For the latter measure, animals of different ages were given a single injection of alpha-methyl-p-tyrosine, an inhibitor of norepinephrine biosynthesis, and the decline in transmitter levels evaluated in the ensuing 2.5 hr period.
The simultaneous occurrence and same recovery times on all transmitter levels, but with different changes in amplitude, indicates that these early/fast events were produced by localized ionization due to strong lightning with a large charge moment change located overhead, or very near the receiver.
In the same vein, it remains to be determined if maternal cocaine administration at these experimental doses is able to penetrate the placental barrier and alter fetal brain monoamine transmitter levels sufficiently to mediate these types of epigenetic alterations.
To facilitate comparison of treatment effects across regions with widely differing transmitter levels or turnovers, some results are presented as the percentage change from control values.
Overall expression and coexpression of N/E and NPY in the RVLM were, however, not different at the light microscopic level, indicating that the same neuronal population has increased transmitter levels and cotransmission in the hypertensive strain.
This process is important not only for limiting the duration of synaptic currents and preventing extrasynaptic spillover, but also for replenishing presynaptic transmitter levels (Edwards, 2007; Conti et al., 2011).
Using measures of transmitter levels in the hypothalamus of D15 and D20 pregnant rats, Glaser et al. (1992) also detected a significant decrease in NA levels and corresponding rise in MHPG/NA ratio (usually taken as an index of increased turnover).
Sjöstrand and Swedin showed that androgens have no substantial direct effect on adrenergic innervation per se, but that they do affect the transmitter levels of the male organs indirectly through changes in the number, size and relative proportion of the target cells of the adrenergic nerves, that is, the smooth muscle cells [ 41].
Transmitter levels were calculated as nanograms per region, and, because there were no treatment-related differences in brain region weights, the same effects were obtained with calculation as nanograms per gram of tissue or per milligram of protein (data not shown).
Blue line represents the total transmitter power level, P t, whereas the red line represents the power reserved for transmission to the strong user, P s, during transmission.
