On mechanism of action of ethanol-induced contraction of frog rectus abdominis.

Ethanol in low doses (0.5 to 4 M) causes contraction of isolated frog rectus abdominis muscle. Higher concentration did not produce any further increase in maximum response. Pretreatment with dantrolene produced partial but equal inhibition of acetylcholine (Ach) induced as well as ethanol-induced contraction in equieffective doses. Pretreatment with pancuronium produced right and downward shift of ethanol induced contraction. Pretreatment with succinylcholine produced persistent contraction of tissue and this response remained unaffected on subsequent treatment with Ach as well as ethanol. Pretreatment with hemicholinium abolished ethanol induced contraction, although tissue remained viable as confirmed on addition of Ach. The contraction induced by ethanol decreased on pretreatment with dantrolene as well as in Ca2+ free ringer. The results indicate that ethanol induced contraction may be due to release of Ach or Ach like neurotransmitter at neuromuscular junction and calcium acts as mediator to produce these effects.

Studies on rectal temperature of rats in relation to seasonal air temperature and morphine administration.

The present findings demonstrate that seasonal air temperature does not only influence the basal core temperature of rats, but also modifies the physiological/pharmacological actions of drugs. Thus, at low ambient temperature, intracerebroventricular on intraperitoneal administration of morphine produces mainly hypothermia followed by a secondary rise in rectal temperature. On the other hand, at high ambient temperature, the drug produces hyperthermia only. The hypothermic response at low ambient temperature is abolished by pretreatment of rats with 6-hydroxydopamine but not with phenoxybenzamine administration. This suggests that catecholamine pathway in the central nervous system is involved in morphine induced hypothermic response. Further, the role of cholinergic neurons in such response is also indicated.