Table 2. ¹³C Enrichment of cerebral amino acids from [U-¹³C₆]glucose and [2-¹³C]acetate in different brain regions.

Brain Regions	Treatment Groups	13C Enrichment (%)
		Glu4	GABA2	Gln4	Glu3	GABA3	Glu3/Glu4	GABA3/GABA2
Cortex	Control (n = 6)	29.8±1.2	17.5±0.5	23.5±1.5	10.6±0.8	9.0±0.5	0.35±0.01	0.51±0.02
	Nic (0.5 mg, n = 6)	31.0±1.0	20.7±0.7**	24.2±1.5	13.1±0.5	11.0±0.5	0.42±0.01**	0.53±0.01
	Nic (2.0 mg, n = 6)	34.8±1.0**	22.1±0.6**	27.7±1.6	14.9±0.7**	12.2±0.5**	0.43±0.01**	0.55±0.02
Subcortex	Control (n = 6)	30.5±1.3	16.6±0.8	27.2±1.3	10.8±0.8	8.0±0.5	0.35±0.01	0.48±0.01
	Nic (0.5 mg, n = 6)	31.5±0.9	18.5±0.4	26.6±1.7	13.3±0.4*	9.5±0.2*	0.42±0.01**	0.51±0.01
	Nic (2.0 mg, n = 6)	35.8±1.2*	20.5±0.8**	33.2±1.8*	15.4±0.5**	10.8±0.5**	0.43±0.01**	0.53±0.01*
Cerebellum	Control (n = 6)	27.3±1.1	20.9±1.1	22.7±1.5	9.2±0.7	10.3±1.0	0.34±0.01	0.49±0.02
	Nic (0.5 mg, n = 6)	29.4±1.0	24.3±0.8*	23.1±1.3	12.0±0.5*	14.2±0.9*	0.41±0.01**	0.58±0.02*
	Nic (2.0 mg, n = 6)	32.5±1.0**	26.5±1.2**	28.0±1.3*	12.8±0.6**	15.1±0.7**	0.39±0.01**	0.57±0.01**
Olfactory Bulb	Control (n = 6)	36.6±1.5	13.9±0.5	28.7±1.8	14.9±1.0	6.5±0.4	0.41±0.02	0.46±0.01
	Nic (0.5 mg, n = 6)	36.1±1.9	14.8±0.5	26.9±1.9	16.3±0.8	8.4±0.4*	0.45±0.01*	0.54±0.02**
	Nic (2.0 mg, n = 6)	42.0±3.1	17.5±0.8**	34.4±2.1	19.7±1.4*	9.1±0.5**	0.47±0.01**	0.52±0.01**

Percent ¹³C enrichment was measured in brain tissue extract using ¹H-[¹³C]-NMR spectroscopy. Values represent mean±SEM.

^* p<0.05,

^** p<0.01 indicate significance of differences when compared to respective control.