An abnormal distribution of melatonin receptors in the newborn rat with inherited prenatal hydrocephalus.

Melatonin binding in the brain of hydrocephalic H-Tx rats was examined by autoradiography. At the time of birth, hydrocephalic animals showed an abnormality in the distribution of high-affinity melatonin receptors dorsal to the cerebral aqueduct when compared to controls. Whereas newborn rats of the H-Tx strain that were unaffected by hydrocephalus had melatonin receptors in a tectal midsagittal strip overlying the aqueduct and spanning the anterior half of the tectum, hydrocephalic rats lacked melatonin receptors in the most anterior part of this region.

Release of vasopressin in response to altered plasma volume and sodium concentrations following pinealectomy in the rat.

Pinealectomy has been shown to alter daily rhythms of neurohypophysial hormone release, with plasma hormone concentrations being elevated in the morning, as compared to intact rats. To determine whether pineal removal also altered the response to known stimuli of hormone release, vasopressin concentrations were measured in control, sham-operated, and pinealectomized animals during extracellular fluid hypertonicity produced by an intraperitoneal (i.p.

The role of the pineal in the control of the daily patterns of neurohypophysial hormone secretion.

Plasma concentrations of neurohypophysial hormones show clear rhythms over 24 hr which can be suppressed by exposure to constant light, an observation consistent with pineal involvement. A study has therefore been performed on the changes in the hormone levels in the hypothalamus, posterior pituitary, and plasma over 24 hr in control, pinealectomised, and sham pinealectomised animals to determine if the pineal could play a role. Water intake, urine excretion, packed cell volume, plasma osmolality, and electrolytes were also monitored.