Disinhibition of maternal behavior following neurotoxic lesions of the hypothalamus in primigravid rats

• Published in: Brain research 2004-10, Vol.1025 (1), p.51-58
• Main Authors: Mann, Phyllis E., Babb, Jessica A.
• Format: Article
• Language: English
• Subjects: Anatomical correlates of behavior; Animals; Behavioral psychophysiology; Biological and medical sciences; Dorsomedial Hypothalamic Nucleus - drug effects; Dorsomedial Hypothalamic Nucleus - physiology; Dorsomedial nucleus of the hypothalamus; Female; Fundamental and applied biological sciences. Psychology; Gravidity - drug effects; Gravidity - physiology; Hypothalamus - drug effects; Hypothalamus - physiology; Maternal Behavior - drug effects; Maternal Behavior - physiology; N-Methylaspartate - toxicity; Nerve Net - drug effects; Nerve Net - physiology; Neurotoxin; NMDA; Pregnancy; Psychology. Psychoanalysis. Psychiatry; Psychology. Psychophysiology; Rats; Rats, Sprague-Dawley; Ventromedial Hypothalamic Nucleus - drug effects; Ventromedial Hypothalamic Nucleus - physiology; Ventromedial nucleus of the hypothalamus
• ISSN: 0006-8993; 1872-6240
• DOI: 10.1016/j.brainres.2004.07.064

Virgin female rats do not respond maternally to foster pups due to an endogenous neural circuit that actively inhibits the display of maternal behavior. Once pregnant, primigravid rats will continue to avoid foster pups until just prior to or at parturition. Anosmia or lesions of the olfactory tract, medial amygdala, and areas of the hypothalamus will stimulate virgin females to display maternal behavior rapidly, but little is known of the effect of these lesions in primigravid rats. The objective of the present study was to determine if neurotoxic lesions of the dorsomedial (DMH) and ventromedial nuclei (VMH) of the hypothalamus will advance the onset of maternal behavior in primigravid rats. Nulliparous Sprague–Dawley female rats were mated and then on day 8 of gestation bilaterally infused with N-methyl- d-aspartic acid (NMDA; 8 μg/0.2 μl/side) or vehicle directed toward either the DMH or VMH. Beginning on day 15 of gestation until parturition, females were tested daily for maternal responsiveness. DMH and VMH lesions significantly advanced the onset of maternal behavior (5–6 days vs. 0–1 day before parturition) in first-time pregnant rats. These results indicate that the DMH and VMH are involved in the regulation of maternal behavior and may be part of an endogenous neural circuit that inhibits maternal behavior during pregnancy.