3.1 BLA astrocytes were activated in rats with DNP
Within 3 days following an i.p. injection of STZ, blood glucose levels
were significantly higher in the diabetic rats than in the control rats
(Fig. 1A). All STZ-treated rats exhibited polydipsia, polyuria and
polyphagia. Although food and water intake significantly increased, body
weights of the STZ-treated rats were profoundly reduced (Fig. 1B). In
addition, mechanical allodynia was consistently present in the diabetic
rats, compared with the control rats, 7 days after STZ injection,
indicating that the diabetic rats developed mechanical allodynia (Fig.
1C).
Anxiety-like behavior is a common comorbidity of chronic neuropathic
pain. Next, we assessed the effect of STZ-induced chronic pain on
anxiety-like behavior in rats. In the open field test, the total
distance of the rats in the open field and the distance in the central
area of the open field differ significantly between DNP rats and
controls (Fig. 1E-1G). In the elevated plus maze test, we observed DNP
rats significantly reduced the number of entries into the open arms and
the time spent in the open arms compared to controls (Fig. 1H-1J).
To investigate the dynamic changes in astrocytes in the BLA of the
diabetic rats that displayed tactile allodynia, BLA tissues were taken
by perfusion, and immunofluorescence histochemical staining was
performed. The distribution of astrocytes in the control, day 3 and day
7 groups was reduced, and the immunofluorescence intensity was weak.
However, 14 days after STZ injection, we observed a large number of
GFAP-labeled astrocytes in the BLA, and the intensity of
immunofluorescence was markedly enhanced, reaching a peak at 21 days and
lasting at least 28 days (Fig. 1K-1M). The significantly increased
expression of GFAP in the BLA after the development of DNP suggests a
potential role of BLA astrocytes in the pathogenesis of DNP.