title: Daily rhythmic changes in synaptic vesicle contents of nerve endings on adrenomedullary adrenaline cells, and their modification by pinealectomy and sham operations.
abstract: Nerve endings on adrenaline cells in male rat adrenal medullas were investigated by quantitative electron microscopy, with sampling at 8 times during a standard light: dark (12:12) photoperiod. Number (N) per unit area of 2 vesicle types (small clear vesicle, SCV; large granular vesicle, LGV) and % of LGV per total vesicle N were determined. Normal (non-operated) animals showed a circadian rhythm (p less than 0.005) in mean SCVN and one with nearly opposite phase relations in % LGVN. Doubly sham-operated animals had a similar rhythm in %LGVN but diminished circadian change in SCVN. Pinealectomized animals had a circadian pattern in SCVN, but this differed from that of normals in having a 2nd peak, a delay or phase shift of the primary peak, and an increased amplitude of the rhythmic changes.
mesh_terms: D000313:Adrenal Medulla / Q000378:metabolism*; D000818:Animals; D002940:Circadian Rhythm; D004837:Epinephrine / Q000378:metabolism*; D008297:Male; D008928:Mitochondria / Q000378:metabolism; D009411:Nerve Endings / Q000378:metabolism* / Q000648:ultrastructure; D010870:Pineal Gland / Q000502:physiology*; D051381:Rats; D013572:Synaptic Vesicles / Q000378:metabolism* / Q000648:ultrastructure
chemical_list: D004837:Epinephrine