Table 1

Regional distribution of specific mouse brain 125I-α-CtxMII binding in the presence and absence of 20 nM cytisine.

Total 125I-α-CtxMII Binding125I-α-CtxMII Binding with Cytisine (20 nM)% Cytisine-Resistant (of total)
fmol/mg wet wt.
Telencephalon
 Neocortex
  Olfactory tubercles0.58  ± 0.050.11  ± 0.0318.9
 Basal ganglia
  Nucleus accumbens, core1.44  ± 0.070.66  ± 0.0645.8
  Nucleus accumbens, shell0.86  ± 0.040.39  ± 0.0345.3
  Striatum0.81  ± 0.020.38  ± 0.0746.9
  Substantia nigra0.75  ± 0.190.39  ± 0.1352.0
  Ventral tegmental area1.29  ± 0.060.96  ± 0.1174.4
 Septum
  Lambdoid septal zone0.82  ± 0.130.34  ± 0.0841.5
Diencephalon
 Metathalamus
  Dorsolateral geniculate nucleus5.00  ± 0.202.55  ± 0.2651.0
  Olivary pretectal nucleus5.97  ± 0.123.20  ± 0.3953.6
  Ventrolateral geniculate nucleus5.84  ± 0.183.31  ± 0.2956.7
 Epi- and subthalamus
  Lateral habenula0.83  ± 0.110.43  ± 0.0351.8
  Medial habenula1.11  ± 0.050.68  ± 0.0761.3
Mesencephalon
 Interpeduncular nucleus1.38  ± 0.041.05  ± 0.0376.1
 Superior colliculus, optic nerve layer1.21  ± 0.030.65  ± 0.0353.7
 Superior colliculus, superficial grey4.13  ± 0.012.23  ± 0.1054.0
 Superior colliculus, zonal layer5.33  ± 0.103.47  ± 0.0665.1
Pons
 Medial vestibular nucleus0.50  ± 0.040.15  ± 0.0230.0
 Prepositus hypoglossal nucleus0.56  ± 0.050.39  ± 0.0669.6
Fiber Tracts
 Anterior commissure, anterior0.26  ± 0.070.03  ± 0.0311.5
 Fasciculus retroflexus0.80  ± 0.150.58  ± 0.0772.5
 Oculomotor nerve (or root)4.71  ± 0.563.52  ± 0.2574.7
 Optic tract/brachium superior colliculus2.66  ± 0.151.66  ± 0.1962.4
 Supraoptic decussation2.48  ± 0.041.44  ± 0.1558.1

Mouse brain sections (14 μm) were incubated in the presence of125I-α-CtxMII (0.5 nM) with or without 20 nM cytisine. Binding of 125I-α-CtxMII was detected by exposing βmax film to the sections, followed by digital densitometry of the autoradiographic images. Amounts of ligand bound were calculated by reference to 125I-containing tissue paste standards. Because levels of 125I-α-CtxMII nonspecific binding varied noticeably between brain regions, nonspecific binding was determined in each region, and was used to calculate specific binding (presented in terms of femtomoles of 125I-α-CtxMII bound per milligram of tissue weight). Measurements were made six times in each region, in each mouse, where possible. Values are the mean ± S.E. of binding measured in three different mice.