Prolactin and LH release induced by kainic acid administration within the preoptic-suprachiasmatic region in behaving male rats

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Abstract
Adult male rats were chronically implanted with a multiple metal cannula assembly to allow for the administration of kainic acid within the POA-SCH region. Kainic acid was applied in its solid form at two dose levels: 2 μg and 4 μg. A chronic heart cannula implanted through the external jugular vein allowed for sequential blood sampling. Animals were subjected to two different regimes, with 2–3 days difference, one in which blood sampling took place without kainic acid administration, and a second one in which the drug was administered after a first, control sample was obtained. Administration of kainic acid at both dose levels induced motor hyperactivity that lasted for more than 1 h in the group that received the higher dose. Prolactin concentration in plasma rose by 30 min and declined thereafter in the “low” dose group, or remained high for at least 90 min in the “high” dose group. LH levels increased significantly only after administration of the “high” dose. These results are indicative of the presence of facilitatory elements for the release of prolactin (and LH) which originate within the POA-SCH region, probably involving glutamatergic receptors. Stimulation of these elements, rather than passing fibers, are probably responsible for the observed hormonal results.