Identification of PAC1 receptor isoform mRNAs by real-time PCR in rat suprachiasmatic nucleus.

The pituitary adenylate cyclase-activating polypeptide (PACAP) has been implicated in the photic resetting of the rodent circadian clock in the suprachiasmatic nucleus (SCN). PACAP can exert its effects via VPAC1, VPAC2 and PAC1 G-protein coupled receptors. PAC1 and VPAC2, but not VPAC1, mRNA is expressed in rat SCN.

Gastrin-releasing peptide phase-shifts suprachiasmatic nuclei neuronal rhythms in vitro.

The main mammalian circadian pacemaker is located in the suprachiasmatic nuclei (SCN) of the hypothalamus. Gastrin-releasing peptide (GRP) and its receptor (BB(2)) are synthesized by rodent SCN neurons, but the role of GRP in circadian rhythm processes is unknown. In this study, we examined the phase-resetting actions of GRP on the electrical activity rhythms of hamster and rat SCN neurons in vitro.

Expression of mt(1) melatonin receptor subtype mRNA in the entrained rat suprachiasmatic nucleus: a quantitative RT-PCR study across the diurnal cycle.

Melatonin acts on specific receptors in the suprachiasmatic nuclei (SCN) to phase-dependently regulate the phase of the circadian clock. How the gating of melatonin's effect is restricted to particular times of day is not known, but may be related to temporal differences in receptor availability. In the present study, we used a competitive reverse transcription-polymerase chain reaction (RT-PCR) method to determine if the expression of mt(1) melatonin receptor subtype mRNA in rat SCN varied across the 12:12 light-dark (LD) cycle.

Sexual dimorphism in N-acetyltransferase and melatonin levels in the giant freshwater prawn Macrobrachium rosenbergii de Man.

N-acetyltransferase (NAT) and melatonin were determined in the optic lobe of the giant freshwater prawn Macrobrachium rosenbergii de Man. The prawns were divided into three groups: fast-growing "jumper" males; slow-growing "laggard" males; and females. Both NAT and melatonin levels in the jumper and laggard males were comparable, whereas those of the female were significantly lower.

N-acetyltransferase, hydroxyindole-O-methyltransferase and melatonin in the optic lobes of the giant tiger shrimp Penaeus monodon.

The activities of the enzymes N-acetyltransferase (NAT) and hydroxyindole-O-methyltransferase (HIOMT) and the hormone melatonin were studied in the optic lobe of the subadult giant tiger shrimp Penaeus monodon. Compared with the level in other species, a relatively high level of NAT activity that was temperature- and pH-dependent were observed. The NAT enzyme had a relatively high maximum velocity (Vmax, 100 pmol/hr/micrograms protein) and low Michaelis constant (Km, 22 microM), when tryptamine is used as substrate.

Continuous light increases N-acetyltransferase activity in the optic lobe of the giant freshwater prawn Macrobrachium rosenbergii de Man (Crustacea: Decapoda).

Giant freshwater prawns, Macrobrachium rosenbergii de Man, were reared under three different lighting conditions: continuous darkness (DD), 12 hr of light and 12 hr of darkness (LD 12:12) and continuous light (LL). After one month, the prawns were sacrificed and optic lobes isolated from the eyestalks were determined for N-acetyltransferase (NAT) activities and melatonin concentrations. Gonads were weighed and examined under light microscopy.