Testosterone removal in rats results in a decrease in social aggression and a loss of social dominance.

Alpha male rats from mixed sex colony groups were tested for aggressiveness toward nonaggressive male intruders. Afterward, they were castrated and implanted with testosterone filled Silastic tubes, castrated and implanted with empty tubes, or sham castrated and implanted with empty tubes. There were significant declines in the aggressiveness (lateral attacks, bites, and piloerection but not on-top) of castrated rats without testosterone replacement but not in castrated rats with testosterone replacement. At a second operation, castrated animals had their testosterone capsules removed or had their empty capsules replaced with testosterone filled capsules. When tested for aggression toward nonaggressive intruders, those alpha males which had testosterone removed declined in aggressiveness while those which had it implanted returned to a level of aggressiveness close to that emitted by sham castrated control animals. Subordinate males became dominant when alpha males were castrated and not given testosterone replacement. In a final series of observations, sham castrated males were found to be more aggressive than castrated males when pitted against one another. It is argued that testosterone plays a primary role in intermale social aggression and that the decline in aggressiveness following castration is typically accompanied by a loss of social dominance.

An easily constructed durable chronic intracerebral cannula system.

A simple, inexpensive, and rugged intracerebral cannula system is described and construction details are provided for both guide and injection cannula assemblies. The guide cannula assembly is easily and quickly molded from dental acrylic cement and has a protective acrylic collar surrounding the end of the actual guide cannula. This system is believed to offer some advantage over current methodologies in terms of expense, durability and ease of construction and is well suited to use in rodents.

A convenient and inexpensive method for chronically implanting multiple intracranial cannulae.

A simple and inexpensive method is described for the chronic implantation of multiple cannulae in small animals. This method employs a simple die cast from dental acrylic cement which is then repeatedly used to retain the cannulae during implantation. No special workshop tools are required and assembly is rapid.