PARENT SESSION
PLATFORM SESSION 15. NEUROENDOCRINOLOGY

Tuesday, August 3, 2004
4:30 PM–6:30 PM
Buchanan A104
Chair: Matt Hardy Co-Chair: Leslie Jackson

(557) A NEURONAL PATHWAY REGULATING PROLACTIN AND LUTEINIZING HORMONE SECRETION IN THE TURKEY HYPOTHALAMUS.

Kang, Seong¹, Al-Zailaie, Khaled¹, Thayananuphat, Aree¹, Youngren, Orlan¹, El Halawani, Mohamed¹, ¹ University of Minnesota, St. Paul, MN

ABSTRACT- It has been suggested that a hypothetical pathway running from the medial preoptic area (mPOA) to the infundibular nuclear complex (INF) in the caudal hypothalamus regulates prolactin (PRL) and luteinizing hormone (LH) secretion in the turkey (Youngren et al., Biol. Reprod. 1989). The suggestion is based on findings utilizing electrical stimulation (ES) and lesioning techniques. ES within the mPOA of the turkey hypothalamus induces the secretion of PRL and LH from the anterior pituitary gland. The double in situ hybridization/immunocytochemistry (ICC) study was designed to further clarify this neural pathway utilizing c-fos mRNA expression as a marker for neural activation in combination with ES. Unilateral ES (100 microamperes) was delivered to the mPOA for 30 min followed by a 15 min post-ES period (n = 8 birds). Blood samples for PRL and LH radioimmunoassay were collected before, during, and after ES. Control birds (n = 6 birds) received no ES, but were otherwise treated the same. The expression of c-fos mRNA was observed in several ipsilateral hypothalamic areas, including the mPOA, anterior hypothalamus (AM), ventromedial nucleus of the hypothalamus (VMN), paraventricular nucleus (PVN), bed nucleus of the pallial commissure (nCPa), and the INF. None, or very weak expression of c-fos mRNA, was found on the side contralateral to the ES stimulation site. ES increased plasma PRL from a baseline of 96.4 ± 10.3 ng/ml to 336.2 ± 56.8 ng/ml and plasma LH from 2.4 ± 0.3 ng/ml to 3.2 ± 0.8 ng/ml. Double in situ/ICC showed c-fos mRNA was colocalized with approximately 20% of the total VIP neuron population in the INF. In addition, c-fos mRNA was coexpressed with GnRH-I immunoreactive neurons in the nCPa and with dopamine (DA) neurons in the medial mammillary nucleus (ML) and caudal INF. This study provides additional evidence that a neural pathway projects from mPOA to the tuberal hypothalamus and that it influences GnRH, VIP, and DA neurons.

KEY WORDS: electrical stimulation, in situ hybridization, turkey hypothalamus, c-fos mRNA