Rodent spermatozoa as well as other mammalian spermatozoa exhibit sequential changes in their motility characteristics during passage through the male reproductive tract and during capacitation in the female reproductive tract [Gaddum, 1968;Yanagimachi, 1970; Mohri and Yanagimachi, 19801. They seem to be suitable for analyzing the regulatory mechanism of flagellar movement, provided that the motor apparatus itself, the tubulin-dynein system and related structures, does not change significantly during maturation and capacitation process. In addition, rodent spermatozoa possess sickleshaped heads that allow us easily to determine direction of flagellar bending under the light microscope. The principal bend occurs in the direction in which the tip of the sickleshaped head points. Using a morphological marker, the posterior lobe of the sperm head, it has been revealed that the convex edge of the principal bend contains outer doublet No. 1, whereas the convex edge of the reverse bend contains outer doublets Nos. 5 and 6 [Woolley, 19771 (Fig. 1). These facts together with other experimental data would give us useful information about the fundamental mechanism of flagellar movement.
So far, reactivation by ATP of demembranated mammalian spermatozoa has been reported in golden hamster, bull, guinea pig, and human spermatozoa [