Copulation-illness associations in male rats: lithium chloride dose and delay manipulations

Male rats that receive an injection of lithium chloride (LiCl) after each pairing with an estrous female gradually decrease their copulatory behaviors. In the present experiments we demonstrated that a 6.0 mEq/kg (0.3 M, 20 ml/kg) dose of LiCl injected after trials spaced twice weekly at 3-4-day intervals induced more rapid acquisition of copulation-illness associations than a 3.0 mEq/kg (0.15 M, 20 ml/kg) dose. Contingent 0.3 M saline or noncontingent 0.3 M LiCl injections did not affect copulatory behaviors. The location of the male rat (home cage or test chamber) during a portion of the aversive state induced by LiCl did not influence rate of acquisition. Copulation-illness associations, once established, were retained over a 60-day interval. Comparable decrements in copulatory behaviors were evident when LiCl was injected at 1-, 5-, or 15-min intervals after pairings with estrous females when the males were detained in the test chambers during the delay intervals; decrements were not observed when the interval was increased to 30 or 60 min. An electric shock analog to the aversive state induced by LiCl did not induce decrements in copulatory behaviors. It was suggested that odor-illness associations may, in part, account for the decrements in copulatory behaviors in this paradigm.