Alterations in regulatory behaviors induced by medial septal lesions and superior cervical ganglionectomy

Abstract

Following medial septal (MS) lesions peripheral sympathetic fibers, orginating from the superior cervical ganglia (SCG), grow into the hippocampus and habenula. To assess their effect on regulatory behaviors, body weight, and food and water consumption were studied under ad libitum and pharmacological stress conditions, after MS lesions, superior cervical ganglionectomy (Gx) or MS lesion + ganglionectomy (MSGx). Twenty-two animals completed the study: control ( n = 7), MS lesion ( n = 6), Gx ( n = 6), MSGx ( n = 4). No differences were observed preoperatively. Postoperatively, body weight fell but over time all groups gained weight. However, animals with MSGx were lighter than MS or Gx animals (which were equivalent), which in turn were lighter than controls ( P < 0.0001). Hypophagia was observed in the Gx and MSGx animals when compared to the MS and control groups ( P < 0.05), while hyperdipsia was seen in the MS and Gx groups ( P < 0.001). Administration of both 1 M NaCl and isoproterenol (25 μg/kg) increased drinking in all animals ( P < 0.001), with the MSGx group consuming significantly less than all others ( P < 0.025). Food intake increased following 2-deoxy- d-glucose (500 mg/kg) ( P < 0.0001), while epineprine (120 μg/kg) treatment produced anorexia only in the MS group ( P < 0.05). Hyperthermia was found in the Gx and MSGx groups. The results of this study suggest that both MS region and SCG contribute to the maintenance of normal regulatory behaviors, with combined loss of these neural systems resulting in severe disturbances, both qualitatively and quantitatively different from either MS lesion or Gx. Although the MS lesion group clearly regulated better than the MSGx group, it is unclear whether this is due to ingrowth or just the presence of the SCG.