Table 3

Regional distribution of specific [³H]epibatidine binding [total, + cytisine (100 nM), and + cytisine (100 nM) + α-CtxMII (50 nM)]

	Total [³H]Epibatidine Binding	[³H]Epibatidine Binding with Cytisine (100 nM)	% Total Binding in Presence of Cytisine	[³H]Epibatidine Binding with Cytisine (100 nM) + α-CtxMII-(50 nM)	% Total Binding in Presence of Cytisine + α-CtxMII	α-CtxMII (50 nM) Sensitive [³H]Epibatidine Binding	% α-CtxMII-Resistant (of Cytisine-Resistant)
	fmol/mg protein wet wt.		fmol/mg protein wet wt.		fmol/mg protein wet wt.
Telencephalon
Neocortex
Cingulate cortex	18.4 ± 1.8	N.D.	None	N.D.	N/A	None	N/A
Frontal cortex	16.0 ± 1.6	0.2 ± 0.1	1.0	N.D.	0None	0.2 ± 0.1	100
Olfactory tubercles	13.7 ± 0.8	2.7 ± 0.3	19.7	0.5 ± 0.3	18.5	2.2 ± 0.01	81.5
Olfactory bulbs
Accessory olfactory bulbs, glomerular layer	82.2 ± 8.7	66.7 ± 2.7	81.1	48.6 ± 1.7	72.8	18.1 ± 2.5	27.2
Accessory olfactory bulbs, mitral cell layer	37.6 ± 2.7	30.1 ± 0.9	80.0	21.5 ± 1.8	71.6	8.5 ± 1.3	28.4
Olfactory bulbs, glomerular layer	5.7 ± 0.5	2.2 ± 0.4	38.8	2.0 ± 0.3	88.9	0.2 ± 0.1	11.1
Olfactory bulbs, internal plexiform layer	6.6 ± 0.5	2.1 ± 0.3	31.3	1.8 ± 0.3	85.1	0.3 ± 0.1	14.9
Basal ganglia
Nucleus accumbens, core	15.7 ± 0.8	2.3 ± 0.3	14.4	0.6 ± 0.3	25.9	1.7 ± 0.1	74.1
Nucleus accumbens, shell	13.4 ± 0.5	1.4 ± 0.4	10.7	0.4 ± 0.2	26.8	1.0 ± 0.2	73.2
Striatum	17.2 ± 0.7	1.4 ± 0.3	8.0	0.4 ± 0.2	30.0	1.0 ± 0.1	70.0
Substantia nigra	29.8 ± 1.7	3.3 ± 0.1	10.9	1.8 ± 0.9	56.3	1.4 ± 0.9	43.8
Ventral tegmental area	32.3 ± 2.3	3.5 ± 0.4	10.9	1.1 ± 0.5	33.1	2.3 ± 0.9	66.9
Septum
Lambdoid septal zone	12.7 ± 0.3	1.2 ± 0.2	9.1	0.2 ± 0.1	18.7	0.8 ± 0.2	81.3
Hippocampus
Dentate gyrus	14.1 ± 0.8	N.D.	None	N.D.	N/A	None	N/A
Subiculum	43.5 ± 1.3	0.7 ± 0.3	1.6	N.D.	None	0.7 ± 0.3	100
Diencephalon
Thalamus
Anteroventral thalamic nucleus	71.7 ± 4.0	4.5 ± 0.4	6.3	3.7 ± 0.1	82.5	0.8 ± 0.5	17.5
Metathalamus
Dorsolateral geniculate nucleus	69.4 ± 6.1	13.3 ± 0.6	19.3	3.1 ± 0.3	23.6	10.2 ± 0.6	76.4
Medial geniculate nucleus	39.3 ± 2.2	6.6 ± 0.8	16.7	3.5 ± 0.7	53.9	3.1 ± 0.5	46.1
Olivary pretectal nucleus	79.0 ± 6.1	21.0 ± 1.1	26.6	3.4 ± 0.2	16.2	17.6 ± 0.9	83.8
Ventrolateral geniculate nucleus	59.4 ± 5.1	15.5 ± 0.3	26.0	3.1 ± 0.2	20.2	12.3 ± 0.5	79.8
Epi- and subthalamus
Lateral habenula	69.6 ± 7.0	41.8 ± 5.4	60.0	31.9 ± 1.7	76.4	9.9 ± 3.8	23.6
