Recovery of spatial alternation deficits following selective hippocampal destruction with kainic acid

Elimination of hippocampal CA3 and CA4 pyramidal cells with kainic acid (KA) induces a performance deficit on a forced-choice alternation task, which recovers over time. In order to determine whether superior cervical ganglion (SCG) fibers sprouting into the hippocampus contribute to behavioral recovery, 31 Sprague-Dawley rats were first trained on a forced-choice task. After reaching criterion performance levels, animals received either KA or saline injections into the hippocampus and were again tested on the forced-choice task. Half of the rats had their SCG removed 35 days after injections, and all were again tested on the forced-choice task. Analysis of variance showed animals receiving KA took significantly longer to reach criterion following injections. Removal of the SCG after recovery reintroduced the performance deficit of KA-treated rats on the alternation task; no other group showed any effect for SCG removal. Results are interpreted as indicating that the SCG may have a modulatory effect in behavioral recovery, although other mechanisms may also be operating.