Activation of neurons in the hypothalamic dorsomedial nucleus via hypothalamic projections of the nucleus of the solitary tract following refeeding of fasted rats

• Published in: The European journal of neuroscience 2010-01, Vol.31 (2), p.302-314
• Main Authors: Renner, Eva, Szabó-Meltzer, Kinga I., Puskás, Nela, Tóth, Zsuzsanna E., Dobolyi, Arpád, Palkovits, Miklós
• Format: Article
• Language: English
• Subjects: Animals; c-fos activation; Dorsomedial Hypothalamic Nucleus - cytology; Dorsomedial Hypothalamic Nucleus - metabolism; Eating; Fasting; Feeding Behavior - physiology; Food Additives - pharmacology; food intake; Male; Neural Pathways - anatomy & histology; Neural Pathways - physiology; Neurons - cytology; Neurons - drug effects; Neurons - metabolism; Oncogene Proteins v-fos - genetics; Oncogene Proteins v-fos - metabolism; Prolactin-Releasing Hormone - metabolism; prolactin-releasing peptide; Rats; Rats, Wistar; satiety; Sodium Glutamate - pharmacology; Solitary Nucleus - anatomy & histology; Solitary Nucleus - physiology; surgical transections
• ISSN: 0953-816X; 1460-9568
• DOI: 10.1111/j.1460-9568.2009.07053.x

We report that satiation evokes neuronal activity in the ventral subdivision of the hypothalamic dorsomedial nucleus (DMH) as indicated by increased c‐fos expression in response to refeeding in fasted rats. The absence of significant Fos activation following food presentation without consumption suggests that satiation but not craving for food elicits the activation of ventral DMH neurons. The distribution pattern of the prolactin‐releasing peptide (PrRP)‐immunoreactive (ir) network showed remarkable correlations with the distribution of activated neurons within the DMH. The PrRP‐ir fibers and terminals were immunolabeled with tyrosine hydroxylase, suggesting their origin in lower brainstem instead of local, hypothalamic PrRP cells. PrRP‐ir fibers arising from neurons of the nucleus of the solitary tract could be followed to the hypothalamus. Unilateral transections of these fibers at pontine and caudal hypothalamic levels resulted in a disappearance of the dense PrRP‐ir network in the ventral DMH while PrRP immunoreactivity was increased in transected fibers caudal to the knife cuts as well as in perikarya of the nucleus of the solitary tract ipsilateral to the transections. In accord with these changes, the number of Fos‐expressing neurons following refeeding declined in the ipsilateral but remained high in the contralateral DMH. However, the Fos response in the ventral DMH was not attenuated following chemical lesion (neonatal monosodium glutamate treatment) of the hypothalamic arcuate nucleus, another possible source of DMH inputs. These findings suggest that PrRP projections from the nucleus of the solitary tract contribute to the activation of ventral DMH neurons during refeeding, possibly by transferring information on cholecystokinin‐mediated satiation.