Flank-marking behavior and the neural distribution of vasopressin innervation in golden hamsters with suprachiasmatic lesions

In golden hamsters, microinjections of arginine-vasopressin (AVP) within th e anterior hypothalamus trigger a stereotyped scent-marking behavior, flank marking. Our experiment was carried out to test the contribution of AVP ne urons within the suprachiasmatic nucleus (SCN) in the control of this behav ior. Our results suggest that the SCN does not contribute to flank-marking behavior. Whereas SCN lesions disrupted circadian rhythms of wheel running, the same lesions did not disrupt flank-marking. The results also suggest t hat neurons located outside the SCN contribute significantly to the vasopre ssinergic innervation of the brain and the expression of AVP-dependent beha viors, such as flank-marking behavior. Although AVP-immunoreactive fibers w ere severely (ca. 95%) depleted from several forebrain areas in SCN-lesione d hamsters, the effect of the lesions was much more limited within the fore brain areas involved in flank-marking behavior as well as within the midbra in and hindbrain.