heroin and octanoic-acid

Cerebral functional activity was measured as changes in distribution of the free fatty acid [1-14C]octanoate in autoradiograms obtained from rats during brief presentation of a tone previously paired to infusions of heroin or saline. Rats were trained in groups of three consisting of one heroin self-administering animal and two animals receiving yoked infusions of heroin or saline. Behavioral experiments in separate groups of rats demonstrated that these training parameters imparts secondary reinforcing properties to the tone for animals self-administering heroin while the tone remains behaviorally neutral in yoked-infusion animals. The optical densities of thirty-seven brain regions were normalized to a relative index for comparisons between groups. Previous pairing of the tone to heroin infusions irrespective of behavior (yoked-heroin vs. yoked-saline groups) produced functional activity changes in fifteen brain areas. In addition, nineteen regional differences in octanoate labeling density were evident when comparison was made between animals previously trained to self-administer heroin to those receiving yoked-heroin infusions, while twelve differences were noted when comparisons were made between the yoked vehicle and self administration group. These functional activity changes are presumed related to the secondary reinforcing capacity of the tone acquired by association with heroin, and may identify neural substrates involved in auditory signalled conditioning of positive reinforcement to opiates.

Topics: Acoustic Stimulation; Animals; Autoradiography; Brain; Caprylates; Carbon Radioisotopes; Conditioning, Operant; Heroin; Male; Organ Specificity; Rats; Rats, Inbred Strains; Reinforcement, Psychology; Self Administration

Brain activity was measured autoradiographically using [1-14C]octanoate (OCTO) as a fast functional tracer in rats receiving either saline, heroin or cocaine. Regional optical densities were normalized to a relative optical density index for comparisons of OCTO labeling between treatment groups. Heroin significantly increased labeling in the dentate gyrus and cocaine increased density in the anterior cingulate cortex, globus pallidus, hippocampus CA3-4, lateral septum, hypothalamus and ventral tegmentum. Heroin and cocaine induced significant, but opposing effects in medial cortex and bed nucleus of the stria terminalis. Both drugs decreased labeling density in the nucleus accumbens and piriform cortex, and increased density in the substantia nigra, subthalamus, medial septum, claustrum, lateral hypothalamus and hippocampus CA2. These results demonstrate the ability of the OCTO method to discriminate the brief metabolic effects of different drug classes, and suggest that heroin and cocaine may activate a common functional system in the brain.

Topics: Animals; Autoradiography; Brain; Caprylates; Cocaine; Heroin; Injections, Intravenous; Male; Rats; Rats, Inbred Strains