Reproductive and regulatory behaviours in the female hamster following transections of the lateral connections of the medial preoptic area-medial anterior hypothalamic continuum

Miceli, Mario (1981) Reproductive and regulatory behaviours in the female hamster following transections of the lateral connections of the medial preoptic area-medial anterior hypothalamic continuum. Masters thesis, Memorial University of Newfoundland.

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Abstract

Parasagittal knife cuts with a varied mediolateral position were placed along the medial preoptic area-medial anterior hypothalamic continuum (MPOA-MAH) in female hamsters. Near lateral (NL) knife cuts severed mediolateral connections between the MPOA-MAH and the medial forebrain bundle (MFB) while far lateral cuts (FL) were placed more laterally, sparing MPOA-MAH - MFB connections. Across the knife cut condition, hamsters were either allowed to construct and maintain a food hoard or given daily food rations. Prior to, and after surgery, animals were tested for male-soliciting ultrasonic vocalizations and maternal behaviours. Both NL and FL cuts reduced rates of ultrasonic calling. These cuts also converted into cannibals those animals which previously behaved maternally towards foster pups in preoperative virgin maternal tests. These cuts were less effective in this respect if the hamsters were allowed to hoard. These same animals were then mated and later tested for maternal behaviour with their own young. The results of the behavioural testing early in the postpartum period revealed no differences among the experimental groups in various maternal behaviours. Throughout lactation, however, the majority of NL and FL hamsters given daily food rations progressively cannibalized their entire litters. NL and FL counterparts with the hoarding opportunity, on the other hand, cannibalized fewer pups and reared healthy, moderate-sized litters that were smaller than those of appropriate surgical controls. This is the first study to demonstrate that rodents with (NL) hypothalamic cuts which ordinarily disrupt maternal behaviours, will, under appropriate testing conditions, rear litters. In view of this finding, the nature of the maternal deficit following hypothalamic cuts is discussed. That FL cuts were just as effective as NL cuts in reducing ultrasonic calling and disrupting maternal processes suggests that mediolateral connections of the MPOA-MAH, other than with the MFB, are important for these behaviours. Possible amygdalar-hypothalamic pathways mediating these behaviours are discussed. The effects of the knife cuts and hoarding condition on body weight and other regulatory behaviours are also evaluated.

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