An appraisal of some lesioning methods applied to the posterior hypothalamus in rats

The behavioral changes and histological damage to the brain of rats were examined following lesions of the midlateral posterior hypothalamic area (MLPHA) made by passing electrical current through a metal electrode or through a glass pipette containing hydrogen ion (HCl) or kainic acid. Control experiments included placement of pipettes containing saline and imposing the same current as used in kainic-acid-containing electrodes (sham). Subcutaneous injections of kainic acid assessed damage that may be attributed to general neuronal cytotoxicity or limbic seizures. The effect of diazepam on alleviating behavioral changes and structural damage in kainic-acid-injected rats was examined. The current used to inject kainic acid produced significant damage to both neurons and axons of passage at the injection site. Degeneration of nerve terminals following kainic acid injections in the MLPHA was widespread, not predictably reduced by diazepam premedication and differed in only minor details from degeneration induced by subcutaneous injections.