Interaction of oxotremorine with atropine, chlorpromazine, cyproheptadine, imipramine and phenoxybenzamine on the flexor reflex of the chronic spinal dog

Influence of adrenergic and cholinergic mechanisms in baclofen induced analgesia

1. Baclofen induced analgesia was confirmed by means of the mouse hot plate test. 2. Physostigmine significantly increased the response to baclofen whilst neostigmine was ineffective. Baclofen analgesia was reduced by atropine. 3. The response to baclofen was increased by the administration of tolazoline, propranolol and nadolol. In contrast, the analgesic response to morphine was attenuated by the antiadrenergic drugs phenoxybenzamine, tolazoline and nadolol.

Actions of amphetamine and antagonists on pupil diameter in the chronic sympathectomized dog

The left superior cervical ganglia were removed from 5 dogs. Beginning 30 days postoperatively, epinephrine (10 microgram/kg/min), norepinephrine (10 microgram/kg/min), and d-amphetamine (1.0 mg/kg) were infused i.v. for 10 min following either vehicle, phenoxybenzamine, pimozide, or haloperidol. Epinephrine and norepinephrine dilated the pupil and retracted the nictitating membrane of the denervated side, whereas amphetamine dilated both pupils and retracted both nictitating membranes. Phenoxybenzamine (4 mg/kg) constricted primarily the pupil of the innervated iris and completely antagonized the effects of the catecholamines on the irides and amphetamine on the nictitating membranes, but only partially antagonized amphetamine-induced mydriasis. Haloperidol (1.0 mg/kg) constricted both pupils, possessed only modest alpha-adrenergic blocking activity, and was as effective as phenoxybenzamine in antagonizing amphetamine-induced mydriasis. Pimozide (0.1 mg/kg) constricted both pupils, had no significant alpha-adrenergic blocking activity, and did not antagonize amphetamine-induced mydriasis. Pimozide and haloperidol, but not phenoxybenzamine, blocked amphetamine-induced stereotyped head bobbing. These results suggest that amphetamine produces mydriasis in the dog through a peripheral sympathetic action and also through a central mechanism involving inhibition of the oculomotor nucleus. However, the role of dopamine is not clear.