, respectively), paraventricular (584 + or - 85, N = 8; 682 + or - 62, N = 9) or periventricular (743 + or - 118, N = 7; 990 + or - 158, N = 7) nuclei of the hypothalamus. The absence of an effect on the number of dopaminergic cells in the hypothalamus indicates that the reduction in the amount of neurons induced by neonatal handling, as shown by other studies, is not a general phenomenon in the brain
Subject(s)
Animals , Male , Female , Rats , Behavior, Animal/physiology , Handling, Psychological , Hypothalamus, Anterior/physiology , Neurons/physiology , Tyrosine 3-Monooxygenase/metabolism , Animals, Newborn , Anterior Hypothalamic Nucleus/enzymology , Anterior Hypothalamic Nucleus/physiology , Dopamine/physiology , Hypothalamus, Anterior/enzymology , Neurons/immunology , Physical Stimulation , Rats, Wistar , Stress, Psychological , Tyrosine 3-Monooxygenase/immunologyABSTRACT
The effects on ovulation at the next strus after unilaterally implanting pilocarpine in the preoptic-anterior hypothalamic area (POA-AHA) of rats on each day of the estrous cycle were analyzed. Implantation on the left side of POA-AHA on the day of estrus blocked ovulation in all animals, whereas implantation on the right side did not (0/5 vs. 4/4, p<0.05). Implantation on diestrus 1 or 2 on either side of the POA-AHA blocked ovulation. Implatation on the righ side of the POA-AHA at the day of proestrus blocked ovulation (1/6 animals ovulated), while 10/12 with pilocarpine on the left side ovulated (p<0.05).The administration of 3.7 µg of GnRH at 13:00 h o the expected day of proestrus induced ovulation in 36/42 treated animals. In rat with a pilocarpine implant, the injection of estradiol benoznate on diestrus 2 restored ovulation only in those animals with the pilocarpine implant placed in the left side of the POA-AHA, performed on the day of estrus. The results support the previous estatements that in the adult rat POA-AHA, the cholinergic mechanism regulating preovulatory GnRH release, is lateralized. In addition, at the beginning of the estrous phase, the PAO-AHA-cholinergic system needs to remain undisturbed for normal ovulation to take place at the next estrus