The role of the extraocular muscles in the rabbit nictitating membrane response: a re-examination.

Berthier and Moore showed that the rabbit nictitating membrane (NM) response principally results from contracting the retractor bulbi muscle which pulls the globe into the socket thereby passively effecting NM extension. They concluded that the remaining extraocular muscles can effect NM extension if the retractor bulbi is denervated. A re-examination of the role of the recti and oblique extraocular muscles in nictitating membrane extension was undertaken in the light of recent results of Marek et al., suggesting that the facial nerve, and not the extraocular muscles, participates in extension of the NM. In contrast to Marek et al., the present results indicated that section of the extraocular muscles was necessary to abolish eyeshock or tactilly elicited NM extension when the abducens and facial nerves were severed. It is therefore likely that extraocular (recti and oblique) muscles participate in globe retraction and NM extension, as originally noted by Lorente de No.