Vasoactive intestinal peptide modulates luteinizing hormone subunit gene expression in the anterior pituitary in female rat

Pyramidal neurons are "neurogenic hubs" in the neurovascular coupling response to whisker stimulation

The whisker-to-barrel cortex is widely used to study neurovascular coupling, but the cellular basis that underlies the perfusion changes is still largely unknown. Here, we identified neurons recruited by whisker stimulation in the rat somatosensory cortex using double immunohistochemistry for c-Fos and markers of glutamatergic and GABAergic neurons, and investigated in vivo their contribution along with that of astrocytes in the evoked perfusion response. Whisker stimulation elicited cerebral blood flow (CBF) increases concomitantly with c-Fos upregulation in pyramidal cells that coexpressed cyclooxygenase-2 (COX-2) and GABA interneurons that coexpressed vasoactive intestinal polypeptide and/or choline acetyltransferase, but not somatostatin or parvalbumin. The evoked CBF response was decreased by blockade of NMDA (MK-801, -37%), group I metabotropic glutamate (MPEP+LY367385, -40%), and GABA-A (picrotoxin, -31%) receptors, but not by GABA-B, VIP, or muscarinic receptor antagonism. Picrotoxin decreased stimulus-induced somatosensory evoked potentials and CBF responses. Combined blockade of GABA-A and NMDA receptors yielded an additive decreasing effect (-61%) of the evoked CBF compared with each antagonist alone, demonstrating cooperation of both excitatory and inhibitory systems in the hyperemic response. Blockade of prostanoid synthesis by inhibiting COX-2 (indomethacin, NS-398), expressed by ∼40% of pyramidal cells but not by astrocytes, impaired the CBF response (-50%). The hyperemic response was also reduced (-40%) after inhibition of astroglial oxidative metabolism or epoxyeicosatrienoic acids synthesis. These results demonstrate that changes in pyramidal cell activity, sculpted by specific types of inhibitory GABA interneurons, drive the CBF response to whisker stimulation and, further, that metabolically active astrocytes are also required.

Induction of ovulation and natural oestrous cycling in the Stripe-faced Dunnart, Sminthopsis macroura

Induced ovulation allows reproduction by otherwise infertile females, and is ideal for the captive breeding of endangered species where the population is aged or breeding is unsuccessful. A predictable time of ovulation after induction has not yet been achieved in polyovular marsupials. Ovulation was induced inSminthopsis macrourausing an initial injection of 20 IU equine serum gonadotrophin (eSG; Day 0), followed on Day 4 by either 20 IU eSG (n= 25) or 0.5 mg porcine luteinizing hormone (n= 26). I.p. hormone injection was given in the morning or early evening, and reproductive status was established prior to induction. Five non-cyclic animals began to cycle naturally following induction and one gave birth to a litter. The time of ovulation after the 1st injection (7.8 ± 0.9 days) was significantly shorter (P= 0.000) and less variable than the previous study, mimicked the timing of natural cycling, and both natural and induced animals ovulated in the early morning.In vitrooocyte movement through the oviduct, observed for the first time in a marsupial, occurred in pulses. We estimated one group of oocytes could travel the length of the oviduct in 40 min, but it was probably around 4 h. The entire ovulation time (including multiple ovulations) was estimated at 7.5 h. This study has achieved a predictable timing of ovulation after stimulation, and induced noncyclic animals to cycle naturally and give birth, providing a modified methodology for use in captive breeding programs of endangered dasyurid marsupial species with low fecundity.