Medial habenula	380.2 ± 14.5	251.5 ± 20.7	66.1	214.3 ± 4.0	85.2	37.2 ± 16.9	14.8
Mesencephalon
Inferior colliculus, dorsal cortex	28.3 ± 0.1	10.8 ± 1.0	38.3	7.6 ± 0.6	70.5	3.2 ± 0.6	29.5
Interpeduncular nucleus	308.1 ± 8.9	185.1 ± 15.2	60.1	139.9 ± 4.9	75.6	45.2 ± 10.3	24.4
Superior colliculus, optic nerve layer	28.4 ± 1.0	3.1 ± 0.42	10.9	1.4 ± 0.3	44.6	1.7 ± 0.4	55.4
Superior colliculus, superficial grey	49.1 ± 1.9	16.3 ± 2.0	33.2	3.9 ± 0.5	24.2	12.3 ± 2.2	75.8
Superior colliculus, zonal layer	70.9 ± 2.6	33.8 ± 1.9	47.7	7.4 ± 0.3	22.0	26.4 ± 2.0	78.0
Pons
Medial vestibular nucleus	23.1 ± 1.3	7.4 ± 0.6	31.9	5.1 ± 0.8	68.8	2.3 ± 0.2	31.2
Prepositus hypoglossal nucleus	25.2 ± 1.7	8.2 ± 1.0	32.5	6.3 ± 0.8	76.8	1.9 ± 0.4	23.2
Pontine nuclei	22.3 ± 2.1	N.D.	None	N.D.	N/A	None	N/A
Reticular nuclei	8.1 ± 0.3	0.3 ± 0.2	3.7	N.D.	None	0.3 ± 0.2	100
Fiber tracts
Anterior commissure, anterior	2.7 ± 0.6	N.D.	None	N.D.	N/A	None	N/A
Corpus callosum	2.4 ± 0.2	N.D.	None	N.D.	N/A	None	N/A
Fasciculus retroflexus	98.6 ± 7.7	64.8 ± 4.3	65.7	48.4 ± 7.0	74.7	16.4 ± 10.2	25.3
Oculomotor nerve (or root)	74.6 ± 6.4	43.4 ± 4.4	58.2	6.6 ± 0.5	15.2	36.8 ± 4.0	84.8
Optic tract/brachium superior colliculus	15.7 ± 1.2	4.8 ± 0.5	30.6	1.0 ± 0.4	21.8	3.7 ± 0.4	78.2
Supraoptic decussation	17.5 ± 1.9	5.5 ± 0.5	31.3	0.8 ± 0.2	14.7	4.7 ± 0.3	85.3

Sections (14 μm) were incubated in the presence of 500 pM [³H]epibatidine (total [³H]epibatidine), 500 pM [³H]epibatidine + 100 nM cytisine or 500 pM [³H]epibatidine + 100 nM cytisine + 50 nM α-CtxMII. Binding of [³H]epibatidine was detected by exposing βmax ³H-sensitive film to the sections, followed by digital densitometry of the resultant autoradiograms. Specific binding was calculated by reference to ³H-containing tissue paste standards, and is presented in terms of femtomoles of [³H]epibatidine bound per milligram of tissue weight. The amount of α-CtxMII-sensitive [³H]epibatidine binding in each region was calculated as the difference between the [³H]epibatidine binding in the presence of cytisine (100 nM) alone and that with both cytisine (100 nM) and α-CtxMII (50 nM) present. Six individual measurements were made from each region, under each condition in each mouse where possible. Each value represents the mean ± S.E. of binding measured in three different mice.

N.D., not detectable; N/A, not applicable.