Kivonat:
Tuberoinfundibular peptide of 39 residues (TIP39) and the PTH-2
receptor (PTH2R) constitute a peptide-receptor neuromodulator
system. Based on the abundance of TIP39 fibers and axonal
terminals as well as PTH2R-containing neurons and their
processes in the hypothalamic para- and periventricular and
arcuate nuclei TIP39 has been suggested to play a role in
neuroendocrine regulation. We showed previously that TIP39
expression decreased dramatically by adulthood. In the present
study, using in situ hybridization histochemistry, real-time RT-
PCR, and immunohistochemistry, we found that TIP39 mRNA and
peptide expression levels are markedly elevated in the
posterior intralaminar complex of the thalamus (PIL) of
lactating dams, one of the three locations of TIP39-containing
cell bodies in the brain. In addition, in mother rats, these
TIP39 neurons showed Fos expression in response to pup
exposure. Transection of TIP39 fibers originating in the PIL
resulted in an ipsilateral disappearance of TIP39
immunoreactivity throughout the mediobasal hypothalamus of
mother rats, suggesting that TIP39 fibers there arise from the
PIL. To elucidate the function of TIP39 activation in dams,
mothers separated from their pups for 4 h on postpartum d 9
received injection of a PTH2R antagonist into the lateral
ventricle 5 min before returning the pups. Blood samples were
taken seven times during the experimental period through jugular
cannulae. The PTH2R antagonist administered in two different
concentrations markedly inhibited suckling-induced elevation of
plasma prolactin levels in a dose-dependent manner. These
results suggest that TIP39 neurons in the PIL may regulate
suckling-induced prolactin release in rat dams.
