Rewarding affective properties of intra-nucleus accumbens injections of testosterone.
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On alternating days, adult male Long-Evans rats implanted with bilateral cannulas in the nucleus accumbens received intracerebral injections of testosterone in a water-soluble cyclodextrin inclusion complex (0.125, 0.25, or 0.5 microg/0.5 microl saline) or saline immediately prior to being confined for 30 min to 1 of 2 compartments of a place-preference apparatus. All rats received 8 days of pairings (4 hormone and 4 saline). On Day 9 the rats were given a 20-min test session during which they had access to all compartments of the apparatus. No hormone was injected prior to the test session. On the test day, rats spent significantly more time in the compartment previously paired with bilateral intra-accumbens injections of testosterone (0.25 and 0.5 microg/0.5 microl saline) than in the compartment previously paired with saline injections. The findings indicate that intra-accumbens injections of testosterone are sufficient to produce reward.