Unix timestamp , unix timestamp with microseconds ?

I read the documentation well (PG 7.3.3 ) , it seems that there is not a native support for data type UNIX TIMESTAMP and "unix timestamp expressed as microseconds"

ie there it is impossible to direct insert and select

seconds_from _Epoch
seconds_from _Epoch (period) microseconds_part
seconds_from _Epoch(no period here)microseconds_part

without some data conversion ?

Thanx for help