Sagittal knife cuts in the near and far lateral preoptic area-hypothalamus reduce ultrasonic vocalizations in female hamsters.

Although it has been reported that lesions of the medial preoptic area reduce ultrasonic vocalizations in female hamsters, the neural connections of this area important for ultrasound production have not been investigated. We, therefore, tested vocalizations in female hamsters following sagittal cuts along the medial preoptic area-medial anterior hypothalamic continuum (MPOA-MAH) at either the medial (Near Lateral or NL cuts) or lateral (Far Lateral or FL cuts) border of the medial forebrain bundle (MFB). Bilateral NL and FL cuts did not affect spontaneously occurring vocalizations or vocalizations occurring during contact with males, but were equally effective in substantially blocking increases in vocalizations following exposure to males. Another group of animals with a unilateral NL cut and a contralateral FL cut showed a vocalization deficit comparable to that in NL and FL groups, suggesting that NL and FL cuts severed a common pathway important for ultrasonic calling. These results indicate that the lateral connections of the MPOA-MAH are critical for ultrasonic vocalizations. Alternatively, a ventral pathway from the medial amygdala to the bed nucleus of the stria terminalis, one which crosses the plane of both NL and FL cuts, is discussed in relation to the deficits observed.