Using data that are available in various publications, a quantitative analysis has been made of the geniculocortical input to layer IVC of the macaque striate cortex. The data suggest that only 1.3-1.9% of the excitatory, or asymmetric synapses in layer IVC alpha of striate cortex are provided by the neurons of the magnocellular layers of the LGN. This amounts to only 18-40 of the 1000-2100 asymmetric synapses that the average layer IVC alpha neuron receives. The parvicellular afferents to layer IVC beta, on the other hand, provide 3.7-8.7% of the asymmetric synapses formed by the average layer IVC beta neuron, or 37-191 synapses to each neuron. If it is assumed that the boutons in the geniculocortical axonal plexuses are evenly spread, it can be calculated that the input to an individual layer IVC neuron is provided by some 24 axonal plexuses. This is regardless of whether the neuron lies in layer IVC alpha or in IVC beta. This calculation suggests that a single axonal plexus provides not more than one or two of the excitatory synapses received by an individual layer IVC alpha neuron, and between one and eight excitatory synapses for a layer IVC beta neuron. Consequently, it is unlikely that the response properties of a particular cortical neuron are dominated by its input from a single geniculate neuron. Since the geniculocortical input essentially determines the response properties of neurons in layer IV of macaque striate cortex, it is surprising that this input amounts to such a small number of synapses to an individual neuron, although we obtained a somewhat similar result in our earlier quantitative analysis of the geniculate input to the striate cortex of the cat (Peters and Payne, 1993). But it has to be questioned whether the low values obtained are correct. Interestingly, the geniculocortical input to cortex has been largely neglected in favor of analyses of intracortical circuitry, but in view of the basic importance of this afferent input, it is suggested that more quantitative data about it should be generated, so that a better assessment can be made of its extent.

Afferent Pathways↗

PubMedDate not supplied

Biological properties of the angiotensin-converting enzyme inhibitor cilazapril.

Cilazapril is the monoethyl ester prodrug form of a potent, specific. long-acting antihypertensive inhibitor of angiotensin-converting enzyme (ACE). The biochemical and pharmacological properties of this compound have been compared with those of captopril and enalapril. In all test systems, cilazapril was the most potent and the longest acting. The active diacid of cilazapril was more potent than the corresponding diacid of enalapril in inhibiting the cleavage of angiotensin I and of Hip-His-Leu by ACE in vitro, in antagonising the angiotensin I-induced contractions of the isolated ileum of the guinea pig, in potentiating the vasodepressor responses to bradykinin, and in reducing the angiotensin I-induced rise in blood pressure of the rat. Parent drug absorption and diacid bioavailability in the rat were higher than for enalapril, and the inhibition of plasma ACE of longer duration. Single doses of cilazapril were more potent than enalapril in lowering the blood pressure of spontaneously hypertensive rats (SHR) and two-kidney renal hypertensive rats. On repeated daily oral dosing to SHR, both compounds had a cumulative antihypertensive effect. The acute antihypertensive effect was enhanced by simultaneous treatment with hydrochlorothiazide.

Angiotensin I↗

PubMedDate not supplied

Early syphilis. Relationship to sex, drugs, and changes in high-risk behavior from 1987-1990.

A case-control study was conducted to evaluate two main questions: 1) which specific sex- and drug-use behaviors are associated with the acquisition of early syphilis; and 2) whether changes in sex- and drug-use behaviors from 1987-1990 associated with acquisition of early syphilis. Risk factors associated with significant odds ratio were greater than four sex partners and lack of condom use in the past 3 months. Crack use within the past 3 months was the only specific drug-related risk factor with a significantly elevated odds ratio. However, a number of risk factors associated with both sex and drugs had significantly elevated odds ratios: number of drug-using partners, number of partners exchanging sex for drugs and money, and number of partners with whom the respondent shares sex and drugs. Risk estimates for early syphilis were uniformly higher for women as compared with men. Women appeared to be at higher risk of syphilis than men when engaged in the same high-risk activities. From 1987-1990, there was a significant change from lower-risk to higher-risk behaviors among patients. Patients showed an increase in their number of sex partners, in drug use, and in other high-risk activities. Increasing rates of syphilis can be attributed to a particular set of sex- and drug-related behaviors, and an increase in the adoption of these behaviors has probably contributed significantly to the increased rate of early syphilis in Trenton, NJ, during the period from 1987-1990.

Adult↗