Drugs online research references
Sens Processes. 1978 Dec;2(4):388-95.
Effects of catecholamines on the horizontal cell membrane potential in the fish retina.
Negishi K, Drujan BD.
The effects of catecholamines (CA) and certain related compounds on the horizontal cell membrane potential were examined in the retina of the teleost (Eugerres plumieri). Each CA compound (dopamine, noradrenaline, and adrenaline) had a similar effect on each class of horizontal cell (photopic L- and C-type, scotopic L-type). The threshold effect, seen with 25-50 microM CA, was an enlargement of both center and surround responses in general. At higher concentrations (100-200 microM), CA augmented the center response and attenuated the surround considerably; these reciprocal changes usually were associated with moderate depolarization. Recovery took place in 15-20 min. The results indicate that up to a certain concentration CA do not affect directly the transmission from photoreceptors to horizontal cells. The lateral propagation of S-potential, however, appears selectively affected by CA. alpha-Methylnoradrenaline, 5-hydroxydopamine, and serotonin caused the same effect on horizontal cells as CA. Reserpine, clonidine, and L-dopa mimic the CA effect only after prior application of CA. Phentolamine blocked while propranolol, haloperidol, and pimozide did not influence the DA effect. We conclude that alpha-adrenergic receptors probably are involved in the CA-induced changes observed in horizontal cells.
online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=755294&dopt=Abstract
Clin Exp Hypertens. 1978;1(1):1-9.
Sympathetic nervous function and renin activity in hypertensives on long term drug treatment with propranolol, methyldopa or bendrofluazide.
Polak G, Reid JL, Hamilton CA, Jones DH, Dollery CT.
Plasma noradrenaline and plasma renin activity were measured as indices of sympathetic activity and renin angiotensin system in similar groups of hypertensive patients receiving either propranolol, bendrofluazide or methyldopa. Plasma renin activity was similar in the propranolol and methyldopa groups and significantly lower (p less than 0.01) in both these groups than the diuretic treated subjects. Plasma noradrenaline was significantly lower (p less than 0.01) on methyldopa than either propranolol or bendrofluazide. These different effects on the renin angiotensin system and the sympathetic nervous system of these drugs may be relevant in the choice of long term therapy in hypertension.
online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=755641&dopt=Abstract
J Pharmacol Exp Ther. 1995 Oct;275(1):53-62.
Noradrenergic involvement in the discriminative stimulus effects of cocaine in squirrel monkeys.
Spealman RD.
Harvard Medical School, New England Regional Primate Research Center, Southborough, Massachusetts, USA.
Noradrenergic involvement in the discriminative stimulus (DS) effects of cocaine was investigated in squirrel monkeys by using a two-lever drug discrimination procedure in which responding was maintained by a fixed-ratio schedule of stimulus-shock termination. Monkeys initially were trained to discriminate a relatively high dose of cocaine (1.0 mg/kg i.m.) from saline and subsequently were retrained to discriminate a 3.3- to 5.6-fold lower dose of cocaine (0.30 or 0.18 mg/kg i.m.). The selective norepinephrine[fnc] uptake inhibitors talsupram, tomoxetine, nisoxetine and desipramine substituted for cocaine in the majority of subjects under the low-dose training condition, whereas the selective dopamine uptake inhibitor GBR 12909 [1-(2-[bis(4-fluorophenyl)methoxy]ethyl)-4-(3-phenylpropyl) piperazine] substituted for cocaine under both training conditions and the selective serotonin uptake inhibitor citalopram failed to substitute for cocaine under either condition. Representative alpha-1 [St 587 (2-(2-chloro-5-trifluoromethyl-phenylimino)imidazolidine] and SDZ NVI 085 [(-)-(4aR, 10aR)-3,4,4a,5,10,10a-hexahydro-6-methoxy-4- methyl-4-methyl-9-(methylthio)-2H-naphth[2,3-b]-1,4-oxazine)], alpha-2 (clonidine and UK 14,304 (5-bromo-N-(4,5-dihydro-1H-imidazol-2-yl)-6-quinoxalinamine]) and beta (clenbuterol) adrenoceptor agonists did not consistently substitute for cocaine under either condition in which they were studied. Pretreatment with the alpha-1 adrenoceptor blocker prazosin antagonized the DS effects of cocaine under both training conditions as well as the cocaine-like effects of talsupram and tomoxetine, but not GBR 12909, under the low-dose training condition. Pretreatment with the alpha-2 blocker efaroxan, the nonselective alpha blocker phentolamine and the beta blocker propranolol failed to alter the DS effects of cocaine consistently under either condition in which they were studied. Pretreatment with talsupram, at doses that did not substitute for cocaine when administered alone, enhanced the cocaine-like effects of GBR 12909 under both training conditions. The results support a role for norepinephrine uptake and alpha-1 adrenoceptor mechanisms in the DS effects of cocaine, possibly reflecting a facilitory noradrenergic influence on mesocorticolimbic dopamine activity.
online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=7562595&dopt=Abstract
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