Central catecholamine metabolism and hypothalamic self-stimulation behaviour in two inbred strains of mice

These experiments were conducted in order to better understand the role of catecholaminergic neurons in intracranial self-stimulation behaviour (ICSS) elicited from the lateral hypothalamus (LH). Two strains of mice which differ in their ICSS rate and their thresholds were studied. In a first time, we compared the catecholamine (CA) content and activity in various parts of the brain including cell bodies and nerve terminals of the man CA bundle. We used for this determination a high performance liquid chromatographic separation and an electrochemical detection. We observed that the BALB/c strain is distinguished by a higher CA activity than the DBA/2 strain. This correlates with a higher ICSS response rate in the BALB/c strain. The effects of stimulation on CA metabolism were then investigated, the electrodes being implanted specifically either in the dorsal or the ventral part of the LH and the biochemical data obtained analysed separately. Significant enhances of CA turn-over (TO) were noted in nerve terminals as hippocampus, cortex and accumbens. These results provide further evidence for the involvement of dorsal noradrenergic bundle and mesolimbic dopaminergic bundle in LH ICSS. Stimulation in the dorsal part of the LH produced the higher ICSS rate and seemed to induce a large variation of the CA TO. We noted also that the CA metabolism was always more altered in the DBA/2 than in the BALB/c strain, which is surprising in regard to the behaviour and remains unclearly explained.