Today, one of my lab mates was ordained as a doctor……of philosophy. Of course, this title generates numerous (not so nice) questions, the most common being:
So you aren’t a real doctor?
When are you going to get a job? My taxes pay you…….
What exactly can you do with your degree??
So how does your research address world poverty, hunger, and health?
Her dissertation focused on neuropeptide regulation of photic and nonphotic signaling within the circadian clock, all of which can be found in three publications:
All of these neuropeptide are endogenously expressed within the SCN. GRP and VIP are concentrated within the ventromedial region of the nuclei, near the optic chiasm. This anatomical placement is meaningful given that it largely directs photic signaling within the clock. AVP is primarily expressed within the dorsomedial region of the nuclei, which is also nonaccidentally convenient because it is involved with integrating nonphotic information arriving from brainstem and thalamic regions of the brain, and also with the regulation of circadian clock output (behavior, metabolism, and hormone release). NPY is ubiquitously expressed within heterogenous cell populations of the SCN, but like AVP, helps integrate nonphotic information.
Basically, Jessie found that all of these neuropeptides show a circadian pattern of release, with most of these neuropeptides’ expressions peaking in the middle of the day. This is also when peak spontaneous neuronal firing within the SCN occurs. NPY release can be prematurely induced during the day when the animal is behaviorally stimulated (forced to run, gently handled, moved to a different cage), which then advances behavioral circadian rhythms. Secondly, Jessie has found, among other advances to the field, that VIP release can be attenuated by the presentation of serotonin. This is in general agreement with previous work showing the nonphotic stimuli can inhibit light-induced shifts of behavioral rhythms and vice versa.
I also learned during Jessie’s defense today that potassium is incredibly important for regulating neuron exocytosis and endocytosis. Within my basic neuroscience courses, I have, of course, been taught that calcium and sodium largely control neuron exocytosis and subsequent depolarization of neighboring neurons, but I didn’t think (or was perhaps too ignorant to believe) that potassium can gate neuron exocytosis while simultaneously controlling action potentials.
Glass, J., Guinn, J., Kaur, G., & Francl, J. (2010). On the intrinsic regulation of neuropeptide Y release in the mammalian suprachiasmatic nucleus circadian clock European Journal of Neuroscience, 31 (6), 1117-1126 DOI: 10.1111/j.1460-9568.2010.07139.x
Francl JM, Kaur G, & Glass JD (2010). Regulation of vasoactive intestinal polypeptide release in the suprachiasmatic nucleus circadian clock. Neuroreport, 21 (16), 1055-9 PMID: 20838260
Francl JM, Kaur G, & Glass JD (2010). Roles of light and serotonin in the regulation of gastrin-releasing peptide and arginine vasopressin output in the hamster SCN circadian clock. The European journal of neuroscience PMID: 20731711