Mammalian pineal glands contain, and may secrete, an octapeptide, arginine vasotocin (AVT), in addition to characteristic methoxyindoles such as melatonin. We have developed a sensitive and specific radioimmunoassay (RIA) for AVT, and propose to use it to examine in vivo, and in vitro factors that control AVT secretion, and to compare these factors with those that control melatonin release. We will measure melatonin levels using an RIA and, when appropriate, a bioassay, both of which are fully operational in our laboratories. We will also assay samples for vasopressin and oxytocin by RIA, to ensure the specificity of AVT's response to treatments that modify the levels (i.e., the immunoreactivity) of this peptide in tissues and biologic fluids. Initially, we will characterize the ranges of AVT concentrations at various times of day and night in pineals, plasmas, and urines from adult rats exposed to normal (12:12) diurnal lighting. Subsequently, we will examine the effects on AVT and melatonin levels of: (a) normal prenatal and postnatal development; (b) exposing rats to continuous light or darkness; (c) blinding of animals, denervating pineals, or subjecting animals to secretion; (d) giving rats drugs known to modify the functional activity of pineal noradrenergic synapses; (e) pinealectomizing rats; and (f) castrating rats, and treating some with steroid hormones, or obtaining pineal, blood, an urine samples from intact animals at different phases of the estrous cerebrospinal fluid, and, if successful, to study its clinical physiology. Finally, we will explore possible mechanisms for controlling the synthesis and release of AVT in the pineal using rat pineal organ cultures, and cell suspension systems prepared using fresh bovine pineal glands.