Acetazolamide increases locomotion, exploratory behavior, and weight loss following social stress: A treatment for emotional eating?

Abstract

Sympathomimetics are effective, centrally acting drugs that induce weight loss through their potent anorexic and locomotor properties. We reported that sympathomimetics antagonize catecholamine-dependent, alpha-2 adrenergic receptor-dependent signal transduction mediated by chloride/bicarbonate transport. We posit that other drugs that target cellular chloride/bicarbonate antiport would similarly demonstrate anorectic properties, induce locomotion, and diminish weight gain. Male and female inbred mice were housed in groups or stressed by prolonged social isolation. Mice consumed either normal chow or a high fat, high fructose corn syrup, (i.e. "Western") diet. To inhibit chloride/bicarbonate transport, acetazolamide (ACT, 3 mM) was added to the drinking water. Rodents underwent evaluations of exploratory locomotion and learning with the object recognition test. Mice consuming a "Western" diet gain more weight compared to mice given a normal diet. When placed on a "Western" diet, stressed mice gained weight more rapidly than unstressed. The body weight of mice fed a normal diet with ACT was significantly reduced compared to control mice not given ACT (weight, g ± SEM), 23.7 ± 0.8 v. 21.0 ± 0.5, p = 0.02. ACT did not reduce weight gain in animals chronically maintained on a "Western" diet. Compared to unstressed mice, living in social isolation reduced spontaneous exploratory locomotion time, an indicator of anxiety, in male mice (sec +SEM) from 22.8 ± 3.5 to 12.2 ± 2.1 (p < 0.001), and in female mice, from 47 ± 5.7 to 19.6 ± 2.3 (p < 0.001). ACT had no effect on exploration time in unstressed mice, but ACT completely restored the diminished exploratory locomotion time found in stressed mice compared to unstressed mice. The ratio of time spent exploring new objects compared to familiar items (discrimination ratio [DR]) was reduced following social isolation in males from 2.6 ± 0.5 to 1.2 ± 0.2 (p < 0.05) and in females from 3.8 ± 0.6 to 1.5 ± 0.2 (p < 0.01). ACT normalized the DR ratio of the stressed mice. Decreased food consumption and greater locomotor activity induced by ACT may contribute to acute weight loss; this effect is diminished when rodents were maintained on an unhealthful Western diet. Inhibition of chloride/bicarbonate transport through agents such as acetazolamide could offer a safe, new approach to achieving weight loss.

Fig. 1

Total body weight and total body water in group housed mice fed a healthy, control diet or a high fat, high corn syrup “Western” diet with and without acetazolamide (ACT). (Left) Group housed, female mice fed a standard, nutritious, control rodent chow over four months gained less weight compared to animals similarly fed but who were also given acetazolamide (ACT, 3 mM) in their drinking water. The control diet mice achieved a weight of (all values expressed in grams ± SEM) 23.7 ± 0.75 compared to mice fed the standard diet with ACT, 20.95 ± 0.52. When mice were changed to a high fat, high fructose corn syrup diet, their weight increased significantly, but ACT had no effect on this chronic weight gain in group housed mice. (Right) The lower weight gains in animals fed the standard diet and given ACT was not due to the diuretic effect of this drug, as in these animals, total body water (TBW) actually increased (values expressed as percentage body water per gram body weight ± SEM) from 65.11% ± 0.77% vs 68.98% ± 0.92%.

Fig. 2

Effect of social isolation stress on weight gain, appetite, and locomotion in animals fed a high fat, high fructose corn syrup “Western” diet. (Left) When placed in the stress of social isolation and while on a high fat, high fructose corn syrup, compared to group housing, female mice gain weight at a significantly greater rate. We observed nearly a 300% greater rate in weight gain in socially isolated mice over one month when compared to group housed mice fed a high fat, high fructose corn syrup “Western” diet. (Middle) ACT decreased food consumption (all values expressed in grams ± SEM/12 h) fell from 1.64 ± 0.14 to 1.11 ± 0.09 in mice undergoing the stress of social isolation but fed a nutritious diet. (Right) In contrast, exploratory locomotion (all values expressed in meters ± SEM/12 h) increased from 104.85 ± 10.27 to 178.07 ± 16.34.

Fig. 3

Effect of social isolation stress in male and female mice on total exploratory locomotion time and time spent exploring new objects over 5 min of exposure. (Left). Compared to male mice, female mice express more spontaneous, exploratory behavior. However, social isolation stress diminished the time spent exploring new territory among both male and female mice. Stress induced by social isolation reduced the time male mice (all values expressed in seconds ± SEM) spent exploring new territory from 22.8 ± 3.5 to 12.2 ± 2.1, and among females from 47 ± 5.7 to 19.6 ± 2.3. (Right). Similarly, the time mice spent exploring new objects was decreased in male from 15.9 ± 2.7 to 6.23 ± 1.1, and in female mice from 36.7 ± 5.6 to 10.8 ± 1.2.

Fig. 4

The time spent exploring new objects correlated with the total time male and female mice spent exploring new territory. The time group housed mice, or mice stressed by social isolation, spent exploring new, “novel” objects was highly correlated with the time the mice spent exploring new “territory.” The linear correlations among these two cohorts were virtually superimposable (y = 1.1(x) + 4.2 and y = 1.2(x) + 3.4).

Fig. 5

Acetazolamide (ACT) did not increase exploratory locomotion time or the investigation of novel objects in group housed mice, but ACT increased both exploratory locomotion and novel exploration in mice subjected to the stress of social isolation. (Left) In unstressed male mice, reared in socially grouped housing, ACT had no effect on the total exploratory locomotion time, 22.8 ± 3.5 vs. ACT 20.2 ± 1.9, p = n.s., or on time spent exploring novel objects, 15.9 ± 2.7 vs. 14.0 ± 2.5. (Right) However, in male and female mice stressed by social isolation, ACT restored total exploratory locomotion time, 11.2 ± 1.4 vs. 21.9 ± 2.7, and also increased time spent exploring new objects, 5.8 ± 0.8 vs. 15.5 ± 1.9.

Fig. 6

The stress of social isolation diminished the discrimination ratio (DR) in both male and female mice. Grouped male mice spent more time exploring novel objects relative to known objects, i.e. the DR, than their counterparts stressed by social isolated (values expressed in arbitrary units ± SEM), 2.6 ± 0.5 vs. 1.2 ± 0.2. A similar decrement in DR was found among the isolated female mice, 3.8 ± 0.6 vs. 1.5 ± 0.2.

Fig. 7

Acetazolamide (ACT) increased the discrimination ratio (DR), i.e. relative time mice spent exploring new objects in new territories, only in mice stressed by social isolation. There was no difference in the DR among grouped male rodents who were not given ACT and those who had consumed ACT; the values for the DR were identical (values expressed in arbitrary units ± SEM) 2.6 ± 0.5. However, among mice stressed with social isolation, ACT normalized their DR to that of the group housed mice as seen in males, 1.2 ± 0.2 vs 2.8 ± 0.5, and females, 1.08 ± 0.18 vs 2.34 ± 0.09.