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M Makimura

Publications and source records attributed to M Makimura.

40 records · Page 3Linked to original sources
PubMed1982

The effect of denervation of the cyclic nucleotides levels of the vas deferens.

We measured the cyclic nucleotides in levels of the rat vas deferens surgically denervated in order to investigate the relationship between denervation supersensitivity and cyclic nucleotides. Two days after denervation, cyclic AMP slightly decreased to 90.4% of control and cyclic GMP also decreased but not significantly. So it is assumed that almost all of the cyclic nucleotides are not neurogenic but myogenic. When the rat vas deferens was incubated with l-norepinephrine 10(-4) for 3 min, the cyclic GMP level in the vas deferens denervated for seven d was significantly higher than that in the intact specimen, and the cyclic AMP level in the intact one was almost the same as in the denervated preparation. Denervation produced leftward shift of the dose response curve in cyclic GMP level to l-norepinephrine. After incubation with acetylcholine (10(-4)M), however, cyclic GMP and cyclic AMP levels in the denervated vas deferens were almost the same as in the intact one. Therefore, it is suggested that cyclic nucleotides don't relate to the induction of nonspecific supersensitivity by denervation in the rat vas deferens.

Acetylcholine↗
PubMedDate not supplied

Acute and chronic intracerebroventricular morphine infusions affect long-term potentiation differently in the lateral perforant path.

Experiments were performed to investigate the effects of acute and chronic intracerebroventricular (icv) morphine infusions via osmotic minipumps on long-term potentiation (LTP) in the lateral perforant path (LPP)-granule cell synapse of the rat dentate gyrus. Although significant antinociceptive activity was observed when morphine was infused (25 nmol/microl/h) for 30 min or 1 h, the activity was not observed in rats receiving morphine chronically for 72 h, and the tail-flick latency of this group was comparable to that of rats receiving saline. LTP induction was significantly attenuated after acute morphine infusion (1 h) in LPP-granule cell synapses of the dentate gyrus. In contrast, LTP induction was augmented after chronic morphine infusion for 72 h. Bath-perfused morphine augmented the baseline population spike (PS) amplitude in rats treated with saline, whereas it attenuated the LTP induced by chronic morphine infusion. Returning the LTP to the level of saline infusion after in vitro morphine perfusion suggests that enhancement of the LTP is a withdrawal-like phenomenon. These results suggest a difference between the effects of acute and chronic intracerebroventricular morphine infusions on synaptic plasticity in the LPP-granule cell synapses of the dentate gyrus.

Analgesics, Opioid↗