NEUROCHEMICALS IN HYPOTHALAMIC SIGNALING AFTER COITUS

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DESCRIPTION: (adapted from the applicants abstract) Coitus induces a concatenation of neurohumoral events in New Zealand White rabbits that includes increased secretion of norepinephrine (NE), gonadotropin-releasing hormone (GnRH), luteinizing hormone (LH), ovarian steroids, and finally the release of ova. Brainstem neurons that synthesize NE are a likely component of the signaling pathway as enhanced expression of tyrosine hydroxylase (TH) and NE transporter (NET) mRNAs occurs by 15-min postcoitus in locus coeruleus (LC), while intrahypothalamic infusion of either prazosin (alpha1 adrenergic blocker) or desipramine (NET blocker) alters the GnRH/LH surge. The P.I. proposes three new aims to extend the understanding of this neurochemical process. Aim 1 would identify neurotransmitters and neuronal circuits that relay coital signals to the LC and/or hypothalamus. Neuropeptide Y (NPY) mRNA expression was not observed in the rabbit LC; however, TH, NPY and/or NET mRNAs were co-localized in the paragigantocellularis (nPGi) or praepositus hypoglossi (nPH) nuclei--two brainstem nuclei that innervate the LC. The P.I. hypothesizes that vaginal signals reach the nPGi and/or nPH where they excite interneurons (i.e., NPY, acetylcholine [ACH]) that either stimulate the NE/NET neurons in LC or project directly to hypothalamic cells. Aim 1a will identify by in situ hybridization (ISH) cfos-labeled brainstem neurons for evidence of early postcoital activated cells. Aim 1b will identify cells for TH, NET, NPY, NPY receptors, ACH esterase (Ache) and glutamic acid decarboxylase (GAD) in the LC, nPGi and nPH by ISH. Aim 1c will define the specific cell types after coitus that dual stain for the above and also express cFos protein (ISH for mRNAs, immunocytochemistry for cFos protein). Aim 2 will examine if ACH and gamma aminobutyric acid (GABA) affect the postcoital GnRH/LH surge by action through brainstem/hypothalamic connections. The P.I. will administer a specific ACH blocker ( alpha-conotoxin) and GABAA agonist (muscimol) either locally into the hypothalamus or into the 4th ventricle near brainstem-relevant neurons. Mating-induced GnRH/LH secretion and brainstem TH/NET/NPY mRNAs will be measured in rabbits with and without drug treatment. Aim 3 will target brainstem loci by either microinjection of antisense oligonucleotides or electrical lesioning. Aim 3a will decipher if administration of TH or NET antisense oligonucleotides into the LC blocks the coital-induced NE/GnRH release. Aim 3b will determine if electrical lesions of the nPGi and/or nPH prevent either the postcoital expression of LC cFos protein, TH/NET mRNAs or the LH surge. These studies may provide information on neurologically related infertility.