Inhibitory effects of beta-phenylethylamine on photic-evoked potentials in the visual cortex of the cat

We investigated the effects of beta-phenylethylamine (PEA) on photic-evoked potentials recorded from the cerebral cortex (visual cortex) in the anesthetized cat. The photic-evoked potential consisted of negative (N) and positive (P) components in the cerebral cortex, with peak times of 39.4 +/- 15.4 msec and 57.5 +/- 16.3 msec, respectively. Intravenous administration of PEA (6.5, 12.5 and 25 mg/kg) induced a dose-dependent decrease in the amplitude of the N component of photic-evoked potentials. PEA-induced decreases in the amplitude of photic-evoked potentials (at 12.5 mg/kg) were antagonized by yohimbine (2 mg/kg). Prazocin (2 mg/kg, i.v.) and propranolol (0.5 mg/kg, i.v.) did not change the PEA-induced decrease of photic-evoked potentials. Methysergide (2 mg/kg, i.v.), haloperidol (1 mg/kg, i.v.) and naloxone (0.5 mg/kg, i.v.) also failed to alter the inhibitory effect of PEA. Pretreatment with alpha-methyl-p-tyrosine or reserpine did not completely attenuate the PEA-induced decrease of photic-evoked potentials. According to these results, PEA inhibits the photic-evoked potentials in the visual cortex partially through the noradrenergic alpha 2-receptor.