Table 1.

Connexin expression in identified neurons

Connexin	Bipolar interneurons		Fusiform interneurons		Stellate cells		Basket cells
	Common primers	Specific primers	Common primers	Specific primers	Common primers	Specific primers	Common primers	Specific primers
Cx36	ND	13/28	ND	20/42	ND	7/28	ND	8/21
Cx26	7/24	0/21	0/23	0/17	0/23	1/20	0/23	6/21
Cx32	5/24	4/24	0/23	0/17	0/23	0/20	0/23	0/21
Cx33	4/24	ND	0/23	ND	0/23	ND	0/23	ND
Cx43	5/24	0/19	3/23	0/21	0/23	ND	0/23	ND

In the visual cortex layer, two-thirds of the bipolar interneurons Cx36 could be amplified in 13 of 28 cells. After amplificaition with generic Cx primers, Cx26, Cx32, Cx33, and Cx43 were detected in the compound PCR product. Of these, only Cx32 (4 of 24 cells) but not Cx26 and Cx43 could be amplified with intron-spanning subunit-specific primers. Cx33-specific primers were not used, because previous work had indicated that this Cx is not expressed in the brain. These results indicate that amplification of Cx26, Cx33, and Cx43 with common primers was from genomic DNA. In somatosensory cortex layer four, an RT-PCR product with Cx36-specific primers was obtained in 20 of 42 fusiform interneurons and in 7 of 28 stellate cells. For the fusiform interneurons, the amplification of Cx43 with common primers was deduced to be of genomic origin, because none of 21 fusiform interneurons showed Cx43 expression when intron-spanning specific Cx primers were used. In basket cells of the hippocampus, Cx36 was detected in 8 of 21 neurons, and Cx26 was found in 6 of 21 neurons. ND, not determined.