Results
It has been shown previously that after injection of the
PITS-composition, the rat body temperature decreased by about 7.5 ˚C,
while the half-width of the temperature curve was about 16.5 h, at
ambient temperature of 22˚C to 23˚C (Fig.1). For comparison, we
investigated the effect of anesthetic xylazine, which is also able to
reduce the body temperature of animals, often in combination with
ketamine . In our experiments, xylazine initiated a decrease in the rat
body temperature by about 5.5 ˚C, at ambient temperature of 22˚C to
23˚C.The half-width of the temperature curve was about 3 hours (Fig.1).
It has been shown previously that after intravenous injection of
PITS-composition, there was a reversible decrease in metabolic rate and
body temperature. Both parameters changed almost simultaneously (Fig.
2). We used these data to compare E in a pharmacological and
natural torpid state (Fig.3). It has been found (Fig.3) that in the
pharmacological torpor lasting typically one day in rats (Rats-PITS),E = -0.56±0.03 eV which was close to the corresponding value in
daily heterotherms E = -0.57±0.04 eV. In true hibernators, this
value was significantly higher (E = -0.80±0.04 eV), while in
anesthetized animals it was significantly lower (E = -0.17±0.071
eV). In addition, in rats treated with xylazine, the small value of the
coefficient of determination (r2 = 0.12)
indicates a wide spread of the experimental points and poor quality of
the regression model. Therefore, it is necessary to evaluate in more
details how the metabolic rate depends on the temperature during
anesthesia with xylazine.
The analysis shows (Fig.4A) that in the presented experimental data
obtained on rats anesthetized with xylazine there was a time lag between
the temperature curve and the heat production curve. The question arises
whether this lag could be a reason for low E andr2 values? We have found that a significantly
better coincidence of the curves was observed when the heat production
curve shifted by Δt = 1 hour (Fig.4A). In addition, to confirm
this assumption, we performed a numerical shift of the heat production
data (Fig. 4B) and find the imaginary dependence of E on the
shift (Fig.4C). The minimal E was observed at the shift Δt= 1 hour and considered the corrected Ec=-0.67±0.11 eV, which in this experiment corresponded to two intervals
between measurements: Shift +2 (Fig.4 D). It should also be noted that
as a result of the shift, the coefficient of determinationr2 increased significantly from 0.12 (Fig.3A)
to 0.70 (Fig.4 C), which indicates an improvement in the model of
regression analysis.
Since in homeothermic animals, the change in the body temperature occurs
as a result of changes in heat production, the lag between the
temperature and the heat production is associated with a limited rate of
the body heat conductivity and heat dissipation. Therefore, it takes a
time (Δt ) to achieve a balance between the metabolic rate and the
body temperature. This nonequilibrium situation could be the reason of
an incorrect estimation of E . The correctedEc = -0.68±0.17 eV obtained at the imaginary
numerical Shift+2 (Fig.3) is significantly (p < 0.0001) larger
than that, obtained (Fig.3), in daily heterotherms (E = -0.57±0.04
eV) and in artificial hibernation, lasting for a day (E =
-0.56±0.03 eV), but smaller than that in true hibernators (E =
-0.8 eV), hypothermia of which lasts for weeks and even months.
The influence of the imaginary shift on the E was studied on rats
after injection of the PITS-composition (Fig. 5). In this case, the
minimal E was obtained without any shift (Shift 0), which
indicated the state of equilibrium between heat production and heat
dissipation during pharmacological torpor, which was significantly
longer than that in anesthesia.