TABLE 1.

Mean ± standard error of the mean density (spines/10 μm) of stubby and branched spines on first-order to fourth-order branches of BLA pyramidal neurons in the left and right hemispheres of unstressed rats vs. stressed rats that have either undergone fear conditioning and extinction (behavioral testing) or have not undergone fear conditioning and extinction (non-tested)

	Left				Right
	Non-tested		Behavioral testing		Non-tested		Behavioral testing
	Unstressed	Stressed	Unstressed	Stressed	Unstressed	Stressed	Unstressed	Stressed
Stubby
1st	0.81 ± 0.25	1.24 ± 0.31	0.54 ± 0.22	0.30 ± 0.13*	0.75 ± 0.27	1.39 ± 0.27	1.41 ± 0.32	0.66 ± 0.16*,†
2nd	0.36 ± 0.17	0.48 ±0.11	0.40 ± 0.09	0.82 ± 0.15†	0.32 ± 0.05	0.61 ± 0.24	0.44 ± 0.08	0.65 ± 0.13
3rd	0.31 ± 0.10	0.22 ± 0.04	0.49 ±0.12	0.71 ± 0.07*	0.39 ± 0.15	0.41 ± 0.08	0.58 ± 0.12	0.62 ± 0.08
4th	0.21 ± 0.03	0.22 ± 0.10	0.52 ± 0.10‡	0.61 ± 0.11*	0.26 ± 0.04	0.22 ± 0.03	0.53 ± 0.08‡	0.61 ± 0.01*
Branched
1st	0.13 ± 0.08	0.02 ± 0.02	0.01 ± 0.01	0.03 ± 0.02	0.12 ± 0.05	0.02 ± 0.02	0.00 ± 0.00‡	0.02 ± 0.02
2nd	0.15 ± 0.05	0.17 ± 0.02	0.05 ± 0.03	0.12 ± 0.06	0.12 ± 0.02	0.13 ± 0.05	0.02 ± 0.02‡	0.09 ± 0.04
3rd	0.34 ± 0.10	0.18 ± 0.04	0.17 ± 0.13	0.14 ± 0.07	0.32 ± 0.08	0.41 ± 0.12	0.04 ± 0.03‡	0.19 ± 0.09
4th	0.36 ± 0.06	0.35 ± 0.06	0.13 ± 0.09	0.20 ± 0.09	0.39 ± 0.05	0.52 ± 0.13	0.14 ± 0.09	0.21 ± 0.10

BLA, basolateral amygdala.

^*P < 0.05 relative to stressed rats that have not undergone fear conditioning and extinction.

^†P < 0.05 relative to unstressed rats that have undergone fear conditioning and extinction.

^‡P < 0.05 relative to unstressed rats that have not undergone fear conditioning and extinction. All comparisons are within a particular hemisphere.