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 1 a will identify by in situ hybridization (ISH) cfos-labeled brainstem neurons for evidence of early postcoital activated cells.
Aim 1 b 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 1 c 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 3 a will decipher if administration of TH or NET antisense oligonucleotides into the LC blocks the coital-induced NE/GnRH release.
Aim 3 b 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.
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