Non-NMDA Glutamate Receptor Antagonist Injected into the Hypothalamic Paraventricular Nucleus Inhibits the Prolactin Response to Formalin Stress of Male Rats
The aim of the present investigations was to test the involvement of the glutamatergic innervation of the hypothalamic paraventricular nucleus in the prolactin response to stress. A non-NMDA (6-cyano-7-nitroquinoxaline-2,3-dione disodium, CNQX) or an NMDA glutamate receptor antagonist (dizocilpine hydrogen malate, MK-801) was injected bilaterally into the paraventricular nucleus of freely moving male rats and 15 min later the animals were exposed to formalin stress. Blood samples for prolactin and corticosterone were taken at different time points before and after administration of formalin. CNQX, when injected into the paraventricular nucleus, inhibited the formalin-induced rise in plasma prolactin and not significantly the increase in corticosterone. A similar effect was not observed if MK-801 was administered into the paraventricular nuclei or CNQX was injected outside the cell group. The findings indicate that the glutamatergic innervation of the paraventricular nucleus is involved in the mediation of the formalin-induced prolactin release.
KeywordsParaventricular nucleus Glutamatergic innervation Glutamate receptor Stress Prolactin Corticosterone
The authors are grateful to Mrs. I. Salamon for excellent histochemical work, to Mrs. M. Mészáros and Mrs. M. Balázs for their excellent technical assistance and Mrs. E. Pirity for typing the manuscript. This work was supported by the Ministry of Health (ETT 054/2003 to B.H.), National Scientific Research Fund (OTKA T-042516 to B.H.) and the Hungarian Academy of Sciences.
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