Characterization of self-stimulation elicited from rat dorsolateral pariaqueductal gray.

Rats were stereotaxically implanted with chronic bipolar electrodes aimed at the periaqueductal central gray (PCG) and were subsequently tested for intracranial self-stimulation (ICSS) behavior. Consistent and reliable ICSS behavior was elicited from both the midventral and dorsolateral portions of the PCG, the latter result occurring in loci previously reported as predominantly aversive. Midventral PCG ICSS rates were significantly higher than dorsolateral PCG ICSS rates. The higher rates were not accounted for by either current intensity used or motor artifacts. Moreover, both sites displayed reliable ICSS behavior characterized by regular low-variability rates and no seizure activity, seen with other brainstem ICSS sites, but unlike diencephalic and telencephalic ICSS behavior which is characterized by irregular bursts of responding which are highly variable and sometimes accompanied by seizures. The differential ICSS responsivity between PCG structures suggests that they may be mediated by different anatomically-localizable substrates.