This paper deals with the effect of temperature (t degrees), ions, prostaglandin (PGE2) and testosterone on the rate of release of LHRH from the superfused medial basal hypothalamus (MBH) of normal or castrated male rats in an effort to further validate the biological properties of this preparation. LHRH in the perfusate is nondetectable when the MBH is at 0 C, warming to 37 C produces a sharp rise in LHRH and then stabilization at a level at least threefold the one calculated for the 0 C experiment. Basal release rate of LHRH is t degrees and calcium dependent, as is the stimulatory action of potassium. Infusion of high K+ induces approximately a fivefold increase in the release rate of LHRH and stays at this high level for as long as the infusion lasts (50 min). LHRH stimulation by PGE2 (pulse) proceeds in the absence of external calcium, and the effect lasts longer than the potassium (pulse) action. Surprisingly, MBHs from long-ter castrated males (60-90 days) release less LHRH per minute than intact male MBHs during the steady state phase of LHRH secretion; testosterone propionate (TP, 200 microgram/100 g BW x 3 days) increases significantly the rate of release in castrate rats and is not related to the amount of LHRH assayed in the MBH. MBHs of untreated castrated rats or castrated rats treated with TP, show a reduced LHRH secretion in response to PGE2. It is concluded that this preparation can be used at advantage to study the rate of LHRH release in a variety of experimental paradigms.

Animals↗

PubMedDate not supplied

Aging alters opiate inhibition of potassium (K+)-stimulated dopamine release from the corpus striatum of male rats.

The effect of Leu-enkephalin (Leu-ENK), Met-enkephalin (Met-ENK), and naloxone on potassium (K+)-evoked endogenous dopamine (DA) release from striatal tissue fragments was examined in young (2-4 month) and old (20-25 month) male rats. The K(+)-evoked DA release was significantly lower in old compared to young animals. Leu-ENK significantly reduced K(+)-evoked DA release in young animals, but neither opiate affected DA release in old animals. Naloxone, which had no effect in young animals, raised the K(+)-evoked DA response in old animals to levels seen in young control preparations. These results suggest that the age-dependent decrease in K(+)-evoked DA release may in part be due to a stronger opiate inhibitory tonus in the CS of older rats.

Age Factors↗

PubMedDate not supplied

Sex differences in amphetamine-elicited rotational behavior and the lateralization of striatal dopamine in rats.

Sex differences are described in both a lateralized behavior (amphetamine-elicited rotation) and in the lateralization of striatal dopamine (DA) content. Amphetamine (AMPH) elicited significantly more partial turns, total rotations and lateralized (net) rotations in female, than in male rats. The two sexes also differed in their pattern of net rotations over time. In females, but not males, the striatum containing higher DA levels after amphetamine was consistently found to be contralateral to the dominant direction of rotation observed in the first 5 min interval after AMPH. No relationship was found between rotational behavior and medial frontal cortex DA or norepinephrine. The results are discussed in reference to cerebral lateralization in humans, and to possible sex differences in the modulatory effects of gonadal steroid hormones on striatal function.

Animals↗

PubMedDate not supplied

Short-term steroid treatment on plasma LH and FSH in castrated rats from birth to puberty.

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Aging↗