Acute stress or systemic insulin injection increases flunitrazepam sensitive-GABA_A receptor density in synaptosomes of chick forebrain: Modulation by systemic epinephrine

Figures & data

Figure 1 Binding maximum of [³H]-flunitrazepam in forebrain synaptosomes from non-stressed and stressed chicks following insulin administration. Insulin (in the range 0.25–5.00 IU/kg bw) or saline was administered ip 15 min before the chicks were killed. Bars represent the means ± SEM, n = 6 per group. ^*p < 0.01 compared to corresponding treatment in the non-stressed condition. ^#p < 0.03 compared to saline in the non-stressed condition (Newman–Keuls test).

Table I.  Plasma glucose concentrations 15 min after different doses of insulin (IU/kg) in non-stressed and stressed chicks.

Insulin doses (ip) IU/kg	Non-stressed	Stressed
0.00 (saline)	266 ± 12	264 ± 17
0.25	219 ± 16	236 ± 20
0.50	259 ± 32	208 ± 16
1.25	203 ± 23	256 ± 19
2.50	210 ± 13	219 ± 15
5.00	269 ± 28	278 ± 37

Each value represents the mean ± SEM, n = 6 chicks/group.

Table II.  Effects of different concentrations of insulin on K_d values of GABA_A R in forebrain synaptosomes from non-stressed and stressed chicks.

	Kd (nM)
Insulin (IU/kg)	Non-stressed	Stressed
Saline	1.88 ± 0.17	1.58 ± 0.09
0.25	1.78 ± 0.09	1.84 ± 0.14
0.50	1.79 ± 0.09	1.72 ± 0.09
1.25	1.74 ± 0.04	1.54 ± 0.10
2.50	1.67 ± 0.04	1.89 ± 0.18
5.00	1.81 ± 0.16	1.82 ± 0.16

Each value of K_d represents the mean ± SEM of values obtained by non-linear regression of experimental data from saturation curves. n = 6 chicks/group.

Figure 2 Binding maximum of [³H]-flunitrazepam in forebrain synaptosomes from non-stressed and stressed chicks following epinephrine administration. Epinephrine (0.25 and 0.50 mg/kg bw) or saline was administered ip 15 min before chicks were killed. Bars represent the means ± SEM, n = 10–14 per group. ⁺p < 0.01 compared to corresponding treatment in the non-stressed condition. ^~ p < 0.01 compared to saline in the stressed condition. ^~ p < 0.01 compared to saline and epinephrine 0.25 mg/kg, in the stressed condition (Newman–Keuls test).

Table III.  Effects of different doses of epinephrine on K_d values of GABA_A R in forebrain synaptosomes from non-stressed and stressed chicks.

	Kd (nM)
	Non-stressed	Stressed
Saline	1.85 ± 0.25	1.79 ± 0.18
Epinephrine 0.25 (mg/kg)	1.88 ± 0.24	1.92 ± 0.31
Epinephrine 0.50 (mg/kg)	1.95 ± 0.20	1.74 ± 0.17

Each value of K_d represents the mean ± SEM of values obtained by non-linear regression of experimental data from saturation curves. n = 10–14 chicks/group.

Figure 3 Binding maximum of [³H]-flunitrazepam in forebrain synaptosomes, from non-stressed chicks, following co-administration of insulin plus epinephrine. Bars represent the means ± SEM, n = 6 per group. ^*p < 0.001 compared to saline. ⁺p < 0.05 and ^#p < 0.01 compared to insulin alone condition (Newman–Keuls test).

Table IV.  Effects of co-administration of insulin and different doses of epinephrine on K_d values of GABA_A R in forebrain synaptosomes from non-stressed chicks.

	Kd (nM)
Saline	1.80 ± 0.46
Insulin 2.5 IU/mg	1.94 ± 0.38
Insulin 2.5 IU/mg + Epinephrine 0.25 (mg/kg)	1.52 ± 0.42
Insulin 2.5 IU/mg + Epinephrine 0.25 (mg/kg)	1.78 ± 0.20

Each value of K_d represents the mean ± SEM of values obtained by non-linear regression of experimental data from saturation curves. n = 6 chicks/group.