Table 1.

Pre- and postsynaptic nicotinic responses are absent in β2 knock-out mice

	Wild type		β2 knock-out
	Postsynaptic	Presynaptic	Postsynaptic	Presynaptic
VB	100%	62%	0%	0%
	(45/45)	(28/45)	(0/12)	(0/12)
DLG	96%	48%	0%	0%
	(218/226)	(106/226)	(0/16)	(0/16)
Reticularis	100%	0%	0%	0%
thalamus	(15/15)	(0/15)	(0/4)	(0/4)

Percentage of cells having a pre- or postsynaptic response in the VB, DLG, and reticularis thalamus. Numbers in parentheses correspond to (number of cells with a pre- or postsynaptic response)/(number of cells tested). The occurrence of pre- and postsynaptic response to 10 μm DMPP was tested in four knock-out mice (7, 8, 9, and 11 d old). Nicotinic responses in the medial habenula persisted in knock-out animals (Picciotto et al., 1995) and therefore were used as a control for the correct functioning of the perfusion system.