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The purpose of this work was to investigate the effects of electrical afterdischarge on protein kinase C (PKC) activity from bag cell neurons (BCNs) of Aplysia. Bilateral clusters of BCNs were divided: one cluster was stimulated to afterdischarge, the other was a control. Clusters were processed for PKC activity assay 5-120 min after electrical stimulation.(More)
The purpose of this work was to test the hypothesis that an electrical afterdischarge (AD) causes prolonged elevation in cytosolic calcium levels that is associated with prolonged secretion of egg-laying hormone (ELH) from peptidergic neurons in intact nervous tissue of Aplysia. Using a combination of radioimmunoassay measurement of ELH secretion,(More)
Seasonal reproduction in the ewe is generated by an endogenous circannual rhythm of reproductive neuroendocrine activity. Exposure to as few as 70 days of photoperiodic information a year is sufficient to synchronize the rhythm. The present study was conducted to identify which portions of the photoperiodic cycle are utilized for synchronization. For this(More)
A single gene defect of the circadian clock (tau mutation) has recently been described that results in a shortening of the circadian activity cycle of the Syrian hamster. In the homozygous animal, free running activity is shortened by 4 h, resulting in a circadian period of approximately 20 h. Here, we examine the effect of the tau mutation on noncircadian(More)
The bag cell neurons of the marine mollusk Aplysia have been used extensively for investigating the electrophysiology and molecular biology of neurosecretory cells. However, there has been little attempt to carefully describe the pattern of secretion of the 36-amino acid peptide hormone that controls egg-laying behavior. This egg-laying hormone (ELH) is(More)
Experiments were conducted to examine whether the refractoriness of the Suffolk ewe to the reproductive effects of day length is associated with a deficit in the generation of the circadian rhythm of melatonin secretion or in the postpineal processing of this photoperiodic message. Using serum luteinizing hormone (LH) concentrations in ovariectomized ewes(More)
Kisspeptin (product of the kiss1 gene) is the most potent known activator of the hypothalamo-pituitary-gonadal axis. Both kiss1 and the kisspeptin receptor are highly expressed in the hypothalamus of vertebrates, and low doses of kisspeptin have a robust and long-lasting stimulatory effect on the rate of action potential firing of hypophysiotropic(More)
The insulin receptor is a tyrosine kinase receptor that is found in mammalian brain and at high concentrations in the bag cell neurons of Aplysia. We show here that insulin causes an acute rise in intracellular Ca2+ concentration ([Ca2+]i) in these neurons and triggers release of neuropeptide. The insulin-sensitive intracellular Ca2+ pool differs(More)
Endogenous opioid peptides (EOPs) are an important class of modulators of the hypothalamo-pituitary axis; treatment with opiates leads to inhibition of GnRH and LH secretion and suppression of reproductive functions. However, little work has been done to investigate the effect of opiates on the electrical activity of GnRH neurons, which ultimately controls(More)