Nembutal treatment of the VMH (rat): effects on feeding and sexual behaviour.

In male rats two brain cannulae were implanted bilaterally and directed to an area just dorsal of the ventromedial hypothalamic nucleus. The behaviour of these animals was observed before and after the injection through these cannulae of either 1 micronl saline or 1 micronl Nembutal. Injections were performed under three behavioural conditions: (1) animal alone in cage with food, (2) animal in the presence of an oestrous female and (3) animal in cage with food and oestrous female. Following the Nembutal injection, sniffing and feeding are disinhibited temporarily in condition 1, whereas in condition 3 only sniffing, but not feeding, is disinhibited. In conditions 2 and 3 male sexual behaviour is not influenced by the Nembutal except for an increase of sniffing at the female. It is concluded that a temporary elimination of the VMH leads to a disinhibition of feeding only if the external conditions are favourable for feeding. The same elimination of the VMH does not influence the occurrence of male sexual behaviour under the conditions used in these experiments.