The effect of dorsomedial hypothalamic lesions (DMNL) on brain norepinephrine (NE) and dopamine (DA) and the consumatory responses to phenformin
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DMNL rats are hypophagic and hypodipsic compared to shams (S) and show regulatory deficits in glucose monitoring (Bellinger et al AJP 235 R 168.1978). We first investigated the effects of DMNL on hypothalamic (HYP) and forebrain (FB) NE and DA levels. Secondly we investigated the effect of phenformin, a drug that produces anorexia possibly through changes in brain catecholamines or glucose utilization on DMNL rats. Exp 1, rats were DMNL or S operated, at sacrifice the body weight (BW) and nasoanal length (NAL) of the DMNL was less (P<0.001) than S (262.213.8g vs 344.210.1g; 214.82.2 mm vs 2361.Omm). FB NE, DA and HYP DA did not differ, however HYP NE was less (P<0.02) in DMNL (n=6, 1.09+0.8g/g vs n=7, 1.380.7 g/g. Exp 2, rats were DMNL (n=7) or S (n=8) operated. All the rats were fed for 6 hr/day beginning at the start of the dark period. In a counter balance design the rats were injected 30 min. before feeding with saline or 10 or 15mg/kg of Phenformin and then FI and WI were recorded hourly for 6 hrs. Both the 10 and 15mg/kg dose depressed FI and WI during the first hr and all subsequent hours (P<0.01), but WI was normal compared to saline controls by the sixth hr. The percentage depression of FI and WI were similar in DMNL and S. At sacrifice the BW and NAL of DMNL were less (P<0.01) than S (320.27.6 vs 414.07.1g; 223.91.6mm vs 238.42.3mm P<0.01